Advanced Light Microscopy magnifies scope of research
A sample is shown in the foreground that can be used in the digital light sheet microscope at MU’s Advanced Light Microscopy Core as Anand Chandrasekhar explains how he uses it to study neuronal development in zebrafish. | photo by Roger Meissen, Bond LSC
By Phillip Sitter | MU Bond Life Sciences Center
Microscopes have come a long way since Anton van Leeuwenhoek first looked at single-cell organisms in the 1600s.
Now, cutting-edge microscopes allow scientists a better look at how cells interact and work.
The results were easy to see Tuesday morning when a new digital light sheet illuminated all the cells in a zebrafish embryo of Anand Chandrasekhar, a Bond Life Sciences Center scientist and professor of biological sciences. The fish, with its two eyes, brain and spinal cord lit up like a green-colored digital ghost floating in invisible black waters of the monitor screen.
This new microscope joins an array in the Advanced Light Microscopy Core, or MCC, located at Bond LSC. The MCC is one of nine core facilities at MU that provide vital services across campus, from DNA sequencing to imaging.
Researchers and staff at the MCC showed on Tuesday how the new capabilities of the technology give them and MU a competitive edge in their research through better visualizations of their experiments.
The digital reconstruction produced by the light sheet combines “a whole bunch of images over an extended period of time,” Chandrasekhar said. Thousands of images of a cell or organism can be generated by the new equipment, at speeds of hundreds of frames per second, creating a picture that can easily take up a terabyte of hard drive space.
At those speeds, Chandrasekhar said he can “literally watch neurons in the brain light up” in real time. He observes how neuron changes occur in the fish’s brain as the animal goes about its different routine behaviors like avoiding possible predators and searching for food. With this capability, researchers like him can study how neuronal networks develop.
The new digital light sheet uses less damaging light than traditional microscopes and allows for clearer pictures, often with a 3-D look at their structure. More advanced imaging equipment also allow for faster, larger volume experiments that are gentler on the biological samples used in them.
Thomas Phillips, MCC Director and professor of biological sciences, explained how his center now can better serve scientists across campus.
In addition to the digital light sheet imaging system, the MCC also has two new super-resolution microscopy systems, what Phillips said researchers across campus expressed they needed most. The presence of these super-resolution systems in particular puts MU at the forefront of microscopic research.
“Whereas every school has a confocal, less than 10 percent have super-resolution capabilities,” Phillips said, and now MU has two super-resolution systems. “The new equipment adds totally new capabilities without interfering with the traditional confocal activities.”
Traditional confocal microscopy systems, while still useful, have limitations in their resolution which super-resolution systems overcome by how the specimens are illuminated.
In addition to having technology other institutions do not, MU has a higher quality version of super-resolution. Phillips explained that while systems at other institutions use two different lasers in the internal mechanisms of their imaging equipment, MU is one of less than 10 or 12 schools that has access to a super-resolution system that has a unique three laser combination that increases the resolution of the system.
“Super-resolution microscopy allows us to see how individual proteins are interacting inside cells in ways we haven’t been able to before,” he said.
Sergiy Sukhanov uses one of the super-resolution microscopes in cardiology research that looks at failure of organ systems. Sukhanov studies heart failure and atherosclerosis — the chronic, dangerous build-up of plaque in arteries that can create blockages that lead to heart attacks, strokes and death.
Sergiy Sukhanov explains how he uses a confocal microscope in MU’s Advanced Light Microscopy Core to study atherosclerosis and heart disease. | photo by Roger Meissen, Bond LSC
The associate research professor at MU’s School of Medicine showed on Tuesday images of protein interactions in the smooth muscle cells that line arteries. The goal of understanding these interactions is to help keep these smooth muscles in the healthy condition they need to be in to prevent catastrophic blockages.
With its capability of a resolution of up to 30 nanometers, Sukhanov said that the new equipment’s advantage for him is that he can actually see the cell he’s working on. Soon, he hopes to be able to work with live cells so he can observe changes in their protein structures in response to changes in their environment in real time.
Availability of the new equipment lured Sukhanov and his research team to MU over other institutions in 2014. He explained that he struggled to find the equipment he needed for his experiments at Tulane University in New Orleans or elsewhere in Louisiana. Other systems at other institutions usually only have a resolution of up to 50 nanometers.
Sukhanov’s decision is an example of the growth that the new imaging capabilities at the MCC can promote. As director Phillips explained, “you don’t plan experiments ahead of time if you don’t have the apparatus for it.”
MCC not only provides services across campus, but can give scientists insight into how to better look at their specimens.
First-year graduate student Jennifer Wolf displayed a super-resolution image of cancerous liver cells infected with Hepatitis C that been treated with a drug thought to prevent the virus from spreading. The drug aggregates viral capsid molecules – the outer part of a virus – within the infected cells to effectively contain them.
Jennifer Wolf, a first year grad student working in Stefan Sarafianos’ lab, explains an image of hepatitis C infected liver cancer cells captured by a super-resolution 3-D microscope housed at MU’s Advanced Light Microscopy Core. | photo by Roger Meissen, Bond LSC
Wolf said with the new equipment she is now able to see an individual molecule, and using that see the overlap of proteins, RNA and DNA fragments, which can help determine the effectiveness of drugs in treatment.
Associate director of the MCC Alexander Jurkevich explained that the super-resolution equipment also allows for the compilation of separate images into an even more detailed 3-D projection.
Wolf pulled up an image of green-colored mitochondria surrounded by red micro-tubules, green hubs of cellular activity connected by red highways that looked almost like a city from space at night. Wolf used the 3-D capability and rotated the image. She turned the biological intricacy on its side until it looked something like a galaxy on a cosmic horizon, only this view that maybe even fewer people have witnessed is microscopic.
“It’s important to use new technology like this to help the University of Missouri to stay on top,” Wolf said.
Bond LSC’s Matt Will explores the science behind food cravings in his research on mice.
Erik Potter from Mizzou Creative’s Eureka! Podcast tells us more in this month’s segment. Hear more of their science stories at news.missouri.edu/eureka
New outreach program teaches CAFNR students to make plant science knowledge accessible to a younger audience Written by Stephen Schmidt | Science Writer in the College of Agriculture, Food and Natural Resources
Although abundant light was shining through the windows, it was the quiet before the storm. Andrew Ludwig, a University of Missouri sophomore majoring in plant sciences, surveyed the small tables and chairs spread out before him in the laboratory of the Benton STEM Elementary School on a recent Monday afternoon. He sifted through his notes. He was ready, even though it was his first time stepping foot in the building — and he was about to talk to a crowd of students spanning from the first to the fifth grade.
MU graduate student Michael Gardner addresses the students gathered at a recent meeting of the Benton Elementary Science Club. Gardner co-presented a talk called “How Do Flowers Drink?” as part of the “It’s All About Plants” series that was launched earlier this spring. | Photo by Roger Meissen, Bond LSC
“I’m just going to try to stay enthused about everything because I’ve talked to some of my friends who are education majors and the big thing with conveying information to them is just being enthusiastic about it,” Ludwig said about his strategy on the “How Do Flowers Drink?” presentation he was about to give with fellow MU student Michael Gardner.
MU sophomore Andrew Ludwig talks with Leo Batchelder-Draper during an exercise exploring how plants absorb nutrients as his mother, Miriam Batchelder, looks on. | photo by Justin Stewart, Bond LSC
“I think the key is keeping them moving along, keeping them interested, because as soon as you lose their attention, they’re going to do whatever they want to do, so it’s going to be keeping things moving along at a pace that they’re still getting it, but that they’re not bored out of their minds,” added Gardner, who is a fifth-year graduate student specializing in plant stress biology. “We’re talking about water transport in a plant, which is a concept you can spend a semester on in a college-level course and still not be considered an expert on the topic.”
Both Ludwig and Gardner are a part of the team at the Bond Life Sciences Center lab of Melissa Mitchum, an associate professor in the Division of Plant Sciences. It was Mitchum who was able to launch the new “It’s All About Plants” series this spring with the Benton Elementary Science Club thanks to the science outreach portion of a new National Science Foundation grant that will further delve into a deeper understanding of the interactions between plants and parasitic nematodes she received in August and a partnership with the MU College of Education’s ReSTEM Institute, MU Office of Undergraduate Research and Columbia Public Schools.
The end result is a program that fosters learning of all varieties: The elementary students learn about plants, while the college students learn how to take complex ideas and break them down to a more accessible level. Furthermore, the program pairs undergraduate students such as Ludwig with graduate students such as Gardner and principal investigator mentors from across campus — involving the existing NSF-funded initiative Freshman Research in Plant Sciences (FRIPS) and the Students for the Advancement of Plant Pathology (SAPP) in the process.
Deanna Lankford, a research associate from the MU ReSTEM Institute who helped found the Benton Elementary Science Club, helps Adrion Bradshaw open a container of blue food coloring as his twin brother Amahdrion fills writes out some observations with the help of volunteer Alp Kahveci. | photo by Justin Stewart, Bond LSC
“I think it’s a challenge for all of us who have advanced degrees to really think about where we were long ago and bring the concepts down to a basic level,” Mitchum said, “but I think it’s very important for us to be able to communicate our science at that level to really get the kids excited about research.”
Melissa Mitchum | photo by Roger Meissen, Bond LSC
She added that the program “really reinforces the concept of engagement and active learning.” In particular, it reinforces hands-on learning through a variety of activities. “I think that makes a big difference in learning,” said Mitchum, who will have sat with the children for five of the 10 presentations that started on Feb. 22. “I think that’s one of the reasons why I’m such a strong advocate of undergraduate research and getting in a lab and learning how to work in a lab. The same thing applies here. When the kids are doing experiments in the science club, they’re going to retain that information a lot more.”
School’s in session
“Class! Class! Class!”
“Yes! Yes! Yes!”
With those loud words reverberating through the room Ludwig had the attention of those before him — for a moment, anyway. The chatter had quieted down as he began to explain the main activity of the day, which would involve carnation flowers and six solutions of household items (sugar, salt, baking soda, vinegar, soda and food coloring) mixed with water in the same-sized cups – and one scenario with just water.
With the help of several volunteer MU students (whose hours are coordinated by Mitchum’s co-PI, Deanna Lankford, a research associate in the College of Education), the assignment was to pour 100 millimeters into each one of the cups.
The cups were then labeled with the name of the solution. This procedure was repeated three times. The white carnations were then cut to the height of the cup and placed in the water as a discussion ensued on what solutions would help the plant (besides plain water) and which ones would hurt.
Afterwards through the help of a video, the class was introduced to the idea of setting up controls and variables. The one variable, in this case, was the solution. All other factors (such as flower height, flower type, cup size and amount of liquid) were controlled, Ludwig explained. “We use the control to compare our other variables,” he said.
A moment later, Ludwig posed a question to the class: “Raise your hand if you think putting the flower in food coloring is going to change the color of the flower.” A collection of hands sprouted upward.
“We have some flowers that we put in the dye yesterday,” Ludwig continued, as he unveiled carnations that had white petals either tinged in red or blue to pass around to the class.
“Woah!”
“I was right!”
“I knew it!”
“Do we get to keep them?”
A white carnation begins to show traces of blue food coloring in its petals after sitting in a solution with food coloring and water for a short period of time. | photo by Justin Stewart, Bond LSC
A white carnation begins to show traces of blue food coloring in its petals after sitting in a solution with food coloring and water for a short period of time.
Following a brief video showing a similar experiment relating to celery and food coloring, Gardner explained the phenomenon to the class: “The plant is basically a big straw, so as the water evaporates up the plant, it pulls more water with it and then the food coloring too, so it gets to the very top of the plant, either the leaves of a tree or the top of a flower, and when it gets there the water will be able to evaporate, but the food dye can’t so that’s why your flowers are turning blue or red, OK?”
The food coloring portion of the afternoon turned out to be the top highlight for many of the participants. When asked about all of the projects he had worked on during the spring, Amahdrion Bradshaw, a second grader, proclaimed that “the funnest one was about dying the plants.”
Haily Korn, a fellow second grader, agreed, saying that her favorite part of the program is when you “do fun experiments” and that her favorite experiment was “when you get to dye stuff.”
A perfect fit
Lankford and the ReSTEM Institute formed the Benton Elementary Science Club, which meets one afternoon every week during the school year, seven years ago — the same time Benton officially became a part of the STEM (Science, Technology, Engineering and Mathematics) program.
“The science club has allowed our students to continue to expand their understanding of a variety of science topics through hands-on experiences after school,” said Heather McCullar, a STEM specialist who works at Benton. “The kids always leave club excited to share what they have learned with their families.”
Over the years, Lankford has helped many principal investigators with the education portion of their grants. When Mitchum asked her about getting involved with an existing partnership, Lankford immediately thought about the science club with its previously established learning format.
“Melissa said ‘I need help with this.’ And I said ‘Great, let’s talk,’” Lankford said, “And we did and we came up with the idea and it has been wonderful. I really like the fact that we have mentors and mentees doing the presentations.”
Under Mitchum’s direction, a series of meetings were set up with mentors and mentees last fall to develop the curriculum and lesson plans that would form the backbone of the course. Given that the grant is funded for a total of three years, the plan is to continue to teach the “It’s All About Plants” program, which has been well-received by students and school administrators alike, at Benton next spring.
Besides Mitchum, the other PI mentors from CAFNR who have taken part in the program are Gary Stacey, Curators Professor of Plant Sciences; Lee Miller, assistant professor of plant sciences; Xi Xiong, assistant professor of plant sciences; Walter Gassmann, professor of plant sciences; John Boyer, Distinguished Research Professor of Plant Sciences; Harley Naumann, assistant professor of plant sciences; Kevin Bradley, associate professor of plant sciences; Heidi Appel, senior research scientist, plant sciences; Jack Schultz, professor of plant sciences and director of the Bond Life Sciences Center; and Scott Peck, associate professor of biochemistry. PI mentors from the College of Arts and Science Division of Biological Sciences included Paula McSteen, Chris Pires, and Mannie Liscum.
The CAFNR students who took part in the science club series planning also recently hosted an outreach booth on t the Science Sleuth event on “Plants and Microbes” the MU campus April 16. In addition, Mitchum gave a talk at the Exploring Life Sciences symposium at the Bond Life Science’s Center recent Missouri Life Sciences Week.
Furthermore, the end goal is to take all of the lessons that are being created and turn them into a booklet that is easily accessible for teachers in Columbia Public Schools, and beyond, by posting the material online.
In the meantime, the lessons are being molded by the interactions of CAFNR students and those at Benton.
At a recent session of the “It’s All About Plants” series at the Benton Elementary Science Club, students learned about how plants transport water by conducting tests with a variety of solutions made up of household products, including, from left, baking soda, salt and vinegar. | photo by Justin Stewart, Bond LSC
“You have some students who can’t write their names yet, and other people who know everything we’re trying to tell them before we start,” Gardner said, afterwards, referring to the beginning of the class when a student at the front of the room recited a brief and succinct view of a plant’s water transport system. “Apparently his grandma told him all of this stuff already. So yeah that was definitely a challenge that I think we did OK at it.”
“I think it’s really great for everyone involved from the elementary school students who are getting to learn about specific topics from people who are very well informed about it to undergraduate and graduate students who are getting a wider arrange of presentation skills,” Ludwig added. “You can get locked in your head about your research. It’s good to be reminded that the knowledge we gain through research also has a real-world application and that part of the scientific process is sharing.”
It’s a challenge that Mitchum said could serve as a benefit to anyone in the scientific community.
“It’s not easy for us to do many times,” Mitchum said of breaking complex idea down into something easy enough for a child to understand, or even an average adult. “It takes practice. So. It’s something we have to learn. Science communication is very important these days. Especially when we talk about what we’re doing in a lab, it’s very molecular, very cellular, but we have to find a way to make it relevant.”
She added that programs such as this one show children that not all scientists have “crazy hair with the goggles and lab coat. They see ‘Oh, these guys are just like everyday people.’ This is a realistic career for them.”
Would Amahdrion be interested in such a career path?
“Nope,” he said. “I want to be a basketball player.”
Still, when given the choice of attending the science club sessions or just going home after school, he has a quick reply: “Spending extra time at school because you learn more.”
Work on HIV capsid proteins earns prestigious retrivology award
Anna Gres studies HIV capsid protein using X-ray crystallography. She recently won the 2016 von Schwedler Prize, which awards her $1,200 and gives her the oppportunity to speak this spring at the Cold Spring Harbor Retrovirus Meeting, one of the largest retroviral research conferences in the world. | photo by Roger Meissen, Bond LSC
Science is all about structure in the work of Anna Gres.
For the past four years, she’s looked closely at one HIV protein to figure out its shape in order to stop the virus.
“Capsid protein is extremely important during the HIV life cycle. About 1,500 copies of it come together to form the protective core around the viral genome,” said Gres, a graduate student in the lab of Bond Life Sciences Center’s Stefan Sarafianos and a Mizzou Ph.D. candidate in chemistry. “So, if you are able to somehow disrupt the interactions between the proteins or make them different, the virus loses its infectivity.”
Gres takes her work on this protein to a national stage next month when she speaks at the Retroviruses meeting at Cold Spring Harbor Laboratory — one of the most prestigious international conference on retroviruses — as the recipient of the 2016 Uta Von Schwedler prize. The prize recognizes the accomplishments of one distinguished graduate student as they complete their thesis.
HIV capsid protein has been studied for almost 30 years, but it’s been tricky to get a precise depiction of what it looks like. Gres uses X-ray crystallography to essentially capture the protein in all its 3-D glory. This method gives scientists the higher resolution picture to study the molecular structure of capsid protein. Her work allows the Sarafianos lab and others to study how it interacts and connects with other capsid proteins and the host protein factors of the cell HIV is trying to take over.
“In the past scientists had been splitting the capsid protein in two halves and crystallizing them separately. Another approach was to introduce several mutations to make it more stable,” Gres said. “You would think that it shouldn’t really matter if we have a few mutations, but the protein behaves in such a way that even slight changes result in subtly different interactions that are enough for the virus to lose its infectivity. We were able to crystallize the native protein without any mutations and that should give us more accurate picture.”
Now that the Sarafianos lab and Gres have a good idea of what that native protein looks like, they’ve moved on to other mutated versions of the protein that impair virus infectivity. This could give them insight into how scientists can stop HIV.
“Many labs reported numerous mutations in the capsid protein over the past 25 years that either increase or decrease the stability of the core, which often results in a noninfectious virus,” she said. “Right now we are interested in seeing what structural changes accompany these mutations and how they can affect the overall stability of the core.”
It’s been almost a week since the 2016 MU Life Sciences and Society Program Symposium, “Confronting Climate Change” wrapped up. If you missed the event, check out our Flickr gallery to see a little bit of the excitement.
We also had the chance to chat a few minutes with most of the LSSP speakers who graciously shared their insight on climate change in our lives. Check out these conversations on our YouTube page from the link at the top of the page.
Last but not least, we put together a radio piece for KBIA giving some speaker highlights. Visit our SoundCloud to see more.
How unruly data led MU scientists to discover a new microbiome By Roger Meissen | MU Bond Life Sciences Center
This seminal vesicle contains a newly-discovered microbiome in mice. Some of its bacteria, like P. acnes, could lead to higher occurrences of prostate cancer. | contributed by Cheryl Rosenfeld
It’s a strange place to call home, but seminal fluid offers the perfect environment for particular types of bacteria.
Researchers at MU’s Bond Life Sciences Center recently identified new bacteria that thrive here.
“It’s a new microbiome that hasn’t been looked at before,” said Cheryl Rosenfeld, a Bond LSC investigator and corresponding author on the study. “Resident bacteria can help us or be harmful, but one we found called P. acnes is a very important from the standpoint of men. It can cause chronic prostatitis that results in prostate cancer. We’re speculating that the seminal vesicles could be a reservoir for this bacteria and when it spreads it can cause disease.”
Experiments published in Scientific Reports — a journal published by Nature — indicate these bacteria may start disease leading to prostate cancer in mice and could pass from father to offspring.
A place to call home
From the gut to the skin and everywhere in between, bacterial colonies can both help and hurt the animals or humans they live in.
Seminal fluid offers an attractive microbiome — a niche environment where specific bacteria flourish and impact their hosts. Not only is this component of semen chockfull of sugars that bacteria eat, it offers a warm, protected atmosphere.
“Imagine a pond where bacteria live — it’s wet it’s warm and there’s food there — that’s what this is, except it’s inside your body,” said Rosenfeld. “Depending on where they live, these bacteria can influence our cells, produce hormones that replicate our own hormones, but can also consume our sugars and metabolize them or even cause disease.”
Rosenfeld’s team wasn’t trying to find the perfect vacation spot for a family of bacteria. They initially wanted to know what bacteria in seminal fluid might mean for offspring of the mice they studied.
“We were looking at the epigenetic effects — the impact the father has on the offspring’s disease risk — but what we saw in the data led us to focus more on the effects this bacterium, P. acnes, has on the male itself,” Rosenfeld said. “We were thinking more about effect on offspring and female reproduction — we weren’t even considering the effect the bacteria that live in this fluid could have on the male — but this could be one of the more fascinating findings.”
But, how do you figure out what might live in this unique ecosystem and whether it’s harmful?
First, her team found a way to extract seminal fluid without contamination from potential bacteria in the urinary tract.
“We gowned up just like for surgery and we had to extract the fluid directly from the seminal vesicles to avoid contamination,” said Angela Javurek, primary author on the study and recent MU graduate. “You only have a certain amount of time to collect the fluid because it hardens like glue.”
Once they obtained these samples, they turned to a DNA approach, sequencing it using MU’s Genomics Technology Core.
They compared it to bacteria in fecal samples of the same mice to see if bacteria in seminal fluid were unique. They also compared samples from normal mice and ones where estrogen receptor genes were removed.
The difference in the data
It sounds daunting to sort and compare millions of DNA sequences, right? But, the right approach can make all the difference.
“A lot of it looks pretty boring, but bioinformatics allow us to decipher large amounts of data that can otherwise be almost incomprehensible,” said Scott Givan, the associate director of the Informatics Research Core Facility (IRCF) that specializes in complicated analysis of data. “Here we compared seminal fluid bacterial DNA samples to publicly available databases that come from other large experiments and found a few sequences that no one else has discovered or at least characterized, so we’re in completely new territory.”
The seminal microbiome continued to stand out when compared to mouse poop, revealing 593 unique bacteria.
One of the most important was P. acnes, a bacteria known to cause chronic prostatitis that can lead to prostate cancer in man and mouse. It was abundant in the seminal fluid, and even more so when estrogen receptor genes were present.
“We’re essentially doing a lot of counting, especially across treatments to see if particular bacteria species are more common than others,” said Bill Spollen, a lead bioinformatics analyst at the IRCF. “The premise is that the more abundant a species is, the more often we’ll see its DNA sequence and we can start making some inferences to how it could be influencing its environment.”
Although this discovery excites Rosenfeld, much is unknown about how this new microbiome might affect males and their offspring.
“We do have this bacteria that can affect the male mouse’s health, that of his partner and his offspring,” Rosenfeld said. “But we’ve been studying microbiology for a long time and we still find bacteria within our own bodies that nobody has seen before. That blows my mind.”
Bond LSC is now producing monthly segments for KBIA, Columbia’s NPR station at 91.3 FM.
This month highlights the work of Melissa Mitchum, a molecular plant nematologist at Bond LSC and an associate professor of Plant Sciences in the College of Agriculture, Food and Natural Resources.
She studies nematodes, a pest that cost soybean farmers billions of dollars each year. Her lab recently helped discover that this tiny parasite produces molecules that mimic plant hormones in order to siphon nutrients from soybean roots.
Tune in at 12:30 to hear her profile or visit the Soundcloud link above to hear the segment.
Female rats struggle to find their way in BPA study from MU and the NCTR/FDA
Cheryl Rosenfeld is one of 12 researchers partnering with the NCTR/FDA to study BPA
Despite concerns about bisphenol A (BPA), academic and regulatory scientists have yet to reach a consensus on BPA’s safety.
The National Institute of Environmental Health Sciences (NIEHS), the National Toxicology Program (NTP), the Food and Drug Administration and independent university researchers are working together to change that.
“The idea of this Consortium is to examine the potential systems that have been previously suggested to be affected by BPA,” said Cheryl Rosenfeld, an associate professor of biomedical sciences at the University of Missouri and one of twelve researchers involved in the project.
Rosenfeld’s group looked at spatial navigation learning and memory. They found that prenatal exposure to BPA could potentially hinder the ability of female rats to learn to find their way through a maze. This effect was not seen in male rats.
Approved by the FDA in the early 1960s, BPA can be found in a wide variety of products, including plastic food and drink containers with recycle codes 3 or 7, water and baby bottles, toys, the linings of metal cans and water pipes, even patient blood and urine samples.
BPA has structural similarities to estrogen and can potentially act as a weak estrogen in the body.
In Rosenfeld’s experiment, researchers at the National Center for Toxicology Research gave pregnant rats a fixed dose of BPA every day: a low, medium, or high dose.
After the baby rats were born, researchers continued to dose the babies, both male and female, according to what their mothers had received.
When these rats reached three months old, they were tested in a circular maze with twenty possible exit holes, one of which was designated as the correct escape hole. Every day for seven days, researchers tested the rats’ abilities to solve the maze in five minutes and timed them as they ran.
Rats solve mazes in three ways, Rosenfeld said.
They can run through the labyrinth in a spiral pattern, hugging the outer walls, and work their way in until they find the correct exit hole in what is called a serial search strategy.
Or they might move aimlessly in the maze using an indirect search strategy, Rosenfeld said. “In this case, the rats seemingly find the correct escape hole by random chance.”
Lastly, they can travel directly from the center of the maze to the correct escape hole. The third strategy is considered the most efficient method because the rats find their way swiftly, Rosenfeld said.
Sarah Johnson, a graduate student and first author on the paper, assessed each rat’s performance in the maze using a three-point tracking program that recognizes the rat’s nose, body, and tail.
Using the program, Johnson measured their performances in terms of the total distance traveled, the speed at which the rat ran the maze, how long it took the rats to solve the maze (latency), and how often the rat sniffed at an incorrect hole.
The last two parameters are considered the best gauges of spatial navigation learning and memory.
“What you expect to see is that they should start learning where that correct escape hole is,” Rosenfeld said. “Thus, their latency and sniffing incorrect holes should decrease over time.”
Rosenfeld’s group found that female rats that had been exposed to the highest dose of BPA since fetal development were less likely to find the escape hole than rats that hadn’t been exposed to BPA.
As for how this study may translate to people, Rosenfeld said, “the same brain regions control identical behaviors in rodents and humans.”
She considers it a starting point for setting up future experiments that take into consideration sex differences in cognitive behaviors and neurological responses to BPA.
Immediate next steps for the Rosenfeld group include analyzing tissue collected from the brains of rats that had undergone maze testing. Rosenfeld’s team of researchers will measure DNA methylation and RNA expression in the brain to determine which genes might be involved in navigational learning and memory. Their overarching goal is to determine how changes in observed sex- and dose-dependent behaviors occur on the molecular level.
NIEHS grant U01 ES020929 supported this research. Additional coauthors include Mark Ellersieck and Angela Javurek of the University of Missouri, Thomas H. Welsh Jr. of Texas A&M University, and Sherry Ferguson, Sherry Lewis, and Michelle Vanlandingham of the National Center of Toxicological Research/Food and Drug Administration. Read the full study on the Hormones and Behavior website and browse the supplementary data for this work.
Scientists find how nematodes use key hormones to take over root cells
This Arabidopsis root shows how the beet cyst nematode activates cytokinin signaling in syncytium 10 days after infection. The root fluoresces green when the TCSn gene associated with cytokinin activation is turned on because it is fused with a jellyfish protein that acts as a reporter signal. Contributed by Carola De La Torre
Roger Meissen | Bond Life Sciences Center
This is a story about spit.
Not just any spit, but the saliva of cyst nematodes, a parasite that literally sucks away billions in profits from soybean and other crops every year.
Researchers are working to uncover exactly how these tiny worms trick plant root cells into feeding them for life.
Cytokinin is normally produced in plants, but these researchers determined that this growth hormone is also produced by nematode parasites that use it to take over plant root cells.
“While it’s well-known that certain bacteria and some fungi can produce and secrete cytokinin to cause disease, it’s not normal for an animal to do this,” said Melissa Mitchum, an MU plant scientist and co-author on the study. “This is the first study to demonstrate the ability of an animal to synthesize and secrete cytokinin for parasitism.”
Not Science Fiction
Reprogramming another organism might sound like a far out concept, but it’s a reality for plants susceptible to nematodes.
Cyst nematodes hatch from eggs laid in fields and quickly migrate to the roots of nearby plants. They inject nematode spit into a single host cell of soybean, beet and other crop roots.
Carola De La Torre
“Imagine a hollow needle at the head of the nematode that the parasite uses to penetrate into the plant cell wall and secrete pathogenic proteins and hormone mimics,” said Carola De La Torre, a co-author of the study and plant sciences PhD student with Mitchum’s lab. “Nematodes use the spit to transform the host cell into a nutrient sink from which they feed on during their entire life cycle. This de novo differentiation process greatly depends on nematode–derived plant hormone mimics or manipulation of plant hormonal pathways caused by effector proteins present in the nematode spit.”
These effector proteins and other small molecules in their spit cause the root cell to forego normal processes and create a huge feeding site called a syncytium. In a short period of time, this causes hundreds of root cells to combine into a large nutrient storage unit that the nematode feeds from for its entire life.
Being able to convince a root cell to do the nematode’s bidding starts with a takeover of the plant host cell cycle — which regulates DNA replication and division. This implies that a plant hormone like cytokinin is involved, says Mitchum. Cytokinin normally regulates a plant’s shoot growth, leaf aging, and other cell processes.
Proving the relationship
While Mitchum’s lab had a hunch that cytokinin was key to this takeover, proving it took some creative science.
De La Torre and Demosthenis Chronis, a postdoctoral fellow MU at the Bond LSC depended on mutant Arabidopsis plants to explore the relationship. “One of the great things about using Arabidopsis as our host plant is the vast genetic resources of cytokinin and hormone mutants that are available through the scientific community,” De La Torre said.
She infected Arabidopsis that contained a reporter gene called TCSn/GFP with nematodes. This gene is associated with cytokinin responses within the plant cells and is fused with a jellyfish protein that glows green when turned on. So, De La Torre saw nematodes activated cytokinin responses in the plant early after infection when her plants emitted a green fluorescent glow under the microscope.
Next, she infected plants missing the majority of their cytokinin receptors with nematodes. Then she started counting nematodes present.
“After a careful evaluation of nematode infection, we observed less female nematodes developing in the receptor mutants compared to the wild type” De La Torre said. “The nematodes could not infect well, and that was a clear piece of evidence suggesting that cytokinin plays a main role in plant–nematode interactions.”
Another experiment looked at Arabidopsis containing a reporter gene called GUS that was fused to the regulatory sequences of the cytokinin receptor genes. All three cytokinin receptor genes were activated where the nematode was feeding.
A final experiment used a mutant that created an excess of an enzyme that degrades cytokinin, finding that a base level of plant cytokinin was also necessary for nematode growth.
“The simple statement is that the cytokinin receptors were activated in response to nematode infection and the mutants did not support growth and development of the nematodes,” Mitchum said. “This shows that if you take away the ability of the plant to recognize cytokinin the worms are unable to fully develop.”
An international collaboration
Mitchum’s team did not work alone.
The lab of Florian Grundler at Rheinische Friedrich-Wilhelms-University of Bonn, Germany, was also on a mission to uncover if genes in the nematode controlled cytokinin activation. They had identified a key gene in the beet cyst nematode that makes the cytokinin hormone. When they took away the ability of the nematode to secrete cytokinin certain cell cycle genes were not activated at the feeding site and the nematodes did not develop. Now we know that the nematode is also secreting cytokinin to modulate the pathways.
De La Torre took that information and found the same gene in the soybean cyst nematode.
Now, Mitchum’s team is trying to find how this key gene might work differently in other nematode types, like root-knot nematode as part of a new National Science Foundation grant. They hope this will help lead to better resistance in future crops.
“Understanding how the nematode modulates its host is going to help us exploit new technologies to engineer plants with enhanced resistance to this terribly devastating pathogen,” Mitchum said. “Technology is changing all the time, we’re gaining new tools constantly, so you never know when something new is going to allow us to do something specific at the site of nematode feeding that will lead to a breakthrough.”
The next time you slather mustard on your hotdog or horseradish on your bun, thank caterpillars and brassica for that extra flavor.
While these condiments might be tasty to you, the mustard oils that create their flavors are the result of millions of years of plants playing defense against pests. But at the same time, clever insects like cabbage butterflies worked to counter these defenses, which then started an arms race between the plants and insects.
An international research team led by University of Missouri Bond Life Sciences Center researchers recently gained insight into a genetic basis for this co-evolution between butterflies and plants in Brassicales, an order of plants in the mustard family that includes cabbage, broccoli and kale.
“We found the genetic evidence for an arms race between plants like mustards, cabbage and broccoli and insects like cabbage butterflies,” said Chris Pires, an MU Bond Life Sciences Center researcher and associate professor of biological sciences in the College of Arts and Sciences. “These plants duplicated their genome and those multiple copies of genes evolved new traits like these chemical defenses and then cabbage butterflies responded by evolving new ways to fight against them.”
A biting taste
While you might like the zing in mustard, insects don’t.
Compounds, called glucosinolates, create these sharp flavors in plants to defend against caterpillars, butterflies and other pests. Brassicales species first evolved glucosinolate defenses around the KT Boundary — when dinosaurs went extinct — and eventually diversified to synthesize more than 120 different types of this compound.
For most insects, these glucosinolates prove toxic, but certain ones like the cabbage butterfly evolved ways to detoxify the compounds.
“Seeing the variation in the detoxification mechanisms among species and their gene copies gave us important evolutionary insights,” said Hanna Heidel-Fischer, a lead author on the study based at the Max Plank Institute for Chemical Ecology in Germany.
To look at these genetic differences, the team used 9 existing Brassicales genomes and also generated transcriptomes — the set of all RNA in a cell — across 14 Brassicales families. This allowed the team to map an evolutionary family tree of sorts over the millennia, seeing where major defense changes occurred. This family tree was compared with the family tree of 9 key species of Pieridae butterflies, which includes the cabbage butterfly.
Pires and his colleagues identified three significant evolutionary waves over 80 million years, where plants developed defenses and insects evolved counter tactics.
Pat Edger | Image by Roger Meissen, Bond LSC
“We found that the origin of brand-new chemicals in the plant arose through gene duplications that encode novel functions rather than single mutations,” said Pat Edger, a former MU post doc and lead author on the study. “Given sufficient amounts of time the insects repeatedly developed counter defenses and adaptations to these new plant defenses.”
This back-and-forth pressure resulted in the evolution of many more species of plants and butterflies than in other groups without glucosinolate pressures.
Proving an old concept
Co-evolution is not a new idea.
About 50 years ago two now-renowned biologists, Peter Raven and Paul Erhlich, introduced the idea of co-evolution to science. Using cabbage butterflies and Brassica plants as a prime example, the two published a landmark study in 1964 advancing the idea that two species can mutually influence the development and evolution of each other.
“Using Ehrlich and Raven’s principles and models, we looked at the evolutionary histories of these plants and butterflies side-by-side and discovered that major advances in the chemical defenses of the plants were followed by butterflies evolving counter-tactics that allowed them to keep eating these plants,” Wheat said.
Chris Pires and colleagues mapped the evolution of Brassicales and butterflies to find how each evolved to combat the defenses of the other. | Courtesy Chris Pires
This research provides striking support for the ideas of Ehrlich and Raven published 50 years ago.
“We looked at the patterns 50 years ago, and found conclusions that proved correct,” said Peter Raven, professor emeritus of the Missouri Botanical Garden and a former University of Missouri Curator. “The wonderful array of molecular and other analytical tools applied now under leadership of people like Chris Pires, provide verification and new insights that couldn’t even have been imagined then.”
Understanding more about how plants and insects co-evolve could one day lead to advances in crops.
“If we can harness the power of genetics and determine what causes these copies of genes, we could produce plants that are more pest-resistant to insects that are co-evolving with them—it could open different avenues for creating plants and food that are more efficiently grown,” said Pires.
Proceedings of the National Academy of Sciences (PNAS) published the study, “The butterfly plant arms-race escalated by gene and genome duplications,” in June. The National Science Foundation (PGRP 1202793), the Knut and Alice Wallenberg Foundation and the Academy of Finland provided the funding for this research.
