Scientists explore genetic similarities between plants and mice
University of Missouri PhD Candidate Daniel L. Leuchtman peers through an Arabidopsis plant. Leuchtman has been experimenting with replacing a gene in the plants immune system with a similar gene from mice. | Photograph by Justin L. Stewart/MU Bond Life Sciences Center
By Justin L. Stewart | MU Bond Life Sciences Center
Almost two-thirds of what makes a human a human and a fly a fly are the same, according to the NIH genome research institute.
If recent research at the University of Missouri’s Bond Life Sciences Center is verified, we’ll soon see that plants and mice aren’t all that different, either.
Dan Leuchtman studies a gene in Arabidopsis plants called SRFR1, or “Surfer One.” SRFR1 regulates plant immune systems and tell them when they are infected with diseases or illnesses. Leuchtman studies this model plant as a Ph.D. candidate at MU, splitting time between the labs of Walter Gassmann and Mannie Liscum.
His research involves breeding Arabidopsis plants missing the SRFR1 gene and then replacing it with the MmSRFR1 gene.
A series of Arabidopsis plants show the differences between the plants, from left, without SRFR1, with MmSRFR1 and with SRFR1. | Photograph by Justin L. Stewart/MU Bond Life Sciences Center
So, what is MmSRFR1? Leuchtman and company believe it’s the animal equivalent of SRFR1, though they aren’t fully aware of all of its’ functions.
“We’re actually one of the first groups to characterize it,” Leuchtman said.
Arabidopsis plants missing the SRFR1 gene struggle to grow at all, appearing vastly different from normal plants. Leuchtman says that a plant missing the SRFR1 gene is a mangled little ball of leaves curled in on itself. “It’s really strange looking.”
While his experiments haven’t created statuesque plants equal to those with natural SRFR1 genes present, the Arabidopsis plants with MmSRFR1 show a notable difference from those completely lacking SRFR1. Leuchtman says the plants with MmSRFR1 lie somewhere in between a normal plant and one lacking SRFR1.
University of Missouri PhD Candidate Daniel L. Leuchtman poses for a portrait in a Bond Life Sciences Center greenhouse. Leuchtman has been experimenting with replacing a gene in Arabidopsis plants immune system with a similar gene from mice. | Photograph by Justin L. Stewart/MU Bond Life Sciences Center
“At its’ core, it’s more understanding fundamental biology. How do we work? How do organisms tick? How do you go from DNA in a little bag of salts to a walking, talking organism?” Leuchtman said. “The more you know about how an organism functions, the more opportunities you have to find something that makes an impact.”
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.
Mutant arabidopsis models under lamps in Shuqun Zhang's lab.
Three-month-old mutant arabidopsis models are used to study the function of pollen.
The thought of pollen dispersed throughout the air might trigger horrific memories of allergies, but the drifting dander is absolutely essential to all life.
Science has long linked this element of reproduction with environmental conditions, but the reasons why and how pollen functions were less understood. Now lingering questions about the nuanced control of plants are being answered.
“Pollen is a very important part of the reproductive process and if we understand how pollen develops and how environmental stresses impinge on this process, we might be able to prevent crop loss due to high temperature or drought stress etc.,” said Shuqun Zhang, a Bond Life Sciences Center investigator.
Zhang has developed a new line of seeds that helped him and his lab identify an influential signaling pathway that triggers a chain reaction associated with normal pollen formation and function.
This research could lead to improvement to a plant’s response to disastrous environmental variables like drought to optimize pollen production and increase the production of food crops.
Left: Pollen grains genotypes MAPK3 and MAPK6 are illuminated by red and yellow dye using a fluorescent microscope. RIGHT: Normally developed pollen grains shown by an electronic microscope scan. | Credit: Shuqun Zhang
Seeds of success
Mutant seeds are the key to this work.
Instead of glowing green in the soil like you might see in a science fiction movie, they are providing important insight on plant reproduction and stress tolerance.
Zhang developed these plants from a mutant strain of Arabidopsis, a model plant used in scientific research. Certain genes were “switched off”to pinpoint where important pollen functions were signaled.
Using this mutant plant and seed system, Zhang found that WRKY34and WRKY2, two proteins that turn on/off genes, are regulated by MPK3and MPK6 “signaling” enzymes. These enzymes basically transform proteins from a non-functional state to a functional state, turning on specific duties or functions. Zhang, a professor of biochemistry at MU, began tinkering with the MPK3 and MKP6 pathways more than twenty years ago during his post-doc at Rutgers University.
Zhang’s research shows the newly identified MPK3/MPK6-WRKY34/WRKY2 pathway is a key switch in the hierarchy of the signaling system in pollen formation.
The research showed that the plant’s defense/stress response and reproductive process are linked, and the influential proteins MPK3 and MPK6 were part of the bigger WRKY34/WRKY2control pathway, which is activated in early pollen production.
The system is so useful that researchers across the country won’t stop asking for the seeds, Zhang said.
“We have a lot of requests for seeds,” Zhang said. “This is a very nice system to study pollen formation and function.”
The cascade of control
The functions of MPK3/MPK6 in plants can be compared to a “mother board” switch. The pathway — MPK3 and MPK6 —are part of a hierarchy of response, turning functions on or off. In other words, it’s a switch that controls a lot of different things. Controlling WRKY34/WRKY2 is one of the many roles played by MPK3 and MPK6.
Shuqun Zhang, University of Missouri Bond Life Sciences investigator.
“Whatever is plugged into it is what comes on,” Zhang said. “We are actually very, very interested in the evolutionarily context, how this came to be.”
This signaling process is just one of many in plants. MPK3 and MPK6 are two out the 20 MPKs, or MAPKs (abbreviated from Mitogen-Activated Protein Kinases) in Arabidopsis. They control plant defense, stress tolerance, growth, and development including pollen formation and functions.
“We determined that this MAPK-WRKY signaling module functions at the early stage of pollen development,” Zhang said.
The “loss of function of this pathway reduces pollen viability, and the surviving pollen has poor germination and reduced pollen tube growth, all of which reduce the transmission rate of the mutant pollen,” according to the research.
Zhang and his lab worked with the MU Division of Biochemistry and Interdisciplinary Plant Group on the research, which published in PLoS Genetics in June of this year.
A world without pollen production and defense
Without pollen, plants would not reproduce — there aren’t any Single Bars in the plant world (that we know of) — and if plant generations don’t propagate, there would be no air or food for human life to sustain.
“The factors such as heat and drought stresses cause problems to the plant’s normal developmental process and that’s how pollen fails to develop,” Zhang said. “If we understand the process, and know how environmental factors impact negatively the process, we can then make plants that can handle environmental stress better.”
Zhang and his lab continue to research the complexities of these pathways. Next on the quest is to answer how MPK3/MPK6 are involved in pollen functions such as guiding the pollen tube growth towards ovule to complete the sexual reproduction process in plants.
“It is possible that MPK3 and MPK6 are activated quickly in response to the guidance signals,” he said. “There’s still a long way to go because very few players in this process have been identified, we try to understand the biological process how they work together.” This research is in collaboration with Dr. Bruce McClure, also professor of Division of Biochemistry.
Read more:
1. PLoS Genetics (May 2014): Phosphorylation of a WRKY Transcription Factor by MAPKs is Required for Pollen Development and Function in Arabidopsis — Funded by a Hughes Research Fellowship and grants from the National Science Foundation.
2. Plant Physiology (June 2014): Two Mitogen-Activated Protein Kinases, MPK3 and MPK6, are required for Funicular Guidance of Pollen Tubes in Arabidopsis — Funded by a National Science Foundation grant and a NSF Young Investigator Award.
Jingyou Yu, a graduate student, does cell surface staining in Shan-Lu Liu’s virology lab. The staining illuminates cell marker expressions in experiments that deduce how viruses spread once they are contracted. | Paige Blankenbuehler
News headlines seem to feverishly spread as if they were a pandemic of the brain.
Ebola hemorrhagic fever has been the most talked about disease of the year, appearing in thousands of headlines across the world since May. Through the noise of misinformation and sensationalism, fundamental information about the pandemic becomes harder to distinguish.
In an interview with Decoding Science on Tuesday, Shan-Lu Liu, MD, PhD, a Bond Life Sciences Center investigator who studies Ebola, weighed in on the latest news.
Liu, also an associate professor in the MU School of Medicine’s Department of Molecular Microbiology and Immunology, and his lab are particularly interested in the early behaviors of the virus in transmission and how it can navigate around the host immune response.
Shan-Lu Liu, Bond Life Sciences scientists and associate professor in the MU School of Medicine department of molecular microbiology and immunology.
Q: Talk about the transmission. Ebola doesn’t spread through air, but how easily can it be transmitted through fluids?
A: It’s hard to say. It’s really not like: touch an infected person and you got it. I don’t see that could happen so easily. As an RNA virus, it’s not that stable outside of the body, unlike hepatitis B virus (HBV) where you need to boil the virus for 10 minutes and it becomes not infectious. Because Ebola is not that stable, that should not be the reason why it’s so efficient to transmit.
I think the transmission is one of the biggest things it’s, you know, I don’t think we have a complete understanding. We do know that it spreads by contact through body fluids and many people don’t realize that the handling of the deceased — that’s very dangerous. Touching broken skin or mucous membranes like the nose and mouth is dangerous.
Q: Talk about the incubation period and how that relates to symptoms and spreading of the virus.
A: The incubation time is 2-21 days. At first, the person will have flu-like symptoms, so you know, that’s why it’s hard to notice in the early stages. Some doctors or nurses say ‘just give him antibiotics send him home.’ But in stage two, you get the hemorrhage and it gets serious. The mortality rate is high, from 50 to 90 percent.
I think the fatality is definitely related to the late stages of the disease, especially with the hemorrhaging fever. The early stages are almost unnoticeable but that’s the time transmission might spread easier through contact with an infected person’s fluid. Before symptoms, the virus doesn’t spread.
Q: Last week, an article seemed to contradict with the CDC estimate. The headline: “Some good news about Ebola: It won’t spread nearly as fast as other epidemics.“ What do you make of that?
I don’t know, it’s hard for me to make a comment. Nobody knows. Things can always change. We didn’t expect to see a diagnosis in the United States — like this you know, this patient from Liberia was able to travel on a plane from virus country. Who can expect that? Anything can happen. There seem to have been some mishaps because he came from that area, right? Communication is more important now but it’s hard to predict because anything could happen.
Q: How has the Ebola virus behaved in previous outbreaks?
A: The first outbreak was in 1976 in Sudan and Congo — (Democratic Republic of Congo, known as Zaire at the time). It was from contaminated needles in a hospital and originally came from fruit bats — they are one of those animals that could transmit Ebola from animals to humans. The fruit bats transmitted the virus to primates, primates transmit to humans. It’s hard to notice in the early stages. Editor’s note: The 1976 outbreak was the first occurrence of Ebola in humans. The outbreak affected one village, infecting 318 people that resulted in 280 deaths.
Q: Much of the media has reported a vaccine for ebola was delayed. How could this happen?
A: Drugs and vaccines are a little different. The Ebola vaccine was delayed, that’s for sure. That’s because, the vaccine on trial has to go through tedious steps to get approval and so thats why when this outbreak occurs the NIH (National Institutes of Health) decides to go ahead quickly. One of the things for ebola vaccine is um, the pharmaceutical companies and the industries are not interested in developing vaccines. Do you know why? It is not a big market. Only a hundred — or a thousand or more — people will be infected by ebola, unlike other vaccines like the HPV vaccination where 200 million people need it. The companies are not interested in developing it, because there’s no money in it.
A company needs to spend a lot of money to develop a vaccine, but they don’t see the market — the market can’t do it. But somebody needs to do it. Imagine if, if the virus spread like this, you know, unpredictable, it could be worse. In terms of therapy, the drugs and antibodies, we know they are really effective. And they are specific, so they can reach the market effectively.
Q: Will a drug be enough to prevent wide spreading of Ebola?
I think the companies and governments are speeding up to make those available. To see this prediction (the CDC 1.4 million estimate), they have to be prepared. People have put increasing attention on antibodies because a vaccine is not in the near future. So what’s the approach? A “therapeutic vaccine.” The so-called therapeutic vaccine is an antibody so you engineer, you use you know, molecular engineering technique to generate those antibodies and they can neutralize and block viral infection. It’s more realistic for Ebola and even for HIV. The HIV vaccine has failed so many times. So that’s why I think one of the new approaches is to use a new broad neutralizing antibody.
Q: Does Ebola stay in the body, like chicken pox?
A: Ebola do not cause latent infection. HIV can become latent and become chronic. So influenza virus, ebola viral infection and others normally do not lead to latency. I think for Ebola — for this type of infection — once you block the patient and clear the virus it should be good.
Q: Has the media done a good job in educating the public?
I think in terms of news coverage they are pretty careful. I looked at the news conference by the CDC director and by those doctors in Dallas, and when they make statements they are careful not to exaggerate and also give very cautious measurements. The news media need to be aware of the danger of the virus. In the meantime, you have to be aware of the possibility of being affected.
Again, I think it is a very important problem. It’s important to let the public know the situation. If you see people who have recently traveled from those West African countries, you have to be cautious — air travel is so common. But I think the media have generally done a good job.
Q: Has the government done a good job keeping the pandemic under control?
I don’t know what they do. The air travel is a problem. Intensified screening process, that should definitely be done. It’s very bad for people from the outbreak area, and I just hope that this community won’t be affected.
To control, they should be careful. A person with any sign of the disease — they need to be quickly monitored and treated.
Q: What’s the most important take-away message for the public?
A: I think it’s an important problem and we need to solve it urgently. I hope this outbreak will teach us a lesson in terms of how important emerging infectious viruses are as it comes and goes is to public health. Based on literature and reports, if people do not have obvious symptoms, they do not produce an infectious virus. The incubation time has a big range but again, we are still trying to understand the process better. Infection is a complex process. We need to better understand the viral transmission so I think for now, we need to be very cautious.
Liu and his lab do not work with the contagious Ebola virus on University of Missouri campus. All of the studies involve use of a recombinant or pseudotyped Ebola virus which is not infectious.
Graduate students Yuleam Song and Dan Salamango inoculate a bacteria culture in Johnson’s lab. The inoculation takes a small portion of a virus and multiplies the sample, allowing researchers to custom-make viruses.
By Madison Knapp | Bond Life Sciences Center summer intern
Modern science has found a way to turn viruses —tiny, dangerous weapons responsible for runny noses, crippling stomach pains and worldwide epidemics such as AIDS— into a tool.
Gene therapy centers on the idea that scientists can hijack viruses and use them as vehicles to deliver DNA to organs in the body that are missing important genes, but the understanding of virus behavior is far from exhaustive.
Marc Johnson, researcher at the Christopher S. Bond Life Sciences Center and associate professor of molecular microbiology and immunology in the MU School of Medicine, has been building an understanding of viral navigation mechanisms which allow a virus to recognize the kind of cell it can infect.
Johnson’s research specifically explores the intricacies of the viral navigation system and could improve future direction of gene therapy, he said.
Marc Johnson (left) with Dan Salamango, a graduate student that works in his lab. The lab does important research on the basic function and mechanisms of viral navigation and transport.
Turning a virus into a tool
Conceptualized in the 1970s, gene therapy was developed to treat patients for a variety of diseases, including Parkinson’s, leukemia and hemophilia (a genetic condition that stops blood from clotting).
To treat disease using gene therapy, a customized virus is prepared. A virus can be thought of as a missile with a navigation system and two other basic subunits: A capsule that holds the ammunition and the ammunition itself.
The viral genetic material can be thought of as the missile’s ammunition. When a cell is infected, this genetic material is deployed and incorporated into the cell’s DNA. The host cell then becomes a factory producing parts of the virus. Those parts assemble inside the cell to make a new virus, which then leaves the cell to infect another.
The capsule is made of structural protein that contains the genetic material, and the navigation system is a protein that allows the virus to recognize the kind of cell it can infect.
Viral navigation
Gene therapy uses viruses to solve many problems by utilizing a virus’ ability to integrate itself into a host cell’s DNA; to do this successfully, researchers need to provide a compatible navigation component.
In the body, viruses speed around as if on a busy highway. Each virus has a navigation system telling it which cells to infect. But sometimes if a virus picks up the wrong type of navigation system, it doesn’t know where to go at all.
“What you can do is find a virus that infects the liver already, steal its navigation protein and use that to assemble the virus you want to deliver the gene the liver needs,” Johnson said. “You can basically take the guidance system off of one and stick it onto another to custom design your virus.”
But this doesn’t always work because of incompatibility among certain viruses, he said.
Johnson and his lab are working to understand what makes switching out navigation proteins possible and why some viruses’ navigation systems are incompatible with other viruses.
“I’m trying to understand what makes it compatible so that hopefully down the road we can intelligently make others compatible,” Johnson said.
The right map, the right destination
Johnson creates custom viruses by introducing the three viral components—structural protein, genetic material, and navigation protein—to a cell culture. The structural protein and genetic material match, but the navigation component is the wild card. It could either take to the other parts to produce an infectious virus, or it could be incompatible.
Johnson uses a special fluorescent microscope to identify which viruses assembled correctly and which didn’t.
A successful pairing is like making a match. If a navigation protein is programmed to target liver cells, it’s considered a successful pairing when the virus arrives at the liver cell target location.
The scope of gene therapy continues to widen. Improved mechanisms for gene therapy, and greater knowledge of how a navigation protein drives a virus could help more people benefit from the vehicles viruses can become.
Johnson uses several high-profile model retroviruses, including human immunodeficiency virus (HIV), which affects an estimated 35 million people worldwide each year, according to the World Health Organization.
Understanding nuances of HIV in comparison to other viruses allows Johnson to pick out which behaviors might be common to all retroviruses and others behaviors that might be specific to each virus.
Johnson said his more general approach makes it easier to understand more complex viral features.
“If there are multiple mechanisms at work, it gets a little trickier,” Johnson said. “My angle is more generic, which makes it easier to tease them apart.”
