Brassicales

Lab explores link between genetic differences and domestication in kale

April 28, 2021 By Becca Wolf in Research Tags: Brassicales, gene expression, kale

Tatiana Arias and Chad Niederhuth studied the plant, kale, in this publication. | “Kale” by photofarmer is licensed under CC BY 2.0

By Becca Wolf | Bond LSC

It is said that variety is the spice of life.

When it comes to kale, much of that variation derives from domestication, and genetic differences that evolved over thousands of years resulted in different color of leaves, nutritional value, and habit and length of growth.

Understanding the links between traits and genes could one day help plant scientists create better vegetables for us.

Eight years ago, Tatiana Arias from the Chris Pires lab and Chad Niederhuth from the John Walker and Paula McSteen lab at Bond Life Sciences Center came together to research leaf differences in this species, Brassica oleracea. Brassica oleracea includes many foods from the vegetable aisle from the grocery store like kale, cabbage, and broccoli.

“In general, people do these types of studies to narrow down some specific genes, but we tried to find a bunch of different genes that could serve different purposes in the future for basic science and developmental biology studies, but also for more applied work in crop sciences,” Arias said.

She and Niederhuth’s broad approach looked at genes that they thought could have been selected during domestication of kale. As humans farmed these leafy greens over millennia, they selected for plants that grew more upright with leaves we liked to eat, developed more ornate foliage and flowered later, differentiating kale from its sisters like broccoli and cauliflower where the flowers were the valued food product.

They compared three morphotypes of Brassica oleracea plants: kale, cabbage, and TO1000 — a specific kale line.

“We brought the evolutionary history of how Kale was domesticated from the other Brassica oleracea morphotypes. Tatiana is really good at the microscope and doing really detailed sections of different parts of the plant as they’re growing,” Chris Pires said. “They sequenced using next gen sequencing, which I’d suppose you’d call it old next gen or postmodern sequencing since it’s been so long.”

While sequencing RNA, the labs found thousands of genes expressed in these different vegetable lines.

“I am a classically trained botanist, so for me it was a very new approach to think about genomics for plants,” Arias said.

While the Pires lab handled the RNA sequencing, Niederhuth in the McSteen lab handled the bioinformatics analysis, the mapping of sequence data, and the identification of the differentially expressed genes.

“It was a team effort between Tatiana and I, she was really the expert in studying these different varieties and their morphological differences and she generated a lot of the data,” Niederhuth said. “I brought to that some of my expertise in gene expression data.”

Through their work, Arias and Niederhuth found 3,958 expressed genes that separated kale from cabbage and TO1000. Some of these differences were in genes that regulate vegetative and reproductive transitions — things that create the very different look of cabbage versus kale.

Some genes they found in kale were particularly interesting. These were involved in leaf morphology, plant structure, and nutrition and were expressed differently, allowing them to identify a set of genes that may be important in kale domestication. Those genes would link, for example, to why kale is more upright and cabbage leaves curl into a head or the variation in color of the leaves.

“I didn’t necessarily know what to expect going into it,” Niederhuth said. “It was interesting to see some results that were related to some of the differences in the phenotypes we observed. Before this I had never worked with Brassica oleracea before, it was the first time I was working with genomic data from a species other than Arabidopsis. It helped me begin working with a variety of different species in many ways.”

While this research was conducted over eight years ago, Arias and Niederhuth recently published the findings.

“It’s nice to have one of many projects off my plate, and I’m glad that it’s finally gotten out there,” Niederhuth said. “This is just how life works where people in this career are oftentimes moving and things get set aside. I am glad that after all these years, we’re finally able to come together again and get it finished.”

To read more of Arias’ and Niederhuth’s research, check out the March article published on the Frontiers in Plant Science website titled, “The Molecular Basis of Kale Domestication: Transcriptional Profiling of Developing Leaves Provides New Insights Into the Evolution of a Brassica oleracea Vegetative Morphotype.”

#IAmScience Shawn Thomas

March 5, 2021 By Lauren Hines in #IAmScience Tags: bioinformatics, Brassicales

By Lauren Hines | Bond LSC

Social media botany advocate and self-proclaimed coffee snob, Shawn Thomas is the kind of person to find joy in everything.

Thomas graduated from the University of Georgia in spring 2018 and worked as a bioinformatics technician for a year with Jim Leebens-Mack before joining Chris Pires’ lab at Bond Life Sciences Center as a Ph.D. student in fall 2019. Ever since, he’s been studying how genome duplications affect plant traits in a certain group of plants that include broccoli, cauliflower and kale.

Genome duplications occur when DNA is copied multiple times in a plant when two species hybridize and come together. To study this, Thomas is looking at their wild distant relatives.

“Understanding these ancient genome duplications, how they happened and when they happened can give us an idea of how different evolutionary innovations occur,” Thomas said.

Thomas has been a part of the Pires lab for over a year now and has brought his own set of skills.

“The thing that I’ve been really impressed with him — well, two things — one is he’s very skilled with bioinformatics,” said Pires, Bond LSC principal investigator. “He doesn’t have a computer science degree, but he’s got math skills and coding and a couple of different computer languages for data wrangling genomes. But the other thing is he’s made some really hilarious YouTube videos.”

Mixing his love of plant biology and lab inside jokes, Thomas makes clever YouTube videos for fun and even for grants.

One video includes what it’s really like inside the Pires lab, despite Pires’ expectations. It involves a well-known lab joke about Thomas prioritizing his undergraduate work while putting aside his Ph.D. thesis.

Another video acted as a submission for the PACBIO 2020 Plant and Animal Sciences SMRT grant program. The video was about the need for a reference genome of Cakile — “Sea Rocket” — to enable new studies in polypoid evolution, plant migration and crop improvement. In Europe, arugula is known as “rocket,” and a closely related species to rocket is “Sea Rocket,” so Thomas didn’t miss the opportunity to have some fun with it.

Even outside of YouTube, Thomas is tech-savvy on many fronts.

“I like to play with computers, and I like genetics, so playing around with big data genomic data has been fun,” Thomas said. “The work that I do is more basic research, where we are trying to understand the fundamental concepts behind how plants work and how these different mechanisms work. For me, the curiosity of trying to understand how polyploidy works is what interests me.”

Thomas is active on Twitter talking about everything Brassica — the mustard family — to help get others engaged in the basic research of plant biology.

“When we go to a conference, I’m known for being too much of the Twitter guy, but he’s also in there tweeting all the talks,” Pires said. “So, he’s not afraid to be an advocate for botany. He clearly loves botany, and he wants to have an influence, not just a science influence but an educational outreach kind of influence.”

In the lab, Thomas often helps move things forward by reminding the group about journal clubs, reading papers and corralling the undergraduates through his love of coffee.

“I’m a bit of a coffee snob, so I like to experiment with coffee and try all the new different recipes and techniques,” Thomas said.

Before the pandemic, Thomas would regularly visit Shortwave Coffee and get a pour-over of Ethiopian coffee (he highly recommends it). Now, he makes his own each morning and talks with the undergraduates about coffee while distanced in the lab.

“He’s a good team player, and he’s very social,” Pires said.

While Thomas is still learning how to be a mentor and exploring the diversity of plants, he has even more ahead of him.

“I’m proud of what I’ve done so far,” Thomas said. “I definitely have a long way to go, but I find enjoyment out of being able to create a nice figure or graph or get a good result that works with the story that we’re trying to tell.”

#IAmScience Michael Pisias

January 29, 2021 By Becca Wolf in #IAmScience Tags: #IAmScience, Brassicales, CRISPR

By Becca Wolf | Bond LSC

Michael Pisias came to realize that he wanted to study polyploidy while sitting in an undergraduate genetics lecture class at California State University-Sacramento (CSUS) a few years ago.

This unique phenomenon is when the cells of an organism have more than two paired sets of chromosomes, which intrigued Pisias.

“I knew I liked to figure out how living things work, especially at the smallest, genetic level,” Pisias said. “I find it fascinating that there are some creatures that are able to survive and thrive with doubled genetic information, which would be lethal to almost everything on the planet. I like to see how they’re able to do that.”

As a graduate student in the Chris Pires lab at Bond Life Sciences Center, Pisias indulges this passion studying Brassica. Modern day Brassica include many items in your grocery produce section like cabbage, cauliflower, and broccoli. These hybrids were formed by parent species millions of years ago and have evolved to contain double the genetic information.

“Essentially it’s a way to kind of generate a whole new species. These ones did it on their own, but we can do it synthetically in the lab too,” Pisias said.

Pisias focuses on the effects of the parent species’ genetic information within Brassica. He uses CRISPR to edit genomes to see how the chromosomes interact.

“It’s exciting because it’s really cutting edge,” Pisias said. “I’ve never seen a lot of the work that we’re trying to do within Brassica, a lot of this research is done in monocots like maize or wheat. It’s cool to do this in something that is further outside of what everyone else works on.”

Before Bond LSC, Pisias went to Sierra College and CSUS in his native California.

Pisias worked with local California polyploids after transferring to CSUS and learned how to be an efficient researcher through perseverance and keeping good records of his work.

“I was trying protocols repeatedly and realizing that when you’re doing research, it’s probably not going to work every time. You have to be persistent and creative,” Pisias said.

Pisias’ connections at CSUS led him to connect with Pires, and the rest is history.

“He’s bold, he’s willing to take some risks to try things that haven’t been done before,” Pires said.

At Bond LSC, Pisias has learned the value of collaborating.

“I find that a good part of my time here is spent learning from other scientists and not so much just sitting around reading things on the computer. You can learn something from everyone,” Pisias said.

He goes to neighboring labs for help and advice to advance his research.

“Everyone in the lab and in the Bond Life Sciences Center that I’ve interacted with are very friendly,” Pisias said. “They’re very inviting and I get to work with people from all over the world here. It’s been a very beneficial relationship.”

Pisias has passed it on as a mentor and teacher. He has taught Introduction to Biological Systems Lab and has helped teach a genetics course.

“I want to teach future scientists; a lot of my interest lies in mentoring other people,” Pisias said. “I currently have four undergraduate students to work with me on my research. I like to see how they can learn and grow on their own scientific journey.”

Teaching classes has helped him find undergraduate students who are enthusiastic about science and research that he ends up taking under his wing.

“He’s excited about his science and he wants to share it with people and now he has a small army of undergrads working with him,” Pires said. “He has a white board with plans for each student working on various projects. It’s a pretty serious training plan, but he’s excited for them to have a meaningful research experience.”

While he hopes to get his Ph.D., Pisias also dreams about the future of his mentees.

“I want all of them to primarily gain skills, so they can go on and be successful,” Pisias said. “In the short-term I’m hoping that they get some credit for the work that they do. It would be great if they could get the opportunity to get their names out there, potentially on some papers.”

To wind down from a long day in the lab, Pisias likes to go to the archery range to practice using his bow and arrow.

“I find it to be very relaxing, because you have to be slow and patient, which the opposite of the chaos of mentoring four undergraduate students,” Pisias laughed.

Life in the lab can be hectic, but Pisias would not want it any other way.

“I think that for us as graduate students, we’re in a really unique position. We have the privilege to mentor undergraduates who are all going to be the future scientists,” Pisias said. “I think it’s a really important responsibility that we need to take seriously.”

#IAmScience Hong An

September 7, 2019 By Mariah Cox in #IAmScience Tags: Brassicales

By Mariah Cox | Bond LSC

Broccoli, cauliflower, kale and cabbage all make up an important part of the food system and provide the nutrients we need to stay healthy—yet, there is still much that researchers don’t know about the genetic structure and the ancestral history of Brassicaceae, the mustard and cabbage family.

Hong An, a postdoctoral fellow in Chris Pires lab, has spent the past three years mapping the genetic history of canola seeds, which are in the Brassicaceae family, to find when and where different variations of the vegetables have occurred. Through this research, An can find the timeline of the formation of the vegetables and estimate how they got from one part of the earth to another.

“Canola oil is ranked the second in the world in oil production following soybean oil which makes it a very important agricultural crop,” said An. “Through my research, I’m trying to find specific genes that will help breeders make batter canola oil. “

An can use this research to understand the genes that make up the different breeds of canola seeds around the world. These findings can help researchers modify plants to improve the quality of the oil and optimize the growing of the plant altogether.

Additionally, An studies two subspecies of the canola species, which are rutabaga and Siberian kale, to improve worldwide breeding of these crops.

“I want to find a gene that can improve rutabaga and kale to make them more nutritious and tastier. Rutabaga already tastes good, but kale is bitter, so we want to find the genes in rutabaga that make it tasty and add those to kale to make it taste less bitter,” said An.

An grew up in the north part of China and never saw canola fields until he moved to the south part of China to attend college.

“As soon as I got to college, I remember thinking that [the canola fields] were so beautiful and that I wanted to study them,” said An.

For his Ph.D., An attended Huazhong Agricultural University and obtained his degree in crop genetic breeding. Although he has been working on his post-doc for three years, this isn’t his first time researching at MU. While he was getting his degree, he spent two years as a joint student in the Pires lab.

After his post-doc, An hopes to carry his knowledge of genetic crop breeding to a career at a seed breeding or biotechnology company.

“Many Brassicaceae are very important for us which is why it’s significant to find a way to make them more nutritious,” said An. “It’s important for people to know where our food comes from.”

#IAmScience Shawn Abrahams

December 7, 2018 By Erica Overfelt in #IAmScience Tags: Brassicales

By Erica Overfelt | Bond LSC

“Eccentric” is generally a word you do not want to use for a future boss.

But that’s what led Shawn Abrahams to the Chris Pires’ lab at Bond LSC. Abrahams first met Pires at the Botany 2013 conference in New Orleans.

“If you have ever met Chris before you know he is full of advice. At the time Chris told me about his expectations for grad students, how many papers you should have to be successful and that you should always be considering your 10-year plan,” Abrahams said. “I appreciated it as an undergrad who knew very little about what it took to become a research professor, but I thought to myself, ‘I could never have him as an advisor,’ a bit taken aback by his intensity.

Pires stuck out in Abrahams’ mind from countless other researchers who they had met at the conference.

“When it came to time to think about my future, I considered all the researchers I’d met and thought about who stood out the most?” Abrahams said. “Well, Chris stood out the most.”

Abrahams has been in the lab since the summer of 2015. The lab’s overarching theme is plant evolutionary biology.

“I work in the Brassica part of the lab, and I focus on a tribe of plants in the mustard family that includes about 227 species,” Abrahams said. “My big thing is trying to figure out how they have evolved certain traits within their group, particularly how gene duplication has contributed to some of these novel traits. Understanding their evolution is important for society and agriculture, but it also lets how know how we might expect plants to evolve in the future.”

Glucosinolates, or mustard oils, are an example of one of these unique traits. While most people know these compounds for the taste they give to wasabi, horseradish, or the yellow mustard we put on hot dogs, these compounds are used by plants to defend themselves and can have other effects. Some act as anticarcinogens in humans while others found in wild species are linked to upset stomachs and negative effects.

These evolved defenses are not always exclusive to a family of plants. This convergent evolution happens when organisms developing similar traits to another unrelated organism, and is of particular interest to Abrahams said.

“Some obvious places of convergent evolution are bats and birds who both have wings and fly but they have evolved those abilities separately,” Abrahams said. “In the tribe I work on, you have diverse mustard oils in groups that have been separated for millions of years of evolution, and you see this with some other traits as well. Did you know there are varieties of cauliflower that have been shown to have nicotine in them? But how did it evolve and what is it doing for the plant? Those are the questions I’m after.”

In the beginning, they found them self in a loop thinking constantly about where their research would take them next.

“I would say when I started in the lab I was very focused on how I get to the next step,” Abrahams said. “But if you just focus on the big picture you miss a lot of the details, and I have tried to enjoy the process just as much as the end product. If you are trying to build this as a career, you need to think about what motivates you. Why do I want to run a lab or would I be happier in industry? It is important to understand that for yourself.”

Before coming to MU to pursue their Ph.D. they went to University of Florida for undergrad, where they were involved in three labs. Afterwards, Abrahams experienced life outside of the lab.

“After graduating I did a one-year internship working in the everglades,” Abrahams said. “We looked at how sea level rising was affecting plant communities. Especially as a born Floridian I got to know the environment like very few do. You really get to physically interact with the local environment and understand nature.”

Their internship was physically testing, but the experience is something they carry with them in their daily life.

“I found working in the field was super rewarding but also very back breaking,” Abrahams said. “With 12 hour days working in the hot sun and gator filled marshland, you could potentially die from dehydration. When I entered my Ph.D. I took part of that experience with me. Techniques I used in that research to design mesosums, or artificial environments, came in handy when I wanted to test some ecological interactions.”

Experiences, conferences and people have all aided in Abrahams’ pursuit of their path in science. While Abrahams current life goal is to become an academic, they will be leaving MU in February to continue research in the Netherlands at Wageningen University. This opportunity stemmed from connections made at conferences and through a grant opportunity from the NSF Graduate Research Fellowship Program. They are hoping this experience will inspire new directions for their research and exciting discoveries.

“Science is a global human enterprise,” Abrahams said. “Getting the chance to really engage in that feels like I’m reaching a new level. It’s great.”

Story Note: Abrahams uses gender neutral pronouns them/they/their, which have been used in this article.

#IAmScience Sarah Gebkin

March 1, 2018 By Allison Scott in #IAmScience Tags: Brassicales

Sarah Gebken, a junior biological engineering major, works in the Pires Lab in Bond LSC. | photo by Allison Scott, Bond LSC

By Allison Scott | Bond Life Sciences Center

“#IAmScience because I bring a unique perspective to the world of research.”

They say only an engineer could figure out their way around the engineering building at Mizzou. Now in her junior year, Sarah Gebken boasts the ability to do just that.

Her unique perspective as a biological engineering major translates to her work in Chris Pires’ lab in Bond LSC, too. As both an engineer and a scientist, Gebken is prepared to contribute new ideas when trying to find solutions to complicated issues.

“Engineering classes are geared toward problem-solving, so I’m able to pinpoint where we’re going to have issues,” Gebken said. “It gives me a different view on research.”

The lab focuses on trying to get Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) to work in Brassica oleracea — a species of plants that includes cabbage, cauliflower and kale. Doing so has the potential to transform the farming industry.

“The main goal of our research is to save farmers space and time,” Gebken said.

CRISPR acts like scissors to DNA, which helps Gebken and her lab mates gain valuable understanding of the genes.

“CRISPR codes for a protein that clamps onto the DNA and makes a cut,” Gebken said. “We’re relying on that cut to knock out a gene to see what the gene actually does.”

Although Gebken has been trying to find a solution to the same question since she joined the lab as a freshman, she still finds the research satisfying.

Working with the plasmids is the next piece of the puzzle that the lab is aiming to complete.

“We’re making progress, which is exciting,” Gebken said. “We just ordered our plasmids yesterday.”

Once they figure that out, it’ll allow them to use that understanding to make better plants for the world moving forward.

After she finishes her undergraduate degree next year, Gebken plans to pursue a master’s degree and ultimately earn a Ph.D.

“I want to go on and be an academic professor, which would be a lot of research,” Gebken said. “Even if I went into industry, I’d want to do some kind of research.”

For Gebken, the quizzical nature of science serves as motivation to keep going.

“In a research setting, everything is a question,” Gebken said. “And you don’t have answers to a lot of them.”

#IAmScience Makenzie Mabry

December 1, 2017 By Allison Scott in #IAmScience Tags: Brassicales

Makenzie Mabry, a Ph.D. candidate, stands by the plants she works with in the greenhouse. | Photo by Allison Scott, Bond LSC

By Allison Scott | Bond Life Sciences Center

For Makenzie Mabry, every day is a new puzzle when it comes to science.

That desire to solve new problems led her from wanting to be a veterinarian to considering much less cuddly focus in plants.

“I think the beautiful thing about research is that it evolves itself,” Mabry said.

Although she had an acceptance letter to vet school in tow, she altered her career path to work with a new passion: plants. That led her from California to the lab of Chris Pires at Bond LSC.

“I did all of my undergraduate studies [at San Diego State University] with a vet school plan,” Mabry said. “I took a class my senior year talking about plants — Taxonomy of California Plants — with a great professor [Dr. Michael Simpson], and he really sold me on how unique plants are. They break all the rules.”

With vet school no longer in her plans, Mabry volunteered to work with Dr. Simpson and learn as much about plants as she could.

“I was all ready for vet school and I emailed him a week after I was supposed to start to volunteer,” Mabry said.

After two years of volunteering, Mabry began working toward a master’s degree. During that time, she studied a plant native to her home state of California, Cryptantha. She also studied those which occur in Chile and Argentina by visiting both countries.

“That fueled my passion for research,” Mabry said.

However, it wasn’t until five years ago that Mabry met Chris Pires at a conference in Columbus, Ohio.

“He was very energetic and I had just started learning about polyploidy [which Pires studies]. Three years later, he somehow convinced me to move from California to Missouri,” Mabry said. “I really enjoy the work I’m doing here, and it was a good decision.”

Now as a third year in Pires’ lab at Bond LSC, Mabry uses Brassicales — a family of plants that range from papaya to Brussel sprouts — to explore the multiple genomes of plants. She enjoys her lab work, analyzing data and getting to know the plants.

“Learning the subtle differences between them — whether branches are really close together or their leaves are clustered — is key,” Mabry said. “Being able to account for those differences might mean a lot for being able to find genes that are responsible for them. You have to know what those differences are to know what genes are responsible for it.”

Specifically, Mabry tries to understand how polyploidy — when an organism duplicates their genome to end up with two or more sets of chromosomes — comes about and what impact it has on plant species.

“We want to prove that polyploidy can lead to adaptive variation,” Mabry said. “It can be two different species forming a hybrid, and they keep all of their chromosomes, or a single species that doesn’t go through reduction. That’s the major question our lab is focusing on.”

These extra chromosomes can potentially give a plant new traits that help them react better to the environment or reproduce better without compromising essential plant functions. There are complexities to polyploidy that make deciphering its existence difficult, though. For instance, they’re trying to uncover why certain genes are kept and others aren’t.

“There’s evidence that there’s one genome that’s dominant to the other,” Mabry said. “Polyploids have a larger gene size, so that helps them accommodate.”

And, as a result, Mabry’s research requires coding skills.

“If you want to be successful you need to know how to code. You at least need to know what data is put in and what comes out,” Mabry said. “In the next 10 years, I think it’s going to be even more of a part of the undergraduate curriculum – it’s going to have to be.”

Luckily, Mabry doesn’t work alone.

“I’m really grateful because I have four amazing undergrad students who work with me,” Mabry said. “I could not do it without them. They all have individual projects that they are responsible for and it is very rewarding to watch them succeed in writing grants, presenting their work, and getting results.”

Ultimately, though, the undergraduates she works with are a big reason why she envisions herself in academia.

“Mentoring — that’s what keeps me going every day,” Mabry said.

#IAmScience Julia Brose

November 10, 2017 By Allison Scott in #IAmScience Tags: biochemistry, Brassicales

By Allison Scott | Bond Life Sciences Center

“#IAmScience because I really enjoy discovering and being around people who cultivate a positive learning environment.”

As a freshman at Mizzou four years ago, Julia Brose knew she had a love for plants. That, however, competed with her fascination with biochemistry.

Luckily, she found and was selected for FRIPS, Freshman Research in Plant Sciences, which allowed her to do both. The program is made up of 10 freshman each year who gain valuable hands-on research experience with plants.

“I started working in Bond LSC, and that’s really where I found my love for research,” Brose said. “Working with plants allowed me to explore that interest, while still majoring in biochemistry. I have the best of both worlds.”

Her degree in biochemistry coupled with her research experience has given her a number of unique opportunities. One of which was being a Cherng Summer Scholar at Bond LSC last summer where she studied plants and their protein makeup.

“I was looking at amino acids, which are the building blocks of proteins in plants,” Brose said. “Specifically, I was looking for the content in seeds within Brassica, a species that includes cauliflower and kale.”

Another unique opportunity Brose earned was in summer of 2016. She worked at Stanford University as part of a fellowship for the American Society of Plant Biologists.

“I studied novel plant defense compounds —how plants protect themselves,” Brose said. “People can move around and gain protection that way, but plants need different chemicals to protect themselves.”

Her background in biochemistry and her experience with plant research at Bond LSC in Chris Pires’ lab provided her with the ability to analyze the defense structures in a unique way. As a result, she uncovered something that others had either ignored or overlooked.

“I found that the chemicals we see in leaves are in roots, too,” Brose said. “No one else had looked there before, so it was cool to be the first.”

Her work at Stanford led them to send her to a conference in Hawaii earlier this year. While there, Brose was able to present a poster on her findings as well as network with a number of successful scientists in a variety of fields.

As she nears graduation this spring, Brose has begun looking into graduate school options. Those are largely based upon the experience she had in Hawaii.

“I was able to make connections that have influenced my plans for the future as far as where I’m applying to graduate school,” Brose said.

Wherever she ends up, Brose hopes to teach.

“I like mentoring students and being around a learning environment,” Brose said. “That is really fostered in a university.”

Scientists uncover how caterpillars created condiments

June 22, 2015 By Roger Meissen in Research 19 Comments Tags: Bond LSC, Brassicales, cabbage butterfly, evolution, genetics, plant science

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.

Chris Pires | Image by Roger Meissen, Bond LSC

The team published these new insights online in Proceedings of the National Academy of Sciences (PNAS) in June.

“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.

To explore the genetics of how this works, Pires’ lab partnered with Chris Wheat, professor of population genetics in the Department of Zoology at Stockholm University.

“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.