Undergraduate Research Forum - Part 3/3: Michael Das

  • May 12, 2016
  • Howe lab, future scientists
  • Future Scientists
  • By Igor Houwat
Caterpillar
Caterpillar prowling.
By Aleksey Gnilenkov, https://flic.kr/p/9p2rZK, CC 2011.

The University Undergraduate Research and Arts Forum (UURAF) provides MSU undergrads with the opportunity to showcase their activities in a public setting. According to the website, “undergraduates gain experience in presenting their research, answer questions about their work from audience members and guests, and receive constructive feedback from judges.” Judges interact with presenters at random to ensure research is solidly understood. The best presenter in each category in each of the three sessions wins a $100 award.


Michael Das is a Biochemistry and Molecular Biology undergraduate student in his third year at MSU. He joined the Howe lab in February of 2015, where he has primarily worked under Koichi Sugimoto, a postdoc from Japan, in order to understand how plant defense mechanisms have evolved. 
 

Tomato defenses against insects

Plants have developed two strategies to protect themselves against insect herbivores and other pests: inducible defenses which are activated only when a pest is attacking the plant, and constitutive defenses which are produced continuously throughout the plant’s life.

Tomato species exhibit both these strategies to protect themselves. A classic example of an induced defense are   proteinase inhibitor proteins: when sensing an insect eating them, the plant produces proteins that bind to the insect’s digestive   enzymes, causing reduced food digestion and loss of nutrients needed for the animal to survive. Constitutive plant defenses include such mechanisms as thorns and trichomes, the latter hair-like structures that cover plants and that secrete toxins and repellents.

Image of a close up on trichomes, hair-like protective structures
Trichomes, dangerous ground for miniature herbivores.
By incidencematrix, https://flic.kr/p/FTLK99, CC 2016.

Although cultivated species have similar genetic makeups to their wild counterparts, their defense mechanisms have evolved differently over time. For one, domesticated tomato has lost many of its anti-insect defenses, and little is known about how this has happened. There are also cases, however, where defense mechanisms are stronger in the domesticated species. The Howe lab is examining these differences to understand fundamental principles of how plant defenses evolve.

Michael’s project, in specific, is part of a wider effort to determine how inducible defense mechanisms developed in wild tomato species and their domesticated descendants. One common way of going about it is to find the progenitor line of wild tomatoes – to the best of our knowledge – and to identify their defense mechanisms in order to infer what has been weakened or strengthened during the domestication process.

Michael is looking at a particular gene called ARG2 (arginase 2) responsible for an induced defense strategy. When the plant senses it is being eaten by a caterpillar, ARG2 is activated to produce an enzyme that depletes an essential nutrient – the   amino acid arginine – in the caterpillar gut.

Michael conducted an experiment in which he cross-bred a wild tomato species that has weak ARG2-based defenses with a cultivated species that has strong induced expression of ARG2. (Interestingly enough, the wild species has strong trichome-based constitutive defenses while the cultivated plant is weak in that regard.) He then examined the progeny from this cross to identify genetic factors involved in the expression of ARG2.

Preliminary results, presented by Michael at the UURAF, indicate that the gene itself is significantly different between the wild and domesticated tomato species. Specifically, the DNA sequence variations have a strong effect on whether or not this inducible defense is activated in response to a threat. 

Image of a magnified view of tomato at a genetic level
Zooming into tomatoes at the genetic level

It's still unknown why ARG2 is stronger in the cultivated species. "Perhaps it is a necessary anti-insect function for cultivated species," Gregg Howe, MSU Foundation Professor at the PRL, speculates, "but presumably the wild species does not need that function because it has a strong trichome (constitutive) defense. We just don't know yet."

The implications beyond the lab are exciting. In fact, one major breeding technique is to identify desirable traits in wild plant species and then to breed those traits into cultivated crops, while avoiding undesirable characteristics from wild lines (for example, wild tomatoes can come in small sizes or not be very tasty). This process takes time and much trial and error. The identification of novel genetic factors that control inducible plant defenses – including ARG2, among many other defense genes – might facilitate the future breeding of crops that use the best from both worlds in order to stand up better to insects.
 

Practicing presentation skills early on

A major UURAF goal is to allow undergraduates to practice presentation skills in a public setting. Michael acknowledged as much, given this was his first participation in such an event. “I think that the biggest benefit to the UURAF was experiencing the presentation aspect of research. I previously had only been involved in lab work and discussing the project among my peers. The UURAF forced me to think about the project from the perspective of people who did not already know about it.”

Image of Michael Das in front of his poster at the UURAF
Michael in front of his poster at the UURAF

Much like Hope and Donna, PRL undergrads who also attended the UURAF, Michael took a while to hit his stride. But following multiple iterations, he noticed that he felt a lot more confident and the presentations were a lot smoother. He added, “I feel like the UURAF will help me settle in a lot quicker the next time I go to a similar event.”

Michael, originally from Farmington, MI, plays the trombone in his free time, and when he isn’t in the lab, he is with the MSU marching band supporting Spartan football. “I’ve been doing it for three years now. My last year will be this coming fall - hoping for a good bowl trip to top it off!”