In this series, IISER Pune students bring us glimpses of various facets of the institute such as teaching, research, administration, and campus planning through their interviews with people behind the scenes.

Chemical Ecologist at IISER Pune: Interview with Sagar Pandit

INTERVIEW BY Meenakshi Pardasani and Soumya Bhattacharyya

“I am a botanist at heart. I just love plants,” says Dr. Sagar Pandit, new faculty member in the Biology Discipline at IISER Pune, while munching on kokum leaves from the tree he pointed out to us outside the IISER greenhouse. Dr. Pandit joined IISER Pune in August 2016 and works on chemical and molecular ecology of multitrophic interactions involving plants, herbivores and their natural enemies. Before joining IISER Pune, he led a research group at the Max Planck Institute (MPI) for Chemical Ecology, Jena, Germany. We chatted with him one sunny afternoon in his office about his work and his life as a scientist.

Tell us about your research, what are you currently working on in your newly established laboratory?

I am a molecular and chemical ecologist and I work on multitrophic interactions. The model system I have selected are plants, herbivores and their natural enemies.  I joined IISER Pune in August 2016, and since then I have been working on two plant model systems.

One of them is Arabidopsis--easy to handle and extensively used because of its short life span. Also, one can quickly get results from it in a newly developing laboratory. It is a member of the Brassicaceae family and we study its interactions with its destructive pest, diamondback moth (Plutella xylostella) and also higher order interactions involving parasitoids, hyper-parasitoids and predators. Brassicaceae plants contain chemicals called glucosinolates and an enzyme called myrosinase. They are stored in separate cellular compartments of the leaf. When the larvae of diamondback moth chew the leaves, compartments rupture causing myrosinase and glucosinolates to come in contact with each other. Myrosinase cleaves off a sugar from glucosinolate giving rise to isothiocyanates or mustard oil. Isothiocyanates are toxic for the diamondback moth larvae. This process of compartment rupture and isothiocyanates formation is popularly known as detonation of the mustard oil bomb.

Another one is Brinjal. In India, it is always important to work with crops. Brinjal is a native Indian crop. Lepidopteran insects such as fruit and shoot borers are a trouble for Brinjal. In the recent past, many insecticides have been tested to get rid of this insect and enhance productivity but nothing worked. Therefore, Bt Brinjal was developed assuming that the Bt toxin will confer resistance against borer. However, insects developed resistance to Bt crops too.

We propose that a sustainable borer control strategy can be developed based on the thorough knowledge of the chemical interactions between the crop and borer. This is the interesting chemical ecology aspect of the crop-pest system that my lab is currently exploring.

You worked on flavour biogenesis in Alphonso mango for your PhD. How did the shift from flavour biogenesis work to investigating plant-host interaction come about?

I am a botanist- plant biotechnologist by training so mango work was very much my domain. Before that, during my bachelors I worked in a plant tissue culture laboratory and on weekends I used to visit Western Ghats. I started working on Dr. Madhav Gadgil’s project ‘biodiversity monitoring of Eastern and Western Ghats’ locally headed by Dr. Ghate, India’s leading entomologist, at Modern College, Pune.  During this work I learned from Professor Ghate that plant-insect interactions are chemically-based. Based on my interests, I started with mango flavour biogenesis at NCL. I investigated that certain volatile flavour compounds such as terpenoids are also involved in insect attraction or deterrence. Therefore, studying their biosynthetic pathways was quite useful for my chemical ecology work.

Tell us about your post-doctoral work.

After the mango work, I decided to come back to plant-insect interactions. I wrote applications to several chemical ecologists around the world and eventually joined Ian T. Baldwin’s laboratory at MPI, Jena, Germany. The entire Department of Molecular Ecology there was working on plant-pest interactions, from the point of view of the plant. I wanted to work from the viewpoint of the insect. Manduca sexta is a caterpillar that feeds on the leaves of a wild tobacco plant (Nicotiana attenuata) and is able to tolerate nicotine levels much higher than what we can tolerate. I wanted to find out how this caterpillar could detoxify all this nicotine. However, this work eventually led us on another path. We made a transgenic caterpillar, where a gene thought to be involved in oxidation of the nicotine was knocked out. However, it still seemed to be able to resist nicotine just fine. So we were at a dead end with our candidate gene. However, there was an interesting observation. We had test fields at Utah where we noticed that our transgenic caterpillars reduced in large numbers during nights. We were surprised when we saw armies of a small spider coming out at night and selectively preying on our transgenic caterpillars. Somehow the spiders were able to differentiate between the transgenic and wild type caterpillars. Most of my post-doctoral time was spent studying how this happens.

You led a research group at Max Plank Institute, Germany, and now you’re at IISER Pune. What do you feel are some of the differences and similarities between the two institutes? How are things done differently between Germany and India?

My post-doctoral project at MPI involving applying reverse genetics in lepidopteran insects was an interesting one. I was offered to continue as a group leader and take a couple of graduate students. I find the environment here equally vibrant and laboratories are well equipped. Administrative staff are very helpful. I did not feel too much of a difference making this shift from MPI to IISER Pune. IISER, indeed is a big leap from the traditional Indian system. The only difference I find is that new PhD students who join here are less experienced when it comes to lab-work. So, we need to provide them the basic training, but that is also fun.

Have you started any collaborations?

Yes, I am closely collaborating with Madhusudan and Nixon Abraham, here at IISER Pune.

Many plant compounds target neuronal receptors in their pests. For example, nicotinic acetylcholine receptors in Manduca which binds to nicotine released by tobacco plants. So we know of many plant compounds which can be neurotoxic. In that sense, Nixon being a neuroscientist is the right collaborator for us.

Madhu, because there are structural aspects to these plant-herbivory interactions and thus, we require in silico modelling of these interactions. Other collaborations are in NCL and at field sites in ICAR centres.

Around the world, whose research do you look up to?

I worked with Professor Ian T. Baldwin (MPI, Germany) and then later I worked with Professor Jonathan Gershenzon (MPI, Germany). These two are fantastic ecologists, the best people to follow in the chemical ecology field. In Ithaca, there is Professor Georg Jander (Boyce Thompson Institute, Cornell University), who works with crop plants such as potato, tomato and also with insect physiology. In India, Dr. Shannon Olson (NCBS Bengaluru), a neuroethologist, who is also my colleague from MPI.

Please shed some light on what you think are the current/happening methods in Plant biology/Chemical ecology today.

I strongly feel that in past 5 years and in the next 5 years- genomics, transcriptomics and metabolomics is going to rule this field. We need to integrate expertise from all these techniques. But I guess only for next 5 years because these techniques also have their limitations.

But more laboratories are now trying to gain access to fields for planting transgenic plants. We got such fantastic results because we could plant our transgenics in their native habitat in Utah, USA. This is very important if you wish to understand the ecological function of your target genes in plants.

I am planning an alternative for this, and building a mesocosm in my laboratory. It will mimic the plants’ natural habitat. You can call it a walk-in chamber that will mimic the plants’ natural habitat.

In plant systems, what is the main difference between fundamental and applicable research? Would you call your work application based?

I feel a yes or no answer is not a good idea for this question. When I talk about brinjal, its application based; but when on Arabidopsis, it becomes basic research. Indeed, there is no single answer. When you do chemical ecology of crops, it does become applied. I believe that agricultural researchers should ask more basic questions to gain more.

What got you into science? What kind of support did you get from your family?

Initial motivation during my bachelors and masters came from Professor Ghate, a zoologist, entomologist and a great animal taxonomist and later by my PhD guide Dr. Vidya Gupta, one of the best guides one can work with. No one in my family belongs to science; however, they supported me well.

Would like to give any message to the graduate students of IISER Pune?

If you plan your work systematically, then you do not need to work exhaustively or for long hours. So plan before-hand, and this will actually allow you to save time, energy and resources. Keep asking questions and try falsifying your own hypotheses. And of course, keep reading.