Dr. Sampa Das: Adapting Nature’s defenses

By Joan Conrow

July 1, 2015

Dr. Sampa Das is finding that nature’s own defense mechanisms may hold the key to boosting productivity and reducing pesticide use in India’s important food crops.

Das, whose research career spans 35 years, is one of India’s leading experts on public sector agricultural biotechnology. She works at the Bose Institute in Kolkata, a multi-disciplinary research institution focused on science and technology. Das became interested in plant transformation during her post-doctoral training at the Friedrich Miescher Institute in Switzerland. She began seeking ways to express new genes into different plants to improve their quality or quantity, and working primarily with rice, mustard, and tomato, as well as chickpea and mung bean two important sources of protein for India’s predominantly vegetarian population.

Yield can be boosted directly, by improving a plant’s photosynthetic efficiency, or indirectly, by protecting it from insect and viral attacks and such stressors as salinity, heat, cold and drought.

While the Bt technology has helped protect plants from certain classes of insect pest, it is not effective against some sap-sucking and coleopteran insects, Das explains. These insects, which feed on plants and spread harmful viruses, became more prominent in the fields when Bt crops allowed farmers to reduce applications of broad-spectrum insecticides.

In seeking genes to protect plants from the sap-sucking insects, Das and her colleagues looked at India’s common, edible, indigenous plants, isolating mannose-binding lectin proteins in onion and garlic. Though these lectin proteins are basically storage proteins, they can also serve as defense proteins when attacked by certain enemies, Das says.

“We got curious to know how higher animals or mammals or human beings are not affected, but insects were affected,” she says. “So it stimulated us to investigate in this process.”

Her research has advanced to T3 and T4 generation plants, with very promising results. Most of the sap-sucking insects we targeted are affected by [our] protein, Das says.

If the technology bears out, plants genetically engineered to express that lectin could better repel sap-sucking insects, and thus the viruses they carry.

“The primary benefit is that the plant will be healthy,” Das says. “They will not be attacked by the whitefly and by leaf curl virus, so the plant will grow happily and farmers will get their return. Yield will be more and more.”

Since they are working with a newly identified gene, Das team also has conducted various studies to test for allergenicity, using guidelines established by the World Health Organization. These include digestibility assays, blood sera reactivity, and animal feeding trials.

“So through different types of experiments we found that it is not allergenic,” she says. “And we are taking the edible plants. So it is already in our food chain for so many years, and we don’t have any adverse report against all these lectins. So it is one advantage. One plus point for these lectins.”

“Other studies found the gene has no adverse effect on non-target insects or beneficial insects. Rather, it is effective against the target insect,” Das says. “So in that way it is more or less safe. But large-scale assay, large-scale investigation, is needed, definitely needed.”

Das believes the gene has sufficient commercial potential to attract investors. But she hasn’t yet gotten permission to conduct field trials, and the Bose Institute does not have facilities to carry out large confined tests. Das would like to partner with a private company to help move the technology through the deregulation process, which requires significant funding that public institutions don t have.

It will be very helpful if industry and public institution scientists work together, she says.

Das also believes it’s important for research facilities to collaborate with agricultural institutes and universities that have mechanisms for helping farmers access and understand new agricultural technologies.

Though the new gene holds promise in its own right, it has other possible applications.

Scientists may be able to pair the protein with the Bt technology possibly through a gene-stacking methodology, or by creating a fusion process, Das says. This could help plants like cotton, tomato, and mustard resist a broader array of insects, thus further reducing pesticide use.

“We all know pesticides have hazardous effect on ecology and environment and whole ecosystems,” Das says. “And they are costly. It’s not affordable always for the farmers.”

Such options may become increasingly critical in the decades ahead, as farmers struggle to maintain food production under challenging conditions.

“Climate change is a big issue,” Das says. “And this climate change will impact the plant metabolism, plant growth and plant development as well as the ecosystem. That means the insects and pathogens will also modify themselves. And so the whole ecosystem, the whole eco-balance, is disturbed or disoriented through the climate change issue.”

The increased cloudiness that is expected to result from changes in the planet s aerosol layers will similarly disrupt plant development and ecosystems, she says. This is also another big problem which we should address.

Researchers can develop stronger plants through traditional breeding methods and hybrid technology, and Das thinks such work should continue.

“But it is time-consuming,” Das says. “Biotechnology is a faster methodology. We can express new genes or new proteins in two to three years’ time. Both should come hand to hand.”

Biotechnology has met political resistance in India and elsewhere, largely because the general public is not much aware of the intricacies of the technology, Das says. The problem is compounded because scientists who are not actually handling the technology are leading the public debate.

“They cannot perceive the advantage or disadvantage or any issues,” Das says. ‘They cannot address the issues in depth. I think it’s the duty of scientists who actually practice [the technology] to also provide all the pros and cons clearly, transparently, in a detailed way.”

In the meantime, Das is continuing to research genes that could help plants resist various pathogens while refining her work on lectins that deliver a double punch to sap-sucking insects and viruses two big agricultural enemies.

“So it’s a very important thing,” she says. “And if the people accept this project I will be very happy.”