Research Projects

Herbivorous insects are responsible for destroying one fifth of the world's total crop production annually. The common cutworm, Spodoptera litura and related species are generalist insect pest of the order Lepidoptera and among the most destructive pests in agriculture. For years chemical pesticides have been the preferred method to control insects with devastating effects on environment, health, and biodiversity. Plant roots are exposed to countless microbes that positively impact its health and endophytic fungi, Piriformospora indica is one of them. Induced systemic resistance is a mechanism by which beneficial bacteria/fungi in the rhizosphere prime the whole plant for enhanced defense against a broad range of pathogens and insect herbivores. Plant host resistance against insect herbivores are driven by phytohormones and diverse secondary metabolites which are harmful for insects. Surprisingly, little is known about the ability of P. indica in imparting systemic resistance against S. litura and the identity of novel metabolites shaping the response. P. indica colonization on tomato roots increases primary metabolite, putrescine levels via activation of arginine decarboxylase (ADC)-mediated pathway, which is crucial for hormone-mediated growth promotion. Putrescine biosynthesis can be crucial for systemic resistance as it is associated with greater insect mortality in some hosts and possible role in growth-defense trade off. In tomato, defense responses against herbivory involves secondary metabolites, polyphenols like chlorogenic acid, volatile organic compounds, proteins like polyphenol oxidase (PPO), proteinase inhibitors (PIs) that are anti-herbivore molecules which interfere with insect’s metabolism. Defense against insect herbivory is also correlated with alteration of primary metabolites which can be a vital factor during resource diversion for growth-defense trade-off. The project will study the role of plant growth promoting endophytic fungi, Piriformospora indica for lepidopteran insect, Spodoptera litura control in Tomato, using high throughput metabolomics and functional assays. Through the project, we will dissect novel herbivory relevant metabolite pathways and signaling networks responsible for P. indica mediated induced systemic resistance. We would also test the hypothesis that putrescine biosynthetic gene, arginine decarboxylase (SlADC1) is functionally involved in this tri-trophic interaction and characterize its functional role. Understanding these mechanisms will ultimately enable efficient bioengineering of desirable metabolic traits to enhance stress tolerance in plants without affecting growth and enable the use of fungal endophytes as a sustainable alternative to plant protection.