Deciphering the role of host plant miRNAs in the regulation of herbivore gene expression

Abstract

Plants and their insect herbivores have coexisted for hundreds of millions of years. Insects depend on plants as their primary source of nutrition. This dependence harms the plants immensely and plants produce various defense responses to deter the herbivores in the form of physical barriers and toxic chemicals. Insects, on the other hand, have evolved to counter these defense strategies like detoxification of the chemicals, avoidance, sequestration, etc. It has been shown that along with the various chemicals, plants also possess various sRNAs many of which also get upregulated following herbivory. Although the chemical responses have been studied extensively, the role of naturally occurring sRNAs has not been studied in the context of plant-insect interaction. This study focuses on the role of natural diet-derived Arabidopsis thaliana miRNAs (a class of sRNAs) in the interaction with the specialist pest Plutella xylostella. The miRNAs predicted to be targeting P. xylostella GSS by in silico prediction were selected for the study. GSS plays an important role in the interaction between A. thaliana and the insect herbivore by helping the insect in detoxification of the toxin Glucosinolates. A miRNA free artificial diet was standardized for the specialist insect. Both precursor and miRNA/miRNA* duplex forms of the candidate miRNAs were shown to be stable at room temperatures for up to 24 hours. The candidate miRNAs were in vitro synthesized and fed to the insect via artificial diet. This study reveals that the candidate miRNA Ath-miR824 is induced upon herbivory.