Investigation of host-plant microRNA mediated insect gene regulation

Abstract

Plants and insects interact with each other in a variety of ways. Insects feed on plants in the majority of plant-insect interactions. Plants challenge insect herbivory via several defense mechanisms such as physical barriers to herbivory, secretion of toxic chemicals, and secretion of volatiles that attracts insect’s predators. Insects, in turn, have evolved defense strategies such as rapid excretion, detoxification or sequestration of toxic chemicals, and behavioural avoidance of predators. Small RNAs (sRNAs) are certain molecules that are seen to be upregulated in the plant post-herbivory, the role of which has not yet been studied in this interaction. Our study focuses on exploring the role of Arabidopsis thaliana (plant) – derived miRNAs (type of sRNA) interacting with Plutella xylostella (insect) genes. It is one of the few studies investigating the presence and role of exogenous diet-derived plant miRNAs in an insect herbivore. In this study, three A. thaliana miRNAs targeting P. xylostella GSS transcripts were predicted. The temporal kinetics of these candidate miRNAs was observed in A. thaliana upon herbivory by P. xylostella. Pre and mature forms of the miRNAs are seen to be induced at 12h and 24h post-herbivory. Temporal kinetics of insect GSS genes was also observed. Candidate miRNAs were synthesized via in vitro transcription and fed to P. xylostella larvae via an artificial diet. We were not able to observe silencing of insect GSS genes through diet-fed plant miRNAs.