Title : Engineering defense response in plants through miRNA mediated suppression of regulatory factors
on-coding RNAs are prominent modulators of transcriptional and post-transcriptional expression of genes in a wide range of biological processes. However, the repertoire and functions of microRNAs largely remains unexplored with respect to defense against fungal phytopathogens. In this study, we performed a comparative small RNA profiling of susceptible (Arka Lohit-AL) and resistant (Punjab Lal-PL) chilli cultivars to identify 35 differentially expressed miRNAs responsive to Colletotrichum truncatum, the most belligerent anthracnose pathogen. Excitingly, a novel microRNA canmiRn37a was significantly expressed in PL but reduced in AL genotype post pathogen attack. Overexpression of can-miR37a in transgenic pepper revealed enhanced resistance to C. truncatum as evidenced by decreased fungal growth, up-regulated expression of defense-responsive genes and down-regulated expression of the target regulatory genes encoding ethylene response factors (ERFs). Can-mir37a mediated regulation of ERFs was further confirmed through transient co-repression in Nicotiana benthaminana. Furthermore, knock-out analysis of the ERF transcription factors revealed their role in fungal colonization and immune suppression in chilli. Overall, the present study authenticate can-miR37a as a potential miRNA that engineers anthracnose resistance in chilli pepper.