Can-miRn37a mediated suppression of ethylene response factors enhances the resistance of chilli against anthracnose pathogen Colletotrichum truncatum L.

Pepper anthracnose, caused by Colletotrichum species complex is the most destructive disease of chilli (Capsicum annuum L.). miRNAs are key modulators of transcriptional and post- transcriptional expression of genes during defense responses. In the present study, we performed a comparative miRNA profiling of susceptible (Arka Lohit-AL) and resistant (Punjab Lal-PL) chilli cultivars to identify 35 differentially expressed miRNAs that could be classified as positive, negative or basal regulators of defense against C. truncatum, the most potent anthracnose pathogen. Interestingly, a novel microRNA can-miRn37a was significantly induced in PL but largely repressed in AL genotype post pathogen attack. Subsequent over-expression of can-miRn37a in AL showed enhanced resistance to anthracnose, as evidenced by decreased fungal growth and induced expression of defense-related genes. Consequently, the expression of its three target genes encoding the ethylene response factors (ERFs) was down-regulated in PL as well as in the over-expression lines of AL genotypes. The ability of these targets to be regulated by can-miRn37a was further confirmed by transient co-expression in Nicotiana benthamiana. Additionally, the virus-induced silencing of the three targets in the susceptible AL cultivar revealed their role in fungal colonization and induction of C. truncatum pathogenicity in chilli. Taken together, our study suggests that can-miRn37a provides a potential miRNA mediated approach of engineering anthracnose resistance in chilli by repressing ERFs and preventing fungal colonization.