Roles of Plant Small RNAs in Biotic Stress Responses

A multitude of small RNAs (sRNAs, 18-25 nt in length) accumulate in plant tissues. Although heterogeneous in size, sequence, genomic distribution, biogenesis, and action, most of these molecules mediate repressive gene regulation through RNA silencing. Besides their roles in developmental patterning and maintenance of genome integrity, sRNAs are also integral components of plant responses to adverse environmental conditions, including biotic stress. Until recently, antiviral RNA silencing was considered a paradigm of the interactions linking RNA silencing to pathogens: Virus-derived sRNAs silence viral gene expression and, accordingly, viruses produce suppressor proteins that target the silencing mechanism.…