Identification and characterization of differentially expressed microRNAs in response to Rhizoctonia solani in maize

Abstract

MicroRNAs (miRNAs) are a set of small, non-coding RNAs that negatively and post-transcriptionally mediate their respective target mRNAs by directing the target mRNA cleavage or translational repression. Plant miRNAs have been involved in developmental processes and adaption to biotic and abiotic stresses in their environment. The banded leaf and sheath blight (BLSB) caused by Rhizoctonia solani is extremely harmful to maize. To investigate the functions of miRNAs under R. solani inoculation, miRNA expression in R. solani infected maize (Zea mays L.) was profiled using deep sequencing. In total, 41 significantly differentially expressed known miRNAs and 39 novel R. solani-responsive miRNAs were identified, of which 9 identified miRNAs were further validated by qRT-PCR, and 2 important miRNAs were analyzed by in situ hybridization. Target genes were also predicted for these R. solani-responsive miRNAs; most of these putative target genes encoded transcription factors and proteins associated with metabolic processes or stress responses. In addition, the mRNA expression levels of several target genes that negatively correlated with the levels of corresponding miRNAs under R. solani inoculation were validated by qRT-PCR. These findings hypothesized that these miRNAs play an important role in R. solani resistance in maize, highlighting novel molecular mechanisms of R. solani resistance in plants.