MicroRNA prediction and its function in regulating drought-related genes in cowpea

Cowpea has indigenous drought-tolerant characteristics, but the molecular mechanisms underlying the drought-tolerance are largely unknown. Drought sensitive and resistant cowpea have different responses regarding to drought stress. We applied homology search to predict miRNAs and their corresponding targets. The newly identified cowpea miRNAs were validated by real-time quantitative PCR in the leaves and roots of cowpea plants under drought treatment. Target gene prediction shows that a set of miRNA target genes are involved in the metabolic pathways regarding the physiological changes that are highly related to drought stress. We analyzed the expression levels of some important genes that participate in the physiological responses to drought stress and found that variations in their expression levels correspond well to the different responses of drought sensitive and resistant cowpea to drought stress. The expression levels of the target genes were negatively correlated to those of miRNAs. The same miRNA in different tissues responds differently to drought stress. Our results indicate that miRNAs play important roles in response to drought stress by regulating the expression levels of drought-related genes in cowpea.