Lead-Induced Physiological Changes and Stress-Responsive Mirnas Expression in Cotton (Gossypium hirsutum L.)

The presence of heavy metals in the agricultural soil constrains the crop productivity and even exhibits hazardous influences on human health. MicroRNAs (miRNAs) are a class of endogenous small RNAs that regulate plant growth and development by silencing gene expression at post-transcriptional level. Recently, some literatures have shown that some miRNAs are in response to heavy metals. But there is few study has been performed the miRNA expression profile on the effect of lead-induced in cotton. Therefore, to determine the abiotic stress responses mediated by miRNA, the cotton (Gossypium hirsutum L.), which is one of the important fiber crops in the world, was exposed to different concentrations of plumbum (Pb) 0, 25, 50, and 100mg per liter medium and then the toxicological effects were investigated. The effects of plumbum on changes in the root development, plant biomass and biochemical responses were studied. The results suggested that, exposure of plumbum diminished the biomass content, chlorophyll and affected antioxidant enzyme activities in cultivars. MDA contents were significantly increased under Pb stress. To investigate whether miRNAs function in Pb stress response, 16 Pb-responsive miRNAs and 10 target genes for the Pb-responsive miRNAs were identified in leaves and roots. miR172-MYB68 and miR414-RAX1, miR5658-RAX2, and miR396-RAX3 were validated to show a reciprocal regulation by miRNAs, which were involved in root development. These results would help defining the potential roles of miRNAs in plant adaptation to heavy metal stress and further understanding of miRNA regulation in response to abiotic stress.