Alterations in the Expression of Senescence-Associated miRNAs and Their Target Genes in the mature flag leaf of wheat under Drought Stress

Targeted mRNAs cleavage is directed by a class of tiny RNAs known as microRNAs (miRNAs). Different plant processes are regulated by miRNAs, including senescence, responses to environmental stressors, and development. The current study identified the senescence regulation of miRNAs. It evaluated the impact of miRNA-directed modifications in expression of target genes of Triticum aestivum cultivars in response to drought. Two cultivars of spring wheat, Sahel-1and Gemiza-10 were used in this study. The Fv/Fm ratio, indicative of the maximum quantum efficiency of photosystem II, and the Performance Index (PI), an indicator for assessing sample vitality, exhibited significantly elevated values in the drought-tolerant cultivar relative to the drought-sensitive cultivar.Furthermore, quantitative PCR analyses for the miRNAs families; miR156, miR172, miR164, miR171, miR156, and miR319 and their putative target genes at reproductive phase under drought conditions in the two genotypes were performed. The up-regulation of AP2 in the Sahel-1genotype played a crucial role in leaf wilting and delaying aging under stress of drought. The miR164 down-regulation and up-regulation of NAC1 contributed to the delay of leaf wilting and senescence.