In silico search and biological validation of microRNAs related to drought response in peach and almond.

Plant responses to drought stress are regulated at the transcriptional and post-transcriptional levels through noncoding endogenous microRNAs. These microRNAs play key roles in gene expression, mainly by down-regulating target mRNAs. In this work, an in silico search and validation for microRNAs related to drought response in peach ('G.H. Hill'), almond ('Sefied') and an interspecific peach-almond hybrid ('GN 15') has been performed. We used qPCR to analyse the gene expression of several miRNAs described as being related to drought response in peach, including miR156, miR159, miR160, miR167, miR171, miR172, miR398, miR403, miR408, miR842 and miR2275 under mild and severe water deficit. These miRNAs were in silico selected on the basis of previous works, their conservation in plants and their drought response. qPCR analysis confirmed the implication of these miRNAs in the dehydration stress response in the three assayed genotypes. Comparison of miRNA expression patterns in the three evaluated genotypes indicated that the hybrid GN 15 showed higher expression levels of specific miRNAs which should be related to the observed drought tolerance. mRNA target transcripts of the miRNAs studied were predicted using the Rose database, which includes transcription factors that regulate plant growth and development. In addition, results showed that the promoter region contains responsive elements to hormone-mediated regulatory elements. Network analysis not only unravelled the interaction between miRNAs and their predicted gene targets but also highlighted the roles of miRNAs in response to drought stress.