MicroRNAs behave differently to drought stress in drought-tolerant and drought-sensitive grape genotypes

Drought is a major environmental factor limiting grapevine production and quality. However, the roles of miRNAs in different grape varieties at the post-transcriptional level during drought are largely unknown. In this study, we investigated the miRNA abundance in a drought-sensitive grapevine (Vitis vinifera L. cv. Cabernet Sauvignon) (CS) and a drought-tolerant grapevine (Berlandiari Ressiguier No.2 x Rupestris Martin) (110R) in response to drought using Illumina sequencing. A total of 488 known and 892 novel miRNAs belonging to 48 miRNA families were identified in CS and 110-R, respectively. Various accumulation trends of miRNAs observed in the differential drought tolerance of grapevine genotypes were further confirmed using stem-loop qRT-PCR. The target transcripts are predominantly associated with biological processes, cellular components, and mo-lecular functions. Several significantly different drought-responsive miRNAs were examined by beta-glucuronidase reporter gene activity driven by miRNA promoters in transgenic lines. The results showed drought-induced downregulation of VvmiR169d and VvmiR398a expression and upregulation of VvmiR156b expression. More-over, we noted that VvmiR156b overexpression significantly decreased primary root length and increased lateral root numbers in Arabidopsis lines and observed a higher relative growth rate in grape calli under drought treatment. Therefore, genotype-dependent stress-responsive regulation of miRNA expression contributes to the differential drought tolerance of grapevines, and this finding provides mechanistic insight into the vital roles of miRNAs in drought-stress environments in grapevines.