Spatio-temporal expression of miRNA159 family members and their GAMYB target gene during the modulation of gibberellin-induced grapevine parthenocarpy.

Grapevine, Vitis vinifera, is an important economic fruit crop that is highly sensitive to gibberellin (GA), and the exogenous application of GA can efficiently induce grapevine parthenocarpy. However, the molecular mechanisms underlying this process remain elusive. In this study, morphological changes during flower development in response to GA treatments were examined in the 'Zuijinxiang' cultivar. To obtain insights into the roles of miRNA159s in GA-induced grapevine parthenocarpy, VvmiR159a, VvmiR159b, VvmiR159c, and their target gene VvGAMYB were isolated, sequenced and characterized. Spatial-temporal expression analyses showed that VvmiR159c exhibited the highest expression levels at 4 d before flowering, followed by a gradual decrease, while VvGAMYB displayed an opposite pattern of expression with the lowest expression at the corresponding stage in response to GA treatment. A cleavage interaction between VvmiR159s and VvGAMYB and variations of their cleavage roles were confirmed in grapevine floral development. In addition, the potential roles of VvmiR159s in GA signaling were investigated through DELLA-protein repressors, indicating that GA-DELLA (SLR1)-VvmiR159c-VvGAMYB is the key signaling regulatory module in grapevine. Our findings provide novel insights into the GA-responsive roles of VvmiR159s in modulating grapevine floral development, which have important implications for the molecular breeding of high-quality seedless grapevine berry.