Characterization and regulatory mechanism analysis of VvmiR156a–VvAGL80 pair during grapevine flowering and parthenocarpy process induced by gibberellin

Abstract

MicroRNA156 (miR156) is an important conserved miRNA family in plants. Recently, we revealed VvmiR156a could involve in the modulation of gibberellin (GA)‐mediated flower and berry development process of grapevine (Vitis vinifera L.). However, how to manipulate this process is unclear. For this, we used the GA‐induced grapevine parthenocarpy system to investigate the regulatory roles of VvmiR156a during this process. Here, we cloned the mature and precursor sequences of VvmiR156a in Wink grape and identified its potential target gene VvAGL80, which belongs to the MADS‐box gene family. Moreover, using RNA ligase‐mediated 5′ rapid amplification of cDNA ends (RLM‐RACE) and poly(A)polymerase‐mediated 3′ rapid amplification of cDNA (PPM‐RACE) technologies, it confirmed that VvAGL80 was the true target gene of VvmiR159a. Analysis of promoter cis‐elements and β‐glucuronidase (GUS) staining showed that both VvmiR156a and VvAGL80 contained GA‐responsive elements and could respond to GA treatments. Quantitative real‐time–polymerase chain reaction (qRT‐PCR) analysis exhibited the VvmiR156a and VvAGL80 showed opposite expression trends during grapevine flower and berry development, indicating that VvmiR156a negatively regulated the expression of VvAGL80 during this process. After GA treatment, the expression of miR156 in flowers was downregulated significantly, while that of VvAGL80 was upregulated, thereby accelerating grapevine flowering. Furthermore, GA treatment enhanced the negative regulation of VvmiR156a on VvAGL80 in seed, especially at the seed‐coat hardening stage, which was the key period of seed growth and development. Our findings enriched the knowledge of the regulatory mechanism of the miRNA‐mediated grapevine parthenocarpy process.

Effect of GA₃ Treatment on Berry Development in the Large Berry Mutant of ‘Delaware’ Grapes

“…These results suggest that, just after the first and around the second GA 3 treatment period, the LBM berries have a higher sensitivity than the 'Delaware' berries. Although previous studies on seedless grapes with GA 3 treatment reported differential downstream gene expression of the DELLA proteins in GA signaling (Arro et al, 2019;Cui et al, 2020;Su et al, 2021), no study has yet focused on the high GA sensitivity of grape berries. LBM has characteristics of high GA sensitivity, therefore this study revealed that the high expression of the GA receptor gene may be responsible for the increased GA sensitivity.…”

“…Comprehensive gene expression analysis revealed that VvmiRNA159 regulates GA signaling in floral development (Wang et al, 2018). VvmiR156a negatively regulated VvAGL80 after GA 3 treatment, which promoted grape blooming (Su et al, 2021). Pre-bloom GA and auxin treatment facilitated grape berry parthenocarpy by downregulation of VvIAA9 and VvARF7 via DELLA (Jung et al, 2014).…”