Anthocyanins are the primary color components of grapevine berries and wines. In cultivation practices, a moderate water deficit can promote anthocyanin accumulation in red grape skins. Our previous study showed that abscisic acid (ABA) plays a key role in this process. Herein, we identified a microRNA, vv-miR156b, that is generated in grapevine berries in response to drought stress, along with increasing anthocyanin content and biosynthetic structural gene transcripts. In contrast, vv-miR156b short tandem target mimic (STTM) function-loss callus exhibits the opposite phenotype. Results from in vivo and in vitro experiments revealed that the ABA-signaling-regulated transcription factor VvAREB2 binds directly to the ABA-responsive element (ABRE) of the MIR156b promoter and activates miR156b expression. Furthermore, two miR156b downstream targets, VvSBP8 and VvSBP13, exhibited reduced grape anthocyanin content in their overexpressors but there was a contrary result in their CRISPR-edited lines, the decrease in anthocyanin content was rescued in miR156b and SBP8/13 double overexpressors. We further demonstrated that both VvSBP8 and VvSBP13, encoding transcriptional repressors, displayed sufficient ability to interact with VvMYC1 and VvMYBA1, thereby interfering with MYB-bHLH-WD (MBW) repeat transcriptional complex formation, resulting in the repression of anthocyanin biosynthesis. Our findings demonstrate a direct functional relationship between ABA signaling and the miR156-SBP-MBW complex regulatory module in driving drought-induced anthocyanin accumulation in grape berries.

Summary: Phytochromes are photoreceptors enabling plants to respond to various light conditions. Independent gene duplications resulted in small phytochrome families in mosses, ferns and seed plants. This phytochrome diversity is hypothesised to be critical for sensing and adapting to different light conditions, but experimental evidence for this idea is lacking for mosses and ferns. The moss model species Physcomitrium patens contains seven phytochromes grouped into three clades, PHY1/3, PHY2/4 and PHY5. Here, we used CRISPR/Cas9‐generated single and higher order mutants to investigate their role in light regulation of protonema and gametophore growth, protonema branching and induction of gametophores. We found both specific and partially overlapping roles for the three phytochrome clades in regulating these responses in different light conditions. PHY1/3 clade phytochromes act as primary far‐red light receptors, while PHY5 clade phytochromes are the primary red light receptors. PHY2/4 clade phytochromes have functions in both red and far‐red light. We also observed that PHY1/3 and PHY2/4 clade phytochromes promote gametophore growth in simulated canopy shade and also play a role in blue light. Similar to seed plants, gene duplications in the phytochrome lineage in mosses were followed by functional diversification into red and far‐red light‐sensing phytochromes.