Initiation of organ maturation and fruit ripening in grapevine is controlled by the CARPO-NAC transcription factor [Syrah]

In this study we identified the NAC family member VviCARPO (Controlled Adjustment of Ripening and maturation of Plant Organs) as a key regulator of grapevine maturation. We explored CARPO binding landscapes through DAP-seq and overlapped its bound genes with transcriptomics datasets from stable and transient CARPO overexpressing grapevine plants to narrow a set of high-confidence targets. Among these, we identified key molecular ripening markers. Physiological, metabolic and promoter activation analyses showed that CARPO induces chlorophyll degradation and anthocyanin accumulation through the up regulation of VviSGR1 and VviMYBA1, respectively, with the latter being up-regulated by a VviCARPO-VviNAC03 regulatory complex. CARPO complemented the nor mutant phenotype in tomato, suggesting it may have acquired a dual role as an orchestrator of both ripening- and senescence-related processes. Our results evidenced that CARPO is a master regulator of the grapevine vegetative-to-mature phase organ transition and therefore an essential target for insuring fruit quality and environmental resilience. Transcriptomic changes caused by the VviCARPO overexpression were inspected by a microarray analysis performed on leaf RNA of selected transgenic lines and control plants. Three biological replicates of fully expanded leaves were collected.