VviNAC33 promotes organ de‐greening and represses vegetative growth during the vegetative‐to‐mature phase transition in grapevine

Abstract

Plants undergo several developmental transitions during their life cycle. In grapevine, a perennial woody fruit crop, the transition from vegetative/green to mature/woody growth involves transcriptomic reprogramming orchestrated by a small group of genes encoding regulators, but the underlying molecular mechanisms are not fully understood. We investigated the function of the transcriptional regulator VviNAC33 by generating and characterizing transgenic overexpressing grapevine lines and a chimeric repressor, and by exploring its putative targets through DAP‐seq approach combined with transcriptomic data. We demonstrated that VviNAC33 induces leaf de‐greening, inhibits organ growth and directly activates the expression of STAY‐GREEN PROTEIN 1 (SGR1), involved in chlorophyll and photosystem degradation, and AUTOPHAGY 8f (ATG8f) involved in the maturation of autophagosomes. Furthermore, we show that VviNAC33 directly inhibits AUXIN EFFLUX FACILITATOR PIN1 and RopGEF1 and ATP SYNTHASE GAMMA CHAIN 1T (ATPC1) involved in photosystem II integrity and activity. Our results show that VviNAC33 plays a major role in terminating photosynthetic activity and organ growth as part of a regulatory network governing the vegetative‐to‐mature phase transition.