The VviNAC33 acts a molecular switch by activating leaf degreening and repressing vegetative growth during the immature-to-mature phase transition in grapevine. The VviNAC33 acts a molecular switch by activating leaf degreening and repressing vegetative growth during the immature-to-mature phase transition in grapevine

In this study we demonstrated that the grapevine NAC transcription factor VviNAC33 is directly involved in leaf degreening and organ growth. Through the application of DAP-seq approach we identified several putative targets of VviNAC33, among which the SGR1 involved in the breakdown of chlorophyll. Stable VviNAC33 overexpressing transgenic plants displayed an obvious degreening effect on leaves and an inhibition of leaf growth. Consistently, transgenic plant expressing a chimeric repressor of the VviNAC33 showed the opposite phenotypic alterations. Our results evidenced that VviNAC33 is a direct player of leaf senescence program and propose a blueprint of the complex transcriptional regulatory network that govern organ phase transition in grapevine. Overall design: For transient transformation of Vitis vinifera cv. Sultana, the 35S:VviNAC33 construct was transferred to Agrobacterium tumefaciens strain C58C1 by electroporation. As control, Agrobacterium was also transformed with an empty pK7WG2 containing a non-coding sequence. Eight in vitro six-week-old plants of grapevine cv. Sultana for overexpression and seven for the control were immersed in each bacterial suspension and vacuum infiltrated (2 X 2 min at 90kPa). After agroinfiltration, plantlets were allowed to recover in vitro for seven days before collecting material for RNA extraction and transcriptomic analysis.