The transcription factor VviNAC60 regulates senescence- and ripening-related processes in grapevine

Authors: D'INCA, ERICA - University Of Verona; FORESTI, CHIARA - University Of Verona; ORDUNA, LUIS - University Of Valencia; AMATO, ALLESANDRA - University Of Valencia; VANDELLE, ELODIE - University Of Verona; SANTIAGO, ANTONIO - University Of Valencia; BOTTON, ALESSANDRO - Universita Di Padova; CAZZANIGA, STEFANO - University Of Verona; BERTINI, EDUARDO - University Of Verona; PEZZOTTI, MARIO - University Of Verona; Giovannoni, James; VREBALOV, JULIA - Cornell University; MATUS, JOSE THOMAS - University Of Valencia; TORNIELLI, GIOVANNI - University Of Verona; ZENONI, SARA - University Of Verona

Submitted to: Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/11/2022
Publication Date: 1/30/2023
Citation: D'Inca, E., Foresti, C., Orduna, L., Amato, A., Vandelle, E., Santiago, A., Botton, A., Cazzaniga, S., Bertini, E., Pezzotti, M., Giovannoni, J.J., Vrebalov, J., Matus, J., Tornielli, G., Zenoni, S. 2023. The transcription factor VviNAC60 regulates senescence- and ripening-related processes in grapevine. Plant Physiology. 192(3):1928-1946. https://doi.org/10.1093/plphys/kiad050.
DOI: https://doi.org/10.1093/plphys/kiad050

Interpretive Summary: Grapevine (Vitis vinifera L.) is one of the oldest and most widely cultivated fruit crops in the world. Grape berry development consists of 2 phases of growth: the first, namely “berry formation” or “vegetative/herbaceous phase”, involves pericarp growth due to rapid cell division and elongation; while the second, “ripening”, involves physical and metabolic changes, including accumulation of sugars, loss of organic acids, softening, skin pigmentation, and synthesis of volatile aromas. Ripening is accomplished by chlorophyll degradation, secondary metabolite accumulation and cell wall breakdown and dismantling and involve at least some common signaling and regulatory factors including ethylene and transcription factors. At the molecular level, it has been shown that members of the NAC transcription factor family play key roles in the regulation of leaf senescence and fruit ripening by interacting with other transcription factors, hormones, and environmental signals. Tomato (Solanum lycopersicum) NON-RIPENING (NOR) was the first NAC described as a master regulator of fruit ripening. Here, we present a functional characterization of VviNAC60, a grape homolog of the tomato NOR gene, through combined DNA-binding, transcriptome activity, and functional analyses. Heterologous expression of the VviNAC60 in the tomato nor mutant rescued nor mutation at the same level as the tomato NOR gene. These results define VviNAC60 as a player of the regulatory network controlling processes related to organ senescence and ripening and a target for modification/breeding toward fruit quality in grapevine.

Technical Abstract: Grapevine (Vitis vinifera L.) is one of the most widely cultivated fruit crops because the winemaking industry has huge economic relevance worldwide. Uncovering the molecular mechanisms controlling the developmental progression of plant organs will prove essential for maintaining high-quality grapes, expressly in the context of climate change, which impairs the ripening process. Through a deep inspection of transcriptomic data, we identified VviNAC60, a member of the NAC transcription factor family, as a putative regulator of grapevine organ maturation. We explored VviNAC60 binding landscapes through DNA affinity purification followed by sequencing and compared bound genes with transcriptomics datasets from grapevine plants stably and transiently overexpressing VviNAC60 to define a set of high-confidence targets. Among these, we identified key molecular markers associated with organ senescence and fruit ripening. Physiological, metabolic, and promoter activation analyses showed that VviNAC60 induces chlorophyll degradation and anthocyanin accumulation through the upregulation of STAY-GREEN PROTEIN 1 (VviSGR1) and VviMYBA1, respectively, with the latter being upregulated through a VviNAC60–VviNAC03 regulatory complex. Despite sharing a closer phylogenetic relationship with senescence-related homologs to the NAC transcription factor AtNAP, VviNAC60 complemented the nonripening(nor) mutant phenotype in tomato (Solanum lycopersicum), suggesting a dual role as an orchestrator of both ripening- and senescence-related processes. Our data support VviNAC60 as a regulator of processes initiated in the grapevine vegetative- to mature-phase organ transition and therefore as a potential target for enhancing the environmental resilience of grapevine by fine-tuning the duration of the vegetative phase.