title: A Grapevine TTG2-Like WRKY Transcription Factor Is Involved in Regulating Vacuolar Transport and Flavonoid Biosynthesis.
abstract: A small set of TTG2-like homolog proteins from different species belonging to the WRKY family of transcription factors were shown to share a similar mechanism of action and to control partially conserved biochemical/developmental processes in their native species. In particular, by activating P-ATPases residing on the tonoplast, PH3 fromPetunia hybridapromotes vacuolar acidification in petal epidermal cells whereas TTG2 fromArabidopsis thalianaenables the accumulation of proanthocyanidins in the seed coat. In this work we functionally characterizedVvWRKY26identified as the closest grapevine homolog ofPhPH3andAtTTG2. When constitutively expressed in petuniaph3mutant, VvWRKY26 can fulfill the PH3 function in the regulation of vacuolar pH and restores the wild type pigmentation phenotype. By a global correlation analysis of gene expression and by transient over-expression inVitis vinifera, we showed transcriptomic relationships ofVvWRKY26with many genes related to vacuolar acidification and transport in grapevine. Moreover, our results indicate an involvement in flavonoid pathway possibly restricted to the control of proanthocyanidin biosynthesis that is consistent with its expression pattern in grape berry tissues. Overall, the results show that, in addition to regulative mechanisms and biological roles shared with TTG2-like orthologs, VvWRKY26 can play roles in fleshy fruit development that have not been previously reported in studies from dry fruit species. This study paves the way toward the comprehension of the regulatory network controlling vacuolar acidification and flavonoid accumulation mechanisms that contribute to the final berry quality traits in grapevine.
authors.affiliation: Department of Biotechnology, University of Verona Verona, Italy.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Amato
authors.affiliation: Department of Biotechnology, University of Verona Verona, Italy.
authors.forename: Erika
authors.initials: E
authors.lastname: Cavallini
authors.affiliation: Department of Biotechnology, University of Verona Verona, Italy.
authors.forename: Sara
authors.initials: S
authors.lastname: Zenoni
authors.affiliation: Department of Biotechnology, University of Verona Verona, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Finezzo
authors.affiliation: Department of Agriculture, Food, Natural Resources, Animals and Environment, University of Padova Padova, Italy.
authors.forename: Maura
authors.initials: M
authors.lastname: Begheldo
authors.affiliation: Department of Agriculture, Food, Natural Resources, Animals and Environment, University of Padova Padova, Italy.
authors.forename: Benedetto
authors.initials: B
authors.lastname: Ruperti
authors.affiliation: Department of Biotechnology, University of Verona Verona, Italy.
authors.forename: Giovanni Battista
authors.initials: GB
authors.lastname: Tornielli
keywords: WRKY; flavonoids; grapevine; petunia; vacuolar acidification