The MYB5‐driven MBW complex recruits a WRKY factor to enhance the expression of targets involved in vacuolar hyper‐acidification and trafficking in grapevine

Abstract

† These authors contributed equally to this work. SUMMARYThe accumulation of secondary metabolites and the regulation of tissue acidity contribute to the important traits of grape berry and influence plant performance in response to abiotic and biotic factors. In several plant species a highly conserved MYB-bHLH-WD (MBW) transcriptional regulatory complex controls flavonoid pigment synthesis and transport, and vacuolar acidification in epidermal cells. An additional component, represented by a WRKY-type transcription factor, physically interacts with the complex increasing the expression of some target genes and adding specificity for other targets. Here we investigated the function of MBW(W) complexes involving two MYBs (VvMYB5a and VvMYB5b) and the WRKY factor VvWRKY26 in grapevine (Vitis vinifera L.). Using transgenic grapevine plants we showed that these complexes affected different aspects of morphology, plant development, pH regulation, and pigment accumulation. Transcriptomic analysis identified a core set of putative target genes controlled by VvMYB5a, VvMYB5b, and VvWRKY26 in different tissues. Our data indicated that VvWRKY26 enhances the expression of selected target genes induced by VvMYB5a/b. Among these targets are genes involved in vacuolar hyper-acidification, such as the P-type ATPases VvPH5 and VvPH1, and trafficking, and genes involved in the biosynthesis of flavonoids. In addition, VvWRKY26 is recruited specifically by VvMYB5a, reflecting the functional diversification of VvMYB5a and VvMYB5b. The expression of MBWW complexes in vegetative organs, such as leaves, indicates a possible function of vacuolar hyper-acidification in the repulsion of herbivores and/or in developmental processes, as shown by defects in transgenic grape plants where the complex is inactivated.

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

“…The pK7WG2.0 vectors containing 35S:VviNAC33, VviNAC33-EAR or the eGFP sequence (negative control) were transferred to A. tumefaciens strain EHA105 by electroporation. The genetic transformations were performed as described by Amato et al (2019).…”

“…The VviNAC33 (1320 bp), SGR1 (1558 bp), ATG8f (1616 bp), RopGEF1 (1604 bp), PIN1 (1637 bp) and ATPC1 (1573 bp) promoter regions were amplified by PCR from cv Corvina genomic DNA using KAPA HiFi DNA polymerase. The cloning steps and Dual Luciferase Reporter Assay were carried out as described by Amato et al (2019), using as effector vectors 35S: VviNAC33 with 35S:VviWRKY19 (VIT_07s0005g01710) and 35S:VvibHLH75 (VIT_17s0000g00430), both previously reported by Fasoli et al (2018). Mean AE SD of four biological replicates was calculated.…”

Effects of Grape Polyphenols on the Life Span and Neuroinflammatory Alterations Related to Neurodegenerative Parkinson Disease-Like Disturbances in Mice

“…These compounds are also found in vegetables and seeds of different crops, but in lower concentrations [6,7]. In plants, 2 of 14 polyphenols are secondary metabolites participating in plant protection from a wide range of biotic and abiotic stress factors [8,9].…”

The proanthocyanin-related transcription factors MYBC1 and WRKY44 regulate branch points in the kiwifruit anthocyanin pathway

“…Petunia PH3 and Arabidopsis TTG2, homologous to kiwifruit WRKY44, were able to bind to the WD40 protein of the MBW complex and formed a MBW-W complex required to transcriptionally activate the target genes involved in vacuolar acidification (petunia) and hair development (Arabidopsis 39 ). In grapevine, VvWRKY26, a homologue of petunia PH3 and AtTTG2, is recruited specifically by the VvMYB5a driven MBW complex to enhance the expression of target genes involved in vacuolar acidification, probably via the formation of a MBW-WRKY complex 40 . In kiwifruit, WRKY motifs are located in close proximity to the MYB and bHLH binding motifs on F3′H and F3′5′H promoters, suggesting the possible binding of the MBW-WRKY complex on the promoters for transcriptional activation (Fig.…”

“…In petunia flower petals, the gene PH3 encodes for a WRKY TF that is highly similar to Arabidopsis TTG2, and regulates vacuolar acidification by binding to the MBW complex that transcriptionally activates a vacuolar ATPase 39 . Further investigation has revealed that the grape VvWRKY26, a homologue to petunia PH3 and Arabidopsis TTG2, is recruited by the VvMYB5a to form a MBW-WRKY complex and enhances the transcription of a set of target genes that are involved in vacuolar hyper-acidification 40 . The VvMYB5 gene competes with the anthocyanin activator VvMYBA in the MBW complex and reduces its ability to promote anthocyanin accumulation.…”