Abscisic Acid Is a Major Regulator of Grape Berry Ripening Onset: New Insights into ABA Signaling Network

Abstract

Grapevine is a world-wide cultivated economically relevant crop. The process of berry ripening is non-climacteric and does not rely on the sole ethylene signal. Abscisic acid (ABA) is recognized as an important hormone of ripening inception and color development in ripening berries. In order to elucidate the effect of this signal at the molecular level, pre-véraison berries were treated ex vivo for 20 h with 0.2 mM ABA and berry skin transcriptional modulation was studied by RNA-seq after the treatment and 24 h later, in the absence of exogenous ABA. This study highlighted that a small amount of ABA triggered its own biosynthesis and had a transcriptome-wide effect (1893 modulated genes) characterized by the amplification of the transcriptional response over time. By comparing this dataset with the many studies on ripening collected within the grapevine transcriptomic compendium Vespucci, an extended overlap between ABA- and ripening modulated gene sets was observed (71% of the genes), underpinning the role of this hormone in the regulation of berry ripening. The signaling network of ABA, encompassing ABA metabolism, transport and signaling cascade, has been analyzed in detail and expanded based on knowledge from other species in order to provide an integrated molecular description of this pathway at berry ripening onset. Expression data analysis was combined with in silico promoter analysis to identify candidate target genes of ABA responsive element binding protein 2 (VvABF2), a key upstream transcription factor of the ABA signaling cascade which is up-regulated at véraison and also by ABA treatments. Two transcription factors, VvMYB143 and VvNAC17, and two genes involved in protein degradation, Armadillo-like and Xerico-like genes, were selected for in vivo validation by VvABF2-mediated promoter trans-activation in tobacco. VvNAC17 and Armadillo-like promoters were induced by ABA via VvABF2, while VvMYB143 responded to ABA in a VvABF2-independent manner. This knowledge of the ABA cascade in berry skin contributes not only to the understanding of berry ripening regulation but might be useful to other areas of viticultural interest, such as bud dormancy regulation and drought stress tolerance.

VlbZIP30 of grapevine functions in dehydration tolerance via the abscisic acid core signaling pathway

“…To investigate the potential roles of the 35 identified grapevine genes in ABA and drought stress, two different grapevine-related databases for ABA 1 and drought stress 34 treatments were analyzed. RNA-Seq analysis was performed of grapevine berry skins with or without ABA treatment for 20 and 44 h. A GrapeGene GeneChips ® data analysis was performed on leaves from two Vitis vinifera L. varieties (Trincadeira, TR, and Touriga Nacional, TN) grown under control and drought greenhouse conditions, as well as fully irrigated and non-irrigated field conditions.…”

“…In contrast, there has been little characterization of the 35 grapevine genes, and only 3 were identified as being involved in ABA or drought stress signaling. ABF2/bZIP39 (VIT_18s0001g10450), which was characterized as being involved in ABA signaling in grapevine cell culture, has been reported to transiently trans-activate the expression of NAC17 (VIT_19s0014g03290) and PUB19 (VIT_17s0000g08080) following ABA treatment 1,36 . In addition, overexpression of this gene in A. thaliana enhances tolerance to drought stress through the ABA signaling pathway 22 , suggesting that NAC17 and PUB19 may enhance drought stress in grapevine.…”

“…The heat maps were constructed using HemI software 33 . To identify the predicted grapevine genes, two grapevine-related ABA 1 and drought stress 34 databases were downloaded from the National Center for Biotechnology Information (NCBI) under BioProject accession number PRJNA369777 and the Gene Expression Omnibus database under the number GSE57669.…”

“…Grapevines are among the world’s major fruit crops, and their fruits can be consumed fresh or dried, be processed into wines, spirits, and vinegar, or be transformed into pharmaceutical products that promote human health 1 . However, abiotic stress, such as drought, perturb the metabolism and growth of grapevines, leading to a loss of yield and reduced fruit quality 2 .…”

VlbZIP30 of grapevine functions in drought tolerance via the abscisic acid core signaling pathway

“…Grapevines are amongst the world’s major fruit crops, and their fruits can be consumed either fresh or dried or be processed into wines, spirits and vinegar, or transformed into pharmaceutical products that promote human health (Pilati et al , 2017). However, abiotic stress, such as drought, perturb the metabolism and growth of grapevines, leading to a loss of yield and reduced fruit quality (Ferreira et al , 2004).…”