Abscisic acid catabolism enhances dormancy release of grapevine buds

Abstract

The molecular mechanism regulating dormancy release in grapevine buds is as yet unclear. It was formerly proposed that dormancy is maintained by abscisic acid (ABA)-mediated repression of bud-meristem activity and that removal of this repression triggers dormancy release. It was also proposed that such removal of repression may be achieved via natural or artificial up-regulation of VvA8H-CYP707A4, which encodes ABA 8'-hydroxylase, and is the most highly expressed paralog in grapevine buds. The current study further examines these assumptions, and its experiments reveal that (a) hypoxia and ethylene, stimuli of bud dormancy release, enhance expression of VvA8H-CYP707A4 within grape buds, (b) the VvA8H-CYP707A4 protein accumulates during the natural transition to the dormancy release stage, and (c) transgenic vines overexpressing VvA8H-CYP707A4 exhibit increased ABA catabolism and significant enhancement of bud break in controlled and natural environments and longer basal summer laterals. The results suggest that VvA8H-CYP707A4 functions as an ABA degrading enzyme, and are consistent with a model in which the VvA8H-CYP707A4 level in the bud is up-regulated by natural and artificial bud break stimuli, which leads to increased ABA degradation capacity, removal of endogenous ABA-mediated repression, and enhanced regrowth. Interestingly, it also hints at sharing of regulatory steps between latent and lateral bud outgrowth.

Transcriptome analysis reveals a complex array of differentially expressed genes accompanying a source‐to‐sink change in phytoplasma‐infected sweet cherry leaves

“…In plants, abscisic acid (ABA) plays a crucial role in regulating bud dormancy including its induction, maintenance and release (Lenton, Perry, & Saunders, ; Zheng et al, , ). ABA also plays an important role in host–pathogen interactions (Mohr & Cahill, ; Qi et al, ).…”

ABA‐responsive ABRE‐BINDING FACTOR3 activatesDAM3expression to promote bud dormancy in Asian pear

“…Pear and apple dormancy is induced by low temperatures rather than the photoperiod (Heide and Prestrud ), whereas in poplar, short‐day conditions induce dormancy (Olsen et al, ). Although the environmental cues for establishing dormancy vary among species, ABA is considered to be the key phytohormone for dormancy induction and maintenance (Li, Xu, et al, ; Tylewicz et al, ; Zheng, Acheampong, Shi, Mugzech, et al, ). In poplar, ABA signaling promotes plasmodesmata closure, which is a crucial process during dormancy in response to short‐day conditions (Tylewicz et al, ), and helps regulate the onset of bud dormancy.…”

“…However, a long‐term exposure to low temperatures leads to endo‐dormancy release and a decrease in the ABA content of buds, likely due to the downregulated expression of ABA biosynthesis genes ( XERICO and NECD ) and the upregulated expression of an ABA catabolism gene ( CYP707A ) (Li et al, ; Zheng et al, ). The overexpression of VvCYP707A4 in grape decreases the ABA level and significantly enhances bud break (Zheng et al, ). Thus, ABA is involved in dormancy maintenance.…”

Physiological regulation of bud burst in grapevine

“…Our results suggested that the primary perception and signal cascade to initiate bud burst arises within the bud and are independent of de novo transport of phytohormones or other mobile elements from the cane. In fact, very recently, the induction of in situ catabolism of ABA was demonstrated to be essential for bud break in grapevine (Zheng et al , 2018). Moreover, the authors showed that the transgenic expression of the ABA catabolic enzyme VvA8H-CYP707A4 resulted in enhancement of bud break in grapevine, and reduced apical dominance (Zheng et al , 2018).…”

“…In fact, very recently, the induction of in situ catabolism of ABA was demonstrated to be essential for bud break in grapevine (Zheng et al , 2018). Moreover, the authors showed that the transgenic expression of the ABA catabolic enzyme VvA8H-CYP707A4 resulted in enhancement of bud break in grapevine, and reduced apical dominance (Zheng et al , 2018). Also recently, a transcriptomic study on Prunus mume suggested that low temperature results in the up-regulation of C-repeat binding factor genes, which directly promotes six dormancy associated MADS-box genes to establish dormancy.…”