ABA Represses the Expression of Cell Cycle Genes and May Modulate the Development of Endodormancy in Grapevine Buds.

Ricardo Vergara,Francisco J Pérez,Karla Aravena,Humberto Prieto,Ximena Noriega

doi:10.3389/fpls.2017.00812

Abstract

Recently, the plant hormone abscisic acid (ABA) has been implicated as a key player in the regulation of endodormancy (ED) in grapevine buds (Vitis vinifera L). In this study, we show that in the vine, the expression of genes related to the biosynthesis of ABA (VvNCED1; VvNCED2) and the content of ABA are significantly higher in the latent bud than at the shoot apex, while the expression of an ABA catabolic gene (VvA8H3) showed no significant difference between either organ. A negative correlation between the content of ABA and transcript levels of cell cycle genes (CCG) was found in both tissues. This result suggested that ABA may negatively regulate the expression of CCG in meristematic tissues of grapevines. To test this proposition, the effect of ABA on the expression of CCG was analyzed in two meristematic tissues of the vine: somatic embryos and shoot apexes. The results indicated that cell cycle progression is repressed by ABA in both organs, since it down-regulated the expression of genes encoding cyclin-dependent kinases (VvCDKB1, VvCDKB2) and genes encoding cyclins of type A (VvCYCA1, VvCYCA2, VvCYCA3), B (VvCYCB), and D (VvCYCD3.2a) and up-regulated the expression of VvICK5, a gene encoding an inhibitor of CDKs. During ED, the content of ABA increased, and the expression of CCG decreased. Moreover, the dormancy-breaking compound hydrogen cyanamide (HC) reduced the content of ABA and up-regulated the expression of CCG, this last effect was abolished when HC and ABA were co-applied. Taken together, these results suggest that ABA-mediated repression of CCG transcription may be part of the mechanism through which ABA modulates the development of ED in grapevine buds.

Highlights

The central role of the plant hormone abscisic acid (ABA) in the control of seed dormancy is well established (Graeber et al, 2012)
Transcript levels of the ABA biosynthesis genes VvNCED1 and VvNCED2 were significantly more highly expressed in the latent buds than at the shoot apexes (Figure 1A), while transcript levels of ABA catabolic gene VvA8H3 showed no significant difference between either organ (Figure 1A)
The following cell cycle-related genes have been identified in the Vitis genome: three cyclin-dependent kinases (CDKs), VvCDKA, VvCDKB1, and VvCDKB2; two CDK inhibitors, VvICK5, VvICK7; two INHIBITOR OF CDK/KIP-RELATED PROTEIN (ICK)-like genes, VvICK3-like, VvICK7-like; three type A cyclins, VvCYCA1, VvCYCA2, and VvCYCA3; one type B cyclin, VvCYCB; and three type D cyclins, VvCYCD3.1, VvCYCD3.2a, and VvCYCD3.2b

Summary

Introduction

The central role of the plant hormone abscisic acid (ABA) in the control of seed dormancy is well established (Graeber et al, 2012). The participation of ABA in the development of endodormancy (ED) induced by a short-day (SD)-photoperiod has been proposed, as both the content of ABA and ABA biosynthesis related genes peaked after 3–4 weeks of SD-treatment. A SD photoperiod triggered the development of ED in grapevine buds (Kühn et al, 2009; Grant et al, 2013) and up-regulated the expression of ABA biosynthesis-related genes VvNCED1 and VvNCED2 (Parada et al, 2016). All this evidence supports the hypothesis that ABA promotes ED in grapevine buds. ABA and other hormones, such as gibberellins (GAs), auxin and cytokinin (CK) are well known to control the expression of CCG, which is certainly relevant in the development of ED (Campbell et al, 2014)

Methods

Results

Conclusion