Hydrogen cyanamide breaks grapevine bud dormancy in the summer through transient activation of gene expression and accumulation of reactive oxygen and nitrogen species.

Chih-Sheng Chang,Yung-Fu Yen,Hsiu-Fung Chao,Maurice S B Ku,Boonyawat Sudawan

doi:10.1186/s12870-016-0889-y

Abstract

BackgroundHydrogen cyanamide (HC) and pruning (P) have frequently been used to break dormancy in grapevine floral buds. However, the exact underlying mechanism remains elusive. This study aimed to address the early mode of action of these treatments on accumulation of reactive oxygen species (ROS) and reactive nitrogen species (RNS) and expression of related genes in the dormancy breaking buds of grapevine in the summer.ResultsThe budbreak rates induced by pruning (P), hydrogen cyanamide (HC), pruning plus hydrogen cyanamide (PHC) and water (control) after 8 days were 33, 53, 95, and 0 %, respectively. Clearly, HC was more effective in stimulating grapevine budbreak and P further enhanced its potency. In situ staining of longitudinal bud sections after 12 h of treatments detected high levels of ROS and nitric oxide (NO) accumulated in the buds treated with PHC, compared with HC or P alone. The amounts of ROS and NO accumulated were highly correlated with the rates of budbreak among these treatments, highlighting the importance of a rapid, transient accumulation of sublethal levels of ROS and RNS in dormancy breaking. Microarray analysis revealed specific alterations in gene expression in dormancy breaking buds induced by P, HC and PHC after 24 h of treatment. Relative to control, PHC altered the expression of the largest number of genes, while P affected the expression of the least number of genes. PHC also exerted a greater intensity in transcriptional activation of these genes. Gene ontology (GO) analysis suggests that alteration in expression of ROS related genes is the major factor responsible for budbreak. qRT-PCR analysis revealed the transient expression dynamics of 12 specific genes related to ROS generation and scavenge during the 48 h treatment with PHC.ConclusionOur results suggest that rapid accumulation of ROS and NO at early stage is important for dormancy release in grapevine in the summer, and the identification of the commonly expressed specific genes among the treatments allowed the construction of the signal transduction pathway related to ROS/RNS metabolism during dormancy release. The rapid accumulation of a sublethal level of ROS/RNS subsequently induces cell wall loosening and expansion for bud sprouting.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-016-0889-y) contains supplementary material, which is available to authorized users.

Highlights

Hydrogen cyanamide (HC) and pruning (P) have frequently been used to break dormancy in grapevine floral buds
Budbreak rate After 8 days, the budbreak rates of dormant grapevine buds treated with P, HC (1 % or 12.5 mM hydrogen cyanamide), P and HC (PHC) (P + HC) and water were 33.3, 53.3, 95.3 and 0 %, respectively (Fig. 1a)
Four to five leaf primordia were visible at 12 h and the inflorescence meristem began to develop at 48 h (Fig. 1C-e), and the inflorescence primodia became well developed with complete floral meristem at 96 h post treatment (Fig. 1C-f )

Summary

Introduction

Hydrogen cyanamide (HC) and pruning (P) have frequently been used to break dormancy in grapevine floral buds. Grapevine grown in subtropical regions often exhibits non-uniform or delayed budbreak in early spring due to warm winter that provides inadequate chilling. This represents a major obstacle for the commercial production of table grapes. HC treatment on intact dormant buds in spring is an important grapevine orchard management practice to induce uniform budbreak. In Taiwan, a subtropical region, this treatment is a common practice in mid-summer for the second grapevine harvest in the winter, where paradormant buds on the pruned canes can be treated with HC to ensure effective budbreak. An understanding of the biochemical and molecular bases underlying the release of dormancy by HC is critical for commercial production of grapes in subtropical and tropical regions

Objectives

Methods

Results

Discussion

Conclusion