The Effect of Hydrogen Cyanamide on Dormancy Breaking In Grapevine Buds: Reactive Oxygen Species Accumulation and Related Genes Expression

Abstract

Hydrogen cyanamide (HC) and pruning have frequently been used to break dormancy in grapevine floral buds. This study aimed to address the effects of these treatments on accumulation of ROS and alteration in expression of ROS-related genes in the dormancy breaking buds of grapevine in the summer in sub/tropical. Four treatments were compared, namely: Pruning (P), hydrogen cyanamide (HC), Pruning and hydrogen cyanamide (PHC) and Control (water) and 8 days after treatment the bud break rates were 33%, 53%, 95%, and 0%, respectively. Clearly, HC is effective in stimulating grapevine bud break and pruning further enhanced its potency. In situ detection of various Reactive oxygen species (ROS) and Nitric oxide (NO) in longitudinal bud sections after 12 h of treatments showed that high levels of ROS and NO accumulate in the buds treated with PHC, compared with HC or P only. The amounts of ROS and NO accumulated were closely correlated with the rates of bud break among the treatments. Microarray analysis was conducted with the dormancy breaking buds after 24 h of treatments. Gene ontology (GO) analysis indicated that alteration in expression of ROS related genes is the major factor responsible for bud break. PHC treatment gave rise to dynamic changes in highly up-/down-regulation of antioxidant activity at 24 h post-treatment. Twelve genes were identified as key genes involved in dormancy bud break in the early response. The time course of expression of these genes (examined by qRT-PCR) showed different expression during the 48 h treatment. It is concluded that accumulation of ROS at the early stage is important for dormant bud break, and that the microarray analysis of differentially expressed genes among the treatments allowed the construction of the model pathway related to ROS metabolisms during dormant bud breaking.