| Summary: | 博士 === 國立嘉義大學 === 農業科學博士學位學程 === 104 === Hydrogen 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.
The 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.
Our 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.
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