On the mechanism of dormancy release in grapevine buds: a comparative study between hydrogen cyanamide and sodium azide

Abstract

Sodium azide (NaN 3 ), a well-known inhibitor of mitochondrial respiration, stimulated bud-dormancy release in grapevines similar to hydrogen cyanamide (HC), while HC, a well-known dormancy release agent, inhibited the O 2 uptake in isolated grape bud mitochondria similarly to NaN 3 . Additionally, both chemicals induced transcript expression of the antioxidative enzyme glutathione reductase and glucose-6-phosphate-dehydrogenase (G6PD), therefore upregulated the ascorbate-glutathione cycle (AGC) and the pentose phosphate pathway, respectively. As a result of AGC activation, the ratio of reduced to oxidized glutathione (GSH/GSSG) increased. Both stimuli also upregulated the transcription of 1,3-b-D-glucanase, a key enzyme in dormancy release. Together, these data support mechanistic connection between impaired Mit function and dormancy release, and suggests that as a consequence of O 2 deprivation, increases in glycolysis and in ethanolic fermentation could be responsible for activation of downstream stages in the dormancy release mechanisms.

Effects of hydrogen cyanamide on antioxidant enzymes’ activity, proline and polyamine contents during bud dormancy release in Superior Seedless grapevine buds

“…Such situation is most likely to activate the oxidative pentose phosphate pathway (PPP), a major source of NADPH in non-photosynthetic tissues (Tian et al 1998). This idea is supported by the activation of PPP in response to HC as reflected by a high expression of genes encoding G6PDH during bud endodormancy release in grapevines (Pérez et al 2009;Vergara and Pérez 2010) and kiwi vines (Walton et al 2009). The activation of PPP in response to oxidative stress generates more NADPH for proline biosynthesis and other pathways including antioxidant responses involving peroxidases (Shetty and Wahlqvist 2004).…”

“…Therefore, the transient induction of proline synthesis and POD and APX activity, recorded here, may be associated with the induction of AGC and PPP during dormancy release. In this regard, it was proposed that the rise of H 2 O 2 , owing to both transient CAT inhibition and respiratory perturbation, and its subsequent degradation by the AGC and the activation of the PPP could be crucial steps in the breakage of endodormancy triggered by HC (Halaly et al 2008;Pérez et al 2009;Ophir et al 2009). Based on the above findings, we can hypothesize that the stimulation of proline-linked PPP may be operating through dormancy release induced by HC.…”

Breaking Dormancy of “Tupy” Blackberry in Subtropical Conditions

“…Hydrogen cyanamide has been reported by different authors as the most effective compound for breaking bud dormancy, for anticipation and standardization of budding, flowering and harvest. The application of nitrogen compounds such as Sodium Nitrate (NaN 3 ) and hydrogen cyanamide can cause respiratory and oxidative stress in the bud cells, which results incellular metabolic rearrangement, increasing ATP generation by glycolysis and fermentation, a necessary step for activating a cascade effect on the mechanism to break dormancy [11]. The presence of nitrogen in different forms in the composition of Erger ® nitrogen fertilizer can lead to respiratory stress, such as with hydrogen cyanamide, accelerating the dormancy breaking process of the plants.…”

Treatment of potato tubers with the synthetic cytokinin 1-(α-ethylbenzyl)-3-nitroguanidine results in rapid termination of endodormancy and induction of transcripts associated with cell proliferation and growth

“…Release of dormancy in Vitus vinifera with hydrogen cyanamide has been shown to specifically alter transcripts encoding for proteins involved with the ascorbateglutathione cycle (Pérez et al 2009). Unlike potato, these species respond to both photoperiod and temperature as cues for dormancy cessation.…”