Hypoxia and hydrogen cyanamide induce bud-break and up-regulate hypoxic responsive genes (HRG) and VvFT in grapevine-buds.

It has been reported that dormancy-breaking compound hydrogen cyanamide (HC) stimulates the fermentative pathway and inhibits respiration in grapevine-buds, suggesting in this way, that a respiratory stress must be involved in the release of buds from dormancy. Here, we tested low-oxygen effect (hypoxia) on the bud-break response of endodormant grapevine buds, and HC and hypoxia effects on the expression of hypoxic responsive genes (HRG) PYRUVATE DECARBOXYLASE (VvPDC), ALCOHOL DEHYDROGENASE (VvADH2), SUCROSE SYNTHASE (VvSUSY), non-symbiotic HEMOGLOBIN (VvnsHb), and on FLOWERING LOCUS T (VvFT), a transcription factor related to dormancy release in Vitis. Hypoxia as HC, induce transiently the expression of HRG and VvFT and hasten the sprouting of endodormant grapevine-buds. During the first 24 h after treatment, HRG and VvFT were strongly induced by hypoxia, subsequently, their expressions fell, and 14 days post-treatment increased again above control levels. These results indicate that in the short-term, a respiratory stress, caused either by oxygen deprivation or by inhibitors of respiration, induces transiently the expression of HRG and VvFT, and in the long-term, along with the advancement of bud-break, the expression of these genes move forward in treated buds, suggesting that these second induction that occurs just before bud-break is developmentally regulated.