Expression analysis of ABA- and GA-related genes during four stages of bud dormancy in Japanese apricot (Prunus mumeSieb. et Zucc)

Seasonal dormancy in deciduous fruit trees is a complex physiological state, which is regulated by many plant hormones and genes. Abscisic acid (ABA) and gibberellic acid (GA3) are known to be particularly important in controlling dormancy. We measured the concentrations of these two hormones in flower buds (collected during para-, endo-, and eco-dormancy, and at the dormancy-release stage) and vegetative buds (collected monthly from 20 November 2012 to 20 February 2013) of two cultivars of Japanese apricot (Prunus mume Sieb. et Zucc), ‘Bungo’ and ‘Taoxingmei’, using liquid chromatography and tandem mass spectrometry (LC–MS/MS). Levels of expression of two zinc-finger family genes CCCH and C2H2 and the GA20ox (gibberellin 20 oxidase) gene (GenBank Accession No. Pm013607), as candidates for dormancy-controlling genes, were analysed at each sampling time using real-time RT-quantitative PCR (RT-qPCR). Expression analyses indicated that both zinc-finger family genes exhibited high transcript levels in flower buds of both cultivars during para-dormancy, concomitant with high ABA concentrations. The zinc-finger family genes were relatively highly expressed in vegetative buds of both cultivars on 20 November 2012 (autumn). In addition, high concentration of GA3 in flower buds at the dormancy-release stage suggested that GA3 plays an important role in controlling the release of bud dormancy. High levels of expression of the GA20ox gene during eco-dormancy and at the dormancy-release stage might have a prominent effect on dormancy-release by regulating gibberellin (GA) signalling in Japanese apricot. These results will contribute to increasing our understanding of ABA- and GA-mediated seasonal dormancy mechanisms in Japanese apricot.