Effects of chilling accumulation on DORMANCY-ASSOCIATED MADS-box gene expressions in ‘Satonishiki’ sweet cherry

Abstract

Bud dormancy allows most temperate fruit tree species, including sweet cherry (Prunus avium), to avoid cold injury and synchronize their annual growth patterns. The progression of bud dormancy release is influenced by environmental factors, including chilling accumulation. Global climate changes may affect bud dormancy release, resulting in an irregular bud break. Thus, a more thorough characterization of dormancy is required. The peach (Prunus persica) and Japanese apricot (Prunus mume) genomes contain at least six DORMANCY-ASSOCIATED MADS-box (DAM) genes that may have important roles related to bud dormancy regulation. The DAM gene expression levels are diverse among species. For example, peach DAM1, 2, and 4 expression levels are up-regulated during terminal bud formation, while peach and P. mume DAM5 and 6 expression levels are down-regulated during dormancy release. In this study, we first identified six sweet cherry DAM genes (PavDAM1-6) by mapping short-read transcript sequences for dormant 'Satonishiki' flower buds against reference gene sequences (PmDAM1-6). We then conducted quantitative real-time polymerase chain reaction analyses of PavDAM4-6 expression in 'Satonishiki' lateral buds collected at low-, medium-, and high-chill regions in Japan between November and March. PavDAM4 expression was first up-regulated as chilling accumulated and then down-regulated. In contrast, PavDAM6 expression was down-regulated from November onward. The expression of PavDAM4 was up-regulated faster at high- and medium-chill locations than at the low-chill location where chilling accumulated slowly. The PavDAM5-6 expression patterns were similar at all three locations. These results suggest that chilling treatments induce distinct changes to the expression of PavDAM genes.