Dormancy-Associated MADS-Box (DAM) Genes Influence Chilling Requirement of Sweet Cherries and Co-Regulate Flower Development with SOC1 Gene

Abstract

Floral bud dormancy release of fruit tree species is greatly influenced by climate change. The lack of chilling accumulation often results in the occurrence of abnormal flower and low yields of sweet cherries (<i>Prunus avium</i> L.) in warm regions. To investigate the regulation of dormancy in sweet cherries, six <i>DAM</i> genes with homology to peach <i>DAM</i>, designated <i>PavDAM1-6</i>, have been identified and characterized. Phylogenetic analysis indicate that these genes are similar to <i>DAMs</i> in peach, apple and pear. The expression patterns of the <i>PavDAMs</i> in the low-chill cultivar 'Royal Lee' were different from that in the high-chill cultivar 'Hongdeng'. 'Royal Lee' exhibits lower transcriptional level of <i>PavDAM1</i> compared to 'Hongdeng', especially at the stage of chilling accumulation, and transcriptional levels of <i>PavDAM4/5</i> were high in both cultivars during the endodormancy. Ectopic expression of <i>PavDAM1</i> and <i>PavDAM5</i> in <i>Arabidopsis</i> resulted in plants with abnormal flower and seed development, especially the <i>PavDAM5</i>. Higher transcriptional levels of <i>SOC1</i> were observed in transgenic <i>PavDAM1/5</i> lines, and ectopic expression of <i>PavSOC1</i> had the similar floral phenotype. Further, protein interaction analysis demonstrated that PavDAM1/5 could interact with PavSOC1 in vivo and in vitro, which will help clarify the molecular mechanism of the flower development in sweet cherry or other fruit trees.