Regulatory role of DAM6 on lipid body accumulation and phytohormone metabolism in the dormant vegetative meristem.

Bud dormancy is a crucial process in the annual growth cycle of woody perennials. In Rosaceae fruit tree species, () transcription factor genes regulating bud dormancy have been identified, but their molecular roles in meristematic tissues have not been thoroughly characterized. In this study, molecular and physiological analyses of transgenic apple plants overexpressing the Japanese apricot gene () and Japanese apricot cultivars and F individuals with contrasting dormancy characteristics revealed the metabolic pathways controlled by PmDAM6. Our transcriptome analysis and transmission electron microscopy examination demonstrated that PmDAM6 promotes the accumulation of lipid bodies and inhibits cell division in the dormant vegetative meristem by down-regulating the expression of lipid catabolism genes ( and ) and genes, respectively. Our findings also indicate PmDAM6 promotes abscisic acid (ABA) accumulation and decreases cytokinin (CTK) accumulation in vegetative buds by up-regulating the expression of the ABA biosynthesis gene and the CTK catabolism gene , while also down-regulating the expression of the CTK biosynthesis genes () and . Additionally, PmDAM6 modulates gibberellin (GA) metabolism by up-regulating expression and down-regulating expression. Furthermore, PmDAM6 may also indirectly promote lipid accumulation and restrict cell division by limiting the accumulation of CTK and GA in buds. In conclusion, using our valuable genetic platform, we clarified how PmDAM6 modifies diverse cellular processes, including lipid catabolism, phytohormone (ABA, CTK, and GA) biosynthesis and catabolism, and cell division, in the dormant vegetative meristem.