S11 - Session O2 - Dominant Functions of Japanese apricot PmDAM6 in Vegetative Bud Dormancy by the Controls of Multiple Hormone Metabolism, Lipid Accumulation and Cell Division

Authors: Tzu-Fan Hsiang *, Hisayo Yamane, Mei Gao-Takai, Ryutaro Tao

Bud dormancy plays an essential role in the annual growth cycle of woody perennials. We previously identified an SVP/AGL24 -clade MADS-box gene, DORMANCY-ASSOCIATED MADS box6 ( PmDAM6 ), expressed in dormant vegetative buds of Prunus mume. PmDAM6 has been shown to have a growth inhibition function during the dormancy induction stage and a bud break repression function during the dormancy maintenance stage. Transgenic analysis using PmDAM6 -overexpressing transgenic apple ( Malus × domestica ) ( 35S:PmDAM6 apple) and dexamethasone-inducible PmDAM6 -overexpressing transgenic apple ( 35S:PmDAM6-GR apple) indicated that these PmDAM6 functions were accompanied by the altered endogenous hormone levels. However, it remains unclear how PmDAM6 regulates hormone metabolism in dormant buds. Furthermore, the molecular role of Rosaceae DAM s on cellular metabolism of vegetative bud meristem during dormancy establishment is largely unknown. Here, we found that PmDAM6 promoted abscisic acid (ABA) biosynthesis and cytokinins catabolism by up-regulating Arabidopsis aldehyde oxidase 3 and Cytokinin dehydrogenase , respectively. We also found that PmDAM6 promoted gibberellins (GA) catabolism by directly up-regulating GA 2-Oxidase and indirectly via Agamous-like 15 regulation. To clarify how PmDAM6 is involved in cellular metabolism, we comparatively characterized cell structure of dormant vegetative meristem by using transmission electron microscopy in PmDAM6 -overexpressing transgenic apples and two genotypes of P. mume with contrasting PmDAM6 expression and dormancy characteristics. On the basis of cell structure and associated transcriptome changes, our study demonstrated that PmDAM6 promoted lipid body accumulation in dormant vegetative meristem through directly down-regulating a cluster of GDSL Esterase/Lipase genes during dormancy establishment and maintenance. Moreover, PmDAM6 repressed cell division activity by down-regulating Cyclins possibly through modulating cell wall integrity. PmDAM6 is a multi-modulatory transcription factor with a wide range of effects on bud dormancy induction, establishment, and maintenance by regulating hormone catabolism/biosynthesis, lipid body metabolism, and cell division activity.