Upregulation of TCP18s in dormant buds of transgenic apple expressing Japanese apricot PmDAM6

Bud dormancy plays an important role in the survival response under extreme climates. In the previous study, overexpression of Japanese apricot (Prunus mume) DORMANCY-ASSOCIATED MADS-box6 (PmDAM6), highly expressed in dormant vegetative buds, showed growth inhibition and bud break repression through modifying hormone metabolism in transgenic apple (Malus × domestica). In poplar (Populus spp.), the SHORT VEGETATIVE PHASE-LIKE (SVL), which belongs to the StMADS11 (SVP/AGL24) clade as does PmDAM6, has been reported to inhibit bud break by directly upregulating the expression of the TEOSINTE-BRANCHED1/CYCLOIDEA/ PROLIFERATING CELL FACTOR1 (TCP18). So far, however, little is known about the effects of Rosaceae DAMs on TCP expression. In this study, we first comprehensively searched for the TCP gene family in Malus × domestica GDDH13 Whole Genome v1.1 genome and identified a total of 34 TCP genes. Two MdTCP18s (MdTCP18-1 and MdTCP18-2) genes, which belong to the same sub-clade as poplar and Arabidopsis TCP18s, were identified. Dexametasone (DEX)-induced expression of PmDAM6 in transgenic 35S:PmDAM6-GR apple correlated with significant upregulation of MdTCP18s. Therefore, we hypothesized that the regulation of TCP18s by the StMADS11 clade genes is conserved among woody model plant-poplar and Rosaceae species. In this study, we provide a new insight into PmDAM6 function in the regulation of vegetative bud dormancy.