Abstract
Most temperate fruit tree species enter dormancy in autumn and are released from dormancy after exposure
of a certain amount of chilling. Recent reports suggested the involvement of some MADS-box genes in apple
(Malus x domestica) dormancy regulation. In this review, gene expression patterns of apple MADS-box
genes, named DORMANCY-ASSOCIATED MADS-box1 (MdDAM1), MdDAM2, and FLC-like in relation to
dormancy progress and morphological changes of internal flower structure during autumn until bud break,
were first summarized. Previous studies revealed that these three genes were up-regulated in apple flower
buds during dormancy. MdDAM2 reached at maximum expression level before chilling requirement
fulfillment time whereas MdDAM1 stayed at higher expression levels even after it. FLC-like were
up-regulated by exposure to prolonged chilling. All these MADS-box genes were up-regulated in correlation
with flower organ differentiation and development and then down-regulated at bud break stage. As for
functional characterization, the reported transgenic studies revealed that Rosaceae DAMs may act as bud
break repressors while FLC-like inhibited vegetative growth in Arabidopsis. Taken together, some apple
homologs of MADS-box genes well-known as flowering regulators in Arabidopsis may contribute to
dormancy regulation by acting as growth inhibitors and bud break repressors during dormancy and flower
bud development.
