SVP-like MADS Box Genes Control Dormancy and Budbreak in Apple

Abstract

The annual growth cycle of trees is the result of seasonal cues. The onset of winter triggers an endodormant state preventing bud growth and, once a chilling requirement is satisfied, these buds enter an ecodormant state and resume growing. MADS-box genes with similarity to Arabidopsis SHORT VEGETATIVE PHASE (SVP) [the SVP-like and DORMANCY ASSOCIATED MADS-BOX (DAM) genes] have been implicated in regulating flowering and growth-dormancy cycles in perennials. Here, we identified and characterized three DAM-like (MdDAMs) and two SHORT VEGETATIVE PHASE-like (MdSVPs) genes from apple (Malus × domestica ‘Royal Gala’). The expression of MdDAMa and MdDAMc indicated they may play a role in triggering autumn growth cessation. In contrast, the expression of MdDAMb, MdSVPa and MdSVPb suggested a role in maintaining bud dormancy. Consistent with this, ectopic expression of MdDAMb and MdSVPa in ‘Royal Gala’ apple plants resulted in delayed budbreak and architecture change due to constrained lateral shoot outgrowth, but normal flower and fruit development. The association of MdSVPa and MdSVPb expression with floral bud development in the low fruiting ‘Off’ trees of a biennial bearing cultivar ‘Sciros’ suggested the SVP genes might also play a role in floral meristem identity.

Pleiotropy in developmental regulation by flowering‐pathway genes: is it an evolutionary constraint?

“…For instance, flowering and growth cessation in poplar are regulated by a CO/FT regulatory module (Böhlenius et al ., ), and induction of poplar bud dormancy requires the transcriptional regulation by ABA of an ortholog of SHORT VEGETATIVE PHASE (SVP; Singh et al ., ). Orthologs of SVP have been implicated in seasonal control of growth arrest in apple and kiwifruit (Wu et al ., , ). Multiple FT homologs, as well as FLD, LFY and AP1 homologs, have been identified and associated with bud dormancy in several temperate tree species (Cooke et al ., ; Lloret et al ., ).…”

Unisexual flower initiation in the monoeciousQuercus suberL., a molecular approach

“…Furthermore, plants overexpressing QsSVP4 had flowers with extra petals and sepals. The late flowering and the flower organ number phenotypes derived from overexpressing QsSVP4 were previously described in other studies in which SVP -like genes of several perennial species were overexpressed in perennial and annual species (Li et al 2010, Wu et al 2012, 2017, Jaudal et al 2014). In Q. suber , both QsSVP1 and QsSVP4 are highly expressed during early stages of axillary bud growth cessation, suggesting a conserved role for these genes in growth arrest.…”

“…In perennial species of temperate climates, a subset of meristems needs to remain vegetative to sustain consecutive growth cycles that are interrupted by unfavourable environmental conditions. Axillary bud growth cessation and bud swelling in perennials, like kiwifruit and peach, is controlled by the regulation of the transcription machinery, particularly by SVP -like genes that respond to environmental cues (Li et al 2009, Wu et al 2012, 2017). Of the four QsSVP genes, only QsSVP1 and QsSVP4 were able to delay flowering in transgenic Arabidopsis plants.…”

A New Insight into Flowering Regulation: Molecular Basis of Flowering Initiation in Magnolia × soulangeana ‘Changchun’

“…Previous research has suggested that the openness of flower buds in woody plants was related to dormancy release [13][14][15]. Before the spring flowering of 'Changchun', the long dormancy process of flower buds was released, and the growth amount increased significantly.…”

“…However, to date, the understanding of flowering regulation in woody plants has been based on the molecular mechanisms underlying the regulation of flower bud differentiation.In fact, for temperate perennial woody plants with multiple flowering, the buds formed by reproductive transition can flower after a period of dormancy [11,12]. Taking apical buds and flowers from Malus × domestica 'Royal Gala' as materials, researchers found that MdDAMb (DORMANCY ASSOCIATED MADS-BOX), MdSVPa, and MdSVPb played a role in maintaining bud dormancy, and SVP (SHORT VEGETATIVE PHASE) might play a role in floral meristem identity [13]. The increased level of PpEBB (EARLY BUD-BREAK) induced high levels of transcription of four PpCYCD3 (D-type CYCLIN) genes, which promoted cell division and resulted in a significant increase in the primordia size of Pyrus pyrifolia 'Kosui' lateral flower buds [14].…”