Abstract
DORMANCY-ASSOCIATED MADS-BOX (DAM) genes have recently emerged as key potential regulators of the dormancy cycle and climate adaptation in perennial species. Particularly, PpeDAM6 has been proposed to act as a major repressor of bud dormancy release and bud break in peach (Prunus persica). PpeDAM6 expression is downregulated concomitantly with the perception of a given genotype-dependent accumulation of winter chilling time, and the coincident enrichment in H3K27me3 chromatin modification at a specific genomic region. We have identified three peach BASIC PENTACYSTEINE PROTEINs (PpeBPCs) interacting with two GA-repeat motifs present in this H3K27me3-enriched region. Moreover, PpeBPC1 represses PpeDAM6 promoter activity by transient expression experiments. On the other hand, the heterologous overexpression of PpeDAM6 in European plum (Prunus domestica) alters plant vegetative growth, resulting in dwarf plants tending toward shoot meristem collapse. These alterations in vegetative growth of transgenic lines associate with impaired hormone homeostasis due to the modulation of genes involved in jasmonic acid, cytokinin, abscisic acid, and gibberellin pathways, and the downregulation of shoot meristem factors, specifically in transgenic leaf and apical tissues. The expression of many of these genes is also modified in flower buds of peach concomitantly with PpeDAM6 downregulation, which suggests a role of hormone homeostasis mechanisms in PpeDAM6-dependent maintenance of floral bud dormancy and growth repression.
Highlights
Throughout evolution, perennial plants have developed different strategies to adapt to seasonal changing environmental conditions
BASIC PENTACYSTEINE PROTEIN (BPC) proteins bind and regulate PpeDAM6 expression In plants, GA-repeat motifs are mainly recognized by a specific family of transcription factors called BARLEY B RECOMBINANT (BBR)/BPC, firstly characterized in barley[28] and subsequently in Arabidopsis[30] and cucumber[33]
Further research is needed, this study suggests that PpeBPC1 represses PpeDAM6 transcriptional activity by binding to two of these motifs, located in an intronic region of PpeDAM6 that becomes enriched in H3K27me[3] modification concomitantly with dormancy release events[25]
Summary
Throughout evolution, perennial plants have developed different strategies to adapt to seasonal changing environmental conditions. Prior to bud dormancy induction, cessation of meristem growth and bud set are induced by photoperiod changes (short daylength) and/or low temperature conditions in apical vegetative meristems[3,4], whereas the growth of axillary vegetative meristems and differentiated flowers is stopped by correlative bud inhibition[5]. Bud dormancy completion is favored by prolonged chilling[6]. This chilling requirement for dormancy release is quantitative and specific for different genotypes. Buds become competent for growing, requiring a period of mild temperatures for initiating bud break. This state is widely known as ecodormancy
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