Abstract
Dormancy is a physiological state that plants enter for winter hardiness. Environmental-induced dormancy onset and release in temperate perennials coordinate growth cessation and resumption, but how the entire process, especially chilling-dependent dormancy release and flowering, is regulated remains largely unclear. We utilized the transcriptome profiles of floral buds from fall to spring in apricot (Prunus armeniaca) genotypes with contrasting bloom dates and peach (Prunus persica) genotypes with contrasting chilling requirements (CR) to explore the genetic regulation of bud dormancy. We identified distinct gene expression programming patterns in endodormancy and ecodormancy that reproducibly occur between different genotypes and species. During the transition from endo- to eco-dormancy, 1,367 and 2,102 genes changed in expression in apricot and peach, respectively. Over 600 differentially expressed genes were shared in peach and apricot, including three DORMANCY ASSOCIATED MADS-box (DAM) genes (DAM4, DAM5, and DAM6). Of the shared genes, 99 are located within peach CR quantitative trait loci, suggesting these genes as candidates for dormancy regulation. Co-expression and functional analyses revealed that distinctive metabolic processes distinguish dormancy stages, with genes expressed during endodormancy involved in chromatin remodeling and reproduction, while the genes induced at ecodormancy were mainly related to pollen development and cell wall biosynthesis. Gene expression analyses between two Prunus species highlighted the conserved transcriptional control of physiological activities in endodormancy and ecodormancy and revealed genes that may be involved in the transition between the two stages.
Highlights
In temperate regions, many perennial plants protect their buds and reproductive tissues from winter cold by entering a state of dormancy
Prunus flowers are sensitive to frost damage, and maintenance of winter dormancy for a sufficient time period is essential to prevent frost damage to delicate reproductive tissues, especially during the spring months when temperatures may fluctuate
Our time-series transcriptome profiles in apricot and peach buds allowed us to investigate the gene expression changes as floral bud dormancy progressed towards bloom and to compare complementary data from two closely related species and among genotypes varying in chilling requirements (CR)/blooming date (BD)
Summary
Many perennial plants protect their buds and reproductive tissues from winter cold by entering a state of dormancy. The CR for bud break is an intrinsic part of temperate tree phenology that varies between and within species based on adaptations to the climate of their native range (Luedeling, 2012). Cultivars must be carefully selected for each growing region in order to provide a sufficient amount of cold for regular flowering and reliable fruit or nut production (Luedeling and Brown, 2011). With global climate change, understanding dormancy and its control are critical for the productivity of fruit trees, as increasing or irregular seasonal temperatures impact optimal timing for important phenological traits (Hatfield and Prueger, 2015). Lack of fulfillment of CR due to warm winters affects bud break, resulting in low flowering rates and low fruit yield as the fruit trees do not fulfill their CR (Viti and Monteleone, 1991). Early blooming trees can suffer significant yield loss from frost damage to floral blooms during unusually late periods of freezing in the spring (Rieger, 1989)
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