Abstract
BackgroundBud dormancy is a crucial stage in perennial trees and allows survival over winter to ensure optimal flowering and fruit production. Recent work highlighted physiological and molecular events occurring during bud dormancy in trees. However, they usually examined bud development or bud dormancy in isolation. In this work, we aimed to further explore the global transcriptional changes happening throughout bud development and dormancy onset, progression and release.ResultsUsing next-generation sequencing and modelling, we conducted an in-depth transcriptomic analysis for all stages of flower buds in several sweet cherry (Prunus avium L.) cultivars that are characterized for their contrasted dates of dormancy release. We find that buds in organogenesis, paradormancy, endodormancy and ecodormancy stages are defined by the expression of genes involved in specific pathways, and these are conserved between different sweet cherry cultivars. In particular, we found that DORMANCY ASSOCIATED MADS-box (DAM), floral identity and organogenesis genes are up-regulated during the pre-dormancy stages while endodormancy is characterized by a complex array of signalling pathways, including cold response genes, ABA and oxidation-reduction processes. After dormancy release, genes associated with global cell activity, division and differentiation are activated during ecodormancy and growth resumption. We then went a step beyond the global transcriptomic analysis and we developed a model based on the transcriptional profiles of just seven genes to accurately predict the main bud dormancy stages.ConclusionsOverall, this study has allowed us to better understand the transcriptional changes occurring throughout the different phases of flower bud development, from bud formation in the summer to flowering in the following spring. Our work sets the stage for the development of fast and cost effective diagnostic tools to molecularly define the dormancy stages. Such integrative approaches will therefore be extremely useful for a better comprehension of complex phenological processes in many species.
Highlights
Bud dormancy is a crucial stage in perennial trees and allows survival over winter to ensure optimal flowering and fruit production
The first dimension of the analysis (PC1) explains 41.63% of the variance and clearly represents the strength of bud dormancy where samples on the right of the axis are in late endodormancy (Dec) or dormancy release stages, while samples on the left of the axis are in organogenesis and paradormancy
Pathways involved at different stages of bud dormancy have been investigated in other species and we confirmed that genes associated with the response to cold, abscisic acid (ABA) and development processes were identified during sweet cherry flower bud dormancy
Summary
Bud dormancy is a crucial stage in perennial trees and allows survival over winter to ensure optimal flowering and fruit production. Advances in bud break and blooming dates in spring have been observed for tree species, such as apple, cherry, birch, oak or Norway spruce, in the northern hemisphere, increasing the risk of late frost damages [9,10,11,12,13,14], while insufficient cold accumulation during winter may lead to incomplete dormancy release associated with bud break delay and low bud break rate [15, 16] These phenological changes directly impact the production of fruit crops, leading to large potential economic losses [17]. It becomes urgent to acquire a better understanding of bud responses to temperature stimuli in the context of climate change in order to tackle fruit losses and anticipate future production changes
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