Hormonal Orchestration of Bud Dormancy Cycle in Deciduous Woody Perennials

Abstract

Woody perennials enter seasonal dormancy to avoid unfavorable environmental conditions. Plant hormones are the critical mediators regulating this complex process, which is subject to the influence of many internal and external factors. Over the last two decades, our knowledge of hormone-mediated dormancy has increased considerably, primarily due to advancements in molecular biology, omics, and bioinformatics. These advancements have enabled the elucidation of several aspects of hormonal regulation associated with bud dormancy in various deciduous tree species. Plant hormones interact with each other extensively in a context-dependent manner. The dormancy-associated MADS (DAM) transcription factors appear to enable hormones and other internal signals associated with the transition between different phases of bud dormancy. These proteins likely hold a great potential in deciphering the underlying mechanisms of dormancy initiation, maintenance, and release. In this review, a recent understanding of the roles of plant hormones, their cross talks, and their potential interactions with DAM proteins during dormancy is discussed.

A Conceptual Framework for Winter Dormancy in Deciduous Trees

“…Phytohormones appear to be playing an important role in endo-dormancy maintenance and release (process b.2 in Figure 3). Continued in situ ABA synthesis may be a requirement for the maintenance of bud dormancy, and a decrease of ABA levels below a certain threshold contributes to the release of dormancy [104]. This has been demonstrated by the external application of an ABA synthesis inhibitor (fluridone) to dormant buds, which caused the initiation of new leaf primordia growth [105].…”

“…GA levels, which remain low during maintenance and increase towards release of endo-dormancy, seem to be regulated by the expression of GA-synthetic (GA20ox and GA3ox) and GA-catabolic (GA2ox) genes. GA catabolism was shown to be crucial for the induction and maintenance of bud dormancy [104] in woody species such as rose (Rosa sp.) [107], Japanese apricot [108], and grapevine [86].…”

“…External application of auxins has been shown to accelerate sap flow reactivation [117]. During eco-dormancy, concentrations of ABA drop and levels of growth-promoting hormones such as auxin and gibberellin increase [104].…”

Elucidation of Molecular and Hormonal Background of Early Growth Cessation and Endodormancy Induction in Two Contrasting Populus Hybrid Cultivars

“…Phytohormones have been long known to be involved in the dormancy cycle [23,25,72,[64][65][66][67][68][69][70][71]. Recently, mechanistic relationships between phytohormones and dormancy are being revealed [36,73,74].…”

“…Furthermore, excellent review papers have focused on the molecular changes, gene regulatory pathways, and hormonal regulations during dormancy [18][19][20][21][22][23][24][25], but relatively less is known about the potential role of C-Repeat Binding Factors (CBFs) in dormancy and Dormancy-Associated MADS-box (DAM) genes in Populus hybrid cultivars widely used in agroforestry systems. CBF genes, rst described in Arabidopsis [26][27][28], are among the best-characterized plant transcription factors involved in plant abiotic stress tolerance, especially in cold acclimation.…”