The dynamic nature of bud dormancy in trees: environmental control and molecular mechanisms

Abstract

In tree species native to temperate and boreal regions, the activity-dormancy cycle is an important adaptive trait both for survival and growth. We discuss recent research on mechanisms controlling the overlapping developmental processes that define the activity-dormancy cycle, including cessation of apical growth, bud development, induction, maintenance and release of dormancy, and bud burst. The cycle involves an extensive reconfiguration of metabolism. Environmental control of the activity-dormancy cycle is based on perception of photoperiodic and temperature signals, reflecting adaptation to prevailing climatic conditions. Several molecular actors for control of growth cessation have been identified, with the CO/FT regulatory network and circadian clock having important coordinating roles in control of growth and dormancy. Other candidate regulators of bud set, dormancy and bud burst have been identified, such as dormancy-associated MADS-box factors, but their exact roles remain to be discovered. Epigenetic mechanisms also appear to factor in control of the activitydormancy cycle. Despite evidence for gibberellins as negative regulators in growth cessation, and ABA and ethylene in bud formation, understanding of the roles that plant growth regulators play in controlling the activity-dormancy cycle is still very fragmentary. Finally, some of the challenges for further research in bud dormancy are discussed.

Temperate and boreal forest tree phenology: from organ-scale processes to terrestrial ecosystem models

“…The categorization of bud dormancy into three phases is convenient from a conceptual viewpoint and has thus been incorporated into the building of processbased models (see section 3.1 "Modeling the phenology of leaves and the timing of flowering"). Nevertheless, this definition, originally proposed by Lang et al (1987), is currently under scrutiny because it appears that these three bud dormancy phases are not strictly separated in time, and interactions among these phases have been reported (Cooke et al 2012).…”

“…The physiological processes involved in bud dormancy are complex and interact with environmental cues to optimize the timing of budburst in relation to the mean long-term probability of a late spring frost. In this section, we focus on the environmental cues that affect the phenology of the primary aerial meristems of temperate and boreal trees (budburst, flowering, fruit and cone maturation, and leaf senescence) and refer to the detailed reviews of Wareing and Saunders (1971), Arora et al (2003), Horvath et al (2003), and Cooke et al (2012) for the hormonal and molecular changes involved in these phenophases.…”

EARLY BUD-BREAK 1 (EBB1) is a regulator of release from seasonal dormancy in poplar trees

“…Interestingly, GO analysis of the EBB1 putative target genes identified enrichment of a large number (n = 43) of biological processes (Dataset S4). Among the most represented/enriched were nitrogen metabolic processes (13), developmental process (11), response to stimulus (12), and regulation of transcription (6). Dormancy Induction and EBB1 Share Common Regulons.…”

“…In Arabidopsis, the ability of FT and other floral integrators to respond to inductive signals is controlled by a suite of MADS (MCM1, AGAMOUS, DEFICIENS, SRF) box genes like SHORT VEGETATIVE PHASE (SVP) and FLOWERING LOCUS C (FLC) (14). Similar MADS box genes, known as DORMANCY-ASSOCIATED MADS (DAM) genes (15), appear to be involved in regulation of bud dormancy in several woody perennial species (6). Involvement of ethylene and abscisic acid signaling in bud formation has also been suggested (16,17).…”

“…This event is followed by transformation of the apex into a bud (5) and establishment of poorly known physiological changes collectively known as endodormancy, an inability of the meristem and the youngest leaf primordia to respond to growthpromoting signals. Resumption of bud growth, known as budbreak, occurs after meeting a chilling requirement (exposure for several months to low temperatures, with variable speciesspecific duration) and is controlled almost exclusively by high temperatures (6). The timing of entry and release from dormancy is synchronized with local climates and is highly heritable (7).…”