A molecular framework for seasonal growth-dormancy regulation in perennial plants

Abstract

The timing of the onset and release of dormancy impacts the survival, productivity and spatial distribution of temperate horticultural and forestry perennials and is mediated by at least three main regulatory programs involving signal perception and processing by phytochromes (PHYs) and PHY-interacting transcription factors (PIFs). PIF4 functions as a key regulator of plant growth in response to both external and internal signals. In poplar, the expression of PIF4 and PIF3-LIKE1 is upregulated in response to short days, while PHYA and PHYB are not regulated at the transcriptional level. Integration of light and environmental signals is achieved by gating the expression and transcriptional activity of PIF4. During this annual cycle, auxin promotes the degradation of Aux/IAA transcriptional repressors through the SKP–Cullin-F–boxTIR1 complex, relieving the repression of auxin-responsive genes by allowing auxin response factors (ARFs) to activate the transcription of auxin-responsive genes involved in growth responses. Analyses of transcriptome changes during dormancy transitions have identified MADS-box transcription factors associated with endodormancy induction. Previous studies show that poplar dormancy-associated MADS-box (DAM) genes PtMADS7 and PtMADS21 are differentially regulated during the growth-dormancy cycle. Endodormancy may be regulated by internal factors, which are specifically localized in buds. PtMADS7/PtMADS21 may function as an internal regulator in poplar. The control of flowering time shares certain regulatory hierarchies with control of the dormancy/growth cycle. However, the particularities of different stages of the dormancy/growth cycle warrant comprehensive approaches to identify the causative genes for the entire cycle. A growing body of knowledge also indicates epigenetic regulation plays a role in these processes in perennial horticultural and forestry plants. The increased knowledge contributes to better understanding of the dormancy process and consequently to precise manipulation of dormancy-related horticultural traits, such as flowering time.

Comparative Transcriptome Analysis of Chinary, Assamica and Cambod tea (Camellia sinensis) Types during Development and Seasonal Variation using RNA-seq Technology

“…Moreover, there are still major gaps in understanding molecular mechanisms governing transition to and release from dormancy. In addition, seasonal variation is also known to activate a range of physiological responses including phytohormonal regulations and epigenetic mechanisms1213. The relative expression of genes related to plant hormone metabolism and signal transduction such as ABA, gibberellins, ethylene, brassinosteroid and auxin have been described in other perennial plant species during vegetative growth and seasonal variations1415.…”

Overexpression of DEMETER, a DNA demethylase, promotes early apical bud maturation in poplar

“…Our qRT‐PCR and RNA FISH studies confirm the induction by SD of the poplar closest ortholog of the chestnut CsDML , PtDML6 , in the apical meristem. Previous RNA‐Seq studies have associated PtDML6 , with dormancy induction, in poplar stem and apex (Shim et al, ; Supporting Information Figure S4). These results suggest that activation of a 5mC DML during bud maturation is conserved both in chestnut and poplar.…”

Genetics and Genomics of Tree Architecture

“…Other results suggest that active growth-regulating genes might be under epigenetic regulation, repressed during dormancy induction through chromatin compaction mechanisms, i.e. histone deacetylation and methylation, histone ubiquitination, DNA methylation and polycomb activity (see Shim et al, 2014 as a review).…”

“…They are characterized by the formation of buds that protect the meristematic tissues and make them able to survive winter periods and resume growth at spring. These buds go through a 'dormancy' stage, this generic term including three different physiological states of the bud e ecodormancy, paradormancy and endodormancy (Lang, Early, Martin, & Darnell, 1987;Shim et al, 2014) e depending on whether bud inhibition is conditioned on environmental causes or on a correlation with other tree parts, or lies within the bud itself, respectively. Flowering process is also tightly linked to these annual climatic fluctuations, especially in fruit trees in which flower induction and differentiation occurs in the year preceding bloom and, as vegetative buds, floral buds go through a dormancy period during winter.…”