Cambial meristem dormancy in trees involves extensive remodelling of the transcriptome

Abstract

SummaryThe establishment of the dormant state in meristems involves considerable physiological and metabolic alterations necessary for surviving unfavourable growth conditions. However, a global molecular analysis of dormancy in meristems has been hampered by the difficulty in isolating meristem cells. We used cryosectioning to isolate purified cambial meristem cells from the woody plant Populus tremula during active growth and dormancy. These samples were used to generate meristem-specific cDNA libraries and for cDNA microarray experiments to define the global transcriptional changes underlying cambial dormancy. The results indicate a significant reduction in the complexity of the cambial transcriptome in the dormant state. Although cell division is terminated in the dormant cambium, the cell cycle machinery appears to be maintained in a skeletal state as suggested by the continued presence of transcripts for several cell cycle regulators. The downregulation of PttPIN1 and PttPIN2 transcripts explains the reduced basipetal polar auxin transport during dormancy. The induction of a member of the SINA family of ubiquitin ligases implicated in auxin signalling indicates a potential mechanism for modulation of auxin sensitivity during cambial dormancy. The metabolic alterations during dormancy are mirrored in the induction of genes involved in starch breakdown and the glyoxysomal cycle. Interestingly, the induction of RGA1 like gene suggests modification of gibberellin signalling in cambial dormancy. The induction of genes such as poplar orthologues of FIE and HAP2 indicates a potential role for these global regulators of transcription in orchestrating extensive changes in gene expression during dormancy.

Comprehensive Analysis of NAC Domain Transcription Factor Gene Family in Populus trichocarpa

“…Two subset of NAC genes exhibited specifically high transcript accumulation in active and dormant cambiums respectively, from two independent microarray datasets [85,86], strongly indicating their specific roles in wood-formation (Figure 6A and 6B). In addition, by incorporating the different microarray data, we were capable to identify different subsets of NAC genes displaying specifically high expression levels in phloem, differentiating xylem and mature xylems, respectively.…”

Components Acting Downstream of Short Day Perception Regulate Differential Cessation of Cambial Activity and Associated Responses in Early and Late Clones of Hybrid Poplar

“…In response to short days (SDs) and low temperatures, metabolism shifts toward the production of storage compounds such as vegetative storage proteins (Clausen and Apel, 1991), and other biochemical and physical changes are initiated that allow plants to withstand extremely low temperatures (Weiser, 1970;Welling et al, 2002). The proper temporal orchestration of these SD responses is underpinned by highly coordinated changes in the transcriptome, as has been shown by microarray analyses of global gene expression in the apices and cambia of a variety of tree species (Schrader et al, 2004a;Druart et al, 2007;Ruttink et al, 2007;Holliday et al, 2008).…”

Molecular control of winter dormancy establishment in trees: a review

“…Evidently, disruption of the molecular oscillator would modify the action of the CO/FT module induced by SD, since clock genes are known to directly play a part in regulating the CONSTANS-dependent photoperiodic pathway (Searle and Coupland, 2004;Niwa et al, 2007). Further, it should be highlighted that: a) the circadian clock regulates plant rhythmic growth (Nozue and Maloof, 2006;Nozue et al, 2007); b) it acts in cold signalling pathways in Arabidopsis by gating the low-temperature induction of CBFs and modulates low-temperature Ca 2+ signals (Fowler et al, 2005;Dodd et al, 2006); and c), stopping of the clock in response to winter LT could in part explain the extensive remodelling of meristem transcriptome observed during the transition from growth to dormancy in the vascular cambium of poplar (Schrader et al, 2004;Druart et al, 2007).…”