BACKGROUND: Over the life cycle of perennial trees, the dormant state enables the avoidance of abiotic stress conditions. The growth cycle can be partitioned into induction, maintenance and release and is controlled by complex interactions between many endogenous and environmental factors. While phytohormones have long been linked with dormancy, there is increasing evidence of regulation by DAM and CBF genes. To reveal whether the expression kinetics of CBFs and their target PtDAM1 is related to growth cessation and endodormancy induction in Populus, two hybrid poplar cultivars were studied which had known differential responses to dormancy inducing conditions. RESULTS: Growth cessation, dormancy status and expression of six PtCBFs and PtDAM1 were analyzed. The 'Okanese' hybrid cultivar ceased growth rapidly, was able to reach endodormancy, and exhibited a significant increase of several PtCBF transcripts in the buds on the 10th day. The 'Walker' cultivar had delayed growth cessation, was unable to enter endodormancy, and showed much lower CBF expression in buds. Expression of PtDAM1 peaked on the 10th day only in the buds of 'Okanese'. In addition, PtDAM1 was not expressed in the leaves of either cultivar while leaf CBFs expression pattern was several fold higher in 'Walker', peaking at day 1. Leaf phytohormones in both cultivars followed similar profiles during growth cessation but differentiated based on cytokinins which were largely reduced, while the Ox-IAA and iP7G increased in 'Okanese' compared to 'Walker'. Surprisingly, ABA concentration was reduced in leaves of both cultivars. However, the metabolic deactivation product of ABA, phaseic acid, exhibited an early peak on the first day in 'Okanese'. CONCLUSIONS: Our results indicate that PtCBFs and PtDAM1 have differential kinetics and spatial localization which may be related to early growth cessation and endodormancy induction under the regime of low night temperature and short photoperiod in poplar. Unlike buds, PtCBFs and PtDAM1 expression levels in leaves were not associated with early growth cessation and dormancy induction under these conditions. Our study provides new evidence that the degradation of auxin and cytokinins in leaves may be an important regulatory point in a CBF-DAM induced endodormancy. Further investigation of other PtDAMs in bud tissue and a study of both growth-inhibiting and the degradation of growth-promoting phytohormones is warranted.

• Klíčová slova
• Endodormancy, Gene expression, Growth cessation, Plant hormone, Populus, PtCBFs, PtDAM1,
• MeSH
• chiméra růst a vývoj   MeSH
• genetická variace MeSH
• Populus genetika   růst a vývoj   MeSH
• regulace genové exprese u rostlin MeSH
• regulátory růstu rostlin genetika   MeSH
• rostlinné geny MeSH
• stanovení celkové genové exprese MeSH
• vegetační klid genetika   MeSH
• vývoj rostlin genetika   MeSH
• Publikační typ
• časopisecké články MeSH
• srovnávací studie MeSH
• Názvy látek
• regulátory růstu rostlin MeSH

In perennial plants, seasonal shifts provide cues that control adaptive growth patterns of the shoot apex. However, where these seasonal cues are sensed and communicated to the shoot apex remains unknown. We demonstrate that systemic signals from leaves play key roles in seasonal control of shoot growth in model tree hybrid aspen. Grafting experiments reveal that the tree ortholog of Arabidopsis flowering time regulator FLOWERING LOCUS T (FT) and the plant hormone gibberellic acid (GA) systemically convey seasonal cues to the shoot apex. GA (unlike FT) also acts locally in shoot apex, downstream of FT in seasonal growth control. At the shoot apex, antagonistic factors-LAP1, a target of FT and the FT antagonist TERMINAL FLOWER 1 (TFL1)-act locally to promote and suppress seasonal growth, respectively. These data reveal seasonal changes perceived in leaves that are communicated to the shoot apex by systemic signals that, in concert with locally acting components, control adaptive growth patterns.

• Klíčová slova
• FLOWERING LOCUS T, gibberellic acid, hybrid aspen, photoperiodic, systemic signal,
• MeSH
• Arabidopsis fyziologie   MeSH
• chiméra růst a vývoj   MeSH
• fotoperioda MeSH
• fyziologie rostlin MeSH
• gibereliny metabolismus   MeSH
• proteiny huseníčku metabolismus   MeSH
• regulátory růstu rostlin metabolismus   MeSH
• roční období MeSH
• signální transdukce fyziologie   MeSH
• výhonky rostlin růst a vývoj   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• FT protein, Arabidopsis MeSH Prohlížeč
• gibberellic acid MeSH Prohlížeč
• gibereliny MeSH
• proteiny huseníčku MeSH
• regulátory růstu rostlin MeSH