A molecular timetable for apical bud formation and dormancy induction in Poplar
The Plant Cell: 2007 19:2370-2390
The growth of perennial plants in the temperate zone alternateswith periods of dormancy that are typically initiated duringbud development in autumn. In a systems biology approach tounravel the underlying molecular program of apical bud developmentin poplar (Populus tremula x Populus alba), combined transcriptand metabolite profiling were applied to a high-resolution timecourse from short-day induction to complete dormancy. Metaboliteand gene expression dynamics were used to reconstruct the temporalsequence of events during bud development. Importantly, buddevelopment could be dissected into bud formation, acclimationto dehydration and cold, and dormancy. To each of these processes,specific sets of regulatory and marker genes and metabolitesare associated and provide a reference frame for future functionalstudies. Light, ethylene, and abscisic acid signal transductionpathways consecutively control bud development by setting, modifying,or terminating these processes. Ethylene signal transductionis positioned temporally between light and abscisic acid signalsand is putatively activated by transiently low hexose pools.The timing and place of cell proliferation arrest (related todormancy) and of the accumulation of storage compounds (relatedto acclimation processes) were established within the bud byelectron microscopy. Finally, the identification of a largeset of genes commonly expressed during the growth-to-dormancytransitions in poplar apical buds, cambium, or Arabidopsis thalianaseeds suggests parallels in the underlying molecular mechanismsin different plant organs.
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