title: Differential stage-specific regulation of cyclin-dependent kinases during cambial dormancy in hybrid aspen.
abstract: The cambium of woody plants cycles between active and dormant states. Dormancy can be subdivided into eco- and endodormant stages. Ecodormant trees resume growth upon exposure to growth-promotive signals, while the establishment of endodormant state results in loss of the ability to respond to these signals. In this paper, we analysed the regulation of cyclin-dependent kinases (CDKs) to understand the differential response of cell division machinery to growth-promotive signals during the distinct stages of dormancy in hybrid aspen. We show that 4 weeks of short-day (SD) treatment causes termination of the cambial cell division and establishment of the ecodormant state. This coincides with a steady decline in the histone H1 kinase activity of the PSTAIRE-type poplar CDKA (PttCDKA) and the PPTTLRE-type PttCDKB kinase complexes. However, neither the transcript nor the polypeptide levels of PttCDKA and PttCDKB are reduced during ecodormancy. In contrast, 6 weeks of SD treatment establishes endodormancy, which is marked by the reduction and disappearance of the PttCDKA and PttCDKB protein levels and the PttCDKB transcript levels. The transition to endodormancy is preceded by an elevated E2F (adenosine E2 promoter binding factor) phosphorylation activity of the PttCDKA kinase that reduces the DNA-binding activity of E2F in vitro. The transition to endodormancy is followed by a reduction of retinoblastoma (Rb) phosphorylation activity of PttCDKA protein complexes. Both phosphorylation events could contribute to block the G1 to S phase transition upon the establishment of endodormancy. Our results indicate that eco- and endodormant stages of cambial dormancy involve a stage-specific regulation of the cell cycle effectors at multiple levels.
authors.affiliation: Department of Forest Genetics and Plant Physiology, Umea Plant Science Centre, Swedish University of Agricultural Sciences, 90183 Umea, Sweden.
authors.forename: Ana
authors.initials: A
authors.lastname: Espinosa-Ruiz
authors.forename: Sangeeta
authors.initials: S
authors.lastname: Saxena
authors.forename: Julien
authors.initials: J
authors.lastname: Schmidt
authors.forename: Ewa
authors.initials: E
authors.lastname: Mellerowicz
authors.forename: Pál
authors.initials: P
authors.lastname: Miskolczi
authors.forename: László
authors.initials: L
authors.lastname: Bakó
authors.forename: Rishikesh P
authors.initials: RP
authors.lastname: Bhalerao
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D003001:Cloning, Molecular; D018844:Cyclin-Dependent Kinases / Q000235:genetics* / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic / Q000235:genetics; D018506:Gene Expression Regulation, Plant / Q000235:genetics*; D007700:Kinetics; D008027:Light; D008969:Molecular Sequence Data; D010766:Phosphorylation; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D032107:Populus / Q000201:enzymology / Q000235:genetics / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012621:Seasons; D014934:Wood
chemical_list: D010940:Plant Proteins; D018844:Cyclin-Dependent Kinases