Abstract
Deciduous trees such as poplar show annual periodicity in shoot growth and development. However such periodicity of growth and function of root is not well known. In order to clarify seasonal fluctuation of function of root annually, xylem sap was collected from poplar cut branch and content of sap and gene expression in root were investigated. Many xylem sap components showed seasonal fluctuation and peaks are different by components. PIP and CYCB were strongly expressed in root around April when xylem sap quantity increases and around June when growth of root becomes active, respectively. In addition, the gene for25 kDa protein (XSP25) which most abundantly exists in xylem sap was identified by MS analysis and XSP25 was expressed in root in winter and highly up-regulated by ABA application to autumn root, but not by cold treatment. On the other hand, NCED encoding the enzyme for ABA synthesis was up-regulated in shoot, but not in root of cold-treated plants. This study suggests that ABA synthesized in shoot in response to low temperature in early winter may possibly move to root and promote the synthesis of XSP25 in root to protect shoot tissues against cold and/or dry in winter.
