Abstract
Deciduous trees show annual periodicity in shoot growth and development. However such periodicity of growth and function is not well known in root. Based on the seasonal fluctuations of various xylem sap components in Populus nigra, gene expression patterns related to the several components, especially K, Ca and proteins, were investigated. We analyzed environmentally regulated gene expressions in root of Populus maximowiczii. Two genes encoding putative efflux transporters for K and Ca were strongly expressed in root around dormancy period, possibly corresponding to the K and Ca increases in xylem sap in winter season. The genes for 24 kDa protein (XSP24) and 25 kDa protein (XSP25) which were abundantly existed in P. nigra xylem sap were cloned from P. maximowiczii. XSP24 and XSP25 were found to be expressed under short-day length and low temperature conditions. Homologous genes for these two transporters and XSP25 were known to be ABA responsive, therefore, the effect of ABA application was investigated. The relationship between ABA and gene expressions will be discussed.
