Abstract:

Expansins are a kind of cell wall binding proteins, and can induce cell wall extension without any activating protein at a certain pH condition. On the basis of ESTs isolated from a xylogenesis-specific cDNA library of Chinese Fir(Cunninghamia lanceolata), we successfully cloned 3 full-length expansin genes using RLM-RACE. Sequence analysis showed that ClEXPA 1 cDNA was 1 033 bp in length capable of encoding 247 amino acids, ClEXPA 2 cDNA was 1 374 bp in length capable of encoding 268 amino acids, and ClEXLA 1 cDNA was 1 023 bp in length capable of encoding 272 amino acids. Phylogenetic reconstruction indicated that ClEXPA 1 and ClEXPA 2 belonged to α-expansin (EXPA); whereas ClEXLA 1 belonged to γ-expansin (EXLA). Expression patterns of ClEXPA 1 and ClEXPA 2 were similar, with high transcript levels detected in cambium region, and intermediate levels observed in needle and shoot tip; very low levels in mature xylem, and almost no transcript in root and pollen. In Contrast ClEXLA 1 had different expression pattern: high transcript levels were observed in cambium region and needle; intermediate levels were detected in shoot tip and xylem; low expression levels in pollen and barely detectable in root. These isolated genes would provide an important pool in systematically studying the expression, function and regulation mechanism of expansins during wood formation.

Key words: Cunninghamia lanceolata, xylogenesis, expansin gene, xylem differentiation