Cloning of an Expansin Gene from Chimonanthus praecox Flowers and Its Expression in Flowers Treated with Ethephon or 1-Methylcyclopropene

摘要

Expansins are extracellular proteins that are involved in cell wall modications such as cell wall disassembly, cell separation, and cell expansion. Little is known about expansin gene expression during ower development of wintersweet (Chimonanthus praecox). In the present study, an expansin gene, CpEXP1, was isolated from the wintersweet ower cDNA library through random sequencing; this gene encodes a putative protein of 257 amino acids with the essential features conserved, like in other alpha expansins. The CpEXP1 gene exhibited different transcription levels in different tissues and had a signicantly higher expression in owers than other tissues. It is strongly correlated with the development of the ower. The expression of CpEXP1 increased in the ower buds or whole owers from Stage 1 to 4 and decreased from Stage 5 to 6 during natural opening. Ethephon (an ethylene releaser) treatment promoted cut ower senescence, whereas 1-methylcyclopropene (1-MCP) (an ethylene perception inhibitor) delayed the process of ower wilting. This result is associated with the concomitant lower transcript levels of CpEXP1 in the ethephon-treated samples as well as the steady expression in the 1-MCP-treated samples compared with that in control owers. The studies show the interesting observation that the expression of an expansin gene CpEXP1 is correlated with the development of Chimonanthus praecox owers, the upregulation during ower opening vs. the downregulation during senescence.