月季扩张素蛋白基因在花朵开放过程中的表达及功能分析

以切花月季‘Samantha’为试材，明确了外层花瓣主要在花朵开放前期扩展。从花瓣中克隆鉴定了3个具有α亚族扩张素保守特征域的基因：RhEXPA5、RhEXPA6和RhEXPA7。在月季花朵1 ~ 6级的开放过程中，3个扩张素蛋白基因都有表达，其中RhEXPA7的表达与花瓣快速扩展密切关联；在2级花朵花瓣中RhEXPA5和RhEXPA6的表达几乎不受乙烯影响，而RhEXPA7的表达被乙烯显著抑制。进一步利用35S启动子在拟南芥中过表达RhEXPA7，采用外源ACC处理可明显增加转基因植株幼苗的根毛密度；转RhEXPA7基因种子萌发对ABA的敏感性明显降低，而对NaCl的胁迫耐性明显增加。RhEXPA7与月季花朵开放中花瓣快速扩展进程密切关联，参与了乙烯信号的响应，并可以提高过表达拟南芥的胁迫耐性。

The Expression and Functional Analysis of Expansin Genes During Flower Opening in Cut Rose

This study first investigated the different-layers of petal expansion using cut rose flowers （Rosa hybrida），and then cloned and identified three alpha-expansin genes with its characteristic conserved domains：RhEXPA5，RhEXPA6 and RhEXPA7. The results showed that outer petals had the faster expansion during the early flower opening stages，while the expression of the genes were ubiquitous in most petal layers at 1–6 flower stages，in which RhEXPA7 expression was most closely related to petal expansion. In stage 2 flowers，ethylene obviously suppressed the RhEXPA7 expression，and showed less effect on RhEXPA5 and RhEXPA6. Over-expression of RhEXPA7 enhanced root hairs density of transgenic Arabidopsis seedlings under ACC treatment. RhEXPA7 over-expression also decreased ABA sensitivity and increased NaCl tolerance in seed germination of transgenic lines. Taken together，RhEXPA7 expression was closely related to petal expansion and involved in ethylene signaling response，and over-expression of RhEXPA7 resulted in enhanced stress tolerance in transgenic Arabidopsis.