Abstract: 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.

Key words: cut rose, expansin protein, gene expression, functional identification