Abstract: Petunia PMADS9 gene is a member of the AGL15-like clade of MADS domain regulatory factors，and Arabidopsis AtAGL15 is considered to promote embryogenesis and repress the progression of a specific subset of age-related developmental program in the flowering plant. We cloned the genomic sequence（EU338501）of petunia PMADS9 by PCR and compared the gene structure by comparative analysis of homologous genes. The results showed that both petunia PMADS9 and tomato SIMBP11 had a long third exon and large first and second introns，which is different from other homologous genes. The Southern hybridization result showed that there may be only one copy in the genome. A real-time PCR was performed to observe the expression profiling of PMADS9. The results showed that PMADS9 preferentially expressed in anther and ovary and had low expression in other organs，which is slightly different from Arabidopsis AGL15. By using different chemical and physical treatments to the seedlings of petunia，we found PMADS9 expression responded to 2,4-D and GA3 and increased in different environment stresses which suggested it involved in plant stress resistance.

Key words: petunia, PMADS9 gene, expression pattern, stress resistance