Abstract:

A MADS box gene PtSEP3 was isolated from young female flower of Populus tomentosa using PCR strategy. Alignment and homolog tree analyses show that PtSEP3 is a homologous gene of Arabidopsis SEP3. PtSEP3 expression can be detected not only in pistil and stamen, but young shoot, terminal bud and young leaf of an adult tree. Driven by 35S promoter, PtSEP3 over-expression leads to severe morphologic alterations in leaf phyllotaxis and in leaf form. In transgenic plants, several leaves usually initial from one stem node and leaf base most are cuneate, which are obviously different from alternate phyllotaxis and cordate leaf base in wild type. Ovary-like structures each with 1～2 styles and an ovate-form womb can be induced in volume, when leaf explants or root explants of transgenic lines are incubated on bud differentiation medium. The phenotypes in PtSEP3 over-expression lines combined with its expression pattern suggest it play roles in regulating floral organ initiation, probably in maintenance of shoot meristem property for correct initiation of normal leaves.

Key words: Populus tomentosa, floral organ development, MADS box gene, PtSEP3