Cloning and functional characterization of a novel BpSEP4 gene from Betula platyphylla Suk.

Abstract

SEPALLATA (SEP) genes, members of a family of MADS-box transcription factors, have essential roles in floral organ development and flowering time. In this study, a novel SEP gene, BpSEP4, was identified from Betula platyphylla Suk. The full-length BpSEP4 cDNA was 928 bp, and it contained highly conserved MADS and K domains characteristic of the SEP subfamily. Subcellular location analysis demonstrated that BpSEP4 localized in the nucleus. qRT-PCR analysis showed that BpSEP4 expression was highest in reproductive organs, where it played an essential role in inflorescence development. The ectopic expression of BpSEP4 in Arabidopsis thaliana caused early flowering and aberrant floral organ development. Moreover, delayed flower senescence and abscission were also observed in transgenic Arabidopsis plants. Further studies demonstrated that the early-flowering phenotype in 35S::BpSEP4 transgenic plants was caused by changes in the expression of flowering time genes and flower meristem identity genes, including CO, FT, SOC1, and TFL1. These results indicate that BpSEP4 is a SEP ortholog that may be involved in controlling flowering time and floral development.