Haploid and diploid expression of a Brassica campestris anther-specific gene promoter in Arabidopsis and tobacco.

Abstract

The anther-specific cDNA clone Bcp1 from Brassica campestris is expressed in both the haploid pollen and diploid tapetum, as shown by in situ hybridization. We have isolated Bgp1, a genomic clone homologous to Bcp1. The coding region and extensive 5' flanking sequences of Bgp1 have been sequenced, and the coding region shows 88% identity with Bcp1. RNA gel blot analysis confirmed the expression of Bgp1-specific transcripts in B. campestris pollen. A 767 bp 5' DNA fragment was fused to the reporter gene beta-glucuronidase (gus) and introduced into both Arabidopsis thaliana and Nicotiana tabacum by transformation. This 5' fragment directed high-level expression in the pollen and tapetum of transgenic Arabidopsis. In transgenic tobacco however, the same construct was expressed only in pollen. A series of 5' deletion constructs has been created and used to transform A. thaliana to analyse the 5' region of Bgp1. The results indicate that Bgp1 expression in the tapetum and pollen of Arabidopsis requires the presence of different 5' DNA sequences.