HAPLOID AND DIPLOID EXPRESSION OF A BRASSICA-CAMPESTRIS ANTHER-SPECIFIC GENE PROMOTER IN ARABIDOPSIS AND TOBACCO

The anther-specific cDNA clone Bcp1 from Brassica campestris is expres sed in both the haploid pollen and diploid tapetum, as shown by in sit u hybridization. We have isolated Bgp1, a genomic clone homologous to Bcp1. The coding region and extensive 5' flanking sequences of Bgp1 ha ve been sequenced, and the coding region shows 88% identity with Bcp1. RNA gel blot analysis confirmed the expression of Bgp1-specific trans cripts in B. campestris pollen. A 767 bp 5' DNA fragment was fused to the reporter gene beta-glucuronidase (gus) and introduced into both Ar abidopsis thaliana and Nicotiana tabacum by transformation. This 5' fr agment directed high-level expression in the pollen and tapetum of tra nsgenic 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' regio n of Bgp1. The results indicate that Bgp1 expression in the tapetum an d pollen of Arabidopsis requires the presence of different 5' DNA sequ ences.