THE ANTHER-SPECIFIC PROTEIN ENCODED BY THE BRASSICA-NAPUS AND ARABIDOPSIS-THALIANA A6-GENE DISPLAYS SIMILARITY TO BETA-1,3-GLUCANASES

An anther-specific Brassica napus cDNA, A6, and two corresponding Arabidopsis thaliana genes have been isolated. Sequence analyses of A6 revealed similarity to beta-1,3-glucanases. The deduced A6 protein differs from other beta-1,3-glucanases in the possession of a long C-terminus. Immunoblotting using an antibody raised to the A6 protein detects a temporal 60 kDa protein in B. napus buds, suggesting that the long C-terminal region is present in the mature protein. A6 promoter-GUS and RNase fusions demonstrate that the A6 gene is tapetum-specific and temporally expressed with a peak in activity when the plant normally expresses callase (a complex of endo- and exo-beta-1,3-glucanase activities). The sequence similarity of A6 to other beta-1,3-glucanases, coupled with the temporal and spatial expression data, suggests that A6 may be part of the callase enzyme complex.