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Using dot-differential hybridization, an anther-preferentially expressed cDNA clone, BAN 215 was isolated from a cDNA library constructed from poly(A)^(+) RNAs of anther (from 2.0-5.0 mm long buds) of Chinese cabbage (Brassica campestris L. ssp. pekinensis). During flower development, BAN215 mRNA was first detected at a 2.1 mm bud stage containing a uninucleate microspore, and then the amount of transcripts increased until a 4.5 mm bud stage containing mature pollen. The total size of the BAN215 cDNA clone is 1,913 bp, and its deduced amino acid sequence showed a 98% identity to that of microspore-specific gene, Bpl9, of Brassica napus. Interestingly, the C-terminal region of the BAN215 polypeptide exhibits a sequence similar to that of pectin esterases from plants, bacteria and fungi. Genomic Southern blot analysis with 4 different Brassica species indicates that at least 3 putative pectin esterase gene families exist in each species. Three different groups of genomic clones (GBAN215-4, GBAN215-6 and GBAN215-12) were isolated using BAN 215 cDNA as a probe.
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