A Brassica oleracea gene expressed in a variety-specific manner may encode a novel plant transmembrane receptor

The species Brassica oleracea includes several agricultural varieties characterized by the proliferation of different types of meristems. Using a combination of subtractive hybridization and PCR (polymerase chain reaction) techniques we have identified several genes which are expressed in the reproductive meristems of the cauliflower curd (B. oleracea var. botrytis) but not in the vegetative meristems of Brussels sprouts (B. oleracea var. gemmifera) axillary buds. One of the cloned genes, termed CCE1 (CAULIFLOWER CURD EXPRESSION 1) shows specific expression in the botrytis variety. Preferential expression takes place in this variety in the meristems of the curd and in the stem throughout the vegetative and reproductive stages of plant growth. CCE1 transcripts are not detected in any of the organs of other B. oleracea varieties analyzed. Based on the nucleotide sequence of a cDNA encompassing the complete coding region, we predict that this gene encodes a transmembrane protein, with three transmembrane domains. The deduced amino acid sequence includes motifs conserved in G-protein-coupled receptors (GPCRs) from yeast and animal species. Our results suggest that the cloned gene encodes a protein belonging to a new, so far unidentified, family of transmembrane receptors in plants. The expression pattern of the gene suggests that the receptor may be involved in the control of meristem development/arrest that takes place in cauliflower.