The cDNA Sequence of a Cauliflower apetala-1/squamosa Homolog

The Arabidopsis gene apetala-1 and its Ant irrh inum counterpart squamosa play an important role in regulating floral meristem identity. Functional gene expression is required for the transition of an inflorescence meristem into a floral meristem. This gene interacts with a second meristem identity gene, leafy (Arabidopsis)/flo (Antirrhinum), during the early stages of floral development (Coen and Carpenter, 1993). Other genes such as apetala-2 and cal also interact with the primary genes during floral initiation (Jofuku et al., 1994; Bowman et al., 1993). To extend the knowledge of floral development further we have been characterizing genes associated with the early stages of flowering in cauliflower (Anthony et al., 1993; Jordan et al., 1994). This species is a good model system with which to investigate the difference between inflorescence and floral meristems, because it produces an arrested developmental stage between the vegetative form and floral differentiation, i.e. the characteristic edible white curd. A study of these genes is important for the long-term aims of correcting genetic based floral defects that can seriously reduce the commercial value of the cauliflower. In this paper we report the isolation of an apetala-1 homolog designated boapl. Total RNA (extracted from curd tissue undergoing pedicel elongation) was reverse transcribed. The complete sequence of boapl was obtained by rapid amplification of cDNA ends (Frohman et al., 1988). Interna1 gene priiner sequences were derived by computer comparisons of the squamosa and apetala-1 gene sequences. PCR products were subcloned into pBluescript and sequenced (Table I). The 1051-bp boapl gene encodes a putative protein 256 amino acids long. The deduced amino acid sequence of the boapl gene product in cauliflower was 66% identical with 5QUAMOSA and 95% identical with APETALA-I. These proteins share a very conserved, 56amino acid-long DNA-binding domain (the MADS-box). In addition, they possess a second conserved domain called the K-domain, a region with structural similarity to the coiled-coil domain in keratin (Ma et al., 1991). Proteins