Duplication of the Brassica oleracea APETALA1 floral homeotic gene and theevolution of domesticated cauliflower

Development of the cauliflower phenotype in Arabidopsls thaliana requires m utations at both the CAULIFLOWER and APETALA1 loci. BoAP1 is the Brassica o leracea orthologue to the Arabidopsis API gene, and is present in two copie s in Brassica genomes, The BoAP1-A gene appears to encode a full-length pro tein, but BoAP1-B alleles in B. oleracea contain insertions that lead to pr emature translation termination. The BoAP1-B allele found in most B, olerac ea subspecies, including B. oleracea ssp, botrytis (domesticated cauliflowe r) contains a 9 bp insertion in exon 4, This insertion leads to the formati on of an in-frame translation termination codon, and these alleles can enco de a protein that Is truncated at the K domain of this MADS-box transcripti onal activator. The allele in B, oleracea ssp. oleracea (wild cabbage) lack s this insertion and instead contains a downstream 4 bp frameshift mutation resulting in the formation of a nonsense mutation. The structure of the Bo AP1-B alleles suggests that they are impaired in their ability to perform t heir floral meristem identity function. These mutations, in conjunction wit h mutations at the BoCAULIFLOWER (BoCAL) locus, may be associated with the evolution of domesticated cauliflower.