TERMINAL FLOWER 1-like genes in Brassica species

Brassica napus is an amphidiploid species with an AACC genome. TERMINAL FLOWER 1-like genes were cloned by PCR from the genomic DNA of these species and their structures were characterized. Southern hybridization using one of the PCR clones as a probe showed the presence of at least four copies of TFL1-like genes in the B. napus genome, whereas three different clones, BNTFL1-1, BNTFL1-2 and BNTFL1-3 were obtained from the PCR products. RT-PCR analysis showed that TFL1-like genes were predominantly expressed in flowers. Sequence analysis of these clones revealed that they were highly homologous to each other with only a few amino acid changes. However, marked differences were detected within the regions of the first intron and the 3' untranslated region. Insertions of a stretch of sequences in these regions distinguished BNTFL1-2 from the other two clones, indicating that BNTFL1-1 and BNTFL1-3 may have been duplicated from a single ancestral gene. To examine the possibility that these genes originated from its ancestral genomes AA and CC, we isolated TFL1-like sequences from the genomes of B. rapa and B. oleracea with the allogenic AA and CC genomes, respectively. Our results showed that the unique sequence found in BNTFL1-2 was conserved in the TFL1-like genes from B. rapa and the sequences of BNTFL1-1 and BNTFL1-3 were very similar to those of the genes from B. oleracea, indicating that BNTFL1-2 may have originated from the AA genome and the other two genes from the CC genome.