Expressions and dimerization affinities of three highly identical APETALA3 genes in Brassica napus

Abstract

Three highly identical cDNA clones of APETALA3 (AP3) gene, BnAP3-2, BnAP3-3 and BnAP3-4 were isolated from Brassica napus L. by RT-PCR. The sequence analysis showed that all the three AP3 cDNAs contained a complete open reading frame. Their nucleotide sequences had 91-97 % similarity and their predicted amino acid sequences shared 93-98 % identity. Real-time quantitative RT-PCR result showed that all the three BnAP3 genes were expressed at the transcriptional level in petals as well as stamens. Among the three BnAP3 genes, BnAP3-3 was expressed at the highest level and BnAP3-2 was expressed at the lowest level in petals. The transcription level of BnAP3-3 was 1.59 times than that of BnAP3-2. The transcription levels of BnAP3-2, BnAP3-3 and BnAP3-4 in stamen were 7.75, 5.11 and 3.88 times than those in petal, respectively. The yeast two-hybrid assays results showed that all the three BnAP3 proteins could form strong heterodimers with BnPI, and obviously different dimerization affinities among the three proteins to BnPI were observed. The ratio of the affinity of BnAP3-2, BnAP3-3 and BnAP3-4 to BnPI-1 was 1.27:1:1.62. Although the three BnAP3 genes were highly identical, the differences of their expression and affinity of protein interaction might reflect some functional divergence.