Molecular Cloning and Sequence Analysis of the Toc33cDNA in Brassica napus Line Cr3529

Two primers, designed according to the Arabidoposis thaliana Toc33 sequence, were used to amplify the full coding region of the Toc33 cDNAs in leaves of a chlorophyll-reduced (Cr) mutant Cr3529 and its wild type 3529, Brassica napus, by RT-PCR technique. The RT-PCR results showed that the fragment homologous to Toc33 was expressed in Cr3529 as well as 3529 seedlings. PCR fragments were inserted into the pMD18-T vector and transferred into E. coli, then two cDNA clones, BnToc33-c and BnToc33, were obtained. Sequence analysis showed that the two sequences were 894 bp and the nucleotide and the deduced amino acid sequences were highly homologous to those of A. thaliana. There were three diverged nucleotides between the Cr3529 and the 3529 Toc33 cDNAs, i.e, GGT/AGT, TTG/TTT, AGG/AGT, all which belonged to missense mutation. The amino acid replacement (Leu/Phe) caused by TTG/TTT mutation located in the membrane anchor domain may result in chlorophyll-reduced character in Cr3529.