Abstract：In the present study, a cDNA-AFLP differential fragment was isolated from the stem of tuber mustard (Brassica juncea var. tumida) at different swelling stages, to explain the mechanism of swelling of tumor-like stems. The full-length cDNA (named orf451, GenBank accession: KM213220), was cloned by rapid amplification of cDNA ends (RACE). Both the nucleotide sequence and putative amino acid sequence were analyzed. The results showed that the length of orf451 was 1 512 bp, and it contained a 1 356 bp long open reading frame. The orf451 shared high similarity (90%) with polygalacturonases/glycoside hydrolase in nucleotide sequence, and its protein possessed of the functional domains of polygalacturonases (pectate lyase) and glycoside hydrolase. The expression analysis by Real-time quantitative PCR (qRT-PCR) revealed that orf451 highly expressed at the early stage during the swelling of tumor-like stems and was rich in epidermis and outer cortex. These results suggested that orf451 was highly involved in the hydrolysis of polysaccharides in epidermis and outer cortex during the swelling of tumor-like stems. These study provide basic data for exploring the molecular mechenism of tumor-like stems swelling.
