Cloning and Expression Analysis of an Aldehyde Dehydrogenase Gene from Camellia oleifera

Aldehyde dehydrogenases (ALDHs) are members of the NAD or NADPH-dependent protein superfamily that catalyze the oxidation of highly reactive aliphatic and aromatic aldehyde molecules to their corresponding non-toxic carboxylic acids. In the present study a full-length ALDH cDNA from Camellia oleifera was isolated and cloned using RT-PCR, 3'RACE and 5'RACE. It was named CoALDH (GenBank accession number: KJ910340). The full-length cDNA is 1809 bp with an open reading frame of 1506 bp encoding 501 amino acids. Sequence analysis showed that molecular mass of CoALDH is 54.5137 kDa with a theoretical pI of 5.50. CoALDH has three transmembrane domains and a cytoplasmic transit peptide of 36 amino acid residues. The CoALDH protein contains three highly conserved structural domains that are common to the aldehyde dehydrogenase gene families including a glutamic acid activation site, cysteine activation site and coenzyme binding site. The BL21(DE3) bacteria harboring the pET30a-ALDH was induced to express the 55 kDa target ALDH protein. Real-time quantitative PCR (qPCR) revealed that CoALDH was down-regulated during the early stage of lipid synthesis but up-regulated during the middle and late stage of lipid synthesis in C. oleifera. CoALDH might play an important role in metabolizing excess aldehydes during the stages of lipid synthesis in C. oleifera.