Isolation and characterization of o-acetylserine (thiol) lyase, an enzyme of the cysteine biosynthetic pathway of vetch (Vicia sativa L.)

A putative o-acetylserine (thiol) lyase (OAS-TL; EC 2.5.1.47) gene was successfully cloned and characterized from vetch, Vicia sativa L. cv. Blanche Fleur. The gene, named Voas-tl5 (GenBank Accession No. DQ456491) had a cDNA length of 871 bp with its open reading frame coding for a polypeptide of 68 amino acid residues. In semi-quantitative RT-PCR, mRNA transcription patterns revealed that the Voas-tl5 gene was highly transcribed in leaf, pod and seed tissues. Southern blot analysis indicated that Voas-tl5 was a single-copy gene. Phylogenetic analysis revealed that the gene belonged to the Bsas 5 sub-group. Further, the function of the gene was indicated by over-expression in the E. coli NK3 mutant strain, lacking the ability to synthesize cysteine. The resultant transformed bacteria were able to grow on minimal media lacking cysteine. Understanding the molecular and biochemical properties of enzymes involved in the plant sulfate assimilation pathway, such as OAS-TL, can be applied to the future development of crops with greater agricultural productivity.