[Molecular identification of cytoplasmic male sterility associated gene orf 220 in leaf mustard (Brassica juncea var. multiceps Tsen et Lee)].

The cytoplasmic male-sterility (CMS) was transferred into leaf mustard by inter-varietal hybridization and subsequent backcrosses cms donor as using tuber mustard. Using specially designed primers, one specific band at 600-700 bp was distinctively amplified by PCR from cms plants of different backcrossed generations. It was genetically stable and cytoplasmically inheritable in the various backcrossed progenies. The sequencing result shows it is a 663 bp fragment with its own initiation and termination codons, presumably encoding for 220 amino acids (named orf 220). This deduced polypeptide had two trans-membrane hydrophilic domains and its N-terminus shared high similarity in amino acids constituents with COX III protein from Oenothera berteriana, ATP8 protein from radish and ORFB protein from sunflower. In addition, RT-PCR analysis showed, orf 220 gene was constitutively expressed in leaves, roots and floral buds. However, the direct evidence of its involvement in expression of cms trait needs further confirmation.