Mitochondrial-targeted Expression of orf456 Causes Male Sterility in Chinese Cabbage (Brassica rapa L.)

Cytoplasmic male sterility (CMS) is a phenomenon specific to plant reproduction that has been extensively exploited for hybrid seed production. Orf456 was previously identified as a candidate gene mediating male sterility in pepper. To gain further insight of this candidate gene, we carried out experiments to transform Chinese cabbage (Brassica rapa L.). About 30 T1 transgenic lines were obtained and approximately 50 % of T1 transgenic Chinese cabbage lines showed male-sterility. To evaluate pollen viability, three different approaches including plasmolysis test, staining pollen and in vitro germination assay were used. Analysis of the CMS transgenic lines showed that trasgenic Chinese cabbages produced aberrant pollen development while some were unable to produce pollen. In conclusion, the mitochondrial orf456 gene could induce partial male sterility in transgenic Chinese cabbage. Nevertheless, how the orf456 gene precisely functions to induce male sterility and its biochemical function remains to be discovered.