Relationship between open reading frame 320, a gene causing male sterility in tomatoes, and cytoplasmic male sterility in potatoes

Cytoplasmic male sterility (CMS) is a trait wherein plants cannot develop normal male organs because of mitochondrial genes. In potatoes (Solanum tuberosum), reports on the relevant mitochondrial genes remain scarce. Many potato cultivars express pollen sterility caused by mitochondria, thereby limiting their use as male parents in breeding. Therefore, identifying the causal genes is crucial for potato breeding. In this study, we focused on the T/β cytoplasm type, the most prevalent cytoplasm of potato worldwide, to explore mitochondrial genes involved in CMS in potatoes. We identified a novel gene, open reading frame 320 (orf320) from potato with T/β type cytoplasm by comparing the mitochondrial genomes. The accumulation level of orf320 transcripts was drastically reduced in the anthers of a fertile potato cultivar compared with those of a sterile cultivar. Functional analysis of tomatoes showed that overexpression of orf320 with a mitochondrial transit peptide induced male sterility phenotype accompanying abnormal anther development and pollen abortion. Furthermore, an investigation of orf320 in 124 potato cultivars revealed that this gene is tightly associated with the T/β type cytoplasm and is absent from cultivars with other cytoplasm types. These findings provide evidence that orf320 is a candidate CMS-causing gene in male sterility of T/β type cytoplasm, offering valuable insights for future potato breeding.