Comparative Analysis of orf182 Widespread in Chinese Wild Rice Species for Hybrid Rice Breeding

The utilization of hybrid rice has successfully addressed food security challenges in China. However, the predominant use of wild-abortive (WA) cytoplasmic male sterility (CMS) systems in hybrid rice cultivation raises significant safety concerns. In this study, we have elucidated the distribution patterns of orf182 , a novel CMS gene identified in our previous work, in Chinese common wild rice. Mitochondrial sequencing and assembly of 11 representative wild rice species harboring orf182 revealed 16 novel genes. A total of 469 mitochondrial genes were classified into 36 gene families, with nine families containing single-copy homologous genes, indicating significant gene duplication in mitochondria. We observed a strong positive correlation between mitogenome size and the quantity and size of repetitive sequences. Collinearity analysis revealed extensive mitochondrial variation and large-scale inversions in Guangdong wild rice. Comparative genome analysis uncovered inversions, translocations, and several variations surrounding orf182 , with a 71 bp repeat sequence mediating the formation of the orf182 - nad6 chimeric gene. Gene copy number analysis (GCNV) revealed variable orf182 gene copy counts (1, 2, and 3) in wild rice species. Additionally, successful transformation of orf182 from various sources into sterile lines was achieved. These findings provide valuable resources for advancing hybrid rice development in China, thus contributing to enhanced food security.