Identification of fertility restoration candidate genes from a restorer line R186 for Gossypium harknessii cytoplasmic male sterile cotton.

Background: The utilization of heterosis based on three-line system is an effective strategy in crop breeding. However, cloning and mechanism elucidation of restorer genes for cytoplasmic male sterility (CMS) in upland cotton have yet been realized.

Results: This research is based on CMS line 2074A with the cytoplasm from Gossypium harknessii (D) and restorer line R186. The offspring of 2074A × R186 were used to conduct genetic analysis. The fertility mechanism of 2074A can be speculated to be governed by multiple genes, since neither the single gene model nor the double genes model could be used. The bulked segregant analysis (BSA) for (2074A × R186) F determined the genetic interval of restorer genes on a region of 4.30 Mb on chromosome D05 that contains 77 annotated genes. Four genes were identified as candidates for fertility restoration using the RNA-seq data of 2074A, 2074B, and R186. There are a number of large effect variants in the four genes between 2074A and R186 that could cause amino acid changes. Evolutionary analysis and identity analysis revealed that GH_D05G3183, GH_D05G3384, and GH_D05G3490 have high identity with their homologs in D, respectively. Tissue differential expression analysis revealed that the genes GH_D05G3183, GH_D05G3384, and GH_D05G3490 were highly expressed in the buds of the line R186. The predicted results demonstrated that GH_D05G3183, GH_D05G3384 and GH_D05G3490 might interact with GH_A02G1295 to regulate orf610a in mitochondria.

Conclusion: Our study uncovered candidate genes for fertility restoration in the restorer line R186 and predicted the possible mechanism for restoring the male fertility in 2074A. This research provided valuable insight into the nucleoplasmic interactions.