Genetic, metabolomic and transcriptomic analyses of the cotton yellow anther trait

In the fiber industry, cotton (Gossypium hirsutum L.) is an important crop. One of the most important morphology traits of plants is the color of the anthers, is closely related to pollen fertility and stress resistance. Upland cotton anthers appear white, while island cotton and many wild cotton species have yellow anthers. Carotenoids are natural pigments in plants which involved in many metabolic processes, including photosynthesis, photoprotection, photomorphogenesis, growth and development. Here, we characterized the yellow anther trait of G. hirsutum. Carotenoid and flavonoid profiles in the yellow anthers were greatly altered compared to that in the white anthers, indicating that both carotenoids and flavonoids contribute to the yellow anther phenotype. Map-based cloning identified GhYA (GH_A05G4013) encoding a phytoene synthase to be the candidate gene responsible for anther coloration. GhYA is predominantly expressed in anthers, with its expression level gradually decreasing with the development of anthers. Haplotype analysis revealed that white anthers are associated with two haplotypes, with X74 belonging to HAP1. Through evolutionary analysis, it was found that although there are many white anther Germplasm in upland cotton, the two types of white anther haplotypes were mutated from yellow anthers respectively. Comparative transcriptome analysis between the yellow anther and white anther accessions revealed differentially expressed genes related to both the carotenoid and flavonoid biosynthesis pathways, in line with the changed profiles of the two types of metabolites in yellow anthers; meanwhile, it also indicates potential cross-talk between the flavonoid and carotenoid pathways. According to the results, the PSY gene is critical for the regulation of carotenoids accumulation in cotton anthers.