GhPSY,a phytoene synthase gene,is related to the red plant phenotype in upland cotton (Gossypium hirsutum L.)

Carotenoids are important accessory pigments in plants that are essential for photosynthesis. Phytoene synthase (PSY), a rate-controlling enzyme in the carotenoid biosynthesis pathway, has been widely characterized in rice, maize, and sorghum, but at present there are no reports describing this enzyme in cotton. In this study, GhPSY was identified as a candidate gene for the red plant phenotype via a combined strategy using: (1) molecular marker data for loci closely linked to R1; (2) the whole-genome scaffold sequence from Gossypium raimondii; (3) gene expression patterns in cotton accessions expressing the red plant and green plant phenotypes; and (4) the significant correlation between a single nucleotide polymorphisms (SNP) in GhPSY and leaf phenotypes of progeny in the (Sub16 × T586) F₂ segregating population. GhPSY was relatively highly expressed in leaves, and the protein was localized to the plastid where it appeared to be mostly attached to the surface of thylakoid membranes. GhPSY mRNA was expressed at a significantly higher level in T586 and SL1-7-1 red plants than TM-1 and Hai7124 green plants. SNP analysis in the GhPSY locus showed co-segregation with the red and green plant phenotypes in the (Sub16 × T586) F₂ segregating population. A phylogenetic analysis showed that GhPSY belongs to the PSY2 subfamily, which is related to photosynthesis in photosynthetic tissues. Using a reverse genetics approach based on Tobacco rattle virus-induced gene silencing, we showed that the knockdown of GhPSY caused a highly uniform bleaching of the red color in newly-emerged leaves in both T586 and SL1-7-1 plants with a red plant phenotype. These findings indicate that GhPSY is important for engineering the carotenoid metabolic pathway in pigment production.