GhCDNC and GhCYP706B1 genes mediate gossypol biosynthesis in upland cotton

In cotton the identification and characterization of natural defense is a cost-effective, sustainable, and environment-friendly strategy to combat cotton pests. The secondary metabolites traits in cotton plant i.e., toxic gossypol glands play significant role for development and self-defense mechanism. To utilize gossypol in breeding implements, the understanding of gossypol initiation biosynthesis genes has vital importance at reproductive organ development stages.

Cotton germplasm of 100 genotypes screened visually based on gossypol glandedness and a core set of ten genotypes was developed. Further three genotypes FH-330 (high glanding), F-280 (low glanding) and IRMA-197 (glandless) were used for determining the transcript abundance of twelve gossypol biosynthesis genes.

Out of 100, germplasm categorized as (76) high glanding, (22) medium glanding), one genotype for each (low glanding) and (glandless) category. Real-time qPCR analysis revealed varied expression patterns among selected three genotypes. Out of twelve, three genes CYP706B1, CDNC and 2ODD-1 had strong expression levels in all tested tissues in high glanded genotype, while, slight or no expression of these genes was recorded in low glanding and glandless genotype, respectively. The shell of developing boll (10, 20, 30 DPA), and developing embryo (20, 30 DPA) showed substantially medium to maximum expression, respectively while high to medium expression was recorded in sepals and leaf tissue.

Our study demonstrated that CYP706B1, CDNC and 2ODD-1 are the most promising genes involved in gossypol biosynthesis. Developing boll shell, developing embryo, leaf and sepal also have significant ability to synthesize gossypol. This will provide scientists a way to manipulate gossypol contents in economically important organs of cotton plant for targeted breeding.