Molecular analysis of structural genes involved in flavonoids biosynthesis in naturally colored cotton

In order to facilitate the development of cotton (Gossypium hirsutum L.) strains with colored fiber, the genetic and developmental control of flavonoids in fibers must be understood. The major goal of this study was to determine whether anthocyanidins accumulate in three different natural colored cotton fibers during their development, and to document the expression levels of flavonoid genes necessary for the production of anthocyanidins to determine if differences in expression levels reflect differences in anthocyanidin production. Most flavonoid structural genes were more highly expressed during fiber elongation than before the beginning of secondary cell wall formation. High performance liquid chromatography (HPLC) analyses showed that the abundance of anthocyanidins was higher in brown fibers than in green or white fibers. Anthocyanidins were present at high levels in fibers, starting at 20 d post-anthesis of fiber development, which is almost at the end of the fiber elongation stage. Brown cotton contains higher delphinidin levels than of green and white cotton. This pattern is consistent with greater expression of anthocyanin pathway genes in brown fibers. In naturally colored cotton, the enzyme Lar (leucoanthocyanidin reductase) converted leucoanthocyanidins to catechin, which are proanthocyanins (PAs) precursor subunits. It is suggested that failure to produce anthocyanins is likely due to a combination of insufficient expression of Ufgt (UDP-glucose: flavonoid 3-O-glucosyltransferase) and high expression of Lar and Anr (anthocyanidin reductase).

Automated summary

This study found that the abundance of anthocyanidins in brown cotton fibers was higher than in green or white cotton fibers, and high levels of anthocyanidins began to appear after 20 days of fiber development. Brown cotton contained higher levels of delphinidin compared to green and white cotton. This pattern is consistent with higher expression of anthocyanin pathway genes in brown fibers.