Abstract
The cotton fiber is a unique elongated cell that is useful for investigating cell differentiation. Previous studies have demonstrated the importance of factors such as sugar metabolism, the cytoskeleton and hormones, which are commonly known to be involved in plant cell development, while the secondary metabolites have been less regarded. By mining public data and comparing analyses of fiber from two cotton species, we found that the flavonoid metabolism is active in early fiber cell development. Different flavonoids exhibited distinct effects on fiber development during ovule culture; among them, naringenin (NAR) could significantly retard fiber development. Naringenin is a substrate of flavanone 3-hydroxylase (F3H), and silencing the F3H gene significantly increased the NAR content of fiber cells. Fiber development was suppressed following F3H silencing, but the over-expression of F3H caused no obvious effects. Significant retardation of fiber growth was observed after the introduction of the F3H-RNAi segment into the high-flavonoid brown fiber cotton T586 line by cross. A greater accumulation of NAR as well as much shorter fibers was also observed in the BC1 generation plants. These results suggest that NAR is negatively associated with fiber development and the metabolism mediated by F3H is important in fiber development, thus highlighting that flavonoid metabolism represents a novel pathway with the potential for cotton fiber improvement.