Exogenous Jasmonic Acid Inhibits Cotton Fiber Elongation

Jasmonic acid (JA) is a well-characterized phytohormone that acts in various ways to influence plant development. Its role in cotton fiber development, however, has not yet been thoroughly explored. In this study, JA was proven to be an inhibitor of ovule and fiber development in vitro. Continuous exogenous JA application inhibited fiber elongation. This effect was dependent on development stage and dosage. Fibers and ovules at three different stages of development and different JA dosages were compared. The most serious suppression was detected when ovules 1 day before anthesis (-1 DPA) were cultured in medium with 2.5 μM JA. Genes related to trichome and fiber development responded differently to JA treatment between -1 DPA and 1 day post anthesis (1 DPA). JAs (JA and JA-Ile) quantification showed that JAs content was sharply decreased from -1 DPA to 5 DPA ovules, which indicated that JA was negatively associated with fiber elongation in vivo. In addition, gene expression analysis showed the same trend. Our results demonstrate that there was a negative relationship of JA with fiber elongation in vitro and in vivo. These results are meaningful for uncovering the mechanism of fiber elongation in cotton.