17 April 2016
Optimal H 2O 2 levels and redox state regulated by cytosolic ascorbate peroxidase are key mechanisms regulating fibre elongation in cotton.
High-quality cotton fibre equates to a more comfortable textile. Fibre length is an important index of fibre quality. Hydrogen peroxide (H 2O 2) acts as a signalling molecule in the regulation of fibre elongation. Results from in vitro ovule culture suggest that the alteration of fibre cell H 2O 2 levels affects fibre development. Ascorbate peroxidase (APX) is an important reactive oxygen species (ROS) scavenging enzyme, and we found that GhAPX1A T/D T encoded one member of the previously unrealized group of cytosolic APXs (cAPXs) that were preferentially expressed during the fibre elongation stage. Transgenic cottons with up- and down-regulation of GhAPX1A T/D T were generated to control fibre endogenous levels of H 2O 2. Suppression of all cAPX (IAO) resulted in a 3.5-fold increase in H 2O 2 level in fibres and oxidative stress, which significantly suppressed fibre elongation. The fibre length of transgenic lines with over-expression or specific down-regulation of GhAPX1A T/D T did not show any obvious change. However, the fibres in the over-expression lines exhibited higher tolerance to oxidative stress. Differentially expressed genes (DEGs) in fibres at 10 days post-anthesis (DPA) of IAO lines identified by RNA-seq were related to redox homeostasis, signalling pathways, stress responses and cell wall synthesis, and the DEGs that were up-regulated in IAO lines were also up-regulated in the 10 DPA and 20 DPA fibres of wild cotton compared with domesticated cotton. These results suggest that optimal H 2O 2 levels and redox state regulated by cytosolic APX are key mechanisms regulating fibre elongation, and dysregulation of the increase in H 2O 2 induces oxidative stress and results in shorter fibres by initiating secondary cell wall-related gene expression.