The calcium sensor GhCaM7 promotes cotton fiber elongation by modulating reactive oxygen species (ROS) production

Summary Fiber elongation is the key determinant of fiber quality and output in cotton ( G ossypium hirsutum ). Although expression profiling and functional genomics provide some data, the mechanism of fiber development is still not well understood. Here, a gene encoding a calcium sensor, G h C a M 7 , was isolated based on its high expression level relative to other G h C a M s in fiber cells at the fast elongation stage. The level of expression of G h C a M 7 in the wild‐type and the fuzzless/lintless mutant correspond to the presence and absence, respectively, of fiber initials. Overexpressing G h C a M 7 promotes early fiber elongation, whereas G h C a M 7 suppression by RNA i delays fiber initiation and inhibits fiber elongation. Reactive oxygen species ( ROS ) play important roles in early fiber development. ROS induced by exogenous hydrogen peroxide ( H 2 O 2 ) and C a 2+ starvation promotes early fiber elongation. G h C a M 7 overexpression fiber cells show increased ROS concentrations compared with the wild‐type, while G h C a M 7 RNA i fiber cells have reduced concentrations. Furthermore, we show that H 2 O 2 enhances C a 2+ influx into the fiber and feedback‐regulates the expression of GhCaM7 . We conclude that G h C a M 7, C a 2+ and ROS are three important regulators involved in early fiber elongation. G h C a M 7 might modulate ROS production and act as a molecular link between C a 2+ and ROS signal pathways in early fiber development.