Hydrogen peroxide mediates high-intensity blue light-induced hypocotyl phototropism of cotton seedlings

Phototropism is a classic adaptive growth response that helps plants to enhance light capture for photosynthesis. It was shown that hydrogen peroxide (H(2)O(2)) participates in the regulation of blue light-induced hypocotyl phototropism; however, the underlying mechanism is unclear. In this study, we demonstrate that the unilateral high-intensity blue light (HBL) could induce asymmetric distribution of H(2)O(2) in cotton hypocotyls. Disruption of the HBL-induced asymmetric distribution of H(2)O(2) by applying either H(2)O(2) itself evenly on the hypocotyls or H(2)O(2) scavengers on the lit side of hypocotyls could efficiently inhibit hypocotyl phototropic growth. Consistently, application of H(2)O(2) on the shaded and lit sides of the hypocotyls led to reduced and enhanced hypocotyl phototropism, respectively. Further, we show that H(2)O(2) inhibits hypocotyl elongation of cotton seedlings, thus supporting the repressive role of H(2)O(2) in HBL-induced hypocotyl phototropism. Moreover, our results show that H(2)O(2) interferes with HBL-induced asymmetric distribution of auxin in the cotton hypocotyls. Taken together, our study uncovers that H(2)O(2) changes the asymmetric accumulation of auxin and inhibits hypocotyl cell elongation, thus mediating HBL-induced hypocotyl phototropism. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s44154-023-00111-3.