Hydrogen sulfide upregulates the alternative respiratory pathway in mangrove plant Avicennia marina to attenuate waterlogging-induced oxidative stress and mitochondrial damage in a calcium-dependent manner.

Hydrogen sulfide (H 2 S) is considered to mediate plant growth and development. However, whether H 2 S regulates the adaptation of mangrove plant to intertidal flooding habitats is not well understood. In this study, sodium hydrosulfide (NaHS) was used as an H 2 S donor to investigate the effect of H 2 S on the responses of mangrove plant Avicennia marina to waterlogging. The results showed that 24-h waterlogging increased reactive oxygen species (ROS) and cell death in roots. Excessive mitochondrial ROS accumulation is highly oxidative and leads to mitochondrial structural and functional damage. However, the application of NaHS counteracted the oxidative damage caused by waterlogging. The mitochondrial ROS production was reduced by H 2 S through increasing the expressions of the alternative oxidase genes and increasing the proportion of alternative respiratory pathway in the total mitochondrial respiration. Secondly, H 2 S enhanced the capacity of the antioxidant system. Meanwhile, H 2 S induced Ca 2+ influx and activated the expression of intracellular Ca 2+ -sensing-related genes. In addition, the alleviating effect of H 2 S on waterlogging can be reversed by Ca 2+ chelator and Ca 2+ channel blockers. In conclusion, this study provides the first evidence to explain the role of H 2 S in waterlogging adaptation in mangrove plants from the mitochondrial aspect.