Hydrogen peroxide signaling mediates fertilization and post-fertilization development in the red alga Bostrychia moritziana

Reactive oxygen species (ROS) signaling has a multitude of roles in cellular processes throughout biology. We hypothesized that red algal fertilization may offer an interesting model to study ROS-mediated signaling as the stages of fertilization are complex and unique. We microscopically localized ROS production and monitored the expression of three homologues of NADPH-oxidase in reproductive cells during fertilization. ROS were instantaneously produced by spermatia (sperm) when they attached to female trichogynes, diffused across the cell membrane in the form of H2O2, and triggered ROS generation in the carpogonium (egg) as well as carpogonial branch cells which are not in direct contact with spermatia. The expression of NADPH-oxidase homologues, Bmrbohs, began to be upregulated in the female plant upon gamete binding, peaking during the fertilization process and descending back to their original level after fertilization. Pretreatment with diphenylene iodonium (DPI) or caffeine blocke...