A Study on the Role of Reactive Oxygen Species in Regulating the Growth and Development of Saccharina japonica Gametophytes

In this study, we elucidated the regulatory mechanism underlying vegetative growth and reproductive development of Saccharina japonica gametophytes, thereby provided theoretical underpinnings and technical support for the hybridization breeding and seedling raising from gametophyte clones. This study investigated reactive oxygen species (ROS) level in female gametophytes during its natural growth and development. we investigated gametophyte′s growth and development process by administering exogenous H₂O₂ and a ROS inhibitor, diphenyleneiodonium chloride (DPI). Our findings revealed a notable increase in ROS level following female gametophyte crushing, which peaked at 12 h and subsequently decreased to baseline level by 48 h. This observation suggested that mechanical injury triggers ROS production in female gametophytes. Furthermore, under reproductive development condition, we observed a gradual increase in ROS level during the transition from the vegetative growth stage (days 1—9) to the emergence of seedlings (days 9—12). In contrast, female gametophytes maintained in a vegetative growth state exhibited a peak in ROS level on day 9, followed by a decline to the level comparable to that observed on day 3. Additionally, we examined the effects of diphenyleneiodonium chloride (DPI) and H₂O₂ on gametophyte development. DPI exerted an inhibitory effect on gametophyte development. The degree of inhibition increased with the increase of DPI concentration. Conversely, appropriate concentrations of H₂O₂ promoted gametophyte development, but higher concentrations resulted in decreased promotion or even inhibitory effects. In conclusion, our findings provided compelling evidence that ROS serves as a signaling molecule regulating the growth and development of S. japonica gametophytes. Our findings offered novel insights and methodologies for further investigating the regulatory mechanisms underlying S. japonica gametophyte growth and development.