Combined analysis of reactive oxygen species and symbiotic bacteria profiles reveals their potential effects on the sorus development of Saccharina japonica

Symbiotic bacteria are highly associated with the growth and development of seaweeds, primarily due to their ability to secrete bioactive metabolites. Reactive oxygen species (ROS) play a critical role in regulating growth and development in S. japonica, but the interactions between symbiotic bacterial communities and ROS on the vegetative and sorus areas of S. japonica remain unclear. In this study, the content of ROS (hydrogen peroxide), malondialdehyde (MDA) and NADPH in the vegetative and sorus areas of S. japonica were determined. Results revealed significantly higher concentration of ROS, MDA, and NADPH in the sorus area, indicating an elevated oxidative environment in reproductive areas. Using 16S rRNA gene amplicon sequencing, both epiphytic and endophytic bacterial communities were analyzed. Comparative analysis revealed pronounced divergence in endophytic bacterial diversity and composition between vegetative and sorus areas. Notably, the core genera norank_f_Rhizobiaceae exhibited strong positive correlations with NADPH accumulation, suggesting their potential role in both oxidative process modulation and holobiont functional stability of S. japonica. These findings suggest potential interactions between symbiotic bacteria and ROS metabolism during S. japonica sorus development, offering new perspectives for understanding and potentially improving seaweeds cultivation strategies to enhance stress resilience.