Spermine promotes the formation of conchosporangia in Porphyra haitanensis through superoxide anions

The transition from conchocelis to conchosporangia in Pyropia haitanensis is a critical phase in its life cycle, yet the underlying regulatory mechanisms remain unclear. This study reveals that the polyamine spermine promotes conchosporangia formation through the signaling role of superoxide anions. spermine treatment significantly increased superoxide anions levels, an effect suppressed by the NADPH oxidase inhibitor DPI, indicating that superoxide anions acts as a key signaling molecule in this process. Transcriptomic analysis showed that spermine enhances photosynthesis, carbon assimilation, and respiratory metabolism while activating antioxidant enzymes (SOD, APX, and CAT) to regulate hydrogen peroxide (H2O2) balance and maintain redox homeostasis. Additionally, SPM upregulated genes related to photosynthetic carbon fixation and the C2 oxidative photosynthesis pathway, providing energy and metabolic support for developmental transition. This study proposes that SPM coordinates superoxide anions signaling, photosynthesis, and antioxidant systems to facilitate the transition from conchocelis to conchosporangia in P. haitanensis.