New insights on the impact of light, photoperiod and temperature on the reproduction of green algae Ulva prolifera via transcriptomics and physiological analyses.

Ulva prolifera, a key species in China's massive green tides, is widely used in aquaculture, biofuel, pharmaceutical and cosmetic industries. In this study, we cultured U. prolifera under 100, 200, and 400 μmol m s with 10:14 and 12:12 light/dark at 15 °C and 25 °C, respectively, to investigate the effectiveness of light intensity, photoperiod, and temperature on the reproduction cell formation, oxidative status, photosynthesis on this species, as well as the related genes from transcriptomic perspective. Results showed that 25 °C or 400 μmol m s increased reproduction, although shorter daylength reduced cell numbers, correlating with higher O₂ content. The ascorbate-glutathione cycle activity was enhanced by reproduction, aligning with gene expression changes. Meiosis-specific gene MSH4 expression correlated positively with cell numbers. We speculate that higher temperature, light intensity, and shorter photoperiod enhance reproduction by inducing oxidative stress and signaling via the AsA-GSH cycle to regulate MSH4 expression.