Overexpression of SikPsaF can increase the biomass of Broussonetia papyrifera by improving its photosynthetic efficiency and cold tolerance.

Photosynthesis is essential for the accumulation of organic compounds in plant leaves. Study of photosynthesis in the leaves of Broussonetia papyrifera is crucial for enhancing its biomass production, growth, and development. Here, we cloned the SikPsaF gene associated with photosynthesis from Saussurea involucrata and constructed a vector that was introduced into B. papyrifera to generate a transgenic strain. We then assessed various photosynthesis-related parameters in the transgenic plants and examined the function of this gene and its expression patterns under cold stress. The results showed that SikPsaF was localized to chloroplasts. Its expression was induced by light, and its expression was higher in the leaves than in other tissues. Furthermore, SikPsaF expression increased significantly under cold stress. The biomass of transgenic lines was greater than that of wild-type plants. Overexpression of this gene led to increases in the chlorophyll content and photosynthetic indices, which mitigated cell membrane damage and reduced reactive oxygen species (ROS) accumulation. SikPsaF overexpression also helped maintain high antioxidant enzyme activity and a high content of osmoregulatory substances during stress; the increased enzyme activities were due to up-regulated gene expression. Overexpression of SikPsaF has a major effect on growth and development by enhancing photosynthetic efficiency, improving yield, conferring cold resistance, and reducing damage to the cell membrane and ROS accumulation at low temperatures. In summary, our findings indicate that these transgenic plants have enhanced photosynthetic efficiency and resilience against biotic stresses.