Abstract
Alkaline environments such as alkaline lands, lakes, and industrial wastewater are not conducive to the growth of plants and microorganisms due to high pH and salinity. ChbZIP1 is a bZIP family transcription factor isolated from an alkaliphilic microalgae (Chlorella sp. BLD). Previous studies have demonstrated its ability to enhance alkaline tolerance in Arabidopsis thaliana. However, the potential of ChbZIP1 to confer similar alkaline tolerance in other microalgae remains unclear, and the specific mechanisms are not fully understood. The analysis of cellular physiological and biochemical indicators revealed that the ChbZIP1 transformants exhibited enhanced photosynthetic activity, increased lipid accumulation, and reduced fatty acid unsaturation. Genes associated with cellular reactive oxygen species (ROS) detoxification were found to be upregulated, and a corresponding increase in antioxidant enzyme activity was detected. In addition, the relative abundance of intracellular ROS and malondialdehyde (MDA) was significantly lower in the transformants. In summary, our research indicates that ChbZIP1 enhances the tolerance of Chlamydomonas reinhardtii to alkaline environments through several mechanisms, including the repair of damaged photosynthesis, increased lipid accumulation, improved fatty acid unsaturation, and enhanced antioxidant enzyme activity. This study aims to contribute to a more comprehensive understanding of the mechanisms underlying alkalinity tolerance in microalgae and offers new insights and theoretical foundations for the utilization of microalgae in alkaline environments.