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Cadmium (Cd) is one of the most toxic heavy metals in the environment, and it severely represses photosynthesis, growth, development and nutrient uptake in photosynthetic organisms. Excessive cadmium (Cd) taken up by plants seriously threatens global food security and human health. Therefore, designing an eco-friendly and sustainable strategy that can reduce the accumulation of Cd in plants is a major challenge. Phosphorus (P), as an essential nutrient for plant growth, has been shown to play a pivotal role in mediating Cd-induced stress response. However, the molecular mechanisms underlying the crosstalk between phosphate signaling and Cd stress response remain largely uncharacterized, especially the role of the core phosphate homeostasis regulator Phosphate Starvation Response 1 (PSR1). Here, we used the model green microalga Chlamydomonas reinhardtii to investigate the physiological and transcriptomic responses to Cd stress in wild type (WT, CC-125) and PSR1 loss-of-function mutant (Crpsr1, CC-4267). Our results showed that the Crpsr1 mutant exhibited significantly enhanced Cd tolerance compared with WT under P-sufficient conditions, with a better growth phenotype and a significantly lower Cd accumulation. Transcriptome analysis revealed distinct gene expression profiles between WT and the Crpsr1 mutant in response to Cd treatment. Gene Ontology (GO) enrichment analysis showed that differentially expressed genes (DEGs) were mainly involved in primary metabolism, protein kinase activity, ion binding and transmembrane transport, which are critical processes for mitigating Cd stress. Notably, key genes associated with iron uptake and homeostasis were significantly upregulated in the Crpsr1 mutant under Cd stress, indicating a potential regulatory link between PSR1, iron homeostasis and Cd tolerance. Taken together, our findings establish a functional association between the central phosphate signaling regulator PSR1 and Cd stress response in green microalgae, and provide novel candidate genes and regulatory networks for developing engineered microalgae with enhanced Cd phytoremediation capacity.
Wang et al. (Thu,) studied this question.