Non-Tandem CCCH-Type Zinc-Finger Protein CpZF_CCCH1 Improves Fatty Acid Desaturation and Stress Tolerance in Chlamydomonas reinhardtii

The properties and nutritional value of microalgal bioproducts depend significantly on fatty acid desaturation, which is generally modulated by manipulating the culture conditions or associated gene expressions. Here, we investigated the role of CpZF_CCCH1, a non-tandem CCCH-type zinc-finger (non-TZF) protein, in elevating polyunsaturated fatty acid (PUFA) content (11.00-16.36%) in Chlamydomonas reinhardtii. Through lipidomic and flow cytometry analyses, we observed reduced triacylglycerol accumulation (7.01-21.15%) and elevated levels of membrane lipids containing PUFAs (7.81-46.18%) in C. reinhardtii overexpressing CpZF_CCCH1. Additionally, overexpression of nucleus-located CpZF_CCCH1 downregulated genes associated with triacylglycerol assembly and lipid turnover from 2.00- to 2.90-fold, likely by binding to GCN4 motif and promoter of 3-phosphate-glycerol acyltransferase. Furthermore, overexpression of CpZF_CCCH1 alleviated reactive oxygen species levels by 59.28-73.26% and enhanced stress tolerance under adverse conditions. These findings expanded the roles of non-TZF proteins in lipid metabolism, opening new avenues for metabolic engineering to enhance the nutritional value and stress tolerance of microalgae and agricultural crops.