Research Projects

Phosphorus (P) is an important nutrient for plant growth, essential for synthesizing phospholipids, nucleic acids, and ATP, and it regulates processes such as photosynthesis and energy transport. However, the continuous depletion of phosphate rock reserves, their uneven geographical distribution, increasing population, and rising food scarcity demand a sustainable alternative to traditional chemical phosphate fertilizers. Along with that, P-rich wastewater from industries like dairy, poultry, and agriculture pollutes natural freshwater resources, causing eutrophication. Recovering phosphorus from such wastewater can solve these problems by providing a renewable P source while reducing environmental pollution. Fortunately, microalgae is a promising solution to these dilemmas as they efficiently absorb inorganic phosphate (Pi) and store it as polyphosphate (polyP) granules, constituting 3–4% of their dry cell weight. Unlike bacterial systems, algae-based solutions are renewable, cost-effective, and less bothered by environmental conditions. PolyP accumulation in microalgae is tightly regulated by phosphorus availability and by transcription factors like PSR1, which controls the expression of phosphate transporters and possibly polyP synthesis genes. The vacuolar transport chaperone (VTC) complex, comprising six main subunits, plays an important role in polyP synthesis. While VTC1 and VTC4 functions have recently been characterized, the roles of two putative VTC subunits (Cre01.g005500 and Cre09.g402812) remain unclear. So, in this project, we aim to functionally characterize the aforementioned two uncharacterized VTC subunits in polyP synthesis and storage using CRISPR-Cas9-based knockdown, complementation, and overexpression approaches. Before carrying out this functional characterization, we will perform whole-cell proteomics to identify proteins involved in phosphate stress response with respect to polyphosphate accumulation in Chlamydomonas reinhardtii. We would also like to investigate the regulatory role of PSR1 in controlling VTC gene expression and activity by analyzing the VTC expression patterns in wildtype, PSR1 mutant and overexpression lines. In our initial experiments, we characterized and quantified the growth and polyP accumulation in C. reinhardtii under phosphate-deplete and replete conditions, indicating enhanced polyphosphate accumulation in phosphate-replete conditions. Thus, this project will improve our understanding of polyP storage mechanisms and pave the way for generating phosphate-rich algal biomass, which can be used as a sustainable biofertilizer and a solution for wastewater remediation.