Characterization of a Chlamydomonas reinhardtii mutant strain with increased growth rate and carbon reserve accumulation

DE MARCO A; GUERRA R; CURATTI L; MARTÍNEZ NOËL G

Congreso; SAIB 2023; 2023

The SnRK (Snf1-Related protein Kinase) gene family plays a central role in energy sensing and stress-adaptive responses in plants. Orthologs of the plant SnRK protein exist in the model green algae Chlamydomonas reinhardtii but their functions are still unknown. In this study, we characterized the snrk2.1 strain, which is a null mutant of the SnRK2 protein, that cannot grow under S-deprivation conditions. We showed that, under mixotrophic growth conditions, the snrk2.1 mutant achieved higher cell density (OD750), dry weight, chlorophyll, lipids and starch content than the wild-type (WT) strain. Qualitatively similar results were observed under photosynthetic growth conditions, although growth of all strains was slower. To gain insight into the molecular mechanisms behind these observations, we performed RT-qPCR experiments to analyze the expression of key genes encoding the growth regulator Target Of Rapamycin (TOR), enzymes that regulate the cell-cycle, the transcription factor involved in the P-deficient response PSR1 and an important enzyme in the starch synthesis pathway (PGM1, phosphoglucomutase 1). These assays indicated that the transcript levels of tor, pgm1, and cell-cycle genes were induced in the snrk2.1 mutant, while psr1 decreased. In conclusion, this preliminary characterization of a C. reinhardtii snrk2.1 mutant strain suggested potential for biotechnological applications towards production of biofuels and/or other products obtained by fermentation of non-expensive sugars. Additionally, it may open up new venues for unravelling the regulation of algal growth and production of carbon reserves at the molecular level.