Characterization of a Chlamydomonas reinhardtii snrk2.1 mutant: response to salt and oxidative stress

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

Congreso; SAIB 2022; 2022

In plants, the SnRK (Snf1-Related protein Kinase) gene family plays a central role in energy sensing and stress-adaptive responses. Recent studies have shown that orthologs of the plant SnRK protein exist in the model green algae Chlamydomonas reinhardtii but their functions are still unknown. In this study, we characterize a Chlamydomonas snrk2.1 mutant to start unraveling its role under abiotic stress. With this goal, wild-type (wt) and mutant cells were cultivated in complete TAP media or under salt or oxidative stress conditions, and growth parameters (OD, dry weight), chlorophyll, and starch/lipid content were determined at different time points. We observed that under mixotrophic growth conditions, the snrk2.1 mutant strain reached a higher cell density (OD750), dry weight, chlorophyll, lipids, and starch contents than the wt strain. The snrk2.1 mutant cells tend to form characteristic clusters of 4 cells, which is mostly uncommon in the wt strain. However, the snrk2.1 mutant cells were markedly affected by stressing conditions, showed a 40% reduction in cell density (OD750) upon salt and oxidative stress. On the other hand, the wt strain only decreased its cell density by 20% under salt conditions, in comparison with non-stressed cultures. Furthermore, we performed the same analysis with the well-characterized nnr1 and psr1 mutants, which are null mutants of key proteins for N and P starvation responses, respectively. In conclusion, these results point to SnRK2.1 as a regulator of the stress responses in Chlamydomonas and as a potential target for biomass production and feedstocks for bioenergy and /or other purposes.