Enhancing resistance of Chlamydomonas reinhardtii to oxidative stress fusing constructs of heterologous antioxidant peptides into D1 protein

Algae emerge as leading actors for the development of new strategies to cope oxidative stress, thanks to their availability for genetic manipulation and simple cultivation. This study reports the design of novel mutant strains of the green photosynthetic alga Chlamydomonas reinhardtii, as a model system, able to produce bioactive peptides with high antioxidant capacity by means of a custom-made expression system. The D1 protein of Photosystem II is highly abundant in the chloroplast with a rapid steady-state turnover; the final step of D1 protein processing is thus exploited for the continuous release of antioxidant peptides into the organism. Three antioxidant peptides, isolated from different food sources, were successfully expressed in C. reinhardtii. We show that the in vitro antioxidant activity of algae extract is lower in transgenic lines, while the in vivo antioxidant activity is highly evident towards radical oxygen-generating substances than in the control strain. Moreover, the antioxidant mutant releasing the peptide designed from Hoki fish, showed a longer shelf-life and a better resistance to high light and heat stress than the control. These features can be exploited in the vision of the development of robust biocomponents for bioassay applications. In particular, we described the design of an optical bioassay for herbicides detection, showing the high potential of the proposed mutant strains as robust and sensitive biological recognition elements.