A family of proteins able to enhance the resistance of plants to photo-oxidative stress
The ELIPs (early light-induced proteins) are induced by photo-oxidative stress characterised by the accumulation of reactive oxygen species that can slow and even stop the photosynthetic activity of plants. The ELIPs display marked sequence homologies with the LHC (light harvesting complex) proteins that link the photosynthetic pigments of plants (chlorophylls and carotenoids). Although they have been known for more than twenty years, the exact function of this family of stress proteins was still obscure. The use of a new mutant of Arabidopsis thaliana (chaos) that is unable to accumulate ELIPs rapidly under strong light has made it possible to correlate the level of expression of these proteins with their ability to protect the plant against photo-oxidative stress, and to clarify their exact role.
This mutant suffers from photo-oxidative stress resulting in a spectacular bleaching of its leaves. The wild phenotype, which resists photo-oxidative stress, was restored in the mutant by over-expression of the ELIPs. Measurements of chlorophyll fluorescence lifetimes showed that this effect was characterised, before the appearance of oxidative stress, by the accumulation of free chlorophyll molecules known to generate singlet oxygen, a toxic oxygen species.
Bleaching of the leaves of the chaos mutant under strong light
©CEA
The ELIPs thus seem to prevent the formation of these active oxygen species either by stabilising the photosynthetic complexes, the light-induced breakdown of which releases chlorophyll molecules, or by de-activating the released chlorophyll molecules.
These results have been patented jointly by CEA and Biogemma. They offer a way to increase the resistance of plants to photo-oxidative stress through the use of ELIP proteins or nucleotides coding for these proteins.