16th International Conference on the Cell and Molucular Biology of Chlamydomonas

Session Title: Photosynthesis (Poster)
Program Number: 106

Self-adjusting light harvesting antenna: New ways to deal with the hazards of harnessing sunlight. Sangeeta Negi1, Zoee Perrine2, Anil Kumar2, Amanda Barry3, Richard Sayre1,3. 1) New Mexico Consortium,Los Alamos,NM; 2) Phycal,Inc St. Louis,MO; 3) Los Alamos National Lab, Los Alamos,NM.

At high-light intensities photosynthetic efficiency is compromised due to saturation of photosynthetic electron transfer processes resulting in possible photodamage. Plants and algae have evolved various strategies to protect themselves from photodamage including adjusting the size of light harvesting complexes and their distribution between photosystems as well as dissipating excess energy by non-photochemical quenching mechanisms. Recently, we have generated transgenic algae that are capable of self-modulating the size of the LHC complex as a function of light intensity. This was accomplished by using a redox sensitive, translational inhibitor, NAB1(Nucleic acid binding protein 1), to control the expression of the gene involved in Chl b synthesis (Chl a oxygenase,CAO). In high-light intensities NAB1 protein binds to its respective mRNA binding site  of the CAO gene which catalyzes the synthesis of Chl b and inhibits translation of the CAO gene resulting in a reduced PSII peripheral antenna size. In contrast,under low-light intensities repression by NAB1 expression is reduced and Chlb synthesis increases resulting in an increase in PSII peripheral antenna size. Consistent with our hypothesis these lines show near wild-type antenna size when grown in low-light (Chl a/b ratio 3.1-3.4) and smaller antenna size (Chl a/b ratio 5.4-5.7) in high-light. These lines also show higher photosynthetic rates compared to wild type (2.7-3 fold). Interestingly, an increase in the levels of photoprotective pigments, zea and lutein, was also observed in high-light grown NAB CAO transgenics relative to wild type resulting in higher de-epoxidation. We also examined and compared growth rates of these lines with wild type and complemented wild type in identical bench-top photo bioreactors (Phenometrics) that simulate a pond environment.The NAB CAO lines had up to a 2-fold higher growth and biomass accumulation than wild type. In summary, results presented here demonstrate that algae with self-adjusting antennae have improved photosynthetic efficiency and growth in real-world growth conditions.

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