High light (HL) stress adversely affects growth, productivity and viability of photosynthetic organisms. The green alga Chlamydomonas reinhardtii is a model system to study photosynthesis and light stress.
Comparative proteomics of wild-type and two very high light (VHL)-resistant mutants, VHLR-S4 and VHLR-S9, revealed complex alterations in response to excess light. A twodimensional reference map of the soluble subproteome was constructed representing about 1500 proteins. A total of 83 proteins from various metabolic pathways were identified by peptide mass fingerprinting.
Quantitative comparisons of 444 proteins showed 105 significantly changed proteins between wild type and mutants under different light conditions. Commonly, more proteins were decreased than increased, but different proteins were affected in each genotype. Proteins uniquely altered in either VHLR mutant may be involved in VHL resistance. Such candidate proteins similarly altered without light stress, thus possibly contributing to “preadaptation” of mutants to VHL, included decreased levels of a DEAD box RNA helicase (VHLRS4) and NAB1 and RB38 proteins (VHLR-S9), and increased levels of an oxygen evolving enhancer 1 (OEE1) isoform and an unknown protein (VHLR-S4). Changes from increased levels in HL to decreased levels in excess light, included OEE1 (VHLR-S9) or the reverse change for NAB1, RB38, b-carbonic anhydrase and an ABC transporter-like protein (VHLR-S4).
On June 16, 2007, the First Rebeiz Foundation for Basic Research 2006 Paper Prize was awarded to Drs. Britta Förster, Ulrike Mathesius and Barry J. Pogson For their paper on the “Comparative Proteomics of High-Light Stress in the Model Alga Chlamydomonas reinhardtii (Proteomics 6:4309-4320, 2006)”. For a summary of the paper see above.
Three recognition certificates and the monetary award were mailed to the recipients at the Australian National University, Canberra, and were receivedon June 21, 2007.
Britta Förster has been a postdoctoral fellow funded by the Australian Research Council (ARC), since 2001. She obtained her PhD from the Humboldt-University in Berlin, Germany, with collaborative research at the Duke University in North Carolina, USA. In Australia, she is one of the first to establish research on high- light and oxidative stress tolerance in the green alga Chlamydomonas reinhardtii, using molecular genetics, physiological and proteomics approaches. ,
Ulrike Mathesius, is a Senior lecturer and Chief Investigator in the ARC Center of Excellence for Integrative Legume Research
Barry J. Pogson, is Associate Professor and Chief investigator in the ARC Center of Excellence in Plant Energy Biology,
Together with her co-workers, expertise in proteomics, plant stress and chloroplast biology was combined to explore the proteome alterations in high light stress tolerant Chlamydomonas mutants. Their work shows that our understanding of the physiological phenomena in plants needs to take a holistic approach. The changes at the level of the whole cell proteome in the high light stress resistant algae are distinct but affect diverse cellular processes at the same time. Combined with extensive physiological investigations, their work suggests that there are genetic master switches that co-ordinate and balance the various biological processes contributing to enhanced photo-tolerance. Their work explores the basics underlying the complexity of communication within cells, facilitated through protein networks. It is one of many necessary steps that will eventually enable us to improve specific traits in our crop plants.
The photographs below, depict Förster, Mathesius and Pogson.
Photos courtesy of Britta Forster.