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First published online August 27, 2004; 10.1104/pp.104.039438 Plant Physiology 136:2806-2817 (2004) © 2004 American Society of Plant Biologists Enhanced Photosynthesis and Redox Energy Production Contribute to Salinity Tolerance in Dunaliella as Revealed by Homology-Based Proteomics1Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany (A.J.L., A.S.); and Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel (U.P., A.K.)
Salinity is a major limiting factor for the proliferation of plants and inhibits central metabolic activities such as photosynthesis. The halotolerant green alga Dunaliella can adapt to hypersaline environments and is considered a model photosynthetic organism for salinity tolerance. To clarify the molecular basis for salinity tolerance, a proteomic approach has been applied for identification of salt-induced proteins in Dunaliella. Seventy-six salt-induced proteins were selected from two-dimensional gel separations of different subcellular fractions and analyzed by mass spectrometry (MS). Application of nanoelectrospray mass spectrometry, combined with sequence-similarity database-searching algorithms, MS BLAST and MultiTag, enabled identification of 80% of the salt-induced proteins. Salinity stress up-regulated key enzymes in the Calvin cycle, starch mobilization, and redox energy production; regulatory factors in protein biosynthesis and degradation; and a homolog of a bacterial Na+-redox transporters. The results indicate that Dunaliella responds to high salinity by enhancement of photosynthetic CO2 assimilation and by diversion of carbon and energy resources for synthesis of glycerol, the osmotic element in Dunaliella. The ability of Dunaliella to enhance photosynthetic activity at high salinity is remarkable because, in most plants and cyanobacteria, salt stress inhibits photosynthesis. The results demonstrated the power of MS BLAST searches for the identification of proteins in organisms whose genomes are not known and paved the way for dissecting molecular mechanisms of salinity tolerance in algae and higher plants.
1 This work was supported by The Ministry of Commerce in Israel (MAGNET program), by The Avron-Minerva Center for Photosynthesis, and by Nature Beta Technologies, Eilat, Israel. Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.104.039438. * Corresponding author; e-mail adriana.katz{at}weizmann.ac.il; fax 97289344118. Received February 4, 2004; returned for revision May 31, 2004; accepted June 2, 2004. Related articles in Plant Physiol.:
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