Identification of a glucose-6-phosphate isomerase involved in adaptation to salt stress of Dunaliella salina
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The unicellular green alga Dunaliella salina is a recognized model for studying plant adaptation to high salinity. To isolate some salt-induced proteins at proteomics levels and to identify their expressions at gene levels, algal cells at logarithmic phase cultured in 1.5 and 3.5 M NaCl media were harvested for protein extraction. Solubilized proteins were applied to two-dimensional gel electrophoresis (2-DE) and analyzed by ImageMaster 2D Platinum software. Twenty-one protein spots whose intensities were elevated threefold to 13-fold at 3.5 M NaCl as compared to 1.5 M NaCl were analyzed by matrix-assisted laser desorption/ionization tandem time of flight mass spectrometry. One salt-induced protein isolated from the 2-DE gels was identified as a glucose-6-phosphate isomerase (GPI) from D. salina (DsGPI). A full-length cDNA of DsGPI was obtained using rapid amplification of cDNA end technique, and it was shown by heterologous expression to encode a protein with a molecular weight consistent with the protein spot in the 2-DE gels. Real-time quantitative RT-PCR demonstrated that the mRNA of DsGPI was induced up to eightfold (P < 0.01) by 2.5 M and 14-fold higher (P < 0.01) by 3.5 M NaCl than by 1.5 M NaCl, respectively. It is concluded that the protein isolated through 2-DE is indeed DsGPI and that the DsGPI gene may be involved in adaptation to high salinity.
KeywordsDunaliella salina Glucose-6-phosphate isomerase Halotolerance Salt stress Two-dimensional gel electrophoresis
This study was supported by the grants from International Science and Technology Cooperation Program of the Ministry of Science and Technology of P.R. China (no. 2007DFA01240) and the National Natural Science Foundation of China (No. 30540067 and No. 30700014).
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