Plant & Animal Genome IX Conference

Poster: Sequencing & EST
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TEMPORAL TRANSCRIPTIONAL PROFILING OF SALINITY STRESS RESPONSES USING EXPRESSED SEQUENCE TAG (EST)-BASED MICROARRAYS IN THE COMMON ICE PLANT, MESEMBRYANTHEMUM CRYSTALLINUM.

¹ Faculty of Agriculture, Saga University, Saga 840-8502, Japan

² Department of Biochemistry, University of Nevada, Reno, NV 89557-0014, USA

³ Department of Plant Science, University of Arizona, Tucson, AZ 85721, USA

Mesembryanthemum crystallinum, a facultative CAM halophyte, can shift its photosynthetic mode from C₃ to CAM following exposure to environmental stresses such as high salinity and water deficit. We have simultaneously analyzed changes in the expression patterns of ~3000 selected genes in response to salt stress (500 mM NaCl) using EST-based microarrays. Approximately 30% of transcripts showed significant up- or down-regulation from 3 to 72 hours following the imposition of salinity stress. Distinct sets of transcripts with substantial increases or decreases in expression could be resolved with peaks at 12 and 48 hours. The most pronounced changes in transcript abundance were observed at 48 hours after stress, a time that corresponds temporally to the buildup of CAM enzymatic machinery. Several hundred unique transcripts showed at least a two-fold increase in abundance, whereas in excess of 200 genes were down regulated to a similar extent. Up-regulated genes played functional roles in lipid biosynthesis, ion homeostasis, cell defense, protein folding and degradation, signal transduction and transport facilitation. In contrast, down-regulated genes were mainly involved in photosynthetic processes. Surprisingly, more than 30% of the induced transcripts were functionally unknown, including many novel genes. The detailed temporal dynamics of salinity stress responses revealed by this study provide novel insights into the perception and response mechanisms that contribute to survival following exposure to high salinity stress.