Analysis of salt-inducible genes in barley roots by differential display.

To obtain insight into the comprehensive molecular characteristics related to the mechanisms of salt tolerance, we performed a large-scale screening of salt-inducible genes in barley roots by differential display. A comparative analysis of gene expression between control and salt-stressed conditions led to the detection of 218 cDNA clones induced by salt. Sequence analysis and database searching revealed that 133 cDNA clones have homology to known proteins. Twenty-four salt-inducible clones were identified as genes for signal transduction (e.g., phosphatidylinositol-4-phosphate-5-kinase, mitogen-activated protein kinase, transcription factor, receptor protein kinase, and protein phosphatase 2A). We also detected clones encoding glutathione reductase, thioredoxin-like protein, trehalose-6-phosphate synthetase, and heat shock proteins in the category of typical stress tolerance. Furthermore, we have obtained genes encoding membrane transporters, members of the P450 family, enzymes involved in RNA metabolism or function, and enzymes of sugar or amino acid metabolism. It must be noted that most genes were expressed strongly in roots, but only rarely or weakly in leaves. In addition, some clones were newly found as salt-inducible genes encoding SCARECROW, splicing factor and apoptosis protein. In this research, it was shown that differential display is a powerful tool for a large-scale cloning of cDNAs induced by salt and these results are very useful for understanding the mechanisms of plant salt tolerance.