Microarray analysis of salt-responsive genes in common wheat

We developed oligo-DNA microarrays of common wheat. These microarrays were designed to include approximately 32,000 unique genes represented by a large number of expressed sequence tags (ESTs). In order to characterize the salt-responsive genes in common wheat, the expression profiles of transcripts that responded to salt-treatment were monitored using the microarrays. Two-week-old seedlings of Chinese Spring wheat were treated with 150 mM NaCl for 1 h, 6 h and 24 h, and total RNAs in their roots and shoots were separately subjected to microarray hybridizations. It was observed that 5,996 genes demonstrated a more than 2-fold change in expression. These genes were classified into 12 groups based on their expression patterns. These salt-responsive genes were assigned functions with Gene Ontology (GO) terms. Genes assigned transcription factor, transcription-regulator activity and DNA binding functions were preferentially classified as early-response genes. On the other hand, the genes assigned transferase and transporter activity were classified as late-response genes. These data suggest the existence of multiple signal transduction pathways in response to salt stress in wheat. The expression level of transcription factors (TFs), which have been reported to be involved in the salt-tolerance pathway, were observed to change in response to salt treatment. Only a few of those TFs demonstrated high sequence similarity with genes in rice. Furthermore, comparison of the microarray data for wheat and rice revealed a small number of commonly upor downregulated genes in these plants. These investigations suggest that salt-responsive genes distinct from those observed in rice might exist in wheat. The wheat genes identified in this study are candidates for genes involved in salt-stress tolerance.