Microarray analysis reveals S-adenosylmethionine (SAM) synthetase involvement in salt tolerance of Cyanidioschyzon merolae

We searched for candidate genes for producing salt tolerant plants from the red alga Cyanidioschyzon merolae, which lives in an extreme environment (hot springs). Arabidopsis thaliana plants die under 0.1 M salt culture, whereas the red algal cells survived under 0.3 M salt for 7d. However, their chloroplasts changed from green to white and they soon died under 0.4 M, which is the concentration of seawater. Genes that were selectively expressed at 2 h and 24 h in 0.3 M salt concentrations were examined by microarray analysis. Under salt stress, the numbers of highly expressed genes at 2 h increased from 70 to 95 after culture for 24 h. The highly expressed genes included those encoding proteins similar to low molecular weight heat shock proteins, heat shock protein 70, and S-adenosylmethionine (SAM) synthetase. On the base of the present data and on the known metabolic functions of the proteins, we suggest that the SAM synthetase gene from C. merolae is a candidate gene for genetic engineering to produce salt tolerance plants.