Expression analysis of transcripts responsive to osmotic stress in Deschampsia antarctica Desv.

Abstract

Deschampsia antarctica Desv., the only monocot species thriving in the tough conditions of the Antarctic region, is surrounded by regions with snow and ice where available amount of liquid water is very limited. Considering the species as an invaluable resource for the identification of genes associated with tolerance to osmotic stress, we have characterized the physiological response and the changes in gene expression induced by PEG treatment using a cDNA macroarray. Since relative chlorophyll contents of leaves decreased to 69%, proline levels were changed significantly, and expression levels of dehydrin (DHN) and late embryogenesis abundant protein (LEA) were significantly up-regulated at 1 d after PEG treatment, we used corresponding plant samples as the material for gene expression analysis. As a result of hybridization and analysis of cDNA macroarray, we identified 44 and 20 transcripts that were up-regulated and down-regulated by PEG treatment respectively, and they were divided into several functional categories. Most of the up-regulated transcripts are involved in 'Response to stimulus', 'Amino acid metabolism', and 'Respiration'. On the other hand, most of the down-regulated transcripts are involved in 'Photosynthesis' and 'Translation'. Among the up-regulated transcripts, ？-1-pyrroline-5-carboxylate synthase 2 gene has shown the highest expression level at 1 d after PEG treatment suggesting its possible role as a main player for proline biosynthesis in D. antarctica under osmotic stress. Collectively, these data suggest that the transcripts differentially expressed under osmotic stress may represent candidate genes for dissecting molecular mechanism of adaptation to extreme environment for plants.