Use of SAGE technology to reveal changes in gene expression in Arabidopsis leaves undergoing cold stress.

The genes expressed within an organism determine its biological characteristics. Various internal or external factors can modulate these gene expression patterns, which then elicit physiological or pathological changes. We have characterized the global gene expression patterns of Arabidopsis leaves by serial analysis of gene expression (SAGE). A total of 21,280 SAGE tags were sequenced and 12,049 unique tags were identified. Among these, only 3367 tags (27.9%) were matched to the Arabidopsis cDNA or EST database. Functional analysis of annotated tags indicated that a significant proportion of the genes expressed in normal leaves were involved in energy and metabolism, especially in photosynthesis. To systematically analyze differential gene expression profiles under cold stress, a similar SAGE tag library from cold-treated leaves was constructed and analyzed. A comparison of the tags derived from the cold-treated leaves with those identified in the normal leaves revealed 272 differentially expressed genes (P<0.01): 82 genes were highly expressed in the normal leaves and 190 genes were highly expressed in the cold-treated leaves. After cold stress, in general, many of the genes involved in cell rescue/defense/cell death/aging, protein synthesis, metabolism, transport facilitation, and protein destination were induced. They included various COR genes, lipid transfer protein genes, alcohol dehydrogenase, beta-amylase and many novel genes. By comparison, down-regulated genes were mostly photosynthesis related genes involved in energy metabolism. The expression patterns of several cold responsive transcripts identified by SAGE were confirmed by northern analysis. The results presented here will provide valuable information for understanding the mechanisms of the freezing tolerance of plants.