ESTs analysis and gene expression of heading leaf of Chinese cabbage

To study the expression patterns in heading leaves of Chinese cabbage (Brassica rapa L. ssp. pekinensis), a cDNA library was constructed. After sequencing 2,697 random clones from the cDNA library, 2,372 ESTs were used for further analysis. BLAST searches revealed that 2,241 ESTs matched to the deposited sequences either at the protein or nucleotide level, and the remaining 131 had no match in GenBank. ESTs of the genes involved in the process of protein synthesis were 22.5 percent, the highest of all the analyzed EST functional categories. Transcripts from the cell defense pathway genes were more highly represented than reported for some other plant leaves. These differences might be related to the low-temperature stress and high proliferation rate of heading leaf cells. This was supported by the dot-blot analysis, in which many genes related to the low-temperature stress were found to be up-regulated in the heading leaves of Chinese cabbage.