Expression characteristics of heat shock protein genes in two comparable inbred lines of Chinese cabbage, Chiifu and Kenshin

Heat-shock proteins (HSPs) and heat-shock transcription factors (HSFs) are central components of the heat-shock regulatory network and are involved in cellular responses to various forms of stresses. To examine the differences in heat shock responses (HSRs) of two comparable inbred lines of Chinese cabbage (Brassica rapa), 51 genes were selected from 130,000 Brassica rapa ESTs that belong to an HSF and six HSP families and examined their expression using RT-PCR. Two Chinese cabbage inbred lines, Chiifu and Kenshin, have different geographic origins, in that Chiifu is from temperate regions, while Kenshin is from subtropical and tropical regions. Among the 51 genes, six genes were induced, eleven were stimulated, and three were reduced in both inbred lines in response to heat shock (HS) treatment. However, eleven genes were differentially expressed between the two inbred lines. Among these genes, several appear to be involved in normal growth and chloroplast development. These data suggest that the two Chinese cabbage inbred lines have similar HSRs, but the unique HSRs allow Kenshin to develop at higher temperatures.