Comprehensive expression profile analysis of the Arabidopsis hsp70 gene family

We isolated cDNA clones for two nuclear-encoded, organellar members of the Arabidopsis hsp70 gene family, mtHsc70-2 (AP217458) and cpHsc70-2 (AF217459 ). Together with the completion of the genome sequence, the hsp70 family in Arabidopsis consists of 14 members unequally distributed among the five ch romosomes. To establish detailed expression data of this gene family, a com prehensive reverse transcriptase-polymerase chain reaction analysis for 11 hsp70s was conducted including analysis of organ-specific and developmental expression and expression in response to temperature extremes. All hsp70s showed 2- to 20-fold induction by heat shock treatment except cpHsc70-1 and mtHsc70-1, which were unchanged or repressed. The expression profiles in r esponse to low temperature treatment were more diverse than those evoked by heat shock treatment. Both mitochondrial and all cytosolic members of the family except Hsp70b were strongly induced by low temperature, whereas endo plasmic reticulum and chloroplast members were not induced or were slightly repressed. Developmentally regulated expression of the heat-inducible Hsp7 0 in mature dry seed and roots in the absence of temperature stress suggest s prominent roles in seed maturation and root growth for this member of the hsp70 family. This reverse transcriptase-polymerase chain reaction analysi s establishes the complex differential expression pattern for the hsp70s in Arabidopsis that portends specialized functions even among members localiz ed to the same subcellular compartment.