Biological Resources Division, Japan International Research Center for Agricultural Science, Ministry of Agriculture, Forestry and Fisheries, Tsukuba, Ibaraki, Japan.
Four cDNAs that encode two-component response regulator-like proteins were cloned from Arabidopsis thaliana. Putative proteins (ATRR1-4) contain a receiver domain with a conserved aspartate residue - a possible phosphorylation site - at the N-terminal half. ATRR2 lacks the C-terminal half; the others contain a C-terminal domain abundant in acidic amino acids or proline residues. ATRR1 and ATRR2 are expressed more in roots than in other tissues and are induced by low temperature, dehydration and high salinity. Levels of ATRR3 and ATRR4 were not affected by stress treatments. These results suggest that ATRRs play distinct physiological roles in Arabidopsis, and that some are involved in stress responses.