Abstract
Arabidopsis thaliana has 11 members belonging to the typical type-B ARR (AUTHENTIC RESPONSE REGULATOR) family. Among them, 7 ARRs are implicated as DNA-binding transcription factors in the phosphorelay-mediated cytokinin signal transduction network. To gain insights into the functions of the cytokinin-associated type-B ARRs, here we established an arr1 arr10 arr12 triple loss-of-function mutant, which showed remarkable and severe phenotypes. The observed cytokinin-associated phenotypes of arr1 arr10 arr12 were highly analogous to those reported for certain ahk2 ahk3 ahk4/cre1 triple mutants, which have virtually no cytokinin receptor to propagate the phosphorelay signal transduction. Taken together, it was demonstrated that ARR1, ARR10, and ARR12 together play essential (or general) roles in cytokinin signal transduction. These results will be presented together with the idea that the other type-B ARRs (ARR2, ARR11, ARR14, and ARR18) may play more specific roles spatially and temporally in plants.
