Overlapping and lineage-specific roles for the type-B response regulators of monocots and dicots.
Cytokinins are plant hormones with profound roles in growth and development. Cytokinin signaling is mediated through a 'two-component' signaling system composed of histidine kinases, histidine-containing phosphotransfer proteins, and response regulators. Phylogenetic analysis of two-component signaling elements from the monocot rice and the dicot Arabidopsis reveals lineage-specific expansions of the type-B response regulators, transcription factors that act as positive regulators for the cytokinin signal. We recently reported in Plant Physiology on a functional analysis of rice type-B response regulators. A type-B response regulator from a subfamily comprised of both monocot and dicot type-B response regulators complemented an Arabidopsis type-B response regulator mutant, but a type-B response regulator from a monocot-specific subfamily generally did not. Here, we extend this analysis to demonstrate that the promoter of an Arabidopsis cytokinin primary response gene is induced by type-B response regulators from a shared subfamily, but not by one from a lineage-specific subfamily. These results support a model in which the type-B response regulators of monocots and dicots share conserved roles in the cytokinin signaling pathway but have also diverged to take on lineage-specific roles.
Department of Biological Sciences, Dartmouth College, Hanover, NH, USA.
Hyo Jung
HJ
Kim
Joseph J
JJ
Kieber
G Eric
GE
Schaller
D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D003583:Cytokinins / Q000235:genetics* / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D008954:Models, Biological; D009154:Mutation; D012275:Oryza / Q000235:genetics* / Q000378:metabolism; D010802:Phylogeny; D010937:Plant Growth Regulators / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic; D015398:Signal Transduction; D014157:Transcription Factors / Q000378:metabolism*
D029681:Arabidopsis Proteins; D003583:Cytokinins; D010937:Plant Growth Regulators; D014157:Transcription Factors