In planta functions of the Arabidopsis cytokinin receptor family.
Since their discovery as cell-division factors in plant tissue culture about five decades ago, cytokinins have been hypothesized to play a central role in the regulation of cell division and differentiation in plants. To test this hypothesis in planta, we isolated Arabidopsis plants lacking one, two, or three of the genes encoding a subfamily of histidine kinases (CRE1, AHK2, and AHK3) that function as cytokinin receptors. Seeds were obtained for homozygous plants containing mutations in all seven genotypes, namely single, double, and triple mutants, and the responses of germinated seedlings in various cytokinin assays were compared. Both redundant and specific functions for the three different cytokinin receptors were observed. Plants carrying mutations in all three genes did not show cytokinin responses, including inhibition of root elongation, inhibition of root formation, cell proliferation in and greening of calli, and induction of cytokinin primary-response genes. The triple mutants were small and infertile, with a reduction in meristem size and activity, yet they possessed basic organs: roots, stems, and leaves. These results confirm that cytokinins are a pivotal class of plant growth regulators but provide no evidence that cytokinins are required for the processes of gametogenesis and embryogenesis.
Higuchi
Masayuki
M
Department of Biology, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan.
Pischke
Melissa S
MS
Mähönen
Ari Pekka
AP
Miyawaki
Kaori
K
Hashimoto
Yukari
Y
Seki
Motoaki
M
Kobayashi
Masatomo
M
Shinozaki
Kazuo
K
Kato
Tomohiko
T
Tabata
Satoshi
S
Helariutta
Ykä
Y
Sussman
Michael R
MR
Kakimoto
Tatsuo
T
D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D003583:Cytokinins / Q000378:metabolism*; D015870:Gene Expression; D017343:Genes, Plant; D000071677:Histidine Kinase; D005810:Multigene Family; D016254:Mutagenesis, Insertional; D010641:Phenotype; D018517:Plant Roots / Q000254:growth & development; D018520:Plant Shoots / Q000187:drug effects; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*
D029681:Arabidopsis Proteins; D003583:Cytokinins; D011956:Receptors, Cell Surface; D011494:Protein Kinases; D000071677:Histidine Kinase; C000605492:AHK2 protein, Arabidopsis; C000605493:AHK3 protein, Arabidopsis; C421783:WOL protein, Arabidopsis