Identification of amino acid substitutions that render the Arabidopsis cytokinin receptor histidine kinase AHK4 constitutively active.
In Arabidopsis, three genes (AHK2, AHK3 and AHK4/CRE1) encode histidine kinases (His-kinases), which serve as cytokinin receptors. To understand how the external cytokinin signal activates the His-kinase across the cell membrane, we exploited the power of microbial genetics to isolate several AHK4 mutants that function independently of cytokinin in both prokaryotic and eukaryotic assay systems. In each mutant, a single amino acid substitution within the second membrane-spanning segment, or within the region around the phosphorylation His site, renders the His-kinase constitutively active. These mutant receptors appear to have a 'locked-on' conformation, even in the absence of stimulus. We discuss the implications of these data for the structure and function of the cytokinin receptor His-kinases in plants.
Miwa
Kumiko
K
Laboratory of Molecular Microbiology, School of Agriculture, Nagoya University, Furocho, Chikusa-ku, Nagoya, Japan.
Ishikawa
Kuniko
K
Terada
Kazunori
K
Yamada
Hisami
H
Suzuki
Tomomi
T
Yamashino
Takafumi
T
Mizuno
Takeshi
T
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D017360:Arabidopsis / Q000201:enzymology*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003583:Cytokinins / Q000378:metabolism*; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011494:Protein Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
D029681:Arabidopsis Proteins; D003583:Cytokinins; D011956:Receptors, Cell Surface; D011494:Protein Kinases; C421783:WOL protein, Arabidopsis