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標題: Role of the Putative Osmosensor Arabidopsis Histidine Kinase1 in Dehydration Avoidance and Low-Water- Potential Response
作者: Kumar, M.Nagaraj
Jane, Wann-Neng
Paul, E.Verslues
Project: Plant Physiology, Volume 161, Page(s) 1-12.
The molecular basis of plant osmosensing remains unknown. Arabidopsis (Arabidopsis thaliana) Histidine Kinase1 (AHK1) can
complement the osmosensitivity of yeast (Saccharomyces cerevisiae) mutants lacking Synthetic Lethal of N-end rule1 and SH3-
containing Osmosensor osmosensors and has been proposed to act as a plant osmosensor. We found that ahk1 mutants in either
the Arabidopsis Nossen-0 or Columbia-0 background had increased stomatal density and stomatal index consistent with greater
transpirational water loss. However, the growth of ahk1 mutants was not more sensitive to controlled moderate low water
potential (cw) or to salt stress. Also, ahk1 mutants had increased, rather than reduced, solute accumulation across a range of low
cw severities. ahk1 mutants had reduced low cw induction of D1-Pyrroline-5-Carboxylate Synthetase1 (P5CS1) and 9-cis-
Epoxycarotenoid Dioxygenase3, which encode rate-limiting enzymes in proline and abscisic acid (ABA) synthesis, respectively.
However, neither Pro nor ABA accumulation was reduced in ahk1 mutants at low cw. P5CS1 protein level was not reduced in
ahk1 mutants. This indicated that proline accumulation was regulated in part by posttranscriptional control of P5CS1 that was
not affected by AHK1. Expression of AHK1 itself was reduced by low cw, in contrast to previous reports. These results define a
role of AHK1 in controlling stomatal density and the transcription of stress-responsive genes. These phenotypes may be
mediated in part by reduced ABA sensitivity. More rapid transpiration and water depletion can also explain the previously
reported sensitivity of ahk1 to uncontrolled soil drying. The unimpaired growth, ABA, proline, and solute accumulation of ahk1
mutants at low cw suggest that AHK1 may not be the main plant osmosensor required for low cw tolerance.
DOI: 10.1104/pp.112.209791
Appears in Collections:生物科技發展中心

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