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Query: EC:3.2.1.31 (
beta-glucuronidase
)
7,680
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
RNA gel blot and reverse transcription-polymerase chain reaction experiments were used to identify a single K(+) channel gene in Arabidopsis as expressed throughout the plant. Use of the
beta-glucuronidase
reporter gene revealed expression of this gene,
AKT2
/AKT3, in both source and sink phloem tissues. The
AKT2
/AKT3 gene corresponds to two previously identified cDNAs,
AKT2
(reconstructed at its 5' end) and AKT3, the open reading frame of the latter being shorter at its 5' end than that of the former. Rapid amplification of cDNA ends with polymerase chain reaction and site-directed mutagenesis was performed to identify the initiation codon for
AKT2
translation. All of the data are consistent with the hypothesis that the encoded polypeptide corresponds to the longest open reading frame previously identified (
AKT2
). Electrophysiological characterization (macroscopic and single-channel currents) of
AKT2
in both Xenopus oocytes and COS cells revealed a unique gating mode and sensitivity to pH (weak inward rectification, inhibition, and increased rectification upon internal or external acidification), suggesting that
AKT2
has enough functional plasticity to perform different functions in phloem tissue of source and sink organs. The plant stress hormone abscisic acid was shown to increase the amount of
AKT2
transcript, suggesting a role for the
AKT2
in the plant response to drought.
...
PMID:A shaker-like K(+) channel with weak rectification is expressed in both source and sink phloem tissues of Arabidopsis. 1085 32
The
AKT2
K(+) channel is endowed with unique functional properties, being the only weak inward rectifier characterized to date in Arabidopsis. The gene is expressed widely, mainly in the phloem but also at lower levels in leaf epiderm, mesophyll, and guard cells. The
AKT2
mRNA level is upregulated by abscisic acid. By screening a two-hybrid cDNA library, we isolated a protein phosphatase 2C (AtPP2CA) involved in abscisic acid signaling as a putative partner of
AKT2
. We further confirmed the interaction by in vitro binding studies. The expression of AtPP2CA (
beta-glucuronidase
reporter gene) displayed a pattern largely overlapping that of
AKT2
and was upregulated by abscisic acid. Coexpression of AtPP2CA with
AKT2
in COS cells and Xenopus laevis oocytes was found to induce both an inhibition of the
AKT2
current and an increase of the channel inward rectification. Site-directed mutagenesis and pharmacological analysis revealed that this functional interaction involves AtPP2CA phosphatase activity. Regulation of
AKT2
activity by AtPP2CA in planta could allow the control of K(+) transport and membrane polarization during stress situations.
...
PMID:Physical and functional interaction of the Arabidopsis K(+) channel AKT2 and phosphatase AtPP2CA. 1203 2
