A probable Na+(K+)/H+ exchanger on the chloroplast envelope functions in pH homeostasis and chloroplast development in Arabidopsis thaliana.
Proc Natl Acad Sci U S A
; 101(27): 10211-6, 2004 Jul 06.
Article
em En
| MEDLINE
| ID: mdl-15220473
ABSTRACT
Electroneutral monovalent cation/proton antiport across the chloroplast envelope has been shown previously to have an important regulatory effect on stromal pH and thereby on photosynthetic carbon reduction. Here we report that an Arabidopsis nuclear gene, AtCHX23, encodes a putative Na(+)(K(+))/H(+) exchanger and functions in the adjustment of pH in the cytosol and possibly in maintaining a high pH level in the chloroplast stroma. The AtCHX23 protein is localized in the chloroplast envelope. Plastids from chx23 mutants had straight thylakoids but lacked grana lamellae. chx23 mutant leaves were pale yellow and had a much reduced chlorophyll content. The chlorophyll content of chx23 was increased by growing in medium at low (4.0) pH and decreased by growing at high (7.0) pH. The cytosolic pH in the leaves of the mutant was significantly higher than that in the wild type. chx23 mutants displayed a high sensitivity to NaCl. Together, these data indicate that CHX23 is a probable chloroplast Na(+)(K(+))/H(+) exchanger important for pH homeostasis and chloroplast development and function.
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MEDLINE
Assunto principal:
Cloroplastos
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Arabidopsis
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Trocadores de Sódio-Hidrogênio
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Antiporters
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Antiportadores de Potássio-Hidrogênio
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Proteínas de Arabidopsis
Idioma:
En
Ano de publicação:
2004
Tipo de documento:
Article