A probable Na+(K+)/H+ exchanger on the chloroplast envelope functions in pH homeostasis and chloroplast development in Arabidopsis thaliana
A probable Na+(K+)/H+ exchanger on the chloroplast envelope functions in pH homeostasis and chloroplast development in Arabidopsis thaliana
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DOI：
10.1073/pnas.0403709101
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发表时间：
2004-07-06
影响因子：
11.1
通讯作者：
Zhu, JK
中科院分区：
文献类型：
--
作者：
Song, CP;Guo, Y;Zhu, JK
电子中和的单价阳离子/质子反向转运穿过叶绿体被膜之前已经被证明对基质pH有重要的调节作用，从而对光合作用的碳还原有重要的调节作用。在这里，我们报道了拟南芥核基因AtCHX23，编码一个可能的Na+(K+)/H+交换器，功能是调节细胞质中的pH，并可能维持叶绿体基质中的高pH水平。AtCHX23蛋白定位于叶绿体被膜中。Chx23突变体的质体有直的类囊体体，但缺乏基粒片层。Chx23突变体叶片呈淡黄色，叶绿素含量显著降低。Chx23的叶绿素含量在低pH(4.0)条件下生长增加，在高pH(7.0)条件下生长降低。突变体叶片的胞液pH值显著高于野生型。Chx23突变体对氯化钠高度敏感。综上所述，这些数据表明CHX23可能是一个叶绿体Na+(K+)/H+交换器，对pH动态平衡和叶绿体的发育和功能非常重要。
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.