Cell-Specific Vacuolar Calcium Storage Mediated by CAX1 Regulates Apoplastic Calcium Concentration, Gas Exchange, and Plant Productivity in Arabidopsis
Cell-Specific Vacuolar Calcium Storage Mediated by CAX1 Regulates Apoplastic Calcium Concentration, Gas Exchange, and Plant Productivity in Arabidopsis
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DOI：
10.1105/tpc.109.072769
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发表时间：
2011-01-01
期刊：
影响因子：
11.6
通讯作者：
Leigh, Roger A.
中科院分区：
文献类型：
--
作者：
Conn, Simon J.;Gilliham, Matthew;Leigh, Roger A.
营养物质储存在特定细胞类型的液泡中的生理作用和机制知之甚少。使用微阵列筛选和单细胞定量PCR比较了钙浓度（[Ca]，表皮60 mM）不同的拟南芥叶细胞的转录谱< 10 mM versus mesophyll >。三个tonoplast定位的Ca 2+转运蛋白，CAX 1（Ca 2 +/H+-逆向转运蛋白），ACA 4，和ACA 11（Ca 2 +-ATP酶），被确定为优先表达在富钙叶肉。对相应的功能丧失突变体的分析表明，只有缺乏CAX 1和CAX 3（在CAX 1敲除后在叶中异位表达的基因）表达的突变体具有减少的叶肉[Ca]。叶肉钙积累能力降低导致细胞壁的可伸展性，气孔开度，蒸腾作用，CO2同化，和叶的生长速率降低;增加转录丰度的其他Ca 2+转运蛋白基因;改变细胞壁修饰蛋白的表达，包括果胶甲酯酶，膨胀素，纤维素合成酶，和多聚半乳糖醛酸酶家族的成员;和更高的果胶浓度和更厚的细胞壁。我们表明，这些表型的结果从改变质外体游离[Ca 2 +]，这是三倍以上的cax 1/cax 3比野生型植物。我们建立CAX 1作为一个关键的调节器的质外体[Ca 2 +]通过划分成叶肉液泡，一个机制至关重要的最佳植物功能和生产力。
The physiological role and mechanism of nutrient storage within vacuoles of specific cell types is poorly understood. Transcript profiles from Arabidopsis thaliana leaf cells differing in calcium concentration ([Ca], epidermis < 10 mM versus mesophyll > 60 mM) were compared using a microarray screen and single-cell quantitative PCR. Three tonoplast-localized Ca2+ transporters, CAX1 (Ca2+/H+-antiporter), ACA4, and ACA11 (Ca2+-ATPases), were identified as preferentially expressed in Ca-rich mesophyll. Analysis of respective loss-of-function mutants demonstrated that only a mutant that lacked expression of both CAX1 and CAX3, a gene ectopically expressed in leaves upon knockout of CAX1, had reduced mesophyll [Ca]. Reduced capacity for mesophyll Ca accumulation resulted in reduced cell wall extensibility, stomatal aperture, transpiration, CO2 assimilation, and leaf growth rate; increased transcript abundance of other Ca2+ transporter genes; altered expression of cell wall-modifying proteins, including members of the pectinmethylesterase, expansin, cellulose synthase, and polygalacturonase families; and higher pectin concentrations and thicker cell walls. We demonstrate that these phenotypes result from altered apoplastic free [Ca2+], which is threefold greater in cax1/cax3 than in wild-type plants. We establish CAX1 as a key regulator of apoplastic [Ca2+] through compartmentation into mesophyll vacuoles, a mechanism essential for optimal plant function and productivity.