Characterization of cooperative bicarbonate uptake into chloroplast stroma in the green alga Chlamydomonas reinhardtii.
Characterization of cooperative bicarbonate uptake into chloroplast stroma in the green alga Chlamydomonas reinhardtii.
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DOI：
10.1073/pnas.1501659112
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发表时间：
2015-06-09
影响因子：
11.1
通讯作者：
Fukuzawa H
中科院分区：
文献类型：
--
作者：
Yamano T;Sato E;Iguchi H;Fukuda Y;Fukuzawa H
无机碳（Ci; CO2和HCO 3-）进入细胞涉及动物和植物的许多生物学过程，水通道蛋白和碳酸氢盐转运蛋白在Ci的转运中起作用。虽然运输外部HCO 3-通过叶绿体被膜进入基质是水生光合生物的限速因素之一，在这个过程中的具体分子组成尚未被确定实验。本研究中记录的位于叶绿体包膜和质膜中的对Ci吸收至关重要的蛋白质的分子鉴定有助于理解水生光合生物如何开发机械以适应CO2限制环境并维持足够的光合作用水平以存活或生长。无机碳（Ci; CO2和HCO 3-）的供应是水生光合生物的环境限速因子。为了克服在有限的CO2条件下获取Ci的困难，诱导一种称为CO2浓缩机制（CCM）的活性Ci吸收系统来增加叶绿体基质中的CO2浓度。据报道，ATP结合盒转运蛋白HLA 3和甲酸盐/亚硝酸盐转运蛋白同系物LCIA与HCO 3摄取相关[Wang和Spalding（2014）Plant Physiol 166（4）：2040-2050]。然而，直接证据的HCO 3-摄取的路线从细胞外的叶绿体基质仍然难以捉摸，由于缺乏信息HLA 3的本地化和比较分析的贡献HLA 3和LCIA CCM。在这项研究中，我们发现HLA 3和LCIA分别定位于质膜和叶绿体被膜。HLA 3和/或LCIA的插入突变体表现出降低的Ci亲和力/积累，特别是在碱性条件下，其中HCO 3-是Ci的主要形式。HLA 3和LCIA独立地形成蛋白复合物，并且LCIA的缺乏降低了HLA 3 mRNA的积累，这表明存在从叶绿体到核的未知逆行信号以维持HLA 3 mRNA的表达。此外，尽管在高CO2条件下HLA 3或LCIA的单一过表达不影响Ci亲和力，但HLA 3与LCIA的同时过表达显著增加Ci亲和力/积累。这些结果突出了HLA 3/LCIA驱动的HCO 3-的协同摄取以及LCIA在维持HLA 3稳定性以及CCM中的Ci亲和力/积累中的关键作用。
The entry of inorganic carbon (Ci; CO2 and HCO3–) into cells involves many biological processes in both animals and plants, and aquaporins as well as bicarbonate transporters play roles in Ci transport. Although transporting external HCO3– into the stroma through the chloroplast envelope is one of the rate-limiting factors for aquatic photosynthetic organisms, specific molecular components in this process have not yet been identified experimentally. Molecular identification of proteins essential for Ci uptake located in the chloroplast envelope and in the plasma membrane documented in this study helps in understanding how aquatic photosynthetic organisms developed machinery to acclimate to CO2-limiting environment and to maintain adequate levels of photosynthesis for survival or growth. The supply of inorganic carbon (Ci; CO2 and HCO3–) is an environmental rate-limiting factor in aquatic photosynthetic organisms. To overcome the difficulty in acquiring Ci in limiting-CO2 conditions, an active Ci uptake system called the CO2-concentrating mechanism (CCM) is induced to increase CO2 concentrations in the chloroplast stroma. An ATP-binding cassette transporter, HLA3, and a formate/nitrite transporter homolog, LCIA, are reported to be associated with HCO3– uptake [Wang and Spalding (2014) Plant Physiol 166(4):2040–2050]. However, direct evidence of the route of HCO3– uptake from the outside of cells to the chloroplast stroma remains elusive owing to a lack of information on HLA3 localization and comparative analyses of the contribution of HLA3 and LCIA to the CCM. In this study, we revealed that HLA3 and LCIA are localized to the plasma membrane and chloroplast envelope, respectively. Insertion mutants of HLA3 and/or LCIA showed decreased Ci affinities/accumulation, especially in alkaline conditions where HCO3– is the predominant form of Ci. HLA3 and LCIA formed protein complexes independently, and the absence of LCIA decreased HLA3 mRNA accumulation, suggesting the presence of unidentified retrograde signals from the chloroplast to the nucleus to maintain HLA3 mRNA expression. Furthermore, although single overexpression of HLA3 or LCIA in high CO2 conditions did not affect Ci affinity, simultaneous overexpression of HLA3 with LCIA significantly increased Ci affinity/accumulation. These results highlight the HLA3/LCIA-driven cooperative uptake of HCO3– and a key role of LCIA in the maintenance of HLA3 stability as well as Ci affinity/accumulation in the CCM.
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影响因子：
11.6
作者：
Brueggeman, Andrew J.;Gangadharaiah, Dayananda S.;Ladunga, Istvan
通讯作者：
Ladunga, Istvan
DOI：
10.1073/pnas.081593498
发表时间：
2001-04-24
影响因子：
11.1
作者：
Fukuzawa, H;Miura, K;Ohyama, K
通讯作者：
Ohyama, K
影响因子：
11.6
作者：
Ohnishi, Norikazu;Mukherjee, Bratati;Fukuzawa, Hideya
通讯作者：
Fukuzawa, Hideya
影响因子：
5.1
作者：
Burow, MD;Chen, ZY;Moroney, JV
通讯作者：
Moroney, JV
影响因子：
7.4
作者：
Miura, K;Yamano, T;Fukuzawa, H
通讯作者：
Fukuzawa, H