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标题：The carbonic anhydrase CAH1 is an essential component of the carbon-concentrating mechanism in Nannochloropsis oceanica
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作者：Christopher W. Gee ; Krishna K. Niyogi
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2017
卷号：114
期号：17
页码：4537-4542
DOI：10.1073/pnas.1700139114
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Aquatic photosynthetic organisms cope with low environmental CO₂ concentrations through the action of carbon-concentrating mechanisms (CCMs). Known eukaryotic CCMs consist of inorganic carbon transporters and carbonic anhydrases (and other supporting components) that culminate in elevated [CO₂] inside a chloroplastic Rubisco-containing structure called a pyrenoid. We set out to determine the molecular mechanisms underlying the CCM in the emerging model photosynthetic stramenopile, Nannochloropsis oceanica , a unicellular picoplanktonic alga that lacks a pyrenoid. We characterized CARBONIC ANHYDRASE 1 ( CAH1 ) as an essential component of the CCM in N. oceanica CCMP1779. We generated insertions in this gene by directed homologous recombination and found that the cah1 mutant has severe defects in growth and photosynthesis at ambient CO₂. We identified CAH1 as an α-type carbonic anhydrase, providing a biochemical role in CCM function. CAH1 was found to localize to the lumen of the epiplastid endoplasmic reticulum, with its expression regulated by the external inorganic carbon concentration at both the transcript and protein levels. Taken together, these findings show that CAH1 is an indispensable component of what may be a simple but effective and dynamic CCM in N. oceanica .
关键词：photosynthesis ; carbon-concentrating mechanism ; carbonic anhydrase ; heterokont ; algae