title: The Cytoplasmic Carbonic Anhydrases βCA2 and βCA4 Are Required for Optimal Plant Growth at Low CO2.
abstract: Carbonic anhydrases (CAs) are zinc metalloenzymes that interconvert CO2 and HCO3 (-) In plants, both α- and β-type CAs are present. We hypothesize that cytoplasmic βCAs are required to modulate inorganic carbon forms needed in leaf cells for carbon-requiring reactions such as photosynthesis and amino acid biosynthesis. In this report, we present evidence that βCA2 and βCA4 are the two most abundant cytoplasmic CAs in Arabidopsis (Arabidopsis thaliana) leaves. Previously, βCA4 was reported to be localized to the plasma membrane, but here, we show that two forms of βCA4 are expressed in a tissue-specific manner and that the two proteins encoded by βCA4 localize to two different regions of the cell. Comparing transfer DNA knockout lines with wild-type plants, there was no reduction in the growth rates of the single mutants, βca2 and βca4 However, the growth rate of the double mutant, βca2βca4, was reduced significantly when grown at 200 μL L(-1) CO2 The reduction in growth of the double mutant was not linked to a reduction in photosynthetic rate. The amino acid content of leaves from the double mutant showed marked reduction in aspartate when compared with the wild type and the single mutants. This suggests the cytoplasmic CAs play an important but not previously appreciated role in amino acid biosynthesis.
authors.affiliation: Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70808.
authors.forename: Robert J
authors.identifier: 0000-0002-5056-6868
authors.initials: RJ
authors.lastname: DiMario
authors.affiliation: Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70808.
authors.forename: Jennifer C
authors.initials: JC
authors.lastname: Quebedeaux
authors.affiliation: Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70808.
authors.forename: David J
authors.initials: DJ
authors.lastname: Longstreth
authors.affiliation: Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70808.
authors.forename: Maheshi
authors.identifier: 0000-0003-3123-3731
authors.initials: M
authors.lastname: Dassanayake
authors.affiliation: Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70808.
authors.forename: Monica M
authors.identifier: 0000-0001-7289-9826
authors.initials: MM
authors.lastname: Hartman
authors.affiliation: Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70808 btmoro@lsu.edu.
authors.forename: James V
authors.identifier: 0000-0002-3652-5293
authors.initials: JV
authors.lastname: Moroney
mesh_terms: D000596:Amino Acids / Q000378:metabolism; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism*; D002256:Carbonic Anhydrases / Q000235:genetics / Q000378:metabolism*; D003593:Cytoplasm / Q000201:enzymology*; D018506:Gene Expression Regulation, Plant; D005816:Genetic Complementation Test; D009154:Mutation; D010788:Photosynthesis; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified
chemical_list: D000596:Amino Acids; D029681:Arabidopsis Proteins; D002245:Carbon Dioxide; C000609123:CA1 protein, Arabidopsis; C000609124:CA4 protein, Arabidopsis; D002256:Carbonic Anhydrases