Dataset Information

Effects of reduced carbonic anhydrase activity on CO2 assimilation rates in Setaria viridis: a transgenic analysis.

ABSTRACT: In C4 species, the major ?-carbonic anhydrase (?-CA) localized in the mesophyll cytosol catalyses the hydration of CO2 to HCO3-, which phosphoenolpyruvate carboxylase uses in the first step of C4 photosynthesis. To address the role of CA in C4 photosynthesis, we generated transgenic Setaria viridis depleted in ?-CA. Independent lines were identified with as little as 13% of wild-type CA. No photosynthetic defect was observed in the transformed lines at ambient CO2 partial pressure (pCO2). At low pCO2, a strong correlation between CO2 assimilation rates and CA hydration rates was observed. C18O16O isotope discrimination was used to estimate the mesophyll conductance to CO2 diffusion from the intercellular air space to the mesophyll cytosol (gm) in control plants, which allowed us to calculate CA activities in the mesophyll cytosol (Cm). This revealed a strong relationship between the initial slope of the response of the CO2 assimilation rate to cytosolic pCO2 (ACm) and cytosolic CA activity. However, the relationship between the initial slope of the response of CO2 assimilation to intercellular pCO2 (ACi) and cytosolic CA activity was curvilinear. This indicated that in S. viridis, mesophyll conductance may be a contributing limiting factor alongside CA activity to CO2 assimilation rates at low pCO2.

SUBMITTER: Osborn HL

PROVIDER: S-EPMC5853810 | biostudies-other | 2017 Jan

REPOSITORIES: biostudies-other

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Effects of reduced carbonic anhydrase activity on CO2 assimilation rates in Setaria viridis: a transgenic analysis.

Osborn Hannah L HL Alonso-Cantabrana Hugo H Sharwood Robert E RE Covshoff Sarah S Evans John R JR Furbank Robert T RT von Caemmerer Susanne S

Journal of experimental botany 20161004 2

In C4 species, the major β-carbonic anhydrase (β-CA) localized in the mesophyll cytosol catalyses the hydration of CO2 to HCO3-, which phosphoenolpyruvate carboxylase uses in the first step of C4 photosynthesis. To address the role of CA in C4 photosynthesis, we generated transgenic Setaria viridis depleted in β-CA. Independent lines were identified with as little as 13% of wild-type CA. No photosynthetic defect was observed in th ...[more]

PMID: 27702996

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Project description:Some Brucella isolates are known to require an increased concentration of CO2 for growth, especially in the case of primary cultures obtained directly from infected animals. Moreover, the different Brucella species and biovars show a characteristic pattern of CO2 requirement, and this trait has been included among the routine typing tests used for species and biovar differentiation. By comparing the differences in gene content among different CO2-dependent and CO2-independent Brucella strains, we have confirmed that carbonic anhydrase (CA) II is the enzyme responsible for this phenotype in all the Brucella strains tested. Brucella species contain two CAs of the ? family, CA I and CA II; genetic polymorphisms exist for both of them in different isolates, but only those putatively affecting the activity of CA II correlate with the CO2 requirement of the corresponding isolate. Analysis of these polymorphisms does not allow the determination of CA I functionality, while the polymorphisms in CA II consist of small deletions that cause a frameshift that changes the C-terminus of the protein, probably affecting its dimerization status, essential for the activity. CO2-independent mutants arise easily in vitro, although with a low frequency ranging from 10-6 to 10-10 depending on the strain. These mutants carry compensatory mutations that produce a full-length CA II. At the same time, no change was observed in the sequence coding for CA I. A competitive index assay designed to evaluate the fitness of a CO2-dependent strain compared to its corresponding CO2-independent strain revealed that while there is no significant difference when the bacteria are grown in culture plates, growth in vivo in a mouse model of infection provides a significant advantage to the CO2-dependent strain. This could explain why some Brucella isolates are CO2 dependent in primary isolation. The polymorphism described here also allows the in silico determination of the CO2 requirement status of any Brucella strain.

Dataset Information

Effects of reduced carbonic anhydrase activity on CO2 assimilation rates in Setaria viridis: a transgenic analysis.

Publications

Effects of reduced carbonic anhydrase activity on CO2 assimilation rates in Setaria viridis: a transgenic analysis.

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