Absence of carbonic anhydrase in chloroplasts affects C3 plant development but not photosynthesis

The enzyme carbonic anhydrase (CA), which catalyzes the interconversion of bicarbonate with carbon dioxide (CO2) and water, has been hypothesized to play a role in C3 photosynthesis. We identified two tobacco stromal CAs, β-CA1 and β-CA5, and produced CRISPR/Cas9 mutants affecting their encoding genes. While single knockout lines Δβ-ca1 and Δβ-ca5 had no striking phenotypic differences compared to wild type (WT) plants, Δβ-ca1ca5 leaves developed abnormally and exhibited large necrotic lesions even when supplied with sucrose. Leaf development of Δβ-ca1ca5 plants normalized at 9,000 ppm CO2. Leaves of Δβ-ca1ca5 mutants and WT that had matured in high CO2 had identical CO2 fixation rates and photosystem II efficiency. Fatty acids, which are formed through reactions with bicarbonate substrates, exhibited abnormal profiles in the chloroplast CA-less mutant. Emerging Δβ-ca1ca5 leaves produce reactive oxygen species in chloroplasts, perhaps due to lower nonphotochemical quenching efficiency compared to WT. Δβ-ca1ca5 seedling germination and development is negatively affected at ambient CO2. Transgenes expressing full-length β-CA1 and β-CA5 proteins complemented the Δβ-ca1ca5 mutation but inactivated (ΔZn-βCA1) and cytoplasm-localized (Δ62-βCA1) forms of β-CA1 did not reverse the growth phenotype. Nevertheless, expression of the inactivated ΔZn-βCA1 protein was able to restore the hypersensitive response to tobacco mosaic virus, while Δβ-ca1 and Δβ-ca1ca5 plants failed to show a hypersensitive response. We conclude that stromal CA plays a role in plant development, likely through providing bicarbonate for biosynthetic reactions, but stromal CA is not needed for maximal rates of photosynthesis in the C3 plant tobacco.

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Faculty Opinions recommendation of Absence of carbonic anhydrase in chloroplasts affects C3 plant development but not photosynthesis.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.740636764.793588716 ◽

2021 ◽

Author(s):

Jaume Flexas ◽

Marc Carriquí

Keyword(s):

Carbonic Anhydrase ◽

Plant Development ◽

C3 Plant

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Physiology and Posttranscriptional Regulation of Methanol:Coenzyme M Methyltransferase Isozymes in Methanosarcina acetivorans C2A

Journal of Bacteriology ◽

10.1128/jb.00947-09 ◽

2009 ◽

Vol 191 (22) ◽

pp. 6928-6935 ◽

Cited By ~ 13

Author(s):

Rina B. Opulencia ◽

Arpita Bose ◽

William W. Metcalf

Keyword(s):

Methane Production ◽

Posttranscriptional Regulation ◽

Promoter Strength ◽

Methanosarcina Acetivorans ◽

Vitro Assay ◽

Phenotypic Differences ◽

Fusion Data ◽

Encoding Genes ◽

Similar Growth

ABSTRACT Methanosarcina species possess three operons (mtaCB1, mtaCB2, and mtaCB3) encoding methanol-specific methyltransferase 1 (MT1) isozymes and two genes (mtaA1 and mtaA2) with the potential to encode a methanol-specific methyltransferase 2 (MT2). Previous genetic studies showed that these genes are differentially regulated and encode enzymes with distinct levels of methyltransferase activity. Here, the effects of promoter strength on growth and on the rate of methane production were examined by constructing strains in which the mtaCB promoters were exchanged. When expressed from the strong PmtaC1 or PmtaC2 promoter, each of the MtaC and MtaB proteins supported growth and methane production at wild-type levels. In contrast, all mtaCB operons exhibited poorer growth and lower rates of methane production when PmtaC3 controlled their expression. Thus, previously observed phenotypic differences can be attributed largely to differences in promoter activity. Strains carrying various combinations of mtaC, mtaB, and mtaA expressed from the strong, tetracycline-regulated PmcrB(tetO1) promoter exhibited similar growth characteristics on methanol, showing that all combinations of MtaC, MtaB, and MtaA can form functional MT1/MT2 complexes. However, an in vitro assay of coupled MT1/MT2 activity showed significant variation between the strains. Surprisingly, these variations in activity correlated with differences in protein abundance, despite the fact that all the encoding genes were expressed from the same promoter. Quantitative reverse transcriptase PCR and reporter gene fusion data suggest that the mtaCBA transcripts show different stabilities, which are strongly influenced by the growth substrate.

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Carbonic anhydrases in the C3 -plant leaf cell

Functional Plant Biology ◽

10.1071/pp97137 ◽

1998 ◽

Vol 25 (6) ◽

pp. 673 ◽

Cited By ~ 14

Author(s):

Lyudmila K. Ignatova ◽

Oleg V. Moskvin ◽

Alla K. Romanova ◽

Boris N. Ivanov

Keyword(s):

Carbonic Anhydrase ◽

C3 Plants ◽

Carbonic Anhydrases ◽

Leaf Cell ◽

Ph Change ◽

Ph Optimum ◽

C3 Plant ◽

Mesophyll Protoplasts ◽

Pisum Sativum L ◽

Ph Range

Carbonic anhydrase (CA) activities of the mesophyll protoplasts from Pisum sativum L. leaves (plasmalemma CA), the supernatant after thylakoid precipitation (soluble CA), and the washed thylakoids (thylakoid CA) were studied. It was found that the Km (CO2) were 104 mM for the plasmalemma CA, 20 mM for the soluble CA, and 9 mM for the thylakoid CA. The activity of the last differed from the first two in response to the inhibitor acetazolamide by increasing at submicromolar concentrations of inhibitor. pH-dependencies of Km (HCO3-) for soluble CA and thylakoid CA differed in that the former increased as pH increasd from 7.0 to 8.0, while the latter slightly decreased over this pH change. A comparison of the pH-dependencies of the soluble CA and thylakoid CA dehydrase activities expressed in Wilbur-Andersen units demonstrated that, while the activity of soluble CA was unchanged over pH range 6–8, the activity of thylakoid CA had a distinct pH optimum at pH 6.8–7.0. The possible functions of the three forms of CA in the leaf cell of C3 -plants are briefly discussed.

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Silicon Substitution for Calcium in the Shell of the Fingernail Clam, Musculium Transversum Studied By X-Ray Analysis

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s1431927600002488 ◽

1980 ◽

Vol 38 ◽

pp. 560-561

Author(s):

Judith A. Murphy ◽

Anthony Paparo ◽

Richard Sparks

Keyword(s):

Carbonic Anhydrase ◽

River Water ◽

Food Chains ◽

Well Water ◽

Shell Formation ◽

X Ray ◽

Molluscan Shell ◽

Fingernail Clams

Fingernail clams (Muscu1ium transversum) are dominant bottom-dwelling animals in some waters of the midwest U.S. These organisms are key links in food chains leading from nutrients in water and mud to fish and ducks which are utilized by man. In the mid-1950’s, fingernail clams disappeared from a 100-mile section of the Illinois R., a tributary of the Mississippi R. Some factor(s) in the river and/or sediment currently prevent clams from recolonizing areas where they were formerly abundant. Recently, clams developed shell deformities and died without reproducing. The greatest mortality and highest incidence of shell deformities appeared in test chambers containing the highest proportion of river water to well water. The molluscan shell consists of CaCO3, and the tissue concerned in its secretion is the mantle. The source of the carbonate is probably from metabolic CO2 and the maintenance of ionized Ca concentration in the mantle is controlled by carbonic anhydrase. The Ca is stored in extracellular concentric spherical granules(0.6-5.5μm) which represent a large amount of inertCa in the mantle. The purpose of this investigation was to examine the role of raw river water and well water on shell formation in the fingernail clam.

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