Participation of two carbonic anhydrases of the alpha family in photosynthetic reactions in Arabidopsis thaliana

Abstract

The expression of genes of two carbonic anhydrases (CA) belonging to the α-family, α-CA2 and α-CA4 (according to the nomenclature in N. Fabre et al. (2007) Plant Cell Environ., 30, 617-629), was studied in arabidopsis (Arabidopsis thaliana, var. Columbia) leaves. The expression of the At2g28210 gene coding α-CA2 decreased under increase in plant illumination, while the expression of the At4g20990 gene coding α-CA4 increased. Under conditions close to optimal for photosynthesis, in plants with gene At2g28210 knockout, the effective quantum yield of photosystem 2 and the light-induced accumulation of hydrogen peroxide in leaves were lower than in wild type plants, while the coefficient of non-photochemical quenching of leaf chlorophyll a fluorescence and the rate of CO2 assimilation in leaves were higher. In plants with At4g20990 gene knockout, the same characteristics changed in opposite ways relative to wild type. Possible mechanisms of the participation of α-CA2 and α-CA4 in photosynthetic reactions are discussed, taking into account that protons can be either consumed or released in the reactions they catalyze.

Role of Plant Carbonic Anhydrases under Stress Conditions

“…The knockout of α-ca2 gene has led to the opposite changes in the properties of plants compared with those resulting from the knockout of α-ca4 gene. Fresh leaf weight, chlorophyll a/chlorophyll b ratio, and starch and H 2 O 2 content in leaves of α-CA2 mutants were lower than in the WT plants, while CO assimilation rate was higher [37,134,135]. In α-CA2 knockouts, the effective quantum yield of photosynthetic electron transport was lower than in WT, while NPQ was higher, also due to the energy-dependent component.…”

“…α-CA1 was discovered in chloroplast stroma [10], and α-CA4 was found during proteomic studies among the proteins of the thylakoid membranes [35,36]. Evidence suggests that α-CA2 is present in thylakoid membranes [37]. α-CA3 was found in flowers and pods [5], as well as during proteomic analysis of mature pollen proteins [38,39].…”

“…We have shown that the fresh weight of the plant leaves with knocked-out α-ca4 gene was 10% higher, the starch and H 2 O 2 content was significantly higher, and the rate of CO 2 assimilation in leaves was lower in comparison to WT plants. The effective quantum yield of photosynthetic electron transport at saturating light intensity and CO 2 concentration was higher in mutants than in the WT, while nonphotochemical chlorophyll fluorescence quenching (NPQ ) was lower [13,37,134,135]. The content of transcripts of the At4g20990 gene encoding α-CA4 was two times higher under high (400 μmol quanta m −2 s −1 ) than under low illumination (80 μmol quanta m −2 s −1 ) when grown under "short-day" (8 hours day/16 hours night) and 16 times higher under "long-day" conditions (16 hours day/8 hours night) [6].…”

Transport and Use of Bicarbonate in Plants: Current Knowledge and Challenges Ahead

“…Both the quantum yield at photosystem 2 (PS2) and the electron transfer to O 2 decreased while non-photochemical quenching (NPQ) and CO 2 assimilation were enhanced in plants lacking αCA2. The opposite was observed in αCA4 knock-outs [ 155 ]. The authors hypothesize that these αCAs may participate in the regulation of H + flux into the PS2 protein PsbS, which regulates qE-type NPQ.…”

Proteome Profiling of Paulownia Seedlings Infected with Phytoplasma

“…This protein plays a vital role in the early event of photosynthesis. Zhurikova et al (2016) indicated that the reduction of the activity of CA affected the effective quantum yield of photosystem II, thus, its low abundance might weaken photosynthesis in the phytoplasma-infected plants.…”