The Impact of Photorespiratory Glycolate Oxidase Activity on Arabidopsis thaliana Leaf Soluble Amino Acid Pool Sizes during Acclimation to Low Atmospheric CO2 Concentrations

Abstract

Photorespiration is a metabolic process that removes toxic 2-phosphoglycolate produced by the oxygenase activity of ribulose-1,5-bisphosphate carboxylase/oxygenase. It is essential for plant growth under ambient air, and it can play an important role under stress conditions that reduce CO2 entry into the leaf thus enhancing photorespiration. The aim of the study was to determine the impact of photorespiration on Arabidopsis thaliana leaf amino acid metabolism under low atmospheric CO2 concentrations. To achieve this, wild-type plants and photorespiratory glycolate oxidase (gox) mutants were given either short-term (4 h) or long-term (1 to 8 d) low atmospheric CO2 concentration treatments and leaf amino acid levels were measured and analyzed. Low CO2 treatments rapidly decreased net CO2 assimilation rate and triggered a broad reconfiguration of soluble amino acids. The most significant changes involved photorespiratory Gly and Ser, aromatic and branched-chain amino acids as well as Ala, Asp, Asn, Arg, GABA and homoSer. While the Gly/Ser ratio increased in all Arabidopsis lines between air and low CO2 conditions, low CO2 conditions led to a higher increase in both Gly and Ser contents in gox1 and gox2.2 mutants when compared to wild-type and gox2.1 plants. Results are discussed with respect to potential limiting enzymatic steps with a special emphasis on photorespiratory aminotransferase activities and the complexity of photorespiration.

Simultaneous adjustments of major mitochondrial pathways through redox regulation of dihydrolipoamide dehydrogenase (mtLPD1)

“…Table 2, 3). Impaired BCAAs degradation is shared with classic photorespiration mutants (Timm et al, 2012) and once more serves as evidence for impaired photorespiration and a metabolic connection of both processes mentioned earlier (Florian et al, 2013;Dellero et al, 2021). Interestingly, a clear variation of this response was a consistent decrease of all amino acids in trxo1h2 after 9 h in air, but not in air grown plants, suggesting faster turnover on a short-term (Supp.…”

Thioredoxins o1 and h2 jointly adjust mitochondrial dihydrolipoamide dehydrogenase‐dependent pathways towards changing environments

“…Impaired BCAAs degradation is common in classic photorespiration mutants (Timm et al, 2012) and once more serves as evidence for impaired photorespiration and a metabolic connection of both processes mentioned earlier (Dellero et al, 2021;Florian et al, 2013).…”

Persulfidation protects from oxidative stress under nonphotorespiratory conditions in Arabidopsis

“…4). In addition, the Gly : Ser ratio decreases dramatically in plants under nonphotorespiration (Dellero et al ., 2021), and sulfide treatment had an enhancement effect on the Gly : Ser ratio, reaching an even higher ratio than plants with active photorespiration. Collectively, these data suggest the beneficial role of sulfide in regulating carbon and nitrogen metabolism under nonphotorespiratory conditions.…”