Peroxisomal hydroxypyruvate reductase is not essential for photorespiration in Arabidopsis but its absence causes an increase in the stoichiometry of photorespiratory CO2 release
journal contribution
posted on 2023-05-18, 11:32authored byCousins, AB, Walker, BJ, Prachaoenwattana, I, Steven SmithSteven Smith, Badger, MR
Recycling of carbon by the photorespiratory pathway involves enzymatic steps in the chloroplast, mitochondria, and peroxisomes. Most of these reactions are essential for plants growing under ambient CO2 concentrations. However, some disruptions of photorespiratory metabolism cause subtle phenotypes in plants grown in air. For example, Arabidopsisthaliana lacking both of the peroxisomal malate dehydrogenase genes (pmdh1pmdh2) or hydroxypyruvate reductase (hpr1) are viable in air and have rates of photosynthesis only slightly lower than wild-type plants. To investigate how disruption of the peroxisomal reduction of hydroxypyruvate to glycerate influences photorespiratory carbon metabolism we analyzed leaf gas exchange in A. thaliana plants lacking peroxisomal HPR1 expression. In addition, because the lack of HPR1 could be compensated for by other reactions within the peroxisomes using reductant supplied by PMDH a triple mutant lacking expression of both peroxisomal PMDH genes and HPR1 (pmdh1pmdh2hpr1) was analyzed. Rates of photosynthesis under photorespiratory conditions (ambient CO2 and O2 concentrations) were slightly reduced in the hpr1 and pmdh1pmdh2hpr1 plants indicating other reactions can help bypass this disruption in the photorespiratory pathway. However, the CO2 compensation points (Γ) increased under photorespiratory conditions in both mutants indicating changes in photorespiratory carbon metabolism in these plants. Measurements of Γ*, the CO2 compensation point in the absence of mitochondrial respiration, and the CO2 released per Rubisco oxygenation reaction demonstrated that the increase in Γ in the hpr1 and pmdh1pmdh2hpr1 plants is not associated with changes in mitochondrial respiration but with an increase in the non-respiratory CO2 released per Rubisco oxygenation reaction.
History
Publication title
Photosynthesis Research
Volume
108
Issue
2-3
Pagination
91-100
ISSN
0166-8595
Department/School
School of Natural Sciences
Publisher
Kluwer Academic Publ
Place of publication
Van Godewijckstraat 30, Dordrecht, Netherlands, 3311 Gz
Rights statement
Copyright 2011 Springer Science+Business Media B.V