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Peroxisomal hydroxypyruvate reductase is not essential for photorespiration in Arabidopsis but its absence causes an increase in the stoichiometry of photorespiratory CO2 release.

Abstract：

: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 CO(2) concentrations. However, some disruptions of photorespiratory metabolism cause subtle phenotypes in plants grown in air. For example, Arabidopsis thaliana 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 CO(2) and O(2) concentrations) were slightly reduced in the hpr1 and pmdh1pmdh2hpr1 plants indicating other reactions can help bypass this disruption in the photorespiratory pathway. However, the CO(2) compensation points (Γ) increased under photorespiratory conditions in both mutants indicating changes in photorespiratory carbon metabolism in these plants. Measurements of Γ*, the CO(2) compensation point in the absence of mitochondrial respiration, and the CO(2) 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 CO(2) released per Rubisco oxygenation reaction.

journal_name

Photosynth Res

journal_title

Photosynthesis research

authors

Cousins AB,Walker BJ,Pracharoenwattana I,Smith SM,Badger MR

doi

10.1007/s11120-011-9651-3

subject

Has Abstract

pub_date

2011-09-01 00:00:00

pages

91-100

issue

2-3

eissn

0166-8595

issn

1573-5079

journal_volume

108

pub_type

杂志文章

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Peroxisomal hydroxypyruvate reductase is not essential for photorespiration in Arabidopsis but its absence causes an increase in the stoichiometry of photorespiratory CO2 release.