Abstract
BackgroundThe glyoxylate reductase (GR) multigene family has been described in various plant species, their isoforms show different biochemical features in plants. However, few studies have addressed the biological roles of GR isozymes, especially for rice.ResultsHere, we report a detailed analysis of the enzymatic properties and physiological roles of OsGR1 and OsGR2 in rice. The results showed that both enzymes prefer NADPH to NADH as cofactor, and the NADPH-dependent glyoxylate reducing activity represents the major GR activity in various tissues and at different growth stages; and OsGR1 proteins were more abundant than OsGR2, which is also a major contributor to total GR activities. By generating and characterizing various OsGR-genetically modified rice lines, including overexpression, single and double-knockout lines, we found that no phenotypic differences occur among the various transgenic lines under normal growth conditions, while a dwarfish growth phenotype was noticed under photorespiration-promoted conditions.ConclusionOur results suggest that OsGR1 and OsGR2, with distinct enzymatic characteristics, function redundantly in detoxifying glyoxylate in rice plants under normal growth conditions, whereas both are simultaneously required under high photorespiration conditions.
Highlights
The glyoxylate reductase (GR) multigene family has been described in various plant species, their isoforms show different biochemical features in plants
Our results demonstrate that the two OsGR isoforms, with distinct enzymatic characteristics, are functionally redundant but both are simultaneouly required under high photorespiration conditions in rice
The results indicate that both OsGR1 and OsGR2 are widely distributed in photoautotrophic tissues, and their NADPH-dependent activities contribute mostly to total GR activities in rice
Summary
The glyoxylate reductase (GR) multigene family has been described in various plant species, their isoforms show different biochemical features in plants. Plant glyoxylate reductase (GR; EC 1.1.1.26/79) is a key enzyme involved in aldehydes metabolism, which catalyzes the reduction of glyoxylate and succinic semialdehyde (SSA) to glycolate and γ-hydroxybutyrate using NAD(P) H as a cofactor [1, 2]. Previous evidences found that expression of GR genes was upregulated under abiotic stresses (e.g. salinity, drought and submergence), accompanied by the accumulation of γ-hydroxybutyrate, suggesting that GR is involved in the detoxification of SSA in response to abiotic. Glyoxylate is an efficient precursor for oxalate biosynthesis in plants [14], and various functions have been reported for oxalate, including heavy metal detoxification, ion balance, pathogen defense and tissue support [15, 16]. Oxalate generation from glyoxylate is likely to be regulated in a complex manner, and it has not yet been reported whether GR mediates the regulation of glyoxylate-dependent oxalate accumulation
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