Abstract
Plant NADPH-dependent glyoxylate/succinic semialdehyde reductases 1 and 2 (cytosolic GLYR1 and plastidial/mitochondrial GLYR2) are considered to be of particular importance under abiotic stress conditions. Here, the apple (Malus × domestica Borkh.) and rice (Oryza sativa L.) GLYR1s and GLYR2s were characterized and their kinetic properties were compared to those of previously characterized GLYRs from Arabidopsis thaliana [L.] Heynh. The purified recombinant GLYRs had an affinity for glyoxylate and succinic semialdehyde, respectively, in the low micromolar and millimolar ranges, and were inhibited by NADP+. Comparison of the GLYR activity in cell-free extracts from wild-type Arabidopsis and a glyr1 knockout mutant revealed that approximately 85 and 15% of the cellular GLYR activity is cytosolic and plastidial/mitochondrial, respectively. Recovery of GLYR activity in purified mitochondria from the Arabidopsis glyr1 mutant, free from cytosolic GLYR1 or plastidial GLYR2 contamination, provided additional support for the targeting of GLYR2 to mitochondria, as well as plastids. The growth of plantlets or roots of various Arabidopsis lines with altered GLYR activity responded differentially to succinic semialdehyde or glyoxylate under chilling conditions. Taken together, these findings highlight the potential regulation of highly conserved plant GLYRs by NADPH/NADP+ ratios in planta, and their roles in the reduction of toxic aldehydes in plants subjected to chilling stress.
Highlights
Under stress conditions such as chilling, drought and salinity, toxic aldehydes can accumulate in plants and interact with DNA, lipids and proteins, or influence the transcription of stress-related genes, thereby causing cellular and developmental problems (Weber et al, 2004; Kotchoni et al, 2006; Yamauchi et al, 2011; Mano, 2012; Biswas and Mano, 2015; Srivastava et al, 2017; see references therein)
We demonstrated that: (i) GLYRs from apple and rice, like those from Arabidopsis, display higher affinity and catalytic efficiency for glyoxylate than for Succinic semialdehyde (SSA); (ii) the activity of apple GLYRs is inhibited by NADP+; (iii) the growth of plantlets or roots of various Arabidopsis lines with altered GLYR activity respond differentially to exogenous SSA, generation of 4-hydroxybutyrate (GHB) or glyoxylate under chilling conditions; and (iv) approximately 85 and 15% of the total GLYR activity in Arabidopsis is present in the cytosol and plastids/mitochondria, respectively
Our kinetic analyses showed that recombinant GLYRs from the monocotyledonous rice, as well as the dicotyledonous apple and Arabidopsis, behaved with respect to their catalytic efficiencies (Table 1), probably because of their conserved active site residues and NADPH-binding sequence (Hoover et al, 2013; Brikis et al, 2017)
Summary
Under stress conditions such as chilling, drought and salinity, toxic aldehydes can accumulate in plants and interact with DNA, lipids and proteins, or influence the transcription of stress-related genes, thereby causing cellular and developmental problems (Weber et al, 2004; Kotchoni et al, 2006; Yamauchi et al, 2011; Mano, 2012; Biswas and Mano, 2015; Srivastava et al, 2017; see references therein). SSA is typically oxidized to succinate via SSA dehydrogenase (Tuin and Shelp, 1994; Bouché et al, 2003), but evidence is available for the generation of 4-hydroxybutyrate (GHB) from SSA in response to hypoxia, high light, salinity, drought and chilling (Allan et al, 2003, 2008, 2012; Breitkreuz et al, 2003; Fait et al, 2005). The precursor of glyoxylate in photorespiration, is known to accumulate under hypoxic conditions, and both glycolate and glyoxylate accumulate with the suppression of glycolate oxidase (Narsai et al, 2009; Lu et al, 2014)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
