Natural variation inArabidopsis thalianaidentifies GlyoxalaseI;2 as key for the detoxification of glucose-derived reactive carbonyl species

Abstract

Reactive carbonyl species (RCS) are highly toxic molecules produced during normal metabolism and increased under conditions of oxidative stress. Here we show thatArabidopsis thalianaecotypes exhibit natural variation in the degree of detoxification of RCS. We have isolated the ecotype IP-Pal-0 as an ecotype that has evolved a higher resistance to the toxic effects of glucose-derived RCS by acquiring a higher activity of the glyoxalase system through increased expression of some of its components. In particular, Viridiplantae-specific GLXI;2, GLXII;4 and GLXII;5 isoforms are highly expressed when plants are grown in the presence of 2-keto-D-glucose (KDG; glucosone) or methylglyoxal. We found that specific motif/cis-regulatory elements of the Col-0 and IP-Pal-0 GLXI;2 promoter regions may be involved in the differences in GLXI;2 gene expression associated with KDG detoxification. IP-Pal-0 GLXI;2 contains two different amino acids compared to Col-0, but these do not affect the basic kinetics of the protein. Interestingly, we found that the simultaneous change of these amino acids also occurs together in the GLXI proteins of some other organisms, suggesting a convergence in the simultaneous change of both amino acid residues. Our study of natural variants ofA. thalianasuggests that the Viridiplantae-specific isoforms of the glyoxalase system are involved in the detoxification of glucose-derived RCS, particularly KDG.