Responses of the chloroplast glyoxalase system to high CO₂ concentrations
2018
Shimakawa, Ginga | Ifuku, Kentaro | Suzuki, Yuji | Makino, Amane | Ishizaki, Kimitsune | Fukayama, Hiroshi | Morita, Ryutaro | Sakamoto, Katsuhiko | Nishi, Akiko | Miyake, Chikahiro
Sugar metabolism pathways such as photosynthesis produce dicarbonyls, e.g. methylglyoxal (MG), which can cause cellular damage. The glyoxalase (GLX) system comprises two enzymes GLX1 and GLX2, and detoxifies MG; however, this system is poorly understood in the chloroplast, compared with the cytosol. In the present study, we determined GLX1 and GLX2 activities in spinach chloroplasts, which constituted 40% and 10%, respectively, of the total leaf glyoxalase activity. In Arabidopsis thaliana, five GFP-fusion GLXs were present in the chloroplasts. Under high CO₂ concentrations, where increased photosynthesis promotes the MG production, GLX1 and GLX2 activities in A. thaliana increased and the expression of AtGLX1-2 and AtGLX2-5 was enhanced. On the basis of these findings and the phylogeny of GLX in oxygenic phototrophs, we propose that the GLX system scavenges MG produced in chloroplasts during photosynthesis.
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