Maier, AlexandraFahnenstich, Holgervon Caemmerer, SusanneEngqvist, Martin K. M.Weber, Andreas P. M.Flügge, Ulf-IngoMaurino, Veronica G.2016-02-032016-02-031664-462Xhttp://hdl.handle.net/1885/97912The photorespiratory pathway helps illuminated C(3)-plants under conditions of limited CO(2) availability by effectively exporting reducing equivalents in form of glycolate out of the chloroplast and regenerating glycerate-3-P as substrate for RubisCO. On the other hand, this pathway is considered as probably futile because previously assimilated CO(2) is released in mitochondria. Consequently, a lot of effort has been made to reduce this CO(2) loss either by reducing fluxes via engineering RubisCO or circumventing mitochondrial CO(2) release by the introduction of new enzyme activities. Here we present an approach following the latter route, introducing a complete glycolate catabolic cycle in chloroplasts of Arabidopsis thaliana comprising glycolate oxidase (GO), malate synthase (MS), and catalase (CAT). Results from plants bearing both GO and MS activities have already been reported (Fahnenstich et al., 2008). This previous work showed that the H(2)O(2) produced by GO had strongly negative effects. These effects can be prevented by introducing a plastidial catalase activity, as reported here. Transgenic lines bearing all three transgenic enzyme activities were identified and some with higher CAT activity showed higher dry weight, higher photosynthetic rates, and changes in glycine/serine ratio compared to the wild type. This indicates that the fine-tuning of transgenic enzyme activities in the chloroplasts seems crucial and strongly suggests that the approach is valid and that it is possible to improve the growth of A. thaliana by introducing a synthetic glycolate oxidative cycle into chloroplasts.Financial support was provided by the Deutsche Forschungsgemeinschaft through grant MA2779/4-1 to Veronica G. Maurino and MA2779/7-1 to Veronica G. Maurino and Ulf-Ingo Flügge and WE2231/8-1 to Andreas P. M. Weber as part of the German Photorespiration Research Network Promics (FOR 1186).© 2012 Maier, Fahnenstich, von Caemmerer, Engqvist, Weber, Flügge and Maurino. This is an open-access article distributed under the terms of the Creative Commons Attribution Non Commercial License, which permits non-commercial use, distribution, and reproduction in other forums, provided the original authors and source are credited.chloroplastglycolatephotorespiration2012-02-2810.3389/fpls.2012.000382016-02-24