The impact of short-cutting photorespiration on carbon and nitrogen metabolism

我们最近培育了拟南芥植物，使其能够氧化质体内的乙醇酸。这些植物表现出有益的生长效果，单位面积CO2同化率和叶绿素含量较高。为了实现这一目标，在质体中引入过氧化氢酶来消除乙醇酸氧化酶产生的H2O2至关重要。在这里，我们建议在不产生H2O2的情况下，使用乙醇酸脱氢酶（GlcDH）进一步优化这一原始途径。为此，我们将遵循两种策略，(i)使用Micromonas GlcDH和（ii）联合使用synnechocystis GlcD1和GlcD2。将选择带有新途径的转基因品系，并在不同水平上分析对植物性能的影响。此外，这些活性酶的动力学性质将被深入研究。另一方面，光呼吸已被清楚地证明与其他细胞过程相互作用。在这方面，我们之前的工作表明shm1-1突变体中2-羟基戊二酸（2HG）的光依赖性积累，这与高水平的甘氨酸、2-酮戊二酸和许多氨基酸相关。此外，我们首次发现，在正常条件下生长的野生型植物的叶片提取物中，可以发现2HG、d和L-2HG的对映体形式，尽管含量极低。因此，我们的小组将特别关注光呼吸与涉及2HG的过程（例如衰老，代谢修复）的相互作用。为此，基因组学、生物化学、代谢组学和通量分析方法的组合将应用于一组光呼吸突变体，这些突变体积累不同水平的甘氨酸。

We recently produced Arabidopsis plants engineered to oxidise glycolate inside the plastids. These plants showed beneficial effects on growth and had higher CO2 assimilation rates per unit area and chlorophyll. To achieve this, it was of radical importance to introduce catalase in the plastids to eliminate H2O2 produced by glycolate oxidase. Here, we propose to work further in the optimization of this original pathway using a glycolate dehydrogenase (GlcDH), without production of H2O2. To this end, we will follow two strategies, (i) the use of Micromonas GlcDH and (ii) the combined use of Synechocystis GlcD1 and GlcD2. Transgenic lines bearing the new pathways will be selected and the impact on plant performance will be analysed at different levels. Moreover, the kinetic properties of these activities enzymes will be thoroughly investigated. On the other hand, photorespiration has been clearly demonstrated to interact with other cellular processes. In this regard, our previous work indicated a light-dependent accumulation of 2-hydroxyglutarate (2HG) in the shm1-1 mutant, which was correlated with high levels of glycine, 2-ketoglutarate and many amino acids. Moreover, we showed for the first time that both enantiomeric forms of 2HG, D-and L-2HG can be found, although at extremely low levels, in wild-type leaf extracts of plants growing in normal conditions. Our group will thus specifically focus on the cross-talk of photorespiration with processes involving 2HG (e.g. senescence, metabolic repair). For this purpose a combination of genomic, biochemical, metabolomic and flux profiling approaches will be applied to a set of photorespiratory mutants, which accumulate glycine to different levels.