Biochemistry and physiological importance of alternative photorespiratory pathways in higher plants

除了在过氧化物酶体中氧化乙醇酸作为主要光呼吸途径的一部分外，高等植物也能够在叶绿体或线粒体中转化乙醇酸。来自我们和Promics网络的合作伙伴的数据表明，在绿藻亚分支的蓝藻和绿藻中分别发现了这些额外途径的同源物。这表明进化保护至少持续了4亿年。然而，在高等植物中，这两种替代的乙醇酸转化机会的分子调控和生物学重要性大多是未知的。在这个项目中，拟南芥编码候选通路组分的基因将被过度表达或抑制，并将测量对代谢物谱、光呼吸流速和分离细胞器中乙醇酸转化的影响。此外，三种可能的乙醇酸转化途径的活性将通过产生的系的遗传杂交以组合方式进行调节。由此产生的基因型将受到不同的胁迫条件，如二氧化碳供应减少、氮枯竭或干旱，并将确定相对生长率。这将允许新的见解，以控制替代乙醇酸氧化反应和光呼吸的演变。

Besides oxidation of glycolate in peroxisomes as part of the main photorespiratory pathway, higher plants are also capable of converting glycolate in the chloroplast or the mitochondrium. Data from us and partners in the Promics network indicate that homologues to these additional pathways are found in cyanobacteria and green algae of the chlorophyte subclade, respectively. This suggests evolutionary conservation over a period of at least 400 Million years. However, the molecular regulation and biological importance of these two alternative opportunities for glycolate conversion in higher plants is mostly unknown. In this project, Arabidopsis genes encoding candidate components of the pathways will be overexpressed or suppressed and the effects on metabolite profiles, photorespiratory flow rates, and glycolate conversion in isolated organelles will be measured. Moreover, the activity of the three possible glycolate conversion pathways will be modulated in a combinatorial manner by genetic crossing of the generated lines. The resulting genotypes will be subjected to diverse stress conditions such as reduced CO2 supply, nitrogen depletion, or drought, and relative growth rates will be determined. This will allow new insights into the control of alternative glycolate oxidation reactions and the evolution of photorespiration.