RNA的化学修饰超过150种，显著地影响多种细胞生化反应，如RNA前体剪切，mRNA的稳定性及翻译效率等。目前，关于修饰核苷酸是否会像常见核苷酸一样随着RNA的降解被释放到细胞质后，被进一步分解或者重新利用还不清楚。我们前期鉴定到降解假尿嘧啶核苷酸（ΨMP）的两个定位于过氧化物酶体的蛋白酶，敲除这两个蛋白编码基因，会推迟拟南芥种子萌发。本项目中，我们将深入研究ΨMP的降解机制及生物学意义。评估该途径中关键酶对底物的催化特性及它们的作用方式，揭示ΨMP的代谢机制；人工改造ΨMP代谢途径的亚细胞定位来解析该途径在拟南芥中定位于过氧化物酶体的原因；质谱定量分析拟南芥突变体内相关修饰核苷酸积累情况以及检测各类RNA中假尿嘧啶修饰图谱的变化，阐明该途径缺失导致植株表型变化的分子机制。本项目的研究将丰富我们对RNA修饰及其功能的理解，拓宽RNA表观遗传学的研究领域，完善对生物遗传发育调控机制的认知。

Over 150 chemical modifications of nucleobases exist in the various types of RNA. These RNA modifications influence many biological processes including pre-mRNA splicing, transcript stability, and translation. Upon RNA turnover, the modified nucleosides will be released together with other canonical nucleosides. Cells possess catabolic and recycling pathways to metabolize the canonical nucleosides, however, the metabolic fate of the modified nucleosides is unclear. Recently, we identified a novel pseudouridine catabolic pathway in plants which employs two peroxisome-localized enzymes. Our preliminary data shows that compromising pseudouridine degradation leads a delay of seeds germination. In this project, we will characterize these two enzymes in detail such as the kinetic measurement and the protein-protein interaction study. Moreover, the molecular and phenotypic consequences of genetic abrogation of this pathway as well as of its cytosolic mis-localization will be studied in Arabidopsis thaliana. This research will help us understand the metabolic mechanism of RNA modifications and highlight a novel layer of RNA protection.