种子大小是农作物的重要性状，主要由受精卵调控因子和母系遗传共同影响。本项目前期工作从拟南芥EMS诱变突变体库中得到一株具有种子变大而植株发育严重迟缓且矮化表型的突变体sao，利用图位克隆技术确定其突变基因为AtMDN1。在酵母中，MDN1同源蛋白可以与NLE蛋白互作，共同参与对60S核糖体亚基的前体出核及成熟过程。然而，目前对AtMDN1-AtNLE在植物种子发育过程中的作用仍然未知。本项目将通过免疫共沉淀技术分析MDN1和NLE的体内互作，结合突变体表型分析此两种蛋白是否共同调控种子发育，并明确其功能缺失对胚、胚乳以及种皮发育的影响。由于MDN1-NLE功能缺失可能影响60S核糖体亚基的成熟进而影响蛋白合成，本项目将通过蛋白质组学分析MDN1-NLE功能缺失所影响的下游蛋白，并检测参与突变体中的表达情况，结合遗传学手段和功能互补实验明确MDN1-NLE调控种子大小的分子机理。

Seed size is an important trait with respect to ecology and agriculture, which is known to be influenced by maternal and/or zygotic factors. Our previous work had successfully screened one mutant, sao, which has increased seed size phenotype. The mutated gene in sao is AtMDN1, which was clarified with positional cloning. The homologous genes of AtMDN1 in yeast and potato were proved to be interacted with NLE. Although increased seed size, sao is extremely stunted and dwarf. Taken together, AtMDN1 might be a regulator of maternal and/or zygotic factors. However, AtMDN1-NLE functions in seed development are still unknown. This study would clarify whether AtMDN1 interacts with NLE and functions in seed embryo, endosperm or ovule integument development. According to AtMDN1-NLE functions in 60S ribosome subunit maturation, downstream target proteins of AtMDN1-NLE will be clear based on Proteomic analysis. Furthermore, transcripts of genes which play key roles in regulating seed size will be tested. Together with genetic approaches and complement experiments, this study aims to make the molecular mechanisms of MDN1-NLE in regulating seed size clear.