Dissection of the signaling function of O-acetylserine in plants

目的：植物的初级代谢产物，如氨基酸，常常作为信号分子触发转录反应。然而，信号转导的分子机制并不详细。其中一种信号分子是半胱氨酸的前体，O-乙酰丝氨酸（OAS），它连接碳，氮和硫的三种同化途径。OAS的水平调节一组基因的表达，所谓的“OAS簇”。该项目的目的是剖析OAS簇基因编码的蛋白质的生理作用，并表征OAS在植物中的信号传导和调节作用的分子机制。研究内容：该项目分为三个主要工作包。每个实验都包含几个独立的实验任务。我们将（1）利用现有的拟南芥遗传资源来测试每个突变如何影响植物中的OAS水平，并确定导致夜间开始时OAS增加的机制。我们将（2）确定在OAS触发后负责改变基因表达的转录因子，并找到OAS激活/抑制它们的机制。然后，我们将（3）详细讨论OAS簇基因的功能，特别是SDI 1和LSU 1，它们充当OAS信号的倍增器。这些蛋白质与许多其他蛋白质相互作用并调节它们的功能。我们将剖析它们的蛋白质相互作用网络，并测试OAS水平的变化如何影响由OAS信号的每个“倍增器”控制的下游基因的表达。选题理由：OAS是丝氨酸和乙酰辅酶A通过丝氨酸乙酰转移酶合成的代谢产物，是半胱氨酸合成酶复合物的组成部分。OAS作为半胱氨酸生物合成的底物，由复合物的第二组分O-乙酰丝氨酸（硫醇）裂解酶催化。除了OAS在硫同化中的代谢作用外，OAS在植物中的信号传导和调节功能已被许多已发表和未发表的数据所暗示。我们的初步工作确定了OAS簇基因的表达与OAS水平呈正相关。对所观察到的影响的分子机制的剖析将彻底改变我们对硫代谢控制及其与碳和氮代谢的联系的理解。SIGNALOAS为德国和波兰合作伙伴之间的合作提供了一个独特的机会，每个合作伙伴都专注于与OAS在工厂中的信号功能相关的并行主题之一。不同实验方法的合作和联合结果的综合效果将超过单个合作伙伴单独工作所能获得的结果。由于这种协同方法，我们期望知识的实质性进步。

Objectives: Primary metabolites, such as amino acids, often function as signals to trigger transcriptional responses in plants. However, the molecular mechanisms of the signal transduction are not known in detail. One of such signal molecules is the precursor of cysteine, O-acetylserine (OAS), which links the three assimilatory pathways of carbon, nitrogen, and sulfur. The level of OAS regulates expression of a group of genes, so called “OAS cluster”. The aim of this project is dissecting the physiological role of the proteins encoded by the OAS cluster genes and characterization of the molecular mechanisms of the signaling and regulatory role of OAS in plants.Research to be carried out: The project has been divided into three main work packages. Each of them consists of several separate experimental tasks. We will (1) use available Arabidopsis genetic resources to test how each mutation affects OAS level in plants and identify the mechanisms causing OAS increase at the beginning of the night. We will (2) identify the transcription factors responsible for altered gene expression upon OAS trigger and find the mechanism of their activation/repression by OAS. We will then (3) address in detail the function of the OAS cluster genes, particularly SDI1 and LSU1, which act as multiplicators of OAS signal. These proteins interact with a number of other proteins and modulate their function. We will dissect their protein interaction networks and test how changes in OAS level affects the expression of downstream genes controlled by each "multiplicator" of OAS signal. Reasons for choosing this research topic: OAS is a metabolite synthesized from serine and acetyl-CoA by serine acetyltransferase, a component of cysteine synthase enzymatic complex. OAS serves as a substrate for cysteine biosynthesis catalyzed by a second component of the complex, O-acetylserine (thiol) lyase. In addition to the metabolic role of OAS in sulfur assimilation the signaling and regulatory function of OAS in plants has been suggested by numerous published and unpublished data. Our preliminary work identified the OAS cluster genes with expression positively correlated with OAS level. Dissection of the molecular mechanisms responsible for the observed affect would revolutionise our understanding of control of sulfur metabolism and its links to carbon and nitrogen metabolism. SIGNALOAS provides a unique opportunity of collaboration between the German and Polish partners, each of them focusing on one of concurrent topics related to the signaling function of OAS in plants. The combined effect of collaboration and joint results of different experimental approaches will exceed the results which would be obtained by single partners working separately. Due to this synergistic approach, we expect a substantial advancement of knowledge.