Defining the dynamic interplay of a MAPK signaling cascade involved in plant growth, development and sexual reproduction.

沟通和信息传递是一切，不仅对我们的日常生活，而且对生物体的每一个细胞。细胞中的信息传递被称为信号转导。许多元素参与细胞信号传导，通常通过级联介导刺激的感知和处理。这些分子电路精确地检测、放大和整合外部信号以产生下游响应。因此，对刺激的感知可能导致基因表达、酶活性、蛋白质定位或其半衰期的变化，从而导致细胞稳态的重大变化。蛋白激酶家族就是这样一组主要的信号蛋白的例证。激酶是一种通过在特定氨基酸上添加磷酸基团来修饰其他蛋白质的酶，最常见的目标是丝氨酸、苏氨酸和酪氨酸。这么小的改变怎么会对蛋白质产生深远的影响呢？因为蛋白质中磷酸化的氨基酸作为新的实体，改变了蛋白质表面的化学性质，从而使新的蛋白质相互作用的形成成为可能。为什么它被如此广泛地使用？因为它是可逆的：激酶在底物上添加磷酸基团——这会改变底物的性质，进而影响其相互作用的潜力——然后磷酸酶可以去除磷酸基团。这导致了基于磷酸化的信号传导的写入器-读取器-擦除器三联体。磷酸化作为一种交流手段，在植物等无法摆脱危险或不利环境条件的无根生物中似乎更为重要。这可以通过蛋白质激酶家族在植物中的贡献来说明，与其他真核生物相比，它们代表了蛋白质组（生物体的蛋白质集合）的更大比例。例如，在植物模式物种拟南芥中，激酶占蛋白质组的4%，而在人类、线虫、果蝇或啤酒酵母中约占2%。其中，两个主要家族，受体激酶（RK）家族（bbb600）和MAPK（丝裂原活化蛋白激酶）超家族（>00），占所有拟南芥蛋白激酶的70%。因此，激酶处于信号传导的前沿。我们的整体研究计划一直集中在细胞-细胞通信的多个方面，从花粉-雌蕊相互作用到涉及蛋白激酶的信号级联在配子体发育中的作用，例如，胚珠的胚囊和花粉。在本研究项目中，我们将通过分析缺乏这些激酶的突变植物来确定新组装的MAPK级联在影响植物生长、发育和有性生殖方面的作用。使用广泛的实验方法，包括细胞和分子生物学，生物化学，分子遗传学，基因组学，蛋白质组学和下一代测序，我们将剖析这种信号级联的功能，包括三种激酶：MAP激酶激酶激酶激酶（或MKKK）磷酸化并激活MAP激酶激酶（或MKK），该激酶磷酸化MAP激酶（MAPK或MPK），然后可以调节下游效应物。这些效应物也将被寻找，以便更好地定义信号级联在上述生物过程中的参与。我们的目标是破译模块，将有助于基础，生物技术和应用方面的植物科学。考虑到在植物中发现的完整的MAPK信号级联（MKKK-MKK-MPK）不到5个，我们的研究项目无疑将对该领域做出重大贡献，并导致可应用于作物生产、保护和育种的工具的创建。

Communication and information transfer is everything, not only for our day-to-day lives but also for each and every cell of an organism. Information transfer in cells is better known as signal transduction. Numerous elements take part in cellular signalling and generally act through cascades that mediate sensing and processing of stimuli. These molecular circuits precisely detect, amplify, and integrate external signals to generate downstream responses. Thus, perception of a stimulus can lead to changes in gene expression, enzyme activity, localisation of a protein or its half-life, leading to major changes in cell homeostasis. The protein kinase family exemplifies such a major group of signalling proteins. Kinases are enzyme that modifies other proteins by chemically adding a phosphate group to specific amino acids, the most prevalent targets being serine, threonine and tyrosine. How can such a small modification exert profound effects on proteins? Because phosphorylated amino acids in proteins act as new entities, modifying the chemical nature of the protein’s surface, thereby enabling the formation of new protein-protein interactions. Why is it so widely used? Because it is reversible: the kinase adds a phosphate group on a substrate - this modifies the substrate’s properties, which in turn influence its interaction potential - then a phosphatase can remove the phosphate group. This lead to the writer-reader-eraser triad of phosphorylation based signalling. Phosphorylation as a means of communication seems to be even more important in sessile organisms like plants that cannot flea danger or adverse environmental conditions. This can be illustrated by the contribution of the protein kinases family in plants, which represent a much larger fraction of the proteome (the protein ensemble of an organism) compared to other eukaryotes. For example, in the plant model species Arabidopsis thaliana, kinases represent 4% of the proteome compared to ~2% in human, nematode, fruit fly or brewer’s yeast. Of these, two major families, the receptor kinase (RK) family (>600) and the MAPK (Mitogen-Activated Protein Kinases) superfamily (>100), account for 70% of all Arabidopsis protein kinases. Kinases are thus at the forefront of signalling. Our overall research program has been focusing on multiple aspects of cell-cell communication, from pollen-pistil interactions to the role of signalling cascades involving protein kinases in gametophytes development, e.g., the embryo sac of the ovule and the pollen. In this research project, we will focus on the role of a newly assembled MAPK cascade that affects plant growth, development and sexual reproduction, as determined by the analysis of mutant plants lacking these kinases. Using a wide range of experimental approaches, encompassing cell and molecular biology, biochemistry, molecular genetics, genomics, proteomics, and next generation sequencing, we will dissect the functioning of this signalling cascade that includes three kinases: a MAP kinase kinase kinase (or MKKK) that phosphorylate and activates a MAP kinase kinase (or MKK) that in turn phosphorylates a MAP kinase (MAPK or MPK) which then can modulate downstream effectors. These effectors will also be sought in order to better define the involvement of this signalling cascade in the aforementioned biological processes. Our goal is to decipher modules that will be helpful in fundamental, biotechnological, and applied aspects of the plant sciences. Considering that less than five complete MAPK signalling cascades (MKKK-MKK-MPK) have been characterized in plants, our research project will undoubtedly make significant contributions to the field and lead to the creation of tools that can be applied to crop production, protection and breeding.