The role of tyrosine phosphorylation in the regulation of cell proliferation and differentiation in lower eukaryotes

The review summarizes current data on signaling transduction mechanisms in some unicellular eukaryotes, based on sequential translation of phosphotyrosine signals from the cell surface to the nucleus.     

Signaling mechanisms of apoptosis-like programmed cell death in unicellular eukaryotes

In unicellular eukaryotes, apoptosis-like cell death occurs during development, aging and reproduction, and can be induced by environmental stresses and exposure to toxic agents. The essence of the apoptotic machinery in unicellular organisms is similar to that in mammals, but the apoptotic signal network is less complex and of more ancient origin. The review summarizes current data about key apoptotic proteins and mechanisms of the transduction of apoptotic signals by caspase-like proteases and mitochondrial apoptogenic proteins in unicellular eukaryotes. The roles of receptor-dependent and receptor-independent caspase cascades are reviewed.     

The role of tyrosine phosphorylation in regulation of signal transduction pathways in unicellular eukaryotes

The review summarizes for the first time the current concepts of the role of tyrosine phosphorylation in regulation of signal transduction pathways in unicellular eukaryotes. Evolutionary concepts are developed about the origin of protein tyrosine kinases (PTK)-signaling.     

cAMP-PKA signal pathway in the lower eukaryotes

The review summarizes current data regarding transduction mechanisms by cAMP-PKA signal pathway in unicellular eukaryotes. Conceptions of evolutionary origin of eukaryotic signal transduction systems are developed.     

The role of membrane potential shifts at the initial stages of signal transduction in unicellular eukaryotes

The review summariezes current data about the origin of membrane potentials and their contribution to the signal transduction about changes in temperature, ionic composition of the medium, and chemo-, photo-, gravi-taxis signals in unicellular eukaryotes.     

Pathways of transduction of apoptotic signals in unicellular eukaryotes

The review summarizes current data about transduction mechanism of apoptotic signals by caspase-like enzymes and mitochondrial apoptogenic proteins in unicellular eukaryotes. The role of receptor-dependent and receptor-independent caspase cascades is rewieved. The special attention is given to evolution aspects of problem of apoptosis.     

Exploitation of genomic sequences in a systematic analysis to access how cyanobacteria sense environmental stress

The perception and subsequent transduction of environmental signals are primary events in the acclimation of living organisms to changes in their environment. Many of the molecular sensors and transducers of environmental stress cannot be identified by traditional and conventional methods. Therefore, the genomic information has been exploited in a systematic approach to this problem, performing systematic mutagenesis of potential sensors and transducers, namely, histidine kinases and response regulators, respectively, in combination with DNA microarray analysis, to examine the genome-wide expression of genes in the unicellular cyanobacterium Synechocystis sp. PCC 6803. Using targeted mutagenesis, 44 out of the 47 histidine kinases and 42 out of the 45 response regulators of this organism have successfully been inactivated. The resultant mutant libraries were screened by genome-wide DNA microarray analysis and by slot-blot hybridization analysis under various stress and non-stress conditions. Histidine kinases have been identified that perceive and transduce signals of low-temperature, hyperosmotic, and salt stress, as well as manganese deficiency.     

Tyrosine kinase signaling and the emergence of multicellularity

Tyrosine phosphorylation is an essential element of signal transduction in multicellular animals. Although tyrosine kinases were originally regarded as specific to the metazoan lineage, it is now clear that they evolved prior to the split between unicellular and multicellular eukaryotes (≈600million years ago). Genome analyses of choanoflagellates and other protists show an abundance of tyrosine kinases that rivals the most complex animals. Some of these kinases are orthologs of metazoan enzymes (e.g., Src), but others display unique domain compositions not seen in any metazoan. Biochemical experiments have highlighted similarities and differences between the unicellular and multicellular tyrosine kinases. In particular, it appears that the complex systems of kinase autoregulation may have evolved later in the metazoan lineage.     

Rapid transmission of oxidative and nitrosative stress signals from roots to shoots in Arabidopsis.

Protein kinases play a central role in signal transduction pathways in eukaryotes. A highly conserved group of kinases, termed mitogen-activated-protein kinases (MAPKs) was shown to mediate many diverse stress responses. In plants, MAPKs were shown to function in resistance responses to many biotic and abiotic stresses. Here, we show that exposure of Arabidopsis roots to hydrogen peroxide or to nitric oxide resulted in rapid activation of protein kinases in the shoots that exhibited MAPK properties. The same pattern of kinases was induced by direct injection of these compounds into leaves, indicating accurate long-distance transmission of H2O2 and NO signals. These results are important for the understanding of redox signal transmission from the rhizosphere throughout the plant.     

植物中的MAPK及其在信号传导中的作用

促分裂原活化蛋白激酶(MAPKs)是一类存在于真核生物中的丝氨酸/苏氨酸蛋白激酶。同动物和酵母中MAPKs类似,植物中的MAPK级联途径也是由MAPKs、MAPKKs、MAPKKKs三种类型的激酶组成。植物细胞内受体接受外界刺激信号,然后依次磷酸化激活MAPKKKs、MAPKKs和MAPKs,并影响相关基因表达。目前已经从植物中分离到一些MAPKs、MAPKKs和MAPKKKs,它们参与了植物激素、生物胁迫及非生物胁迫等过程的信号传导。介绍了植物响应外界环境胁迫过程中,不同机制和因子对MAPKs级联途径的调控。     

植物抗逆相关蛋白激酶的结构与功能

植物在遭受外界逆境胁迫时,体内的信号传导系统能够感知、传递逆境胁迫信号,并引起各种生理生化反应以适应环境。植物蛋白激酶在信号感知、传导以及基因的表达调控中起重要的作用。蛋白激酶在信号传导过程的功能是磷酸化修饰目的蛋白,而磷酸化的实现需要蛋白质之间相互作用。本文从植物蛋白激酶的结构、分类、与激素信号传导之间的关系等方面进行了系统的阐述,对蛋白激酶介导的植物抗性与发育的最新研究进展进行了系统的总结,为解析蛋白激酶在植物生长发育中的抗逆机理提供依据。     

Procaryotic genesis and evolution of chemosignaling systems of eukaryotes

The analysis of own and literature data accumulated in the last two decades allowed to check and confirm the author's hypothesis about the prokaryotic origin and endosymbiotic genesis of chemosignalling systems of higher eukaryotes. The comparison of structural-functional organization of these information systems and their components (receptors, GTP-binding proteins, enzymes with cyclase activity, protein kinases etc.) in bacteria and eukaryotes revealed a number of similar features giving evidence for their evolutionary relationship. The conclusion was made that eukaryotic signaling systems have prokaryotic roots. The systems of signal transduction revealed in unicellular eukaryotes according to their architecture and functional properties represent a transient stage in the evolution of chemosignalling systems from prokaryotes to higher eukaryotes. The spreading of signalling systems among three super kingdoms--Bacteria, Archaea and Eukarya occurred as a result of horizontal transfer of bacterial genes and co-evolution of signalling components.     

The role of phosphoinositide signaling in the lower eukaryotes

The recent achievements on phosphoinositide signaling in the unicellular eukaryotes have been reviewed. Special attention is paid to mechanisms of phospholipase C (PLC) activation and its interaction with both cell surface receptors and effector cytoplasm targets. We discuss the role of protein kinase C (PKC) in intracellular signaling, and the relationship between the PI-signal pathway key enzymes with protein kinases of cAMP-PKA and MAP-kinase pathways.     

Evolution of Osmosensory MAP Kinase Signaling Pathways

Mitogen-activated protein (MAP) kinases constitute a large familyof proteins with many functions. They are represented by a multitudeof paralogous isoforms in yeast, vertebrates, and other eukaryotes.A phylogenetically conserved function of MAP kinases is to carryosmotic signals from sensory to target elements of cells. Eventhough this function of MAP kinases is ubiquitous and characteristicof unicellular and multicellular eukaryotes alike the contingenciesbetween individual MAP kinases, sensor elements, and targetelements have been subject to vast modification during evolution.Extensive networking of MAP kinase cascades with other signalingpathways is reflected by the large number of diverse signalsthat can be carried by a single MAP kinase pathway and flexibleactivation kinetics. It is emerging that the most importantfunction of MAP kinase networks may not be signal amplificationbut integration of information about the setpoint of environmentalparameters (including osmolality) with other physiological processesto control cell function. Insight into how this cellular integrationof information is achieved by MAP kinase networks will shedlight on the principles of cell dynamics and adaptation.     

Phytochrome phosphorylation in plant light signaling.

Reversible protein phosphorylation is a switching mechanism used in eukaryotes to regulate various cellular signalings. In plant light signaling, sophisticated photosensory receptor systems operate to modulate growth and development. The photoreceptors include phytochromes, cryptochromes and phototropins. Despite considerable progresses in defining the photosensory roles of these photoreceptors, the primary biochemical mechanisms by which the photoreceptor molecules transduce the perceived light signals into cellular responses remain to be elucidated. The signal-transducing photoreceptors in plants are all phosphoproteins and/or protein kinases, suggesting that light-dependent protein phosphorylation and dephosphorylation play important roles in the function of the photoreceptors. This review focuses on the role of phytochromes' reversible phosphorylation involved in the light signal transduction in plants.     

植物体中的MAPK

促细胞分裂剂激活性蛋白激酶（MAPK）是一类存在于各种真核生物体中的丝氨酸/苏氨酸型蛋白激酶。它被上游激活因子MAPKK磷酸化而激活,并通过将底物蛋白上的丝氨酸和苏氨酸残基磷酸化而传递信号。它与其他一些信号分子组成MAPK级联信号通路,接受外界刺激信号,将信号转入细胞内,影响特定基因的表达,它的作用受到不同因子的调节。本文介绍了植物体中的MAPK的结构特点、作用机理、生物功能以及MAPK级联信号通路的调节。     

Evolutionary relationships of Metazoa within the eukaryotes based on molecular data from Porifera

Recent molecular data provide strong support for the view that all metazoan phyla, including Porifera, are of monophyletic origin. The relationship of Metazoa, including the Porifera, to Plantae, Fungi and unicellular eukaryotes has only rarely been studied by using cDNAs coding for proteins. Sequence data from rDNA suggested a relationship of Porifera to unicellular eukaryotes (choanoflagellates). However, ultrastructural studies of choanocytes did not support these findings. In the present study, we compared amino acid sequences that are found in a variety of metazoans (including sponges) with those of Plantae, Fungi and unicellular eukaryotes, to obtain an answer to this question. We used the four sequences from 70 kDa heat-shock proteins, the serine-threonine kinase domain found in protein kinases, beta-tubulin and calmodulin. The latter two sequences were deduced from cDNAs, isolated from the sponge Geodia cydonium for the phylogenetic analyses presented. These revealed that the sponge molecules were grouped into the same branch as the Metazoa, which is statistically (significantly) separated from those branches that comprise the sequences from Fungi, Plantae and unicellular eukaryotes. From our molecular data it seems evident that the unicellular eukaryotes existed at an earlier stage of evolution, and the Plantae and especially the Fungi and the Metazoa only appeared later.