MAPK级联途径参与ABA信号转导调节的植物生长发育过程

植物激素ABA参与调控植物生长发育和生理代谢以及多种胁迫应答过程,促分裂原活化蛋白激酶（MAPK）级联途径应答于多种生物和非生物胁迫,广泛参与调控植物的生长发育。MAPK级联途径与ABA信号转导协同作用参与调控植物种子萌发、气孔运动和生长发育,本文主要归纳了植物中受ABA调控激活的MAPK级联途径成员,阐述了它们参与ABA信号转导调控植物生理反应和生长发育的过程,并对MAPK级联途径与ABA信号转导的研究方向作出了展望,指出对MAPK下游底物的筛选是完善MAPK级联途径的重要组成部分。     

MAPK和活性氧参与植物抗病防卫反应的信号转导

促分裂原活化蛋白激酶（MAPK）级联途径和活性氧参与调控植物过敏性细胞死亡。本文介绍促分裂原活化蛋白激酶级联途径在植物抗病防卫反应信号转导中的作用研究进展,并对活性氧积累与MAPK之间的关系作了分析。     

MAPK级联及其在植物抗病防卫反应中的研究进展

促分裂原活化蛋白激酶(MAPK)级联信号转导途径参与了生物体生长发育和抗逆胁迫生理。植物MAPK级联途径一般由三个丝氨酸/苏氨酸蛋白激酶组分构成:包括MAPKKK(MEKK、MAP3K)、MAPKK(MEK)和MAPK。植物在响应外界环境刺激时,MAPKKK首先被自磷酸化激活,依次通过磷酸化激活MAPKK和MAPK,进而将外界信号在细胞内传递从而调控目标基因的表达。MAPK级联途径参与植物激素、生物胁迫、非生物胁迫等过程的信号传递,本文就MAPK级联途径在植物抗病防卫反应中的研究进展进行综述。     

蓖麻毒素对肝癌细胞有丝分裂原激活蛋白激酶的影响

为进一步探讨蓖麻毒素的毒作用机理 ,采用 Western印迹和免疫组化方法研究蓖麻毒素对人肝癌细胞内磷酸化状态和有丝分裂原激活蛋白激酶 (MAPK)的影响 .其结果表明 :蓖麻毒素能够影响细胞内的磷酸化状态 ,并能激活细胞内的有丝分裂原激活蛋白激酶 ,对 MAPK的激活有时间依赖性和剂量依赖性 . MAPK信号传导途径参与了蓖麻毒素对肝癌细胞的毒作用 .     

植物MAPK C族基因的研究进展

促分裂原活化蛋白激酶(MAPK)是一类丝氨酸/苏氨酸蛋白激酶,它包括MAPKKK、MAPKK和MAPK等3组,它们共同构成MAPK级联系统.MAPK级联系统通过参与蛋白质磷酸化作用传递和放大信号,调控下游基因的表达,最终引起植物的一系列生理反应.MAPK的基因包括A族、B族、C族和D族4类.就C族MAPK基因的种类和功能,以及近几年来对C族MAPK基因的研究方法作综述.     

植物MAPK级联途径参与调控ABA信号转导

促分裂原活化蛋白激酶(MAPK)级联途径信号通路在真核生物细胞信号的转换和放大过程中起重要作用。MAPK级联途径由三个成员组成,分别是MAPK、MAPKK及MAPKKK,此三个信号组分按照MAPKKK-MAPKK-MAPK的方式依次磷酸化将外源信号级联放大向下传递。大量研究表明,植物MAPK级联途径参与调控脱落酸(ABA)信号转导。因此,该文就ABA和MAPK的生物学功能、ABA信号转导中的磷酸化与去磷酸化以及MAPK级联途径与ABA信号转导之间的关系等方面的研究进展进行综述,以便进一步认识MAPK和ABA信号转导的分子机制。     

PTP及其在植物MAPK途径中的作用

蛋白酪氨酸磷酸酶（protein tyrosine phosphatases,PTPs）是一个结构多样的磷酸酶家族,含有高度保守的催化结构域。在植物体内,PTP主要的靶蛋白是促细胞分裂剂激活性蛋白激酶（mitogen-activated protein kinase,MAPK）。MAPK级联途径参与有机体的发育、细胞增殖、激素调节以及逆境胁迫的信号转导,PTP在MAPK级联途径中主要起负调控作用。本文就PTP的结构和功能、MAPK在植物中的作用及PTP在MAPK级联途径中的功能进行综述,并着重介绍PTP在拟南芥中的研究进展。     

PTP 及其在植物MAPK 途径中的作用

蛋白酪氨酸磷酸酶(protein tyrosine phosphatases, PTPs)是一个结构多样的磷酸酶家族, 含有高度保守的催化结构域。在植物体内, PTP主要的靶蛋白是促细胞分裂剂激活性蛋白激酶(mitogen-activated protein kinase, MAPK)。MAPK级联途径参与有机体的发育、细胞增殖、激素调节以及逆境胁迫的信号转导, PTP在MAPK级联途径中主要起负调控作用。本文就PTP的结构和功能、MAPK在植物中的作用及PTP在MAPK级联途径中的功能进行综述, 并着重介绍PTP在拟南芥中的研究进展。     

植物对盐胁迫响应的信号转导途径

植物通过调控复杂的信号网络来应对盐胁迫。近年来,随着植物基因工程技术的发展,对植物在盐胁迫下信号转导系统的研究取得了一定进展。本文以拟南芥为代表,对盐胁迫下参与调控植物耐盐生理响应的两大类主要信号转导途径——Ca2＋依赖型信号转导通路和丝裂原活化蛋白激酶（MAPK）级联反应途径的研究进展进行综述,主要介绍参与各信号转导通路的组件及诱发的耐盐生理响应等方面,并对该研究领域存在的问题及今后可能的研究方向进行展望。     

PDZ连接激酶，又一新的原癌基因

PDZ连接激酶(PBK)是一种丝-苏氨酸激酶,属于丝裂原活化蛋白激酶激酶(MAPKK)家族成员.PBK能调控细胞周期进程,促进细胞增殖.近年发现,其在乳腺癌、结肠癌、皮肤癌和前列腺癌等多种恶性肿瘤组织中均呈高表达,与多种癌症预后不良关联密切.PBK主要通过Wnt、PI3K/AKT/mTOR和MAPK等信号通路,调控肿瘤细胞有丝分裂,参与多种癌症的增殖、侵袭转移和耐药等,并受miR-216b-3p、miR-770-5p和miR-372-5p等多种microRNA调控.提示PBK可能作为又一新的原癌基因,有望成为抑癌药物新的分子靶点.     

B-Raf is critical for MAPK activation during mitosis and is regulated in an M phase-dependent manner in Xenopus egg extracts

Activation of the MAPK cascade during mitosis is critical for spindle assembly and normal mitotic progression. The underlying regulatory mechanisms that control activation of the MEK/MAPK cascade during mitosis are poorly understood. Here we purified and characterized the MEK kinase activity present in Xenopus M phase-arrested egg extracts. Our results show that B-Raf was the critical MEK kinase required for M phase activation of the MAPK pathway. Consistent with this, B-Raf was activated and underwent hyperphosphorylation in an M phase-dependent manner. Interestingly B-Raf hyperphosphorylation at mitosis occurred, at least in part, as a consequence of a feedback loop involving MAPK-mediated phosphorylation within a conserved C-terminal SPKTP motif. The kinase activity of a B-Raf mutant defective at both phosphorylation sites was substantially greater than its wild type counterpart when incubated in Xenopus M phase egg extracts. Furthermore suppression of MAPK feedback at mitosis enhanced B-Raf activity, whereas constitutive activation of MAPK at mitosis strongly suppressed B-Raf activity. These results suggest that feedback phosphorylation by MAPK negatively regulates B-Raf activity at mitosis. Collectively our data demonstrate for the first time a role for B-Raf at mitosis and provide new insight into understanding the regulation and function of B-Raf during cell proliferation.     

Cell wall regeneration and cell division in isolated tobacco mesophyll protoplasts

Summary Protoplasts were isolated from palisade tissue of tobacco leaves by treatment with pectinase and cellulase under aseptic conditions, and were cultured in a synthetic liquid medium. Calcofluor, a fluorescent brightener, was found to be an excellent stain for plant cell walls and was used to demonstrate regeneration of cell walls in these protoplasts. The cultured protoplasts regenerated cell walls by the 3rd day of culture, giving rise to spherical cells. The majority of the protoplasts regenerating cell walls underwent mitosis and cell division. The cycle of mitosis and cell division was repeated 2–3 times during 2 weeks of culture. Some of the nutritional conditions affecting division in the cultured protoplasts were studied.     

Strasburger’s legacy to mitosis and cytokinesis and its relevance for the Cell Theory

Eduard Strasburger was one of the most prominent biologists contributing to the development of the Cell Theory during the nineteenth century. His major contribution related to the characterization of mitosis and cytokinesis and especially to the discovery of the discrete stages of mitosis, which he termed prophase, metaphase and anaphase. Besides his observations on uninucleate plant and animal cells, he also investigated division processes in multinucleate cells. Here, he emphasised the independent nature of mitosis and cytokinesis. We discuss these issues from the perspective of new discoveries in the field of cell division and conclude that Strasburger's legacy will in the future lead to a reformulation of the Cell Theory and that this will accommodate the independent and primary nature of the nucleus, together with its complement of perinuclear microtubules, for the organisation of the eukaryotic cell.     

Mitogen-activated protein kinase 4 is involved in the regulation of mitotic and cytokinetic microtubule transitions in Arabidopsis thaliana

? A mitogen-activated protein kinase kinase kinase (MAPKKK) double mutant, Arabidopsis homologue of nucleus and phragmoplast associated kinase (anp) anp2anp3, and the mitogen-activated protein kinase (MAPK) 4 mutant mpk4 of Arabidopsis thaliana show prominent cytokinetic defects. This prompted the analysis of mitotic and cytokinetic progression as a function of MAPK signalling. Mutants were compared with wild types untreated or treated with the specific MAPKK inhibitor PD98059. ? This study included phenotype analysis, expression analysis of the MPK4 promoter, immunofluorescent localization of MPK4, tubulin and MAP65-1, and time-lapse microscopic visualization of the mitotic microtubule (MT) transitions in control, mutant and inhibitor-treated cells. ? Mutant and inhibitor-treated cells showed defects in mitosis and cytokinesis, including aberrant spindle and phragmoplast formation and drastically delayed or abortive mitosis and cytokinesis. As a result, bi- and multinucleate cells were formed, ultimately disturbing the vegetative tissue patterning. MPK4 was localized to all stages of the expanding phragmoplast, in a pattern similar to that of its putative substrate MAP65-1. ? In this study, MPK4 is shown to be involved in the regulation of mitosis/cytokinesis through modulation of the cell division plane and cytokinetic progression.     

MAPK inactivation is required for the G2 to M-phase transition of the first mitotic cell cycle.

Down-regulation of MAP kinase (MAPK) is a universal consequence of fertilization in the animal kingdom, although its role is not known. Here we show that MAPK inactivation is essential for embryos, both vertebrate and invertebrate, to enter first mitosis. Suppressing down-regulation of MAPK at fertilization, for example by constitutively activating the upstream MAPK cascade, specifically suppresses cyclin B-cdc2 kinase activation and its consequence, entry into first mitosis. It thus appears that MAPK functions in meiotic maturation by preventing unfertilized eggs from proceeding into parthenogenetic development. The most general effect of artificially maintaining MAPK activity after fertilization is prevention of the G2 to M-phase transition in the first mitotic cell cycle, even though inappropriate reactivation of MAPK after fertilization may lead to metaphase arrest in vertebrates. Advancing the time of MAPK inactivation in fertilized eggs does not, however, speed up their entry into first mitosis. Thus, sustained activity of MAPK during part of the first mitotic cell cycle is not responsible for late entry of fertilized eggs into first mitosis.     

植物丝裂原活化蛋白激酶级联信号转导通路研究进展

丝裂原活化蛋白激酶(MAPK)是酵母、动物和植物等真核生物中普遍存在和高度保守的一类信号转导通路,由MAPKKK、MAPKK和MAPK等3部分组成,在应对生物非生物胁迫、激素、细胞分裂调控及植物生长发育等过程中发挥重要作用。该文对近年来国内外有关MAPK级联通路的组成、在植株体内的生物学功能以及MAPK通路的失活进行了概述,旨在为今后MAPK通路介导的信号转导机制的研究提供参考依据。     

A MAP kinase is activated late in plant mitosis and becomes localized to the plane of cell division.

In eukaryotes, mitogen-activated protein kinases (MAPKs) are part of signaling modules that transmit diverse stimuli, such as mitogens, developmental cues, or various stresses. Here, we report a novel alfalfa MAPK, Medicago MAP kinase 3 (MMK3). Using an MMK3-specific antibody, we detected the MMK3 protein and its associated activity only in dividing cells. The MMK3 protein could be found during all stages of the cell cycle, but its protein kinase activity was transient in mitosis and correlated with the timing of phragmoplast formation. Depolymerization of microtubules by short treatments with the drug amiprophosmethyl during anaphase and telophase abolished MMK3 activity, indicating that intact microtubules are required for MMK3 activation. During anaphase, MMK3 was found to be concentrated in between the segregating chromosomes; later, it localized at the midplane of cell division in the phragmoplast. As the phragmoplast microtubules were redistributed from the center to the periphery during telophase, MMK3 still localized to the whole plane of division; thus, phragmoplast microtubules are not required to keep MMK3 at this location. Together, these data strongly support a role for MMK3 in the regulation of plant cytokinesis.