Rice octadecanoid pathway

Plant jasmonic acid (JA) and structurally similar animal prostaglandins play pivotal roles in regulating cellular responses against environmental cues, including the innate immune response(s). In plants, JA and its immediate precursor 12-oxo-phytodienoic acid (OPDA) are synthesized by the octadecanoid pathway, which employs at least five enzymes (lipase, lipoxygenase, allene oxide synthase and cyclase, and OPDA reductase), in addition to the enzymes involved in the beta-oxidation steps. Genetic, molecular, and biochemical analyses have led to the identification of almost all the genes of the octadecanoid pathway in Arabidopsis--a model dicotyledonous plant. In this regard, rice (Oryza sativa L.)--an important socio-economic monocotyledonous model research plant--remains poorly characterized. Until now, no gene has been specifically associated with this pathway. It is therefore of utmost importance to identify, characterize, and assign the pathway specific genes in rice. In this review, we have surveyed the rice genome, extracted a large number of putative genes of the octadecanoid pathway, and discussed their relationship with the known pathway genes from other plant species. Moreover, the achievements made so far on the rice octadecanoid pathway have also been summarized to reflect the contribution of rice towards extending our knowledge on this critical pathway in plants.     

Novel rice MAP kinases OsMSRMK3 and OsWJUMK1 involved in encountering diverse environmental stresses and developmental regulation

We report isolation of two novel rice (Oryza sativa L.) mitogen-activated protein kinases (MAPKs), OsMSRMK3 (multiple stress responsive) and OsWJUMK1 (wound- and JA-uninducible) that most likely exist as single copy genes in its genome. OsMSRMK3 and OsWJUMK1 encode 369 and 569 amino acid polypeptides having the MAPK family signature and phosphorylation activation motifs TEY and TDY, respectively. Steady state mRNA analyses of these MAPKs with constitutive expression in leaves of two-week-old seedlings revealed that OsMSRMK3 was up-regulated upon wounding (by cut), jasmonic acid (JA), salicylic acid (SA), ethylene, abscisic acid, hydrogen peroxide (H(2)O(2)), protein phosphatase inhibitors, chitosan, high salt/sugar, and heavy metals, whereas OsWJUMK1 not induced by either wounding, JA or SA, showed up-regulation only by H(2)O(2), heavy metals, and cold stress (12 degrees C). Moreover, these MAPKs were developmentally regulated. These results strongly suggest a role for OsMSRMK3 and OsWJUMK1 in both stress-signalling pathways and development in rice.     

Octadecanoid signaling component "burst" in rice (Oryza sativa L.) seedling leaves upon wounding by cut and treatment with fungal elicitor chitosan

Octadecanoid pathway components, 12-oxo-phytodieonic acid (OPDA) and jasmonic acid (JA), are key biologically active regulators of plant self-defense response(s). However, to date these compounds have been studied mostly in dicots, and used large (1-10 g fresh weight, FW) samples for quantification, even when examined in mature rice plants, which is a drawback considering their rapid responsiveness to stress. Focusing on rice--a monocot cereal crop research model--this work describes an efficient and simultaneous quantification of both OPDA and JA using a minimum amount of 200mg FW seedling leaf tissue upon wounding (by cut) and treatment with fungal elicitor, chitosan (CT) by high-pressure liquid chromatography-turboionspray tandem mass spectrometry. Transient OPDA/JA "burst" was consistently and reproducibly detected within 3 min in wounded and CT treated leaves. OPDA peaked dramatically around 5 min and returned to its basal level within 15 min, whereas JA induction upon wounding and CT treatment were in parallel to OPDA production, peaking at 30 and 60 min, respectively. Present results mark a major advance in our understanding of key inducible octadecanoid pathway components in rice, and strongly suggest a role for the octadecanoid pathway downstream of perception of at least these two fundamentally different extracellular stimuli.     

Three Fusarium oxysporum mitogen‐activated protein kinases (MAPKs) have distinct and complementary roles in stress adaptation and cross‐kingdom pathogenicity

Mitogen‐activated protein kinase (MAPK) cascades mediate cellular responses to environmental signals. Previous studies in the fungal pathogen Fusarium oxysporum have revealed a crucial role of Fmk1, the MAPK orthologous to Saccharomyces cerevisiae Fus3/Kss1, in vegetative hyphal fusion and plant infection. Here, we genetically dissected the individual and combined contributions of the three MAPKs Fmk1, Mpk1 and Hog1 in the regulation of development, stress response and virulence of F. oxysporum on plant and animal hosts. Mutants lacking Fmk1 or Mpk1 were affected in reactive oxygen species (ROS) homeostasis and impaired in hyphal fusion and aggregation. Loss of Mpk1 also led to increased sensitivity to cell wall and heat stress, which was exacerbated by simultaneous inactivation of Fmk1, suggesting that both MAPKs contribute to cellular adaptation to high temperature, a prerequisite for mammalian pathogens. Deletion of Hog1 caused increased sensitivity to hyperosmotic stress and resulted in partial rescue of the restricted colony growth phenotype of the mpk1Δ mutant. Infection assays on tomato plants and the invertebrate animal host Galleria mellonella revealed distinct and additive contributions of the different MAPKs to virulence. Our results indicate that positive and negative cross‐talk between the three MAPK pathways regulates stress adaptation, development and virulence in the cross‐kingdom pathogen F. oxysporum.     

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。     

空心莲子草具有较强抗盐能力的原因初探

为了探讨空心莲子草(Alternantheraphiloxeroides(Mart.)Griseb)的抗盐机理,测定了盐胁迫条件下的空心莲子草和水稻中保护酶活性和渗透调节物质的变化。结果表明,在盐胁迫下,空心莲子草中的脯氨酸、甜菜碱以及SOD、POD等含量增加速度比水稻快,膜脂过氧化产物丙二醛的含量在两种植物中虽亦增加,但在空心莲子草叶中的增加幅度小于水稻。证明盐胁迫下保护酶活性和渗透调节物质含量的迅速增加是空心莲子草具有较强抗盐能力的重要生理学基础。     

稻米品质形成的生理基础研究进展

综述了水稻(Oryza sativa L)米质形成的生理基础的研究进展,主要包括稻米品质形成期的源库特征、淀粉合成的关键酶以及淀粉粒的形态、结构及其糊化特性等几个内容,从植物生理学角度来揭示稻米品质形成的规律有着重要的理论意义.     

VEGF and Bcl-2 Interact Via MAPKs Signaling Pathway in the Response to Hypoxia in Neuroblastoma

Tumor hypoxia has been reported to be a negative prognostic factor in a number of tumor sites, which suggests a positive correlation between tumor hypoxia and increased metastatic efficiency. Evidence shows that vascular endothelial growth factor (VEGF) stimulates angiogenesis in tumor growth and mediates neuroprotection to prevent an apoptotic cell death. Human neuroblastoma cells (CHP126) were exposed to moderate hypoxia for different time spans to explore the molecular stress responses. Apoptotic features as an increase of Bax/Bcl-2 ratio and activation of caspase 3 were observed at early period of exposure time, but these effects were reversed with the extension of hypoxic treatment. Hypoxia also activated MAPKs signaling pathways in a time-relative manner, which were involved in the regulation of hypoxia-related resistance of CHP126 cells. Meanwhile, VEGF and its receptor KDR were found to interact with MAPKs signaling pathways except the effect of hypoxia. Furthermore, rhVEGF₁₆₅ was utilized to discern that VEGF increased Bcl-2 and procaspase 3 expressions, contributing to a synergistic relationship of an angiogenic response with Bcl-2 in hypoxia via a cross talk, while the activation of ERK MAPK is important for both productions. These altered signals may be critical to predict a poor outcome; therefore, our knowledge provides new insight into apoptosis and angiogenesis control of tumor cells and suggests a strategy based on the blockade of hypoxia-induced VEGF signaling under hypoxia in neuroblastoma.     

大黄素对HT-29细胞MAPKs信号通路活化及IL-8分泌的影响

目的：研究大黄素对IFN-和LPS刺激的人结肠癌细胞株HT-29细胞的ERK、JNK和p38MARK和IL-8表达的影响。方法：人结肠癌细胞株HT-29细胞与40ng／mL的IFN．共培养12h,再加入100ng／mLLPS刺激15min,用大黄素预处理进行干预。ELISA检测HT-29细胞内的ERK、JNK和p38MARK含量和细胞上清IL-8含量。结果：IFN-1和LPS刺激后HT-29细胞的ERK、JNK和p38MARK磷酸化水平和IL．8分泌明显升高。大黄素对p38和JNK磷酸化有明显的抑制作用,而对ERK磷酸化则没有明显抑制作用;大黄素能显著降低IFN-γ＋LPS所引起的HT-29细胞IL-8的大量产生,并且呈明显的剂量依赖关系。结论：大黄素能有效抑制IFN-γ＋LPS所引起的HT．29细胞p38和ⅢK的磷酸化,并显著降低IL-8分泌。     

施加外源物质对盐胁迫下水稻生长发育的影响

水稻是重要的粮食作物之一,属于不耐盐的甜土植物,土壤盐渍化是影响其产量和生长发育的主要因素。消除或缓解盐胁迫是当务之急,目前主要应用传统育种、转基因技术及外源物质缓解盐胁迫。拟从外源物质对盐胁迫下水稻的影响作一综述,旨在为水稻生产及抗性育种提供理论依据和实践方法。     

不同发育阶段水稻苗高的QTL分析

分析了不同发育阶段控制水稻苗高的QTL,用5个阶段和4个净增长量的数据共检测到9个QTL,分别位于染色体1,4,6,7,8,11,和12号上。SH－4是主基因,它在各个阶段都表达,对苗高的贡献率在20％以上。结果表明,数量性状的发育或形态建成是由数量性状位点基因选择性表达的结果。     

Rice lesion mimic mutants with enhanced resistance to diseases

Lesion mimic mutants are characterized by the formation of necrotic lesions in the absence of pathogens. Such genetic defects often result in enhanced resistance to pathogen infection and constitutive expression of defense response genes. To understand the genetic mechanisms leading to these mutations, we characterized 21 lesion mimic mutants isolated from IR64 rice mutant populations produced by mutagenesis with diepoxybutane (D), gamma rays (G), and fast neutrons (F). Four mutations are controlled by single dominant genes, one of which is inherited maternally. Five lesion mimics are allelic to known spotted leaf (spl) mutants spl1, spl2, spl3, or spl6. In total, 11 new lesion mimic mutations, named spl16, spl17, and spl19 through Spl27, were established based on allelism tests. Two lesion mimics, spl17 and Spl26 showed enhanced resistance to multiple strains of Magnaporthe oryzae, the rice blast pathogen, and Xanthomonas oryzae pv. oryzae, the bacterial blight (BB) pathogen. Co-segregation analyses of blast and BB resistance and lesion mimic phenotypes in segregating populations of spl17 and Spl26 indicate that enhanced resistance to the two diseases is conferred by mutations in the lesion mimic genes. A double mutant produced from two independent lesion mimics showed more severe lesions and higher level of resistance to X. o. pv. oryzae than their single mutant parents indicating a synergistic effect of the two mutations. In mutants that exhibit enhanced disease resistance to both pathogens, increases in expression of defense response genes PR-10a, POX22.3, and PO-C1 were correlated with lesion mimic development and enhancement of resistance. These lesion mimic mutants may provide essential materials for a comprehensive dissection of the disease resistance pathways in rice.     

Fritillaria ussuriensis Extract Inhibits the Production of Inflammatory Cytokine and MAPKs in Mast Cells

Fritillaria ussuriensis (FU, derived from the bulbs of various species of the genus Fritillaria, including Fritillaria thunbergii Miq.) is used in herbal medicine to treat conditions such as eczema, skin burns, and frostbite. In this study, we investigated the mechanism of the anti-allergy effect of FU. FU extract (80 mg/kg), orally administered to Sprague-Dawley (SD) rats, significantly inhibited the passive cutaneous anaphylaxis (PCA) reaction. It inhibited the compound 48/80-induced release of histamine from rat peritoneal mast cells in a concentration-dependent manner. Significant inhibitory effects of the FU extract on IL-6, IL-8, and TNF-α (1, 10, and 100 μg/mL) were observed in HMC-1 cells. Treatment with FU attenuated PMA plus A23187-induced phosphorylation of all three MAPKs, especially at concentrations of 10 and 100 μg/mL. Further, it (80 mg/kg) led to significant inhibition of mast-cell accumulation in ear tissue at the chronic phase. These results indicate that it inhibits allergic reactions.