过氧化氢在水杨酸诱导的蚕豆气孔关闭中的作用

许多植物病原菌可通过气孔进行叶片组织,因此减小气孔开度有利于提高植物的抗性,我们通过表皮条分析和激光扫描共聚显微镜得到的证据表明在保卫细胞中过氧化氢可能是水杨酸信号的中间环节。SA可以浓度依赖的方式诱导气孔关闭（图1A）,H2O2也有类似的作用（图1B）。100μmol/L的水杨酸诱导的气孔关闭作用可明显地被20U/ml的过氧化氢酶或10μmol/L的Vc逆转,但CAT和Vc单独处理时诱导气孔开放的作用很微弱,单细胞中基于荧光探针DCFH的时间进程实验表明直接外加（图版Ⅰ）或显微注射100μmol/L的SA均可诱导保卫细胞中H2O2产生,但以显微注射双蒸水作为对照时对DCFH荧光无影响（图版Ⅱ）,这些结果暗示了植物被病原菌感染时可能通过产生H2O2导致气孔关闭而阻止病原菌继续通过气孔侵入。     

共聚焦显微技术研究SA对蚕豆气孔保卫细胞的影响

水杨酸(salicylic acid,SA)作为植物体内一种内源性的信号分子,具有多种生理功能.实验表明水杨酸以浓度依赖的方式诱导气孔关闭,抑制气孔张开.20U/mL的CAT与SA共同处理时可逆转SA诱导气孔关闭作用的83%~90%.以H2O2荧光探针H2DCFDA结合激光扫描共聚焦显微术直接检测到SA处理可引起保卫细胞内H2O2的产生;在保卫细胞内显微注射CAT可完全阻止SA导致的DCF荧光增强.表明SA诱导的气孔关闭可能与H2O2的产生有关.     

NADPH氧化酶参与水杨酸诱导的蚕豆气孔关闭过程

水杨酸(SA)可以浓度依赖的方式诱导蚕豆叶片的气孔关闭,1～1000μmol·L~(-1)SA所诱导的气孔关闭可以再开放,而10~(-2)mol·L~(-1)的SA导致的气孔关闭则否。质膜NADPH氧化酶抑制剂二亚苯基碘(DPI)可削弱SA作用的45%～60%。表明SA诱导的气孔关闭可能与H_2O_2的产生有关。以H_2O_2荧光探针H_2DCFDA结合显微注射技术直接检测保卫细胞内产生H_2O_2的结果显示,100μmol·L~(-1)SA可引起保卫细胞内荧光素(DCF)荧光快速增强。在DPI存在的情况下,经SA处理的保卫细胞,仅在其叶绿体部位产生H_2O_2,而质膜附近的DCF荧光增强则受到抑制。表明叶绿体可能是保卫细胞内产生H_2O_2的主要部位,质膜NADPH氧化酶也可能参与SA诱导H_2O_2的产生。     

Ca2+参与水杨酸诱导蚕豆气孔运动时的信号转导

在一定条件下,外源水杨酸(SA)可以诱导蚕豆(Vicia faba L.)气孔关闭,阻止气孔张开。以Fluo-3—AM作为Ca^2 的荧光探针,利用激光共聚焦扫描显微技术,对水杨酸调控气孔运动中保卫细胞胞质Ca^2 的变化趋势及Ca^2 的来源进行了研究。结果表明,水杨酸可引起胞质Ca^2 增加,这种变化发生在气孔开度改变之前。Ca^2 螯合剂BAPTA（1,2-bis(2-amino phenox-y)ethane-N,N,N′,N′-tetraacetic acid,1mmol/L)几乎可以完全抑制水杨酸诱导气孔开度减小的作用;胞外Ca^2 螯合剂EGTA(2mmol/L)、质膜Ca^2 通道抑制剂尼群地平(nifedipine,NIF,1μmol/L)和LaCl3(1mmol／L)可不同程度地减弱水杨酸诱导气孔关闭的效应。BAPTA(1mmol／L)预处理后,水杨酸不再引起胞质Ca^2 含量改变;尼群地平能够降低水杨酸引起的胞质Ca^2 增加的幅度。说明Ca^2 可能参与水杨酸诱导气孔运动的信号转导。水杨酸引起胞内升高的Ca^2 可能既来自胞外又来自胞内,胞内Ca^2 库可能是其主要来源。     

NO可能作为H2O2的下游信号介导ABA诱导的蚕豆气孔关闭

ABA、H2O2和硝普钠(SNP)均能诱导蚕豆气孔关闭.NO的清除剂c-PTIO可以减轻由ABA或H2O2所诱导的蚕豆气孔关闭的程度,而过氧化氢酶(CAT)则不能减轻NO诱导的气孔关闭程度.激光共聚焦显微检测结果显示,10μmo1/L的ABA处理后,胞内H2O2的产生速率明显高于NO的产生速率;CAT几乎可完全抑制ABA所诱导的DAF的荧光增加;外源H2O2能显著诱导胞内DAF的荧光增加;c-PTIO对ABA诱导的DCF荧光略有促进作用,但外源SNP不能诱导胞内DCF荧光增加.这些结果表明,在ABA诱导气孔关闭过程中,H2O2可能在NO的上游起作用并受NO的负反馈调节.     

NADPH氧化酶可能参与了ABA诱导蚕豆气孔保卫细胞运动

研究了NADPH氧化酶在ABA（abscisic acid)诱导蚕豆气孔关闭信号转导网络中的作用,荧光光谱实验表明,在嗜中性白血球NADPH氧化酶抑制剂DPI(diphenyleneio-donium)存在的条件下,与对照相比,大大逆转了由ABA引起HPTS（8-hydroxypyrene-1,3,6-trisulfonic acid,trisodium salt)的荧光强度下降。表皮生物分析法显示,10^-6mol/L的DPI和10^3unit/mL的过氧化氢酶（catalase,CAT)在一定程度上也逆转了ABA诱导张开气孔的关闭。因此推测：在ABA诱导蚕豆气孔保卫细胞过程中,质膜上的NADPH气体酶可能催化形成超氧自由基O^-2,再经歧化反应形成H2O2,而形成的H2O2参与了气孔运动调节。     

过氧化氢对蚕豆气孔运动和质膜K+通道的影响

不同浓度H2O2可使蚕豆(ViciafabaL.)叶片气孔关闭,抑制气孔张开,10mmol/L的H2O2最有效,10μmol/L的H2O2仍明显使气孔关闭。且10μmol/L的H2O2抑制气孔张开作用能被EGTA所消除,表明Ca2+参与低浓度H2O2使气孔关闭的过程。2mmol/L的H2O2可使质膜内向K+通道电流明显减小,而外向K+通道电流显著增加。因此,H2O2促进蚕豆气孔关闭主要是通过抑制K+通过保卫细胞质膜内向流入,或加强K+外向流出实现的。     

H_2O_2介导H_2S诱导的拟南芥气孔关闭

以拟南芥（Arabidopsis thaliana）为材料,研究了过氧化氢（H2O2）在硫化氢（H2S）调控气孔运动信号转导中的作用。结果表明,光下H2S的供体硫氢化钠（NaHS）能够诱导拟南芥气孔关闭;且能够显著提高叶片和保卫细胞胞质H2O2含量;H2O2的清除剂AsA和H2O2合成酶的抑制剂可不同程度地抑制NaHS诱导的拟南芥气孔关闭及叶片和保卫细胞胞质H2O2水平的升高;NaHS对AtrbohD、AtrbohF、Atpao2和Atpao4突变体气孔关闭、叶片和保卫细胞胞质H2O2水平升高的诱导作用要明显的小于野生型,但对AtPAO2和AtPAO4过表达株系叶片和保卫细胞H2O2水平的升高较野生型显著。据此推测,来源于NADPH氧化酶、细胞壁过氧化物酶和多胺氧化酶途径的H2O2参与H2S诱导的拟南芥气孔关闭。     

NO和H2O2在光/暗调控蚕豆气孔运动中的作用及其相互关系

借助表皮条分析和激光扫描共聚焦显微镜技术,对NO和H2O2在光/暗调控蚕豆(Vicia faba L.)气孔运动中的作用及其相互关系进行了探索.结果显示,光下外源NO供体硝普钠(SNP)和H2O2促进气孔关闭的效应明显大于暗中,暗中NO专一性清除剂2,4-羧基苯-4,4,5,5-四甲基咪唑-1-氧-3-氧化物(cPTIO)、一氧化氮合酶(NOS)抑制剂NG-氮-L-精氨酸-甲酯(L-NAME)和H2O2清除剂抗坏血酸(Vc)、过氧化氢酶(CAT)对气孔开度的效应明显大于光下,而且光下蚕豆保卫细胞NO和H2O2水平比暗中明显降低.上述结果表明,光/暗通过影响保卫细胞NO和H2O2的水平调控气孔运动.研究还发现,光下H2O2既诱导NO水平增加,也诱导气孔关闭,cPTIO和L-NAME有效地逆转H2O2的这些效应;光下SNP既诱导H2O2水平增加,也诱导气孔关闭,SNP的上述效应又被Vc和CAT有效逆转.这些结果表明,NO和H2O2在生成及效应上均存在明显的相互作用.另外,L-NAME显著逆转暗和光下H2O2处理对气孔关闭和NO生成的效应表明,蚕豆保卫细胞中可能存在NOS,暗和光下H2O2处理可能通过提高NOS的活性促进NO水平增加,进而诱导气孔关闭.     

SB202190调节蚕豆保卫细胞中SA诱导H2O2产生

运用激光共聚焦扫描技术,在p38MAP激酶专一抑制剂SB202190处理下,探索植物促分裂原活化蛋白激酶（mitogen-activated protein kinase,MAP激酶）介导蚕豆（Vicia faba）保卫细胞中H2O2为代表的活性氧（reactive oxygen species,ROS）信号机制,发现：p38MAP激酶专一抑制剂SB202190处理没有导致蚕豆保卫细胞中H2O2和Ca^2＋探针荧光强度增强,与水杨酸（salicylic acid,SA）或脱落酸（abscisic acid,ABA）迅速加强2种探针荧光强度形成鲜明对比;而该抑制剂分别与SA和ABA共同处理,前者H2O2探针荧光强度没有增加,而后者荧光强度仍然能够增加;而进一步使用Ca^2＋螯合剂BAPTA和SB202190＋SA共同处理,H2O2探针荧光强度没有增加。这些结果初步表明：无论胞质Ca^2＋浓度高低,SB202190调节蚕豆保卫细胞中SA诱导H2O2产生,但是不调节植物逆境信使分子ABA此类的反应。因此推测,植物细胞中可能有类似动物和酵母细胞中的p38MAP激酶类,并可能专一调节植物保卫细胞中H2O2信号通路。据我们所知,这是首次报道SB202190和SA共同调节植物保卫细胞中ROS信号过程。     

Role for dopamine in malonate-induced damage in vivo in striatum and in vitro in mesencephalic cultures

Defects in mitochondrial energy metabolism have been implicated in the pathology of several neurodegenerative disorders. In addition, the reactive metabolites generated from the metabolism and oxidation of the neurotransmitter dopamine (DA) are thought to contribute to the damage to neurons of the basal ganglia. We have previously demonstrated that infusions of the metabolic inhibitor malonate into the striata of mice or rats produce degeneration of DA nerve terminals. In the present studies, we demonstrate that an intrastriatal infusion of malonate induces a substantial increase in DA efflux in awake, behaving mice as measured by in vivo microdialysis. Furthermore, pretreatment of mice with tetrabenazine (TBZ) or the TBZ analogue Ro 4-1284 (Ro-4), compounds that reversibly inhibit the vesicular storage of DA, attenuates the malonate-induced DA efflux as well as the damage to DA nerve terminals. Consistent with these findings, the damage to both DA and GABA neurons in mesencephalic cultures by malonate exposure was attenuated by pretreatment with TBZ or Ro-4. Treatment with these compounds did not affect the formation of free radicals or the inhibition of oxidative phosphorylation resulting from malonate exposure alone. Our data suggest that DA plays an important role in the neurotoxicity produced by malonate. These findings provide direct evidence that inhibition of succinate dehydrogenase causes an increase in extracellular DA levels and indicate that bioenergetic defects may contribute to the pathogenesis of chronic neurodegenerative diseases through a mechanism involving DA.     

SSTR5 ablation in islet results in alterations in glucose homeostasis in mice

Somatostatin (SST) peptide is a potent inhibitor of insulin secretion and its effect is mediated via somatostatin receptor 5 (SSTR5) in the endocrine pancreas. To investigate the consequences of gene ablation of SSTR5 in the mouse pancreas, we have generated a mouse model in which the SSTR5 gene was specifically knocked down in the pancreatic beta cells (betaSSTR5Kd) using the Cre-lox system. Immunohistochemistry analysis showed that SSTR5 gene expression was absent in beta cells at three months of age. At the time of gene ablation, betaSSTR5Kd mice demonstrated glucose intolerance with lack of insulin response and significantly reduced serum insulin levels. Insulin tolerance test demonstrated a significant increase of insulin clearance in vivo at the same age. In vitro studies demonstrated an absence of response to SST-28 stimulation in the betaSSTR5Kd mouse islet, which was associated with a significantly reduced SST expression level in betaSSTR5Kd mice pancreata. In addition, betaSSTR5Kd mice had significantly reduced serum glucose levels and increased serum insulin levels at 12 months of age. Glucose tolerance test at an older age also indicated a persistently higher insulin level in betaSSTR5Kd mice. Further studies of betaSSTR5Kd mice had revealed elevated serum C-peptide levels at both 3 and 12 months of age, suggesting that these mice are capable of producing and releasing insulin to the periphery. These results support the hypothesis that SSTR5 plays a pivotal role in the regulation of insulin secretion in the mouse pancreas.     

2018年中国植物科学若干领域重要研究进展

2018年中国植物科学继续呈现快速发展的态势, 我国科学家在国际植物科学主流学术刊物发表论文数量大幅增加, 取得了多项具有重要影响的成果。调控植物生长-代谢平衡实现可持续农业发展入选2018年度中国科学十大进展; 中国被子植物区系进化历史研究入选2018年度中国生命科学十大进展。以水稻为代表的农作物和果蔬等经济作物研究在国际上已呈现出明显的优势, 若干领域已从“追赶”状态跨越到“领跑”地位。该文对2018年中国科学家在植物科学若干领域取得的重要研究成果进行了概括性评述, 旨在全面追踪和报道当前中国植物科学领域的发展前沿和热点, 展示中国科学家所取得的杰出成就。     

我国葫芦科植物离体培养研究进展

葫芦科植物包括多种瓜类蔬菜,对其进行离体培养研究具有重要的理论和实践意义。综述了国内在葫芦科植物器官培养、体细胞胚胎发生、花药培养、原生质体培养和体细胞杂交及离体遗传转化等方面取得的研究进展,并对葫芦科植物离体培养、遗传转化与育种的前景作了展望。     

2018年中国植物科学若干领域重要研究进展

2018年中国植物科学继续呈现快速发展的态势, 我国科学家在国际植物科学主流学术刊物发表论文数量大幅增加, 取得了多项具有重要影响的成果。调控植物生长-代谢平衡实现可持续农业发展入选2018年度中国科学十大进展; 中国被子植物区系进化历史研究入选2018年度中国生命科学十大进展。以水稻为代表的农作物和果蔬等经济作物研究在国际上已呈现出明显的优势, 若干领域已从“追赶”状态跨越到“领跑”地位。该文对2018年中国科学家在植物科学若干领域取得的重要研究成果进行了概括性评述, 旨在全面追踪和报道当前中国植物科学领域的发展前沿和热点, 展示中国科学家所取得的杰出成就。     

2017年中国植物科学若干领域重要研究进展

2017年中国植物科学继续保持高速发展态势, 重大成果频出, 具体表现在中国植物学家在国际顶级学术期刊发表的文章数量平稳上升。中国植物科学领域的研究工作者成果精彩纷呈, 如新型广谱抗病机制的发现、水稻广谱抗病遗传基础及机制和疫霉菌诱发病害成灾机制研究等。2017年中国生命科学领域十大进展评选中, 有两项植物科学领域的研究成果入选。水稻生物学、进化与基因组学和激素生物学等领域学科发展突出。另外, 值得一提的是, 长期从事高等植物与代谢途径调控分子网络研究和水稻品种设计育种的李家洋院士的研究成果“水稻高产优质性状形成的分子机理及品种设计”荣获2017年国家自然科学一等奖。这一具有重大国际影响的开创性贡献标志着中国植物科学在该领域的国际科学前沿居于引领和卓越地位。该文对2017年中国本土科学家在植物科学若干领域取得的重要研究成果进行了系统梳理, 旨在全面追踪和报道当前中国植物科学领域发展的最新前沿动态, 与广大读者共同分享我国科学家所取得的辉煌成就。     

Morphine-potentiated platelet aggregation in in vitro and platelet plug formation in in vivo experiments

The detailed mechanisms underlying morphine-signaling pathways in platelets remain obscure. Therefore, we systematically examined the influence of morphine on washed human platelets. In this study, washed human platelet suspensions were used for in vitro studies. Furthermore, platelet thrombus formation induced by irradiation of mesenteric venules with filtered light in mice pretreated with fluorescein sodium was used for an in vivo thrombotic study. Morphine concentration dependently (0.6, 1, and 5 microM) potentiated platelet aggregation and the ATP release reaction stimulated by agonists (i.e., collagen and U46619) in washed human platelets. Yohimbine (0.1 microM), a specific alpha(2)-adrenoceptor antagonist, markedly abolished the potentiation of morphine in platelet aggregation stimulated by agonists. Morphine also potentiated phosphoinositide breakdown and intracellular Ca(2+) mobilization in human platelets stimulated by collagen (1 microg/ml). Moreover, morphine (0.6-5 microM) markedly inhibited prostaglandin E(1) (10 microM)-induced cyclic AMP formation in human platelets, while yohimbine (0.1 microM) significantly reversed the inhibition of cyclic AMP by morphine (0.6 and 1 microM) in this study. The thrombin-evoked increase in pH(i) was markedly potentiated in the presence of morphine (1 and 5 microM). Morphine (2 and 5 mg/g) significantly shortened the time require to induce platelet plug formation in mesenteric venules. We concluded that morphine may exert its potentiation in platelet aggregation by binding to alpha(2)-adrenoceptors in human platelets, with a resulting inhibition of adenylate cyclase, thereby reducing intracellular cyclic AMP formation followed by increased activation of phospholipase C and the Na(+)/H(+) exchanger. This leads to increased intracellular Ca(2+) mobilization, and finally potentiation of platelet aggregation and of the ATP release reaction.     

我国葫芦科植物离体培养研究进展

葫芦科植物包括多种瓜类蔬菜,对其进行离体培养研究具有重要的理论和实践意义.综述了国内在葫芦科植物器官培养、体细胞胚胎发生、花药培养、原生质体培养和体细胞杂交及离体遗传转化等方面取得的研究进展,并对葫芦科植物离体培养、遗传转化与育种的前景作了展望.     

Progress in glial cell studies in some laboratories in China

Glial cells in the central nervous system(CNS) consist of a heterogeneous population of cell types,each characterized by distinct morphological features,physiological properties,and specific markers.In contrast to the previous view that glial cells were passive elements in the brain,accumulating evidence suggests that glial cells are active participants in various brain functions and brain disorders.This review summarizes recent progress of glial cell studies from several groups in China,ranging from studie...     

Changes in aquatic vegetation in Rhine floodplain streams in Alsace in relation to disturbance

Abstract. Changes are described in aquatic vegetation in oligotrophic, groundwater-fed Rhine floodplain streams in Alsace (eastern France), resulting from disturbance. Disturbance factors include changes in nutrients, either permanent ones - effluent from a waste water treatment plant or trout hatcheries - or periodic ones: flooding. Regular inputs of high levels of phosphate and ammonia modified the macrophyte vegetation in these streams. The floristic composition, which was characteristic of oligotrophic waters upstream of the eutrophicated sector, changed to that of a eutrophic situation as originally found downstream. Periodic disturbance by floods which normally occur once a year, irregularly eutrophicates the small streams, causing the development of a mixture of eutrophic and oligotrophic species. Six macrophyte communities are distinguished, indicating different trophic levels. The aquatic vegetation is adapted to the variations of phosphate and ammonia levels. Hence, aquatic macrophytes can be used as bio-indicators of fluctuations in water nutrient levels in relation to the type of disturbance.