黄腐酸对水稻幼苗根系生长的影响及其与生长素的关系北大核心CSCD

该研究以水稻品种‘宁粳6号’为材料,通过外源使用黄腐酸(FA)与生长素抑制剂共同处理水稻,探究FA对水稻根系生长的影响及其与生长素之间的关系。结果表明:(1)50~800 mg·L^(-1) FA处理水稻幼苗6 d后,当FA浓度超过100 mg·L^(-1)时显著促进水稻种子根的伸长生长;FA浓度超过400 mg·L^(-1)时,与对照组相比水稻的平均侧根长和侧根密度显著增加。(2)与对照相比,低浓度FA处理对水稻幼苗根尖生长素的含量无显著影响,但400 mg·L^(-1) FA处理后显著提高了内源生长素的含量。(3)3μmol·L^(-1)生长素合成抑制剂4-联苯硼酸(BBo)、4-苯氧基苯基硼酸(PPBo)或30μmol·L^(-1)生长素信号转导抑制剂2-(对-氯苯氧)-异丁酸(PCIB)处理均可显著抑制水稻根和侧根的发生;1μmol·L^(-1)生长素极性运输抑制剂三碘苯甲酸(TIBA)可显著抑制水稻种子根的伸长生长与侧根发生,但对侧根长度无显著作用。(4)FA与BBo或PPBo共同处理可显著抑制FA对水稻根系伸长生长与侧根发生的促进作用;TIBA和PCIB分别和FA共同处理水稻,可显著抑制FA对种子根伸长生长的促进作用,且PCIB可显著抑制FA对侧根发生的促进作用,但TIBA对此没有显著影响。研究发现,外源FA可能通过调控植物内源生长素的合成、极性运输或信号转导来调控水稻根的伸长生长和侧根的发育。     

外源抗坏血酸缓解水稻幼苗的铝胁迫效应

为探讨外源抗坏血酸对铝胁迫下水稻氧化损伤的影响,该文以峰1A(不育系,籼稻)和滇优35号(杂交,粳稻)两个水稻品种为材料,采用溶液培养法研究外源抗坏血酸(AsA)对50μmol·L~(-1)Al~(3+)胁迫下水稻根尖H_2O_2和内源AsA含量以及抗氧化酶活性的影响。结果表明:铝胁迫24 h时,水稻根尖内源AsA含量为对照的0.90倍,与对照相比,根尖H_2O_2增加了0.55倍至1.3倍,SOD、POD、CAT及APX活性分别增加了0.83倍至1.6倍、1.0倍至1.3倍、0.85倍至1.2倍、1.0倍至1.8倍;外源AsA处理铝胁迫水稻24 h,水稻根尖内源AsA含量为对照的1.2倍,SOD、POD、CAT及APX活性分别增加了1.2倍至2.2倍、1.5倍至1.6倍、1.3倍至1.7倍、1.2倍至2.6倍,根尖H_2O_2含量增加了0.1倍至0.6倍。这些研究结果说明铝胁迫加剧了细胞膜的过氧化程度,并诱导抗氧化酶活性以清除活性氧,外源AsA通过提高抗氧化酶活性和内源AsA含量以缓解水稻Al~(3+)胁迫引起的氧化损伤,降低细胞膜系统伤害,促进水稻生长,为外源AsA提高水稻适应铝胁迫能力提供了理论依据。     

外源钾对铁胁迫下水稻细胞壁多糖含量及耐铁性的影响

以耐铁毒型水稻品种协优9308和铁毒敏感型水稻品种Ⅱ优838为实验材料,采用溶液培养法研究250mg.L-1Fe2+(EDTA-Fe2+)胁迫下,不同钾水平对两种水稻的生长特性、酸性磷酸酶(APA)、果胶甲酯酶(PME)、根系果胶含量、半纤维素1含量以及半纤维素2含量的影响。结果表明,经250mg.L-1Fe2+处理7d和14d后,协优9308和Ⅱ优838的相对根长明显下降,APA、PME的活性显著升高,果胶含量、半纤维素1含量、半纤维素2含量显著增加,Ⅱ优838酶活性及细胞壁多糖含量提高幅度较大,表现出其铁毒敏感性,并且随着处理时间的延长,铁胁迫对两种水稻相对根长,PME活性,HC1含量及HC2含量的影响越显著,但APA活性和果胶含量则没有明显变化。加入外源钾可以不同程度的降低酶活性及细胞壁多糖含量,外源钾浓度为200mg.L-1,对水稻相对根长,APA活性,HC1含量缓解效果较好;外源钾浓度为400mg.L-1,对PME活性,果胶含量缓解效果较好。随着外源钾浓度升高,水稻铁毒症状得到不同程度的缓解,但钾浓度高于200mg.L-1又会对水稻造成新的胁迫。由此推测,水稻通过提高根系细胞壁多糖含量来增加根尖铁的结合位点,以及细胞壁的厚度和刚性,并降低细胞壁的伸展性,使根细胞的伸长受抑,从而提高其铁耐性。     

外源NO对铝毒下水稻根系生长和抗氧化系统的影响

以水稻品种‘浙辐802’为材料,采用水培法研究铝毒下外源NO对幼苗根系生长、活性氧产生和抗氧化酶活性的影响,探讨外源NO提高水稻耐铝性的生理生化机制。结果显示:(1)0.05mmol/L Al显著抑制水稻根系生长,促使根尖Al、胼胝质、过氧化氢(H2O2)和超氧阴离子自由基(O-·2)含量显著增加;而外源0.1mmol/L的NO供体亚硝基铁氰化钠(sodium nitroprusside,SNP)预处理能使铝毒下水稻幼苗根相对伸长率及根尖NO含量分别增加34.96%和12.86%,根尖Al和相对胼胝质含量分别下降83.04%和31.93%,表明NO可部分缓解铝毒害,且这种作用与内源NO含量变化有关。(2)外源NO同时使铝毒下水稻幼苗根尖H2O2和O-·2含量分别下降15.43%和12.93%,使超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性显著上升,且外源NO的该种作用可以被0.075mmol/L NO清除剂(carboxy-PTIO,cPTIO)所逆转。研究表明,外源NO在调节活性氧代谢以维持细胞膜结构稳定,进而有效减轻Al对水稻根系的损伤上起着重要作用。     

外源IAA增强丹波黑大豆抗铝性的生理机制

以铝耐受型丹波黑大豆(RB)幼苗为供试材料,考察了不同浓度铝胁迫下添加外源IAA对RB根尖内源IAA、H2O2、MDA、铝含量、柠檬酸分泌量以及质膜H+-ATPase活性的影响,探讨外源IAA增强RB抗铝能力的生理机制。结果显示:(1)经25、50和200μmol·L-1 AlCl3胁迫处理24h后,RB根尖IAA含量、柠檬酸分泌量和质膜H+-ATPase活性均表现为先上升后下降的趋势,而H2O2、MDA和根尖铝含量却随着铝处理浓度的增加呈显著上升趋势。(2)与单独25、50和200μmol·L-1 AlCl3胁迫处理相比,添加50μmol·L-1外源IAA后使得RB根尖铝、MDA和H2O2含量均显著降低,同时使RB根尖柠檬酸分泌量分别相应增加到单独处理的2.39、1.73和6.85倍,且其相应的质膜H+-ATPase活性也增加了1.09、1.74和1.45倍。研究表明,外源IAA能通过增强丹波黑大豆根尖柠檬酸的分泌量和质膜H+-ATPase活性来提高其对铝胁迫的抗性,明显缓解铝毒害作用。     

褪黑素对铅胁迫下虎舌红和朱砂根生理响应及DNA损伤的调控效应

铅胁迫是影响植物生长的主要非生物因素之一。以二年生虎舌红(Ardisia mamillata)和朱砂根(A. crenata)为实验材料, 探究外源褪黑素(MT)处理对不同浓度铅胁迫下2种植物生理响应及DNA损伤的调控效应。结果表明, 相同处理时间内, 随着铅胁迫浓度的升高, 虎舌红与朱砂根的3种抗氧化酶活性、脯氨酸(Pro)及可溶性蛋白(SP)含量均先升高后降低, 而丙二醛(MDA)含量先降低后升高, 根尖胼胝质含量持续升高, 根系DNA损伤加剧。施加适宜浓度的外源褪黑素(MT)后, 不同浓度铅胁迫下2种植物的抗氧化酶活性得到有效增强, 且均在100 µmol∙L^-1 MT处理时达到最大值, Pro和SP含量均显著升高, MDA含量则先显著降低而后缓慢升高, 根尖胼胝质含量持续增加, 根系DNA损伤得到改善; 随着MT浓度的持续升高, 其缓解作用逐渐减弱。相较于虎舌红, 朱砂根对铅胁迫的抗性更强, 生理响应更稳定。施加外源MT可有效缓解铅胁迫对虎舌红和朱砂根的毒害作用(缓解效果朱砂根>虎舌红), 增强二者对铅毒的耐受性, 其中100 µmol∙L^-1 MT处理下缓解效果最佳。研究揭示了虎舌红和朱砂根抗铅性的优劣及外源MT对铅毒的缓解效应, 为紫金牛属植物抗铅性研究提供理论参考。     

外源NO缓解紫茎泽兰提取物对黄瓜根边缘细胞的化感胁迫

以津优35号黄瓜为材料,采用根尖悬空气培养的方法,研究了紫茎泽兰提取物对黄瓜根边缘细胞的化感胁迫,以及外源NO缓解化感胁迫的效应.结果表明: 1000 mg·L^-1紫茎泽兰提取物对黄瓜根尖有明显的伤害作用,根尖组织结构被破坏,根尖表层细胞脱落,细胞排列混乱且疏松;这些伤害能够被外源NO有效缓解.与对照相比,紫茎泽兰提取物处理黄瓜幼苗根尖根边缘细胞(RBC)的数量和细胞活率被显著抑制,分别降低54.5%和97.2%,细胞凋亡率升高12.3倍,RBC的黏胶层厚度增加31.4%,根边缘细胞根冠果胶甲基酯酶(PME)活性显著增加.与紫茎泽兰提取物处理相比,提取物胁迫下添加外源NO处理的RBC数量和细胞活率分别增加72.4%和146.0%,细胞凋亡率和RBC黏胶层厚度分别降低30.7%和15.0%,PME活性在处理72 h时降低了14.3%.紫茎泽兰提取物对黄瓜RBC产生细胞毒性,诱导细胞发生凋亡和死亡,破坏RBC对根尖的保护,提取物进一步对根尖产生胁迫伤害,破坏根尖的组织结构.外源NO可以在一定程度上缓解提取物对黄瓜根尖及RBC的化感胁迫伤害.     

生长素介导海藻酸钠寡糖调控水稻对镉胁迫的抗性

采用生长素运输抑制剂,探讨生长素是否介导海藻酸钠寡糖(AOS)缓解水稻镉(Cd)胁迫。结果表明,Cd胁迫明显抑制水稻幼苗的生长发育,表现在苗长、地上部生物量和地下部生物量均有不同程度降低;AOS预处理可显著提高水稻植株超氧化物歧化酶(SOD)、过氧化物酶(POD)和抗坏血酸过氧化物酶(APX)活性,降低O_2~(-·)产生速率,使SOD/O_2~(-·)、SOD/POD、SOD/过氧化氢酶(CAT)和POD/O_2~(-·)的比值增加,丙二醛含量下降,苗长、根长及生物量均有一定程度恢复,但会造成H_2O_2在体内有一定累积。生长素信号被阻断后,AOS预处理(Cd+AOS+Y)对水稻Cd胁迫的缓解效应明显受到削弱,表现为苗长、根长等生长指标和抗氧化酶活性均较生长素信号未阻断处理(Cd+AOS)有所降低,补加外源生长素后(Cd+AOS+Y+NAA),各项指标又有所增加,该结果初步表明,生长素信号介导AOS调控水稻对Cd胁迫的抗性。     

萘乙酸对洋葱根系铜胁迫的缓解作用

以洋葱Allium cepa为材料,采用水培方式,以3μmol·L^–1硫酸铜溶液为基础,外加不同浓度萘乙酸,对洋葱根尖进行处理,探究萘乙酸对铜胁迫的缓解作用。结果表明,3μmol·L^–1硫酸铜溶液处理对洋葱根系生长抑制明显;3μmol·L^–1硫酸铜和1μmol·L^–1萘乙酸处理表现出双抑制作用,并提升细胞SOD活性和MDA含量,根尖细胞有丝分裂指数明显下降,变异率增加。10^–2或10^–4μmol·L^–1萘乙酸溶液处理对洋葱根系生长促进明显。在3μmol·L^–1硫酸铜和10^–2μmol·L^–1萘乙酸共处理下,萘乙酸对洋葱根系铜胁迫有明显缓解作用,洋葱根系生长恢复到对照水平,与3μmol·L^–1硫酸铜溶液处理对比,显著提升根尖细胞有丝分裂指数,降低了畸变率、细胞SOD活性及MDA含量。说明适当浓度萘乙酸对根系铜胁迫有明显缓解作用。     

外源激素对脱毒马铃薯扦插苗生长及生理效应研究

以‘早大白’马铃薯脱毒苗为试验材料,通过人工温室苗床栽培探讨外源激素萘乙酸(NAA)、吲哚丁酸(IBA)和硼酸生根处理对扦插脱毒苗生长和生理特征的影响,为马铃薯微型薯的实际生产提供理论依据。结果显示:(1)外源激素生根处理较对照扦插苗根系长势好,根活力、根系可溶性蛋白含量增加。(2)外源激素生根处理较对照脱毒扦插苗光合速率提高、叶绿素含量增加,光合物质的形成与积累增多。(3)外源激素生根处理较对照叶片SOD、POD、CAT活性和游离氨基酸含量均表现出不同程度的上升,MDA含量下降,衰老减缓。(4)外源激素生根处理有利于小区产量和单株结薯数的增加。研究表明,不同外源激素生根处理可改善脱毒马铃薯扦插苗农艺性状和生理指标,并以NAA 100mg/L+IBA 50mg/L+硼酸17.5mg/L配方处理植株的长势最好,叶绿素含量、保护酶活性及游离氨基酸含量最高,净光合速率大、小薯膨大速度快且单株结薯数量及产量增加显著,更利于发挥脱毒薯的增产优势。     

Recent advances in the study of Kaposi's sarcoma-associated herpesvirus replication and pathogenesis

It has now been over twenty years since a novel herpesviral genome was identified in Kaposi's sarcoma biopsies. Since then, the cumulative research effort by molecular biologists, virologists, clinicians, and epidemiologists alike has led to the extensive characterization of this tumor virus, Kaposi's sarcoma-associated herpesvirus(KSHV; also known as human herpesvirus 8(HHV-8)), and its associated diseases. Here we review the current knowledge of KSHV biology and pathogenesis, with a particular emphasis on new and exciting advances in the field of epigenetics. We also discuss the development and practicality of various cell culture and animal model systems to study KSHV replication and pathogenesis.     

A Unique Protease Cleavage Site Predicted in the Spike Protein of the Novel Pneumonia Coronavirus (2019-nCoV) Potentially Related to Viral Transmissibility

正Dear Editor,In December 2019, a novel human coronavirus caused an epidemic of severe pneumonia(Coronavirus Disease 2019,COVID-19) in Wuhan, Hubei, China(Wu et al. 2020; Zhu et al. 2020). So far, this virus has spread to all areas of China and even to other countries. The epidemic has caused 67,102 confirmed infections with 1526 fatal cases     

Curcuminoids as inhibitors of thioredoxin reductase: A receptor based pharmacophore study with distance mapping of the active site

Curcumin is the yellow pigment of turmeric that interacts irreversibly forming an adduct with thioredoxin reductase (TrxR), an enzyme responsible for redox control of cell and defence against oxidative stress. Docking at both the active sites of TrxR was performed to compare the potency of three naturally occurring curcuminoids, namely curcumin, demethoxy curcumin and bis-demethoxy curcumin. Results show that active sites of TrxR occur at the junction of E and F chains. Volume and area of both cavities is predicted. It has been concluded by distance mapping of the most active conformations that Se atom of catalytic residue SeCYS498, is at a distance of 3.56 from C13 of demethoxy curcumin at the E chain active site, whereas C13 carbon atom forms adduct with Se atom of SeCys 498. We report that at least one methoxy group in curcuminoids is necessary for interation with catalytic residues of thioredoxin. Pharmacophore of both active sites of the TrxR receptor for curcumin and demethoxy curcumin molecules has been drawn and proposed for design and synthesis of most probable potent antiproliferative synthetic drugs.     

Comparative morphology of the carpel in the Liliaceae: Hewardieae, Petrosavieae, and Tricyrteae

The young pistils in the melanthioid tribes, Hewardieae, Petrosavieae and Tricyrteae, are uniformly tricarpellate and syncarpous. They lack raphide idioblasts. All are multiovulate, with bitegmic ovules. The Petrosavieae are marked by the presence of septal glands and incomplete syncarpy. Tepals and stamens adhere to the ovary in the Hewardieae and the Petrosavieae but not in the Tricyrteae. Two vascular bundles occur in the stamens of the Hewartlieae and Tricyrtis latifolia. Ventral bundles in the upper part of the ovary of the Hewardieae are continuous with compound septal bundles and placental bundles in the lower part. Putative ventral bundles occur in the alternate position in the Tricyrteae and putative placental bundles in the opposite. position in the Petrosavieae. The dichtomously branched stigma in each carpel of the Tricyrteae is supplied by a bifurcated dorsal bundle.     

Synthesis and antimicrobial studies of hydrazone derivatives of 4-[3-(2,4-difluorophenyl)-4-formyl-1H-pyrazol-1-yl]benzoic acid and 4-[3-(3,4-difluorophenyl)-4-formyl-1H-pyrazol-1-yl]benzoic acid

Microbial resistance to antibiotics is an unresolved global concern, which needs urgent and coordinated action. One of the guidelines of the Centers for Disease Control and Preventions (CDC) to combat antibiotic resistance is the development of new antibiotics to treat drug-resistant bacteria. In our effort to find new antibiotics, we report the synthesis and antimicrobial studies of 30 new pyrazole derivatives. These novel molecules have been synthesized by using readily available starting materials and benign reaction conditions. Some of these molecules have shown activity with MIC values as low as 0.78?µg/mL against four bacterial strains; Staphylococcus aureus, methicillin-resistant S. aureus, Bacillus subtilis, and Acinetobacter baumannii. Furthermore, active molecules are non-toxic to mammalian cell line.

     

Novel compounds with potent CDK9 inhibitory activity for the treatment of myeloma

Cyclin-dependent kinases (CDKs) and Polo-like kinases (PLKs) play key role in the regulation of the cell cycle. The aim of our study was originally the further development of our recently discovered polo-like kinase 1 (PLK1) inhibitors. A series of new 2,4-disubstituted pyrimidine derivatives were synthesized around the original hit, but their PLK1 inhibitory activity was very poor. However the novel compounds showed nanomolar CDK9 inhibitory activity and very good antiproliferative effect on multiple myeloma cell lines (RPMI-8226).