化感作用抑制有害藻类生长的研究进展

利用植物化感作用抑制有害藻类生长的方法具有生态安全性好、快速高效等优点, 为有效控制有害藻类的爆发提供了新思路。论文从化感作用的概念、化感抑藻机理、陆生植物对藻类的化感抑制作用、水生植物对藻类的化感抑制作用等方面进行了论述, 并对植物化感作用抑藻技术的研究方向进行了展望, 提出对化感物质在环境中的降解特性、化感物质选择性抑藻机理及具有活性的化感物质的人工合成等方面需要做更深入的研究。     

稻、麦秸秆对球形棕囊藻(Phaeocystis globosa)生长的抑制作用

考查了秸秆及其浸出液对球形棕囊藻(Phaeocystis globosa)生长的影响,分析了秸秆附着微生物及秸秆物理吸附作用对秸秆抑藻活性的影响,观察了稻杆浸出液对藻细胞形态的影响。结果显示,一定量的物理破碎稻杆、麦杆及其浸出液均可有效抑制棕囊藻的生长,灭菌与未灭菌秸杆之间抑藻效果相差不大。不同条件处理的秸杆浸出液总酚含量与抑藻作用间均存在很大差异,但两者之间并无明显相关性。原子力显微镜观察发现,秸秆处理组细胞膜破裂、细胞塌陷,结构不完整,细胞粗糙度明显增加。这些结果提示微生物和物理吸附对秸杆抑藻作用的贡献很小,秸秆中存在的或降解产生的抑藻活性成分是秸秆抑藻的主要原因;除了酚酸类物质外,秸杆中可能存在其他可以显著抑制藻类生长的物质;秸秆通过破坏藻细胞的膜结构,导致藻细胞出现空洞,细胞内容物流出,从而抑制或杀灭藻细胞。     

沉水植物化感作用控藻能力评述

沉水植物所释放的化学物质对藻类的抑制作用是浅水湖泊维持清水状态的机制之一.本文从具有化感活性的沉水植物在湖泊中出现的频度、盖度、化感物质的种类、抑藻效应等方面对化感控藻进行了评述.已有研究结果表明：穗花狐尾藻、金鱼藻、伊乐藻等是具有很高活性的沉水植物,尤其是在其生物量达到一定程度,且湖泊中的优势藻为较敏感的种类时,沉水植物分泌的化感物质对浮游藻类的抑制作用更强;沉水植物释放的多酚类等化感物质具有控藻能力;化感物质对于不同种类藻的抑制作用具有选择性,蓝藻和硅藻比绿藻更为敏感,附生藻类通常比浮游藻类具有更高的耐受性;环境因素如光照、营养限制、温度等会显著影响沉水植物化感作用效果.沉水植物的化感控藻研究尚处于初始阶段,关于环境因素对化感作用的影响、化感物质的分离鉴定、选择性抑藻机理以及化感物质代谢途径等方面还有待深入、全面的研究.     

红树植物干粉和新鲜组织水提物对两种赤潮藻的化感抑制效应

通过测定藻细胞密度,研究了5种红树植物木榄、秋茄、海漆、海芒果、小花老鼠簕水提物对赤潮藻球形棕囊藻和赤潮异弯藻的化感抑制效应,探讨了高温处理对化感抑藻效应的影响.研究结果表明,红树植物干粉水提物和新鲜组织水提物对两种赤潮藻均显示出显著的化感抑制作用.第5 d,红树植物干粉水提物对2种赤潮藻的抑制效果依次为:海漆>秋茄>小花老鼠簕>木榄>海芒果.新鲜组织水提物抑藻效果最强的红树植物是木榄和秋茄.秋茄和海漆水提物中的抑藻化感物质对高温相对不稳定,木榄和小花老鼠簕水提物中的抑藻化感物质对高温相对比较稳定.     

不同类型化感物质抑制蓝藻效益比较及联合抑藻效应评述

世界范围内的蓝藻水华持续威胁着水生生态系统功能和人类健康,化感物质凭借其环境安全和对微藻有特异毒性等特征可以短期抑制蓝藻水华的暴发和生长。文章分别概括了酚类化合物、含氮化合物、脂肪酸/酯类、萜类化合物四类化感物质及其衍生物对蓝藻的杀藻效果、潜在机制及特异作用靶点,并依据高效抑藻化感物质(EC₅₀<10 mg/L)的经济成本进一步预估其实际应用潜能。结果表明,单独胁迫下的各类化感物质具不同抑藻特性:脂肪酸/酯类的性价比最优,能以较少剂量对蓝藻产生极强毒性,对蓝藻多样的作用靶点是其具有极强抑制效果的关键,可在0.015—52.95 mg/L浓度范围内将目标蓝藻抑制50%;酚类化合物总数最多、活性普遍较高,半数效应浓度(EC₅₀)为0.05—162.53 mg/L,可通过抑制光合作用、破坏细胞氧化应激平衡和损害细胞壁/膜结构等多种机制抑制蓝藻生长,但高效杀藻酚类化合物的理论成本差异较大,性价比次于脂肪酸位于第二位;含氮化合物对蓝藻生长存在特异性和均匀高效的杀藻作用, EC₅₀集中于0.3—8.14 mg/L,主要通过破坏...     

互花米草浸提液对中肋骨条藻的化感效应

以互花米草凋落物为化感供体材料,研究不同浓度的互花米草凋落物浸提液(0、0.02、0.04和0.10 mg·L~(-1))对中肋骨条藻生长及生理生化特征的化感效应,分离鉴定互花米草浸提液中的抑藻化感物质成分。结果表明:互花米草凋落物浸提液对中肋骨条藻生长的抑制作用随着浸提液质量浓度的增大而增强,当质量浓度为0.10 mg·L~(-1)时,互花米草凋落物浸提液对中肋骨条藻的抑制率达到69.2%;各实验处理组的中肋骨条藻细胞内的叶绿素a含量和抗氧化酶活性均低于对照组,而丙二醛的含量高于对照组;对互花米草凋落物浸提液进行抑藻化感物质的分离鉴定,其化感物质主要为长链脂肪酸,主要成分为十六烷酸、亚油酸、油酸。     

红树植物秋茄叶片水提物的抑藻效应

通过藻细胞密度的测定,探讨了不同浓度(0.5、1.0和2.0g·L-1)红树植物秋茄(Kandelia candel)新鲜叶片水提物对球形棕囊藻(Phaeocystis globosa)和赤潮异弯藻(Heterosigma akashiwo)的化感抑制效应,研究了高温处理对秋茄提取物化感作用的影响.结果表明:秋茄叶片提取物对两种赤潮藻均具有显著的化感抑制作用,不同浓度提取物化感作用强度不同;5 d内,浓度为2.0g·L-1秋茄叶片提取物对球形棕囊藻和赤潮异弯藻的最大抑制率分别为91.6％和77.0％;球形棕囊藻和赤潮异弯藻对红树植物秋茄提取物的敏感性不同,提取物对球形棕囊藻的抑制效果要优于赤潮异弯藻;经高温处理后,秋茄提取物抑藻效果显著降低(P＜0.05);秋茄叶片水提物影响藻细胞膜结构,使藻细胞体积增大、细胞破裂.     

红树植物木榄有机溶剂提取物对球形棕囊藻的抑制效应

基于化感作用原理,利用有机溶剂对红树植物木榄(Bruguiera gymnorrhiza)叶片中的活性物质进行连续提取分离,分别得到正己烷相、乙酸乙酯相、正丁醇相和水相提取物。利用这些提取物进行抑藻实验,通过测定球形棕囊藻(Phaeocystis globosa)的细胞密度发现:四种组分提取物对球形棕囊藻均具有显著的化感抑制作用;正己烷相和乙酸乙酯相提取物对球形棕囊藻的抑制效果明显优于正丁醇相和水相提取物的抑制效果。正己烷相提取物和乙酸乙酯相提取物对球形棕囊藻的48hEC₅₀分别为14.90mg/L和12.18mg/L。研究表明,藻细胞初始接种密度影响提取物的抑藻效应,低接种密度时抑制率极高,而随着接种密度的升高抑制率下降;接种密度极高时,提取物不但不会抑制甚至还会促进藻细胞的生长。     

粉绿狐尾藻（Myriophyllum aquaticum）对铜绿微囊藻（Microcystis aeruginosa）的化感抑制效应及其生理机制

由于生物法,尤其是水生植物化感控藻方法在治理水体富营养化及水华现象中具有多方面的优势,近年来该领域的理论和技术研究备受世界各国关注.采用初始添加种植水和连续添加种植水的方法,研究挺水型粉绿狐尾藻对铜绿微囊藻的化感抑藻效应,并从光合作用的角度探讨其对铜绿微囊藻化感抑制的生理生态机制及作用靶点.研究结果表明:粉绿狐尾藻能够分泌某些化感物质有效抑制铜绿微囊藻的正常生长,其抑藻效应是通过连续释放某些化感物质作用于铜绿微囊藻而实现的,且具有累积性;粉绿狐尾藻分泌化感物质对铜绿微囊藻的Chl a、PC及APC的损伤程度存在差异(如处理5 d后,Chl a、PC、APC的相对含量分别降至52.7%、15.3%、7.6%),其中藻胆蛋白(尤其是APC)比Chl a 更为敏感,说明藻胆蛋白是粉绿狐尾藻化感物质抑制铜绿微囊藻的关键靶点.研究为水生植物化感控藻技术的发展提供了新的材料,并有助于深入了解水体生态系统的化学生态作用及其机制.     

水稻化感物质抑草作用机理的分子生物学研究

水稻化感作用是通过水稻植株体向环境中释放化感物质来实现的．水稻化感物质的主要抑草作用机理有：抑制杂草种子的发芽,影响激素平衡,破坏细胞膜系统的完整性,影响光合作用和呼吸作用,干扰对营养和水分的吸收,影响蛋白质合成和基因表达等．水稻化感作用是由多基因控制的,表现为数量性状．利用分子生物学技术和化感生物检测技术等研究手段检测到了多个水稻化感作用的主效应(QTLs)位点,但不同水稻化感种质其主效应QTLs位点明显不同．通过分子辅助选择和建立近等基因系的方法对检测到的QTLs作进一步的精细定位,最终实现水稻化感抑草有利基因的克隆是今后研究的重要方向。     

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.     

Enterovirus 71 3C proteolytically processes the histone H3 N-terminal tail during infection

Highlights
1. The N-terminal tail of histone H3 is specifically cleaved during EV71 infection.
2. Viral protease 3C is identified as a protease responsible for proteolytically processing the N-terminal H3 tail.
3. Our finding reveals a new epigenetic regulatory mechanism for Enterovirus 71 in virus-host interactions.     

Detection of EBV and HHV6 in the Brain Tissue of Patients with Rasmussen’s Encephalitis

Rasmussen’s encephalitis (RE) is a rare pediatric neurological disorder, and the exact etiology is not clear. Viral infection may be involved in the pathogenesis of RE, but conflicting results have reported. In this study, we evaluated the expression of both Epstein-Barr virus (EBV) and human herpes virus (HHV) 6 antigens in brain sections from 30 patients with RE and 16 control individuals by immunohistochemistry. In the RE group, EBV and HHV6 antigens were detected in 56.7% (17/30) and 50% (15/30) of individuals, respectively. In contrast, no detectable EBV and HHV6 antigen expression was found in brain tissues of the control group. The co-expression of EBV and HHV6 was detected in 20.0% (6/30) of individuals. In particular, a 4-year-old boy had a typical clinical course, including a medical history of viral encephalitis, intractable epilepsy, and hemispheric atrophy. The co-expression of EBV and HHV6 was detected in neurons and astrocytes in the brain tissue, accompanied by a high frequency of CD8⁺ T cells. Our results suggest that EBV and HHV6 infection and the activation of CD8⁺ T cells are involved in the pathogenesis of RE.     

Perinatal Vertical Transmission of Chikungunya Virus in Ruili,a Town on the Border between China and Myanmar

正Dear Editor,Chikungunya virus (CHIKV), an arbovirus in the family of Togaviridae, genus Alphavirus, is transmitted by the A.aegyptii or A. albopictus mosquito, and causes disease in humans characterized by fever, rash, and arthralgia (Silva and Dermody 2017; Suhrbier 2019). It was first reported in 1953 in Tanzania, and caused only a few outbreaks and sporadic cases in Africa and Asia in last century. However, in the epidemic in 2004, CHIKV acquired mutations that conferred enhanced transmission by the A. albopictus mosquito(Schuffenecker et al. 2006). Since then, it has successively caused outbreaks in Africa, the Indian Ocean, South East Asia, the South America, and Europe (Zeller et al. 2016).     

Development of a Novel Reverse Transcription Loop-Mediated Isothermal Amplification Method for Rapid Detection of SARS-CoV-2

In conclusion, the novel visual RT-LAMP assay is a simple, rapid, and sensitive approach for detection of SARS-CoV-2, and it is ready for application in primary care and community hospitals or health care centers, and even patients' own houses in response to the current SARS-CoV-2 epidemic because the assay does not require sophisticated equipment and skilled personnel. Furthermore, it is also ready to be used in fields for screening samples from wild animals and environments to facilitate the identification of potential intermediate hosts that mediate the cross-species transmission of SARS-CoV-2 from bats to humans.