滨海盐渍土壤中不同类型盐生植物富集镉的效应

为了利用被镉污染的滨海盐渍土壤,通过实验对比分析3种不同类型盐生植物对盐渍土中镉的富集效应,以期初步探明不同类型盐生植物在镉污染盐渍土壤修复中的效果。选择的3种盐生植物类型是:聚盐盐生植物,泌盐盐生植物和避盐盐生植物。通过温室盆栽实验,将植物在不同镉含量的盐渍土壤中种植培养60 d,测定和分析不同类型盐生植物对镉的生物浓缩因子、转移系数以及植株内地上部分和根部生物量和镉含量的变化。结果表明,不同镉含量的土壤对碱蓬和芦苇的生长影响较小,对二色补血草的生长影响较大。不同镉含量的土壤中,芦苇地上部分镉的生物浓缩因子变化差异不显著,并且其地上部分吸收镉的百分率较高。碱蓬和芦苇的转移系数大于二色补血草的转移系数,并且碱蓬的转移系数在不同镉含量的土壤中变化不显著;二色补血草的转移系数随着土壤中镉含量的增加而显著增大。3种盐生植物中,碱蓬最具修复镉污染盐渍土壤的潜力,这可能和它是聚盐盐生植物的生理类型有关。芦苇整个植株的地上部分富集镉的总量在3种植物中是最高的,因此,芦苇在镉含量较低时也可以做为镉污染盐渍土壤的修复材料。     

盐胁迫下3种滨海盐生植物的根系生长和分布

我国广大滨海地区的盐土上发育着大量的盐生植物,这些植物的根系对维持土壤稳定性,减小风蚀和水蚀具有重要作用。在水培条件下,针对碱蓬、盐角草和盐地碱蓬3种滨海盐生植物,研究它们在不同盐浓度条件下根系分布的差异。结果表明:一定浓度的盐分可以促进3种盐生植物生长,但较高浓度的盐抑制其生长,特别是对根系生长的抑制作用更大。在同样盐浓度下,盐地碱蓬的生长最快,生物量也最大。在盐分浓度较低时,3种盐生植物的主根长和总根长都有所增加,与对照相比,盐角草增加的幅度较大,但高浓度的盐会抑制根系总长度的增加,其中盐角草较碱蓬和盐地碱蓬抑制的程度轻。盐分对3种植物的根系平均直径没有显著的影响,但有减小的趋势。在水培条件下,碱蓬和盐角草的根系上、中、下部分布的较均匀,而盐地碱蓬的根系中部比上部和下部有显著的增加,盐分对每种植物的根系的分布没有显著的影响。从根系的分布特征可以推断:盐角草比碱蓬和盐地碱蓬具有较强的抗盐性和耐瘠薄能力;碱蓬的耐盐能力较其它两种植物差,盐角草的耐盐性最强。根据3种滨海盐生植物的根系生长和分布特征,证明这3种植物的根系分属于2种功能型,碱蓬是浅根系功能型,盐角草和盐地碱蓬是深根系功能型。根系分布的参数表明3种滨海盐生植物中盐地碱蓬是用来加强土壤稳定性最好的植物。     

盐生植物盐渍适应性及其利用

盐生植物是一类生长在盐渍土壤上有一定的抗盐能力的自然植物区系，现存的94个目有花 植物中，有38个目，约1560种是盐生植物。我国的盐生植物约有400余种，多为种子植物。1980年，格林威(Greenway)给盐生植物一个比较科学的定义，即可在土壤溶液单价盐含量在70mmol/L以上生境中生长并能完成其生活史的一类植物。一、盐渍生境的分类根据生理类型可将盐生植物分为三类：1.稀盐植物（如碱蓬）；2.泌盐植物（如滨黎、补 血草、大米草等）；3.拒盐植物（如芦苇）。根据生态类型可将盐生植物分为旱生盐生植物 、中生盐生植物及水生盐生植物。但…     

新疆3种藜科盐生植物NHX基因的克隆与序列分析比较

从新疆野生植物盐角草(Salicornia europaea)、盐爪爪(Kalidium foliatum)和盐穗木(Halostachys caspica)中分别克隆了约1.7kb的NHX基因cDNA片段,此片段均包含了NHX完整基因,三者之间有较高的同源性,盐角草NHX基因与盐爪爪NHX基因同源性达92.81%,盐角草与盐穗木同源性达92.19%,盐爪爪与盐穗木同源性达97.66%.它们与其它几种藜科盐生植物如滨藜、碱蓬、灰绿藜的NHX基因同源性也很高,达到80%以上,与拟南芥同源性也达到86%.此基因在植物尤其是藜科盐生植物中高度保守,其编码的功能性蛋白可能在影响植物耐盐中起作用.     

真盐生植物囊果碱蓬(Suaeda physophora)脱水种子子叶叶绿素特征及其对植物萌发阶段适应盐渍环境的生态意义

本研究观察到囊果碱蓬(Suaeda physophora)脱水种子子叶含有深绿色色素, 分别在645和663 nm波长下测定了脱水种子子叶和黑暗中在去离子水半浸没12 h的种子子叶内色素含量及其在400~700 nm波长范围内的光谱吸收特征曲线, 并与囊果碱蓬真叶内的叶绿素光吸收特征曲线进行比较, 结果显示这种色素是叶绿素, 其光吸收特征曲线与真叶叶绿素的几乎完全相同, 表明这种叶绿素具有和真叶叶绿素相近的生理功能. 通过光合能力测定发现, 囊果碱蓬脱水种子吸水6 h后就能进行光合放氧. 用电子显微镜观测了在去离子水和700 mmol/L NaCl溶液中处理1天和10天的囊果碱蓬种子的叶绿体形态, 同时对胚根细胞质膜的受损伤程度进行了组织化学染色观测, 并以同为黎科、且脱水种子子叶中也存在叶绿体的旱生植物白梭梭(Haloxylon persicum)为对照进行同步观测. 结果表明, 相对于非盐生植物白梭梭, 高盐度下囊果碱蓬种子的子叶叶绿体结构、胚根细胞质膜均保持完好, 表现出很强的抗盐能力. 黑暗条件下囊果碱蓬种子在去离子水和700 mmol/L NaCl溶液中的萌发过程是渐进式的, 72~84 h才能达到萌发高峰; 但是在700 mmol/L NaCl溶液中浸泡10天而未萌发的种子移到去离子水中以后的恢复萌发则是爆发式的, 在24 h之内即达到萌发高峰, 并且这些种子具有光合能力. 因此可以推断, 高浓度的盐分对于真盐生植物囊果碱蓬的快速恢复萌发具有激发效应, 这种特性保证了种子在自然条件下能够在早春短暂的、适宜的土壤低盐分条件下迅速萌发; 干燥种子子叶中保留的具有完整结构的叶绿体则可通过光合作用保证萌发了的幼苗迅速生长, 建立种群.     

3种荒漠盐生植物根系及根毛形态特征的比较研究

在水培条件下,针对梭梭、囊果碱蓬和钠猪毛菜3种荒漠盐生植物,研究它们苗期在不同盐浓度条件下根系和根毛形态的差异。结果表明：一定浓度的盐分可以促进3种盐生植物生长,但较高浓度的盐抑制其生长,特别是对根系生长的抑制作用更大。在同样盐浓度下,钠猪毛菜的生长最快,生物量也最大。在盐分浓度较低时,3种盐生植物的主根长和总根长都有所增加,与对照相比,囊果碱蓬增加的幅度较大,但高浓度的盐会抑制根系总长度的增加,其中囊果碱蓬较梭梭和钠猪毛菜抑制的程度轻。盐分对3种植物的根系平均直径没有显著的影响,但有减小的趋势。在水培条件下,梭梭和囊果碱蓬的根系上、中、下部分布的较均匀,而钠猪毛菜的根系中部比上部和下部有显著的增加,盐分对每种植物的根系的分布没有显著的影响。3种植物的根毛与根系生长环境中的盐浓度没有明显相关性;3种植物之间,根毛的长度和密度有显著差异。从根系和根毛的形态特征可以推断：囊果碱蓬比梭梭和钠猪毛菜具有较强的抗旱性和耐极薄能力;梭梭的耐盐能力较其它2种植物差,囊果碱蓬的耐盐性最强。     

盐分和水分胁迫对两种盐生植物盐爪爪和盐穗木种子萌发的影响

采用不同浓度NaCl和等渗PEG(分子量为6000)处理2种盐生植物种子(盐爪爪Kalidiumfoliatum、盐穗木Halostachys caspica)。结果表明,(1)NaCl和等渗PEG对种子的萌发均产生抑制作用,且PEG的抑制程度大于等渗NaCl,说明渗透胁迫是影响盐生植物种子萌发的主要因素;(2)盐胁迫和水分胁迫对盐生植物种子的萌发具有明显的抑制作用,降低了种子的萌发率,推迟了种子的初始萌发时间、延长了种子的萌发时间;(3)根据2种盐生植物种子萌发耐盐性比较,两种盐生植物均具有较强的耐盐性,在0~300 mmol.L-1NaCl盐溶液范围内,盐穗木种子相对萌发率达到95%以上,盐爪爪达到80%以上,说明盐穗木比盐爪爪具有更强的耐盐性。盐穗木种子耐盐适宜值为332.5 mmol.L-1,临界值为540 mmo.lL-1,极限值为749 mmo.lL-1;盐爪爪种子耐盐适宜值为246.5 mmol.L-1,临界值为391.8 mmo.lL-1,极限值为537 mmol.L-1;(4)低浓度的NaCl溶液对种子萌发的幼苗生长起着促进作用。在100 mmo.lL-1NaCl处理时,两种盐生植物幼苗的胚...     

盐胁迫下囊果碱蓬出苗状况及苗期抗盐性

研究了盐胁迫对囊果碱蓬出苗、幼苗生长、离子积累以及光合放氧速率的影响.囊果碱蓬生长的最适盐浓度在200 mmol/L NaCl左右.高浓度NaCl(400 mmol/L和600 mmol/L)没有显著降低其出苗率,200 mmol/L NaCl对出苗率具有促进作用.400 mmol/L和600 mmol/L NaCl显著降低了光合放氧速率.囊果碱蓬在高浓度NaCl处理下能够维持叶片较高的K+/Na+ 及含水量可能是其适应高盐生境的重要机制.     

不同温度及盐碱环境下盐地碱蓬的萌发策略

为了研究黄河三角洲优势种盐地碱蓬在不同胁迫环境条件下的萌发策略,分别在不同温度、盐度、碱度以及海水原溶液条件下,进行了室内萌发实验,并且测量了其幼苗体内的Na+和K+含量.结果表明,盐地碱蓬种子发芽所需要的积温和最低温度分别为24.57℃·d和0.62℃,最适发芽温度为20℃～35℃,在温度5℃～40℃下均表现出较高的发芽率而且5℃～35℃下发芽速度随温度升高而显著增加.盐地碱蓬具有较高的耐盐性,当盐浓度达到500 mmol·L-1时,发芽率均高于50%,并且在100%海水溶液浓度下发芽率也能达到38%,高盐条件下未萌发的种子转移到淡水中,均表现出较高的复萌率.盐地碱蓬幼苗体内Na+含量随盐度(NaCl溶液浓度)升高而显著增加,而K+含量在该盐度下差异不显著;幼苗体内Na+、K+含量在高碱度(200和300 mmol·L-1 NaHCO3)中均显著低于其在低碱度(100mmol·L-1NaHCO3溶液)中的含量,说明碱胁迫对幼苗生长产生了显著性影响;Na+、K+含量均随着海水溶液浓度增加而显著增加.因此,盐地碱蓬种子萌发的广温性、高耐盐性、高盐环境中的种子高存活率以及幼苗的较强的耐盐能力是盐地碱蓬种群在黄河三角洲适应滨海盐碱湿地复杂环境的主要生存策略.     

塔里木盆地10种藜科植物种子萌发对干旱胁迫的响应及其抗旱性评价

以塔里木盆地分布的碱蓬、硬枝碱蓬、盘果碱蓬、五蕊碱蓬、星花碱蓬、刺藜、盐节木、盐穗木、盐角草、白茎盐生草等10种藜科植物的种子为材料,利用PEG-6000模拟干旱,研究种子萌发对干旱胁迫的响应规律,并对抗旱性进行综合评价。结果表明:(1)随渗透势的下降,干旱胁迫加重,10种藜科植物种子的最终萌发率受到不同程度的抑制,平均萌发时间逐渐延长,种子的胚根长度受到抑制;解除干旱胁迫后,碱蓬、硬枝碱蓬、盘果碱蓬、盐节木、盐穗木、盐角草和白茎盐生草种子可恢复萌发;(2)10种藜科植物种子萌发期抗旱(PEG)极限值从大到小依次为:盐穗木白茎盐生草盘果碱蓬硬枝碱蓬盐角草五蕊碱蓬盐节木星花碱蓬刺藜碱蓬;(3)采用隶属函数法,选取种子最终萌发率、平均萌发时间、胚根长度和恢复萌发率为主要评价指标,进行抗旱性综合评价,10种藜科植物种子抗旱性由强到弱依次为:盐穗木白茎盐生草硬枝碱蓬盐节木盘果碱蓬星花碱蓬盐角草刺藜碱蓬五蕊碱蓬;抗旱性较强的盐穗木、白茎盐生草、硬枝碱蓬和盐节木的隶属函数加权平均值分别为0.915、0.793、0.762和0.737。     

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.