水分对发状念珠藻生理活性的影响

研究了水分对发状念珠藻(Nostor flagelliforme Born.et Flah.)生理活性的影响作用。结果表明：干藻体在湿润的过程中,呼吸、光合和固氮活性依次恢复;且随水分含量的增加,光合活性和固氮活性逐渐增强,呼吸作用缓慢减弱并在一定水平上保持相对稳定,自由水是束缚水8倍左右时发菜生理活性全面恢复。吸水饱和的藻体在干燥过程中,光合、呼吸、固氮作用依次停止;呼吸作用随水分的丧失逐渐下降;固氮活性、光合活性在水分丧失20％～40％时有一定程度的增强,出现活性高峰;此后,生理活性下降,水分完全丧失时,光合作用终止,呼吸和固氮作用极其微弱。试验证明,水分是发状念珠藻生理活性的重要限制因子,适宜的水分有助于发菜维持正常的生理代谢和生长。     

微生境对耐旱石生毛尖紫萼藓水分保持与散失特性的影响

毛尖紫萼藓(Grimmia pilifera)是典型石生耐旱藓类,水分是其生存繁衍的关键影响因素。为探究微生境对毛尖紫萼藓水分生理的影响,在安徽省大龙山国家森林公园低山丘陵区选择3种典型微生境(竹林遮蔽S-1,向阳裸岩E,薜荔灌丛遮蔽S-2),对比研究毛尖紫萼藓个体大小、饱和含水量及脱水过程中的含水量指标在不同微生境间的差异性,综合判断微生境对苔藓水分胁迫耐受性的影响及其权衡特征。结果表明:3种微生境毛尖紫萼藓个体大小及饱和含水量差异显著,其中竹林遮蔽生境毛尖紫萼藓具有较小的个体但拥有较高的内、外含水量。向阳裸岩和薜荔灌丛遮蔽生境植株大小及外吸水量接近,但前者内含水量更高。两荫蔽生境苔藓外吸水量是内吸水量的7倍,显著高于向阳裸岩生境的5.8倍。脱水过程中相同时间点向阳裸岩生境苔藓各含水量指标均高于两遮蔽生境,且达到相同含水量的时间差也随脱水进程持续而逐渐增大,这为向阳裸岩生境苔藓的有效光合作用(即相对含水量不低于35%时)及脱水后期的生理和结构调整赢得更多时间。综合而言,向阳裸岩生境毛尖紫萼藓比荫蔽生境具有更强的脱水耐受性,但后者可以通过增加外部吸水量来弥补失水过快的缺陷,这可能是不同微生境毛尖紫萼藓对水分吸收和保持的权衡策略。     

吸水和干燥条件下发菜核糖体代谢差异表达基因分析

为解析发菜吸水和干燥条件下的基因差异表达规律以及发菜适应“干 湿”水分节律调控机制,该研究以充分吸水发菜藻体为对照组,干燥状态下的发菜藻体为处理组,采用高通量Illumina HiSeq PE150测序平台结合生物信息学分析方法对发菜吸水和干燥条件下的差异表达基因进行分析。结果显示：(1)发菜吸水和干燥条件下共鉴定到差异表达基因3 383个,其中显著上调和显著下调表达的基因数分别为1 767个和1 616个。(2)GO功能富集分析发现,在吸水和干燥条件下发菜差异表达基因主要富集在蛋白质合成与代谢等相关途径中;KEGG显著性富集分析发现,吸水和干燥条件下发菜有46个差异表达基因被显著富集到核糖体代谢途径,且均为显著上调表达,这些基因可能参与发菜对干旱胁迫的响应。(3)随机挑选6个被显著富集到核糖体代谢途径的基因进行qRT PCR分析发现,其基因相对表达量与转录组测序结果一致。研究表明,发菜在干燥条件下可能通过激活核糖体代谢特定基因表达帮助抗旱相关的蛋白质的合成和正确折叠、并参与渗透调节等重要生理活动进而调控其适应干燥环境条件。     

水分和盐分胁迫对番茄植株生长和木质部水力特性的影响

木质部是植株体内水分传输的主要通路,其水力特性的变化会影响植株的水分关系和果实的水分积累。目前关于番茄植株木质部解剖结构和水力特性对水分和盐分胁迫的响应及其与植株生长和果实含水量之间的关系尚不明确。本研究通过日光温室番茄盆栽试验,设置3个处理:对照,土壤含水量(θ)为75%～95%田间持水量(FC),初始电导率(EC)为0.398 dS·m^-1;水分胁迫,开花前θ为75%～95% FC,开花后至成熟期θ为45%～65% FC,EC为0.398 dS·m^-1;盐分胁迫,θ为75%～95% FC,EC为1.680 dS·m^-1,研究了樱桃型番茄(红宝石)和中果型番茄(北番501)植株在水分和盐分胁迫下的植株生长、果实含水量以及木质部水力特性的变化。结果表明: 与对照相比,水分和盐分胁迫下茎秆横截面积和木质部导管直径分别减小了22.0%～40.7%和10.0%～18.3%,茎秆比导水率和桁架柄比导水率分别降低了8.8%～41.1%和12.9%～28.4%,抑制了植株生长,减少了地上部鲜重、果实大小、果实鲜重和含水量,且与樱桃型番茄相比,中果型番茄的降幅更大。此外,果实含水量分别与茎秆和桁架柄比导水率呈显著正相关。综上,番茄植株在水分和盐分胁迫下木质部水力特性指标减小,生长被抑制,果实鲜重显著降低,最终导致产量降低。其中,中果型番茄相较于樱桃型番茄对水分和盐分胁迫更敏感。     

玉米根、叶质膜透性和叶片水分对土壤干旱胁迫的反应

利用大型活动式防雨旱棚 ,人工控制不同土壤含水量 ,全生育期系统研究了轻度及严重土壤干旱胁迫对夏玉米根系活力、叶片相对含水量、离体叶片保水力和根、叶质膜透性的影响 .结果表明 :土壤干旱胁迫下 ,玉米叶片相对含水量下降、离体叶片保水力降低 ;叶片及根系质膜透性上升 ,并且根的质膜透性比叶片上升快 ,根系活力下降 ;在干旱胁迫下 ,根系、叶片质膜透性与叶片相对含水量呈负相关 ,而根系、叶片质膜透性与离体叶片保水力呈显著正相关 ,根系膜透性与叶片膜透性也呈显著正相关 ,维持根系活力与保持较高的叶片含水量有密切关系 .另外 ,由于严重水分胁迫处理的上述特性和充分供水处理差异显著 ,而轻度胁迫和充分供水不显著 ,因此可以认为轻度水分胁迫 ,即土壤含水量为田间持水量的 6 0± 5 %为夏玉米正常生长发育的下限指标 ,可作为制定节水栽培措施的理论依据 .     

水分胁迫下AM真菌对柠条锦鸡儿(Caragana korshinskii)生长和抗旱性的影响

利用盆栽实验研究了水分胁迫条件下AM真菌对柠条锦鸡儿(Caragana korshinskii)生长和抗旱性的影响.在土壤相对含水量为80%、60%和40%条件下,分别接种摩西球囊霉(Glomus mosseae)和柠条锦鸡儿根际土著菌,结果表明,水分胁迫对AM真菌的接种效果有显著影响.不同水分条件下,接种AM真菌显著提高了宿主植物根系菌根侵染率.土壤相对含水量为40%～60%时,接种株的株高、茎粗、生物干重和叶片保水力明显高于不接种株;接种AM真菌提高了植株对土壤有效N和有效P的利用率,增加了植株全P、叶片叶绿素和可溶性糖含量以及SOD、POD、CAT等保护酶活性.土壤相对含水量为40%时,叶片MDA含量明显下降.水分胁迫条件下,以接种柠条锦鸡儿根际土著菌的效果最佳.AM真菌增强宿主植物的抗旱性可能源于促进宿主植物根系对土壤水分和矿质元素吸收的直接作用和改善植物体内生理代谢活动、提高保护酶活性的间接作用.     

黄土高原六道沟流域不同土地利用方式下土壤水力特性及其对土壤水分的影响

采用地统计学中交互相关系数方法,对黄土高原六道沟流域农田、荒草地、林地、苜蓿地4种土地类型土壤剖面水力特性及其对水分分布的影响进行了分析.结果表明：研究区农田与荒草地的土壤特性相似,苜蓿地与林地相似;相同吸力条件下,土壤水分以农田最大、林地最小,而饱和导水率则相反;除土壤水分消耗期的林地和苜蓿地土壤水分随土层深度增加呈上升趋势外,其他时期各土地利用方式下土壤水分均随土层深度的增加而降低.土壤剖面饱和导水率与土壤含水量之间的影响程度依土壤水分条件而异：水分补偿期,剖面土壤饱和导水率对滞后其空间距离0～40 cm土层内的土壤含水量具有显著影响,而土壤水分含量对饱和导水率的影响范围为0～50 cm;水分稳定期,饱和导水率与土壤含水量的相互影响范围均在0～60 cm;水分补偿期和稳定期,二者之间为正相关;土壤水分消耗期,农田和荒草地饱和导水率与水分含量呈正相关,饱和导水率对土壤水分含量的影响范围在滞后其空间范围0～80 cm土层内,而土壤水分含量对饱和导水率的影响范围在0～60 cm内,林地和苜蓿地则呈负相关,相互影响范围均在0～60 cm土层内.     

西南喀斯特地区四种植物水分生理的初步研究

通过对喀斯特地区的4种植物红背山麻杆、圆叶乌桕、青檀和水冬瓜的水分特征进行测定和比较,结果表明:植物的组织含水量、临界饱和亏缺和需水程度均存在显著差异,其抗旱能力以青檀最强;水分利用效率饱和点以落叶灌木红背山麻杆最高,在600μmol.m-2·s-1左右,光辐射与气孔导度呈对数关系;而三个落叶乔木树种的WUE的光饱和点均在400μmol·m-2·s-1左右,光辐射与蒸腾速率、气孔导度均呈线性极显著相关关系;观测结果没有显示蒸腾饱和现象。     

培养条件下发菜的形态建成

固体培养基培养的发菜(Nostoc flagelliforme)在黑暗与低光强(2·s)条件下细胞发育受到抑制,在光强10、20、30、60 μmol/m2·s 条件下细胞生长良好, 但在60 μmol/m2·s 条件下藻丝体易变黄; 液体充气培养的发菜在光强20、60、180 μmol/m2·s 条件下生长速率、类胡萝卜素与多糖含量均随光强升高而增加。发菜在低营养水平时形成的异形胞较多, 异形胞的发生位置也多样, 有端生、间生和连生。当琼脂浓度为0.5%—4%时发菜具有相同的形态发育特征, 从藻殖段发育至丝状聚集体状态, 再从聚集体中释放藻丝; 当琼脂浓度为6%—8%时发菜发育至丝状聚集体状态, 藻丝包裹在厚胶鞘中, 观察不到藻丝和藻殖段的释放。以上结果表明光照和培养基的含水量对发菜细胞发育具有重要影响。       

温度,含水量和光照对发菜固氮酶活性的影响

陆生蓝藻发菜(Nostoc flagelliforme)固氮酶活性的最适温度为21—28℃;最适藻丝体含水量为1000—1500%;最大饱和光强达150—200焦耳/m~2·秒。在湿润状态下,发菜对较高的温度很敏感。在45℃下1小时,发菜固氮酶失掉活性。在干燥状态下,发菜在55℃高温下,每天5小时,放置21天后,其固氮酶活性保持不变。预先培养4—5天的湿发菜对干燥变得敏感;但在干湿交替循环中,其固氮酶活性逐步提高,并明显地改善了它对干燥的抵抗能力。此外,在高盐浓度下(0.17—0.43mol/LNaCl)发菜的固氮酶活性被强烈地抑制,说明它不能耐盐碱。发菜的固氮生理特性是它对荒漠草原生态条件适应的结果。干湿交替循环或许是发菜维持生存的必需条件。     

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.