根肿病胁迫下外源SA对不结球白菜抗性诱导和生理生化的影响

以不结球白菜‘新矮青’为试验材料,采用菌土接种法接种根肿病菌,研究不同浓度(0.2~0.8mmol·L~(-1))的外源水杨酸(SA)对根肿病胁迫下不结球白菜植株抗性诱导和感病植株生长的影响,以及植株叶片和根系中防御酶系统的变化规律,探讨外源SA对防治不结球白菜根肿病的可行性。结果显示:(1)根肿病显著影响不结球白菜的生长,加剧植物的膜脂过氧化程度;适宜浓度的外源SA能不同程度地缓解不结球白菜所受根肿病的侵害,并以0.6mmol·L~(-1) SA处理效果最好。(2)外源SA显著降低了根肿病的发病率和病情指数,提高了抗根肿病的诱抗效果,并缓解感病对不结球白菜的生长抑制,显著促进感病植株的生长。(3)外源SA提高了不结球白菜叶片和根系中的超氧化物歧化酶(SOD)、过氧化物酶(POD)和抗坏血酸-过氧化物酶(APX)的抗氧化酶活性,以及多酚氧化酶(PPO)、苯丙氨酸解氨酶(PAL)、谷胱甘肽还原酶(GR)的防御酶活性;显著降低了植株叶片和根系中的MDA、H2O2含量及O-·2产生速率。研究表明,外源SA诱导不结球白菜对根肿病的抗性,缓解根肿病的伤害,且具有剂量效应,以根部灌施0.6mmol·L~(-1)SA的效果最好;在根肿病的胁迫下,SA可提高不结球白菜植株抗氧化酶和防御酶的活性,增强渗透调节能力和细胞活性氧清除能力,降低根肿病对植株的伤害,从而促进生长。     

淹水胁迫对不结球白菜根系生长与呼吸酶活性的影响

采用双套盆法,以不结球白菜‘新矮青’和‘新夏青2号’品种为材料,研究了不同时间(1、3、5、恢复7d后)和不同程度淹水处理(根淹、半淹)后不结球白菜根系生长及呼吸代谢的变化规律。结果显示:(1)与对照相比,淹水胁迫下,不结球白菜幼苗根系鲜重、根系长度、根系活力显著下降,且半淹处理的下降幅度大于根淹处理。(2)淹水胁迫下,乳酸脱氢酶(LDH)、乙醇脱氢酶(ADH)活性较对照显著升高,而苹果脱氢酶(MDH)、琥珀酸脱氢酶(SDH)活性显著降低,且半淹处理的降幅大于根淹,淹水5d后与淹水1d后有显著性差异。(3)淹水胁迫下,‘新矮青’乳酸发酵途径弱于‘新夏青2号’,乙醇发酵则相反,导致后者根系中乳酸积累多于前者,细胞质酸化较严重,降低了对淹水胁迫的耐性。研究表明,不结球白菜幼苗期受到淹水胁迫时,其有氧呼吸明显受阻,无氧呼吸代谢被促进,而且随着淹水时间的延长及淹水深度的加深,根系呼吸代谢受到的抑制程度越严重,最终导致根系生长受到抑制。     

淹水胁迫对不结球白菜渗透调节物质含量的影响

以不结球白菜‘新矮青’品种为材料,研究了不同时间(1、3、5、7d)和不同程度(根淹、半淹、全淹)淹水处理及解除淹水恢复生长后叶片内渗透调节物质含量的变化规律。结果表明:(1)在根淹和半淹胁迫处理下,不结球白菜叶片中可溶性糖、可溶性蛋白和游离脯氨酸含量随处理时间的延长呈先上升后下降的趋势;全淹胁迫下,这3种渗透调节物质的含量随处理时间的延长出现不同程度的下降。(2)解除淹水恢复生长7d后,各处理组的不结球白菜叶片中渗透调节物质的含量在短期(1d)淹水下基本恢复正常,在长期淹水条件下未完全恢复;全淹处理组恢复能力较弱,而根淹处理组恢复能力相对较强;可溶性糖的恢复幅度高于可溶性蛋白和游离脯氨酸。     

大蒜叶片活性氧及保护酶系对白腐病菌粗毒素胁迫的响应

以大蒜抗病品种‘汉中红皮’和感病品种‘改良蒜’为材料,研究了它们在苗期用白腐病菌毒素处理后的叶片细胞超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性以及超氧阴离子(O2-.)和丙二醛(MDA)含量的动态变化。结果表明,白腐病菌粗毒素处理后,2个品种大蒜叶片的SOD、POD活性均升高,而CAT活性降低;抗病品种的SOD、POD和CAT活性均高于感病品种,且SOD、POD活性峰值出现早,并以POD对毒素胁迫最敏感。2个品种在白腐病菌粗毒素处理后的O2.-含量始终高于同期对照,而感病品种O2.-含量在毒素处理24h后均高于同期抗病品种。MDA含量变化趋势与O2.-的变化基本相似。研究认为,大蒜叶片的活性氧含量和保护酶活性与其抗病性密切相关。     

番茄‘Ls-89’和‘坂砧2号’幼苗活性氧代谢对南方根结线虫侵染的反应

为了解番茄(Lycopersicon esculentum)砧木幼苗活性氧代谢与抗南方根结线虫(Meloidogyne incognita)的关系,以高感品种‘Ls-89’与高抗品种‘坂砧2号’为材料,采用盆栽人工接种法,研究了南方根结线虫侵染对番茄砧木幼苗活性氧代谢的影响。结果表明,未接种南方根结线虫的番茄砧木幼苗,其根系与叶片活性氧水平及相关酶活性在品种间没有显著差异。接种南方根结线虫后,两品种幼苗根系与叶片的O_2·~–生成速率和H_2O_2含量均升高,且‘坂砧2号’显著高于‘Ls-89’,但‘Ls-89’的MDA含量则显著高于‘坂砧2号’。两品种幼苗根系与叶片的SOD活性均在侵染早期降低,以‘坂砧2号’降幅较大;但POD、CAT活性在侵染早期变化不大,至侵染中后期则显著升高。因此,番茄抗性品种砧木幼苗的膜脂抗氧化能力较强,活性氧水平较高,且SOD活性对南方根结线虫侵染敏感。     

不结球白菜维生素C积累与相关酶活性研究

对不结球白菜‘常州乌塌菜’、‘矮脚黄’和‘二青’生长过程中维生素C(AsA)含量和L-半乳糖酸-1,4-内酯脱氢酶(GalLDH)、抗坏血酸氧化酶(AAO)、抗坏血酸过氧化物酶(APX)、单脱氢抗坏血酸还原酶(MDAR)、脱氢抗坏血酸还原酶(DHAR)的活性进行测定分析,结果显示,AsA含量的积累呈先升高后下降的模式,且‘常州乌塌菜’中的AsA含量显著高于‘矮脚黄’和‘二青’;GalLDH活性与AsA含量变化趋势基本一致,且3个品种中GalL-DH活性与AsA积累之间均呈极显著的正相关关系;AAO和APX活性的变化趋势则与AsA含量变化趋势相反,而‘常州乌塌菜’中AAO活性显著低于其它2个品种,但APX活性无显著差异;MDAR和DHAR的活性则主要表现在生长后期。结果表明,不结球白菜中AsA含量主要受GalLDH酶活性调节,同时AsA代谢酶AAO也对AsA积累起到了重要作用,而MDAR和DHAR酶活性对AsA积累的作用主要在生长后期。     

NaCl胁迫对嫁接黄瓜膜脂过氧化、渗透调节物质含量及光合特性的影响

以日本引进的耐盐品种‘帝王新土佐’南瓜为砧木,以‘津研4号’黄瓜品种为接穗,研究了NaCl胁迫对黄瓜嫁接植株和自根植株的膜脂过氧化、渗透调节物质含量及光合特性的影响。结果表明:在NaCl胁迫下,黄瓜嫁接植株叶片超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)和抗坏血酸过氧化物酶(APX)活性均显著高于自根植株,O·2-产生速率及丙二醛(MDA)含量显著低于自根植株,嫁接植株膜脂过氧化轻于自根植株;嫁接植株叶片游离脯氨酸、可溶性糖、可溶性蛋白质等渗透物质含量均显著高于自根植株;嫁接植株的净光合速率(Pn)、气孔导度(Gs)、胞间CO2浓度(Ci)、叶绿素含量均显著高于自根植株;虽然NaCl胁迫抑制光合作用,但嫁接植株仍表现出优势。以上结果证明,嫁接植株耐盐性优于自根植株。     

人工合成甘蓝型油菜早期世代及其亲本对盐胁迫的生理响应

以白菜‘矮抗青’(基因组AA)和‘中花芥蓝’(基因组CC)及其人工合成异源四倍体甘蓝型油菜(AACC)的早期世代(F1~F4)为实验材料,采用水培方法分别比较它们在100、200mmol/L NaCl处理下的生理指标差异。结果表明:(1)在盐胁迫条件下,‘中花芥蓝’植株的生物量、脯氨酸和叶绿素含量、抗氧化酶(SOD、POD、CAT)活性均最低,而相对电导率、MDA含量则最高。在100mmol/L NaCl处理下,F2代植株的生物量、叶绿素含量、SOD活性最大,MDA含量最低;在200mmol/L NaCl处理下,F4代的生物量、叶绿素含量、POD活性最大,MDA含量最低。研究发现,亲本‘矮抗青’的耐盐特性高于亲本‘中花芥蓝’,它们的杂种后代(异源四倍体)遗传了AA基因组的耐盐特性,从而比二倍体亲本具有更强的抵御盐胁迫的能力。     

南方根结线虫侵染对2个不同抗性番茄砧木幼苗苯丙烷类代谢的影响

为明确不同抗性番茄(Lycopersicon esculentum)砧木幼苗苯丙烷类代谢与抗南方根结线虫(Meloidogyne incognita)的关系,以高感砧木‘Ls-89’和高抗砧木‘坂砧2号’为试材,采用盆栽人工接种二龄幼虫的方法,研究番茄砧木幼苗苯丙烷类代谢的变化。结果表明,未接种根结线虫时,‘坂砧2号’的根系PAL活性与‘Ls-89’无显著差异,而根系PPO活性及叶片PAL、PPO活性和总酚、类黄酮、木质素含量却显著高于‘Ls-89’。接种根结线虫后,两砧木根系与叶片的PAL、PPO活性与总酚、类黄酮含量均呈周期性升高,木质素含量也逐渐升高,但‘坂砧2号’的升幅均显著高于‘Ls-89’。在一个侵染周期内,‘坂砧2号’根系PAL、PPO活性与总酚、类黄酮含量的峰值分别比‘Ls-89’高28.45%、71.47%、54.24%、91.71%,而叶片的分别高47.29%、64.00%、23.33%、52.61%。这说明南方根结线虫侵染使砧木幼苗苯丙烷类代谢活性显著增强,且‘坂砧2号’显著高于‘Ls-89’,表明番茄砧木幼苗苯丙烷类代谢与抗南方根结线虫水平密切相关。     

低氮胁迫对不同苦荞品种苗期生长和根系生理特征的影响

以2个耐低氮苦荞品种(‘迪庆苦荞’、‘广苦1号’)和2个不耐低氮苦荞品种(‘西荞1号’、‘黑丰1号’)为材料,采用盆栽试验研究了低氮胁迫对苦荞苗期生长和根系生理特性以及氮素利用的影响,以揭示苦荞耐低氮胁迫的生理响应机制。结果显示:(1)与正常供氮处理(15mmol/L)相比,低氮(0.5mmol/L)和极低氮(0.05mmol/L)胁迫处理下,苦荞幼苗的株高、茎粗、叶面积、地上部干重、根系平均直径、根系体积及根系表面积均呈下降趋势,主根长和根冠比呈升高趋势,但在低氮(0.5mmol/L)条件下各品种根系干重均有所增加,且耐低氮品种增加幅度较大(13.69%、19.26%)。(2)低氮胁迫使苦荞叶片的叶绿素含量、最大荧光产量(Fm)和最大光化学效率(Fv/Fm)以及根系活力、硝酸还原酶(NR)活性和可溶性蛋白含量显著降低,而叶片初始荧光产量(Fo)及根系超氧化物歧化酶(SOD)活性、过氧化物酶(POD)活性、丙二醛(MDA)、可溶性糖及游离脯氨酸含量呈升高趋势。(3)低氮胁迫使苦荞植株全氮含量及氮积累量显著降低,却使氮素吸收效率显著升高。研究表明,不同耐低氮苦荞品种对低氮胁迫的响应存在显著差异,在低氮胁迫下,耐低氮品种(‘迪庆苦荞’、‘广苦1号’)具有明显的生长优势,不仅农艺性状、叶片光合作用及根系活性受低氮胁迫影响小,而且具有较高的根系保护酶活性、渗透调节物质含量以及全氮量和氮积累量。     

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.     

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     

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.     

鸡传染性法氏囊病病毒研究进展

传染性法氏囊病(Infection bursal disease, IBD)是由鸡传染性法氏囊病毒(Infectious bursal disease virus, IBDV)引起的鸡和火鸡的一种高度接触性传染病,给世界各国的禽养殖业带来了巨大损失.自IBDV发现至今新的变异株不断出现,分子结构的改变导致病毒致病力的改变及宿主对疫苗应答的改变,使得传统的疫苗已不能控制其流行,因此各国学者对其基因组结构和功能进行了广泛深入的研究,并积极研制新型有效的疫苗以达到防治的目的.     

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.     

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).