深畦栽培对干旱胁迫下葡萄叶幕微气候和光合作用的影响

试验以‘京亚’和‘红地球’葡萄品种2年生苗木为材料,在田间遮雨棚内考察了自然干旱胁迫下深畦栽植和平畦栽植葡萄根际土壤湿度、叶幕微气候因子、光合作用参数变化特征,探讨根际土壤湿度与叶幕气候互作对葡萄光合作用的影响。结果显示:(1)在干旱逆境下,葡萄根际土壤湿度和叶幕微气候因子交互作用能通过影响水分条件来影响葡萄的光合作用;土壤湿度阀值是葡萄进行光合作用时水分利用最有效的土壤湿度点值,土壤湿度阀值存在“阀值漂移”现象,与叶幕空气湿度呈明显负相关关系,维持较高的叶幕空气湿度有利于实现在较低的土壤湿度下达到更高的光合效率。(2)在干旱逆境下,与平畦栽植相比,深畦栽植在改善葡萄根际土壤水分和叶幕微气候方面具有明显的优势,在该模式下葡萄具有更强的保水能力和更高的水分利用效率,从而具有更强的光合效率。(3)采用深畦栽植模式时,根际土壤相对含水量30%~50%是显著影响葡萄光合作用的土壤湿度区间;根际土壤相对含水量分别在43.32%~50.00%和40.19%~50.00%是‘京亚’和‘红地球’光合作用适宜的土壤湿度范围,在43.32%和40.19%时分别为2种葡萄光合作用水分利用效率达到最高的最适土壤湿度。研究发现,干旱逆境条件下,葡萄根际土壤湿度和叶幕微气候因子交互作用能改善葡萄的光合作用效率;深畦栽植葡萄光合作用对土壤湿度的需求较低,在相对较低的土壤湿度即可达到相对较高的光合能力;深畦栽植模式可以协调葡萄光合作用和水分消耗之间的关系,具有较高的水分利用效率和光合能力,是干旱地区进行葡萄抗旱节水生产的理想模式。     

干旱胁迫对蒙古黄芪生物量及其根际微生物种群数量的影响

以‘武川’和‘浑源’2个蒙古黄芪地方品种为试材,采用盆栽控水模拟干旱处理,研究干旱胁迫下黄芪生物量及根际微生物数量的动态变化规律。结果显示：随着干旱程度的加剧,2个品种的根际细菌和放线菌种群数量均呈先上升后下降的变化趋势,真菌数量却呈现持续减少,而细菌数量在根际微生物区系中占绝对优势;随干旱强度升高,2个品种黄芪根、叶组织相对含水量均表现出明显的逐渐下降趋势,其地上部生物量、根系生物量也均降低,而根冠比却逐渐增大;黄芪根际各菌类数量与其地上生物量存在显著正相关关系,但与根系生物量无显著相关关系。研究表明,黄芪的生长及其根际微生物数量均受到干旱胁迫的影响,且适度干旱有助于提高黄芪根际细菌及放线菌的数量,从而改变根际微生物群落结构组成,促进黄芪地上生物量的积累。     

干旱胁迫对黑果枸杞幼苗光合特性的影响

以当年生黑果枸杞幼苗为试验材料,通过称重控水的方法设置对照(土壤含水量为32.96%~35.35%)、轻度干旱胁迫(土壤含水量为21.18%~22.32%)、中度干旱胁迫(土壤含水量为12.20%~13.82%)和重度干旱胁迫(土壤含水量为7.89%~8.73%)4个水分梯度,研究了干旱胁迫对黑果枸杞叶片光合色素、光合特性、叶绿素荧光特性的影响,以揭示黑果枸杞对干旱胁迫的适应能力和适应机制。结果显示:(1)随着干旱胁迫强度的增加,黑果枸杞幼苗叶片叶绿素含量、类胡萝卜素含量均呈显著下降趋势。(2)黑果枸杞幼苗叶片净光合速率(P_n)、蒸腾速率(T_r)、气孔导度(G_s)在中度和重度干旱胁迫下显著下降;其胞间CO_2浓度(C_i)、水分利用效率(WUE)随干旱胁迫强度的增加而逐渐增加,而气孔限制值(L_s)随干旱胁迫强度的增加而逐渐降低。(3)随着土壤含水量的降低,黑果枸杞幼苗叶片初始荧光(F_0)和非光化学猝灭系数(q_N)逐渐增加,而其最大荧光(F_m)、PSⅡ最大光化学效率(F_v/F_m)、实际光化学效率(Ф_(PSⅡ))和光化学猝灭系数(q_P)均逐渐降低。研究表明,在干旱胁迫条件下,黑果枸杞叶片过多的能量以热的形式被耗散,反应中心开放程度降低,从而避免PSⅡ反应中心受到损伤,表现出一定的耐旱性;黑果枸杞生长所允许的最大土壤水分亏缺为7.89%,维持黑果枸杞具有较高的WUE和P_n的土壤水分阈值为12.20%~13.82%。     

间作大豆对甘蔗根际土壤细菌及固氮菌多样性的影响

为探讨间作大豆(Glycine max)对甘蔗(Saccharum officinarum)根际土壤细菌及固氮细菌多样性的影响, 收集和开发固氮菌资源, 筛选高效甘蔗联合固氮体系, 选用3个甘蔗栽培品种‘ROC22’、‘GT21’、‘B8’与大豆品种‘Guizao 2’进行间种栽培, 采用巢式PCR特异扩增细菌16S rRNA基因片段和固氮细菌nifH基因片段, 并结合变性梯度凝胶电泳(DGGE)技术, 对间作大豆的甘蔗根际土壤细菌及固氮细菌进行系统演化和多样性分析。聚类分析结果显示, 间作大豆改变了甘蔗根际土壤细菌及固氮细菌原来的群落组成结构, 尤其对固氮菌群落组成的改变更大, 但对群落物种的优势度影响较小。Shannon-Wiener多样性指数和Simpson多样性指数分析结果表明, 甘蔗-大豆间作显著影响甘蔗根际土壤中细菌和固氮菌的多样性, 其中对固氮细菌多样性的影响较大。不同甘蔗品种的根际土壤细菌和固氮菌在间作大豆条件下表现出不同的多样性, ‘ROC22’和‘GT21’间作处理甘蔗根际土壤固氮细菌的Shannon-Wiener多样性指数显著高于单作处理, 而‘ROC22’与大豆间作处理的甘蔗根际土壤固氮菌多样性最为丰富。在大豆生长盛期, 间作处理的甘蔗根际土壤细菌多样性最为丰富, 不同处理间的差异也最大, 随后下降。总体来看, 甘蔗-大豆间作显著地影响根际土壤细菌和固氮菌的群落结构和群落多样性, 有助于对甘蔗合理间作栽培模式的认识和筛选高效甘蔗联合固氮体系。     

Na2CO3胁迫下甜菜幼苗根际土壤环境因子的变化及其相关性

以两个甜菜品种‘KWS0143’(耐盐碱性强)和‘Beta464’(耐盐碱性较弱)为对象,设置4个Na₂CO₃浓度处理[占土壤质量的0%(CK)、0.4%、0.8%和1.2%],采用盆栽方法研究甜菜幼苗时期植株干质量、根际土壤酶活性和微生物数量的变化.结果表明: 与对照相比,0.4%处理的植株干质量明显增加,而0.8%和1.2%处理显著受到抑制,且处理间差异显著. 不同处理下甜菜幼苗根际土壤脲酶、过氧化氢酶和碱性磷酸酶活性表现出相似的变化规律,0.4%处理酶活性较对照有所增加但不显著;0.8%和1.2%处理则显著降低了酶活性,同时‘KWS0143’的土壤酶活性均高于‘Beta464’.与对照相比,0.4%处理土壤微生物群落没有显著变化;0.8%和1.2%处理的根际土壤细菌、真菌和放线菌数量显著减少,且‘KWS0143’的根际微生物数量高于‘Beta464’.两品种植株干质量、土壤酶和土壤微生物之间呈显著正相关;通径分析表明,‘KWS0143’植株干质量决定系数表现为:放线菌>细菌>过氧化氢酶>脲酶>真菌>碱性磷酸酶,‘Beta464’表现为:放线菌>过氧化氢酶>脲酶>真菌>碱性磷酸酶>细菌.     

Na2CO3胁迫下甜菜幼苗根际土壤环境因子的变化及其相关性

以两个甜菜品种‘KWS0143’(耐盐碱性强)和‘Beta464’(耐盐碱性较弱)为对象,设置4个Na₂CO₃浓度处理[占土壤质量的0%(CK)、0.4%、0.8%和1.2%],采用盆栽方法研究甜菜幼苗时期植株干质量、根际土壤酶活性和微生物数量的变化.结果表明: 与对照相比,0.4%处理的植株干质量明显增加,而0.8%和1.2%处理显著受到抑制,且处理间差异显著. 不同处理下甜菜幼苗根际土壤脲酶、过氧化氢酶和碱性磷酸酶活性表现出相似的变化规律,0.4%处理酶活性较对照有所增加但不显著;0.8%和1.2%处理则显著降低了酶活性,同时‘KWS0143’的土壤酶活性均高于‘Beta464’.与对照相比,0.4%处理土壤微生物群落没有显著变化;0.8%和1.2%处理的根际土壤细菌、真菌和放线菌数量显著减少,且‘KWS0143’的根际微生物数量高于‘Beta464’.两品种植株干质量、土壤酶和土壤微生物之间呈显著正相关;通径分析表明,‘KWS0143’植株干质量决定系数表现为:放线菌>细菌>过氧化氢酶>脲酶>真菌>碱性磷酸酶,‘Beta464’表现为:放线菌>过氧化氢酶>脲酶>真菌>碱性磷酸酶>细菌.     

嫁接对辣椒根际土壤环境的影响及其与抗病性和产量的关系

以‘卫士’(WS)和‘部野丁’(BYD)辣椒为砧木,‘新丰2号’(XF)辣椒为接穗嫁接,以‘新丰2号’自根嫁接辣椒(XF/XF)为对照(CK),研究嫁接对辣椒根际土壤微生物量、物理性质、养分含量及土传病害和产量的影响.结果表明: 嫁接辣椒新丰/卫士(XF/WS)与新丰/部野丁(XF/BYD)根际土壤的真菌和放线菌数量较多,放线菌比例较大;定植60 d时,嫁接辣椒根际土壤过氧化氢酶(CAT)和过氧化物酶(POD)活性显著高于CK;定植90 d时,XF/WS根际土壤磷酸酶、蔗糖酶、脲酶、硝酸还原酶(NR)活性显著高于CK;此外,嫁接辣椒根际土壤浸提液中的烃类化合物增多,XF/WS和XF/BYD根际土壤N、P、K含量显著低于CK,根际土壤电导率(EC)略高,XF/WS的pH显著高于CK,而XF/BYD与CK差异不显著.说明嫁接可优化辣椒根际土壤环境,增强其对土传病害的抗性,XF/WS和XF/BYD的产量分别比CK增加40.8%和28.7%.     

土壤水分梯度对灰胡杨光合作用与抗逆性的影响

以塔里木盆地珍稀渐危种灰胡杨(Populus pruinosa Schrenk)幼苗为材料,采用盆栽方法研究土壤水分梯度对灰胡杨光合特征及抗逆性的影响。结果表明:(1)灰胡杨净光合速率(P_n)、蒸腾速率、气孔导度、胞间CO_2浓度和光能利用率均随土壤水分递减而降低,重度干旱比适宜水分依次降低了35.53%、25.32%、48.18%、15.62%和40.92%;而光合午休程度则明显增强,P_n下降主要是由非气孔因素限制造成。轻度干旱能够提高灰胡杨水分利用效率(WUE)3.05%,维持相对较高的P_n和WUE。(2)随土壤水分递降,灰胡杨光照生态幅缩窄,CO_2补偿点升高,RuBP再生受限,光与CO_2利用效率、Rubisco活性和光合效率降低。与适宜水分相比,中度与重度干旱下最大净光合速率(P_(nmax))、表观量子效率、光饱和点、羧化效率、光合能力(A_(max))、光呼吸速率、最大羧化效率、最大电子传递速率和磷酸丙糖利用率均显著降低(P0.05),其中P_(nmax)、A_(max)和生化参数分别降低了42.65%、38.26%、57.10%;63.01%、65.88%、73.43%。(3)土壤干旱显著降低了灰胡杨的枝水势和光合色素含量(P0.01),并且改变了光系统反应中心色素的组成比例,膜脂过氧化程度显著增强(P0.01)。灰胡杨主要通过积累大量脯氨酸和可溶性蛋白质参与渗透调节来减轻土壤干旱对光合机构的损伤。重度干旱对灰胡杨叶片光合系统造成了不可逆的伤害,严重抑制了其正常生长和光合作用。综上所述,塔里木干旱荒漠区灰胡杨生长适宜的土壤相对含水量为60%—65%符合极端干旱区植被恢复与高效节水的管理原则。     

干旱和复水对崖柏光合特性及水分利用效率的影响

以4年生崖柏(Thuja sutchuenensis Franch.)盆栽实生苗为材料,试验干旱和复水对崖柏光合特性及水分利用效率的影响。结果显示,在自然干旱处理过程中,叶片相对含水量(LRWC)在土壤相对含水量(SRWC)降至30%之后开始出现下降;净光合速率(P_n)、蒸腾速率(T_r)、胞间CO₂浓度(C_i)、光饱和点(LSP)和最大光合速率(P_max)随着土壤可利用水分的减少而逐渐降低;而表观量子效率(Q)、表观量子需要量(1/Q)及光补偿点(LCP)未发生明显变化;水分利用效率(WUE)则随着SRWC的下降而逐渐提高。在停止浇水50 d后(SRWC下降约95%),叶片萎蔫,净光合速率接近零,复水后3 d,净光合速率(P_n)恢复至对照的88.59%,WUE降至对照的88.63%。通过干旱-复水一系列生理指标的变化分析认为,崖柏为干旱避免型植物。     

干旱生境中接种根际促生细菌对核桃根际土壤生物学特征的影响

研究了干旱生境下接种假单胞菌YT3、枯草芽孢杆菌DZ1、蜡样芽孢杆菌L90和纺锤芽孢杆菌L13等4株植物根际促生细菌(PGPR)对核桃根际土壤生物学特征的影响.结果表明:干旱对核桃根际土壤养分有效性影响不显著,但高活性有机碳含量降低18.4%,pH由7.34显著提高到7.79.干旱生境下接种L90后,土壤高活性有机碳含量提高14.5%,pH降低至7.41.干旱导致根际土壤微生物总量、微生物生物量碳、氮和根系分泌物含量分别下降36.0%、20.7%、33.5%和30.7%,接种L90后仅分别降低14.1%、10.3%、12.1%和12.7%.核桃根际土壤微生物的末端限制性片段长度多态性分析图谱显示,干旱胁迫导致一些优势细菌群落消失,而接种PGPR对核桃根际土壤细菌群落结构有较大影响.干旱胁迫下核桃根际土壤微生物群落的Margalef指数和Shannon指数显著降低,Simpson指数显著增加;接种L90后,Margalef指数和Shannon指数分别由0.42和0.52增至0.99和0.98,Simpson指数由0.60降至0.39.与接种L90处理相比,干旱生境下接种YT3、DZ1和L13处理核桃根际土壤生物学特征差异不显著,表明L90可有效抑制干旱引起的核桃根际土壤生物学特征的改变.     

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.     

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.

     

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.     

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).