雏鸡源致病性粪肠球菌的分离鉴定及其耐药性分析

【背景】粪肠球菌(Enterococcus faecalis)是人和动物肠道正常菌群之一,也是一种条件性致病菌。近年来,粪肠球菌引起人和动物感染的报道越来越多。【目的】探明引起某养鸡场雏鸡发病死亡的病原及其致病性和有效治疗药物。【方法】结合临床症状和病理剖检,开展病原菌分离、生理生化特性检测和16S rRNA基因序列分析、致病性试验、耐药分析和对患病鸡群的药物治疗。【结果】患病鸡有昏睡、瘫痪或共济失调等临床症状;肝、脾肿大,肝脏发黄、少量出血点、质脆易碎,肠道粘膜增厚、出血,脑轻微水肿;从肝脏组织分离得到一株革兰氏阳性球菌,经纯化培养后命名为CJ517;依据该菌株形态特征、生理生化特性和16S rRNA基因序列分析鉴定为粪肠球菌;致病性试验显示CJ517菌株能致死小鼠,致死率为66.67%;该菌对头孢噻肟、磷霉素、丁胺卡那等药物敏感,对多西环素、卡那霉素、新霉素、氟苯尼考等药物耐药;经用敏感药物和提高免疫力结合治疗后,鸡群病情得到控制。【结论】研究结果可为临床诊断和治疗动物粪肠球菌感染提供参考。     

蔷薇科果树类受体激酶的研究进展

类受体激酶(receptor like kinase,RLK)参与调控植物几乎所有的生命活动,是植物生长发育和环境适应的“中央处理器”。该文对近年来国内外有关蔷薇科果树RLK基因鉴定、进化特征及其在各器官生长发育、非生物和生物逆境中的作用及调控机制等方面的研究进展进行了综述。蔷薇科果树基因组中存在数目庞大的RLKs,不同树种间的RLK数目和各亚家族成员数目都存在较大差异,而且蔷薇科果树RLK存在极为普遍的部分重复和串联重复现象,是导致家族成员迅速变化的重要原因。有研究发现,一些RLKs调控蔷薇科果树器官发育和对环境的适应性。在器官发育方面,LRR RLK亚家族成员调控根系发育,CrRLK1L、LysM RLK和LRR RLK亚家族部分成员参与调控果实发育,CrRLK1L亚家族成员参与调控花粉管发育,LRR RLK、LysM RLK、L LEC RLK和B Lectin RLK亚家族部分成员调控蔷薇科果树对生物逆境的适应。今后RLK功能研究可侧重于蔷薇科果树特色性状,通过提高目标基因的筛选和验证的效率,加速主效RLKs的筛选进程,并通过筛选主效RLKs诱导方式和加速分子育种进程等途径,将研究成果应用于实际生产。     

Genome-Wide Analysis of the Apple (Malus domestica) Cysteine-Rich Receptor-Like Kinase (CRK) Family: Annotation,Genomic Organization,and Expression Profiles in Response to Fungal Infection

Plant Molecular Biology Reporter - Cysteine-rich receptor-like kinases (CRKs) took crucial roles in plant cell growth and development, as well as environmental adaption. Apple (Malus domestica) had...     

基于全基因组从头测序技术盐肤木叶绿体基因组的测序分析

盐肤木是一种重要的经济树种,可为医药和工业染料提供原料。盐肤木具有较强的抗旱、耐寒、耐盐,可在温带、暖温带和亚热带地区生长。本研究首次对盐肤木叶绿体基因组进行从头测序(de novo sequencing)组装研究。结果表明,盐肤木叶绿体基因组长度为159082 bp,具有典型的四部分结构,两个单拷贝区被一对反向重复区分隔。LSC和SSC的长度分别为85394 bp和18663 bp。叶绿体基因组总共编码126个基因,其中包括88个蛋白编码基因,8个rRNA基因,30个tRNA基因。在叶绿体基因组中,61.97%的序列为基因编码区。在盐肤木叶绿体基因组中,只有8个基因含有内含子,除ycf3基因(2个内含子)外,其余均含有1个内含子。盐肤木叶绿体基因组总共存在755个SSR位点。SSR主要由二核苷酸和单核苷酸组成,分别占60%(453)和28.74%(217)。聚类分析结果表明,漆树科与盐肤木最为接近,其次为槭树科和无患子科。本研究为盐肤木的分类提供了分子基础。本研究是关于盐肤木叶绿体基因组的首次报道,对了解其光合作用、进化和叶绿体转基因工程具有重要意义。     

RNA sequencing analysis provides new insights into dynamic molecular responses to <Emphasis Type="Italic">Valsa mali</Emphasis> pathogenicity in apple ‘Changfu No. 2’

Valsa canker caused by the necrotrophic pathogen Valsa mali (Vm) severely affects apple production in Eastern Asia. The molecular basis underlying the apple response to Vm infection is poorly understood. Hence, we performed RNA sequencing (RNA-seq) to investigate the dynamic gene expression profiles of a major apple cultivar, ‘Changfu No.2’, during Vm infection. Compared with the control (C), 104, 313, and 1059 differentially expressed genes (DEGs) were detected from the phloem tissue within the range of 0.9–1.3 cm (T1), 0.5–0.9 cm (T2), and 0.1–0.5 cm (T3) beyond the lesion periphery, respectively. Gene ontology (GO) enrichment analysis revealed that the DEGs associated with plant growth and development were down-regulated, whereas those related to defense responses were up-regulated. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that hormonal and Ca²⁺ signaling and phenylpropanoid biosynthesis were involved in the defense responses. In conclusion, multiple defense responses associated with ABA, JA, ET, Ca²⁺, and cell wall signals contributed to the defense against Vm infection in ‘Changfu No.2’. In contrast, the DEGs with inhibited expression were involved in plant growth and development; auxin signaling and several resistance genes might weaken the resistance of ‘Changfu No.2’ to pathogens. Our results offer a new insight into plant responses against necrotrophs and could benefit programs aimed at breeding for Vm resistance.     

Genome-Wide Identification and Expression Analysis of the CrRLK1L Gene Family in Apple (Malus domestica)

It has been reported that members of the Catharanthus roseus receptor-like kinase1-like kinase (CrRLK1L) gene family detect cell wall integrity, cell-to-cell communication, and biotic and abiotic stress. We performed a comprehensive study including the genome-wide identification, characterization, and gene expression analysis of CrRLK1Ls in apple (Malus domestica). Sixty-seven M. domestica CrRLK1Ls (MdCrRLK1Ls) were identified based on their domain structure. Molecular weight and pI ranged from 52.36–141 kDa and 5.05–8.9, respectively. They were distributed across 16 of the 18 chromosomes and classified into five phylogenetic branches. Exon-intron structural analysis indicated a wide range of exon numbers. Collinearity analysis showed that both segmental-and tandem-duplication contributed to the expansion of this family. Cis-elements in the MdCrRLK1L promoter region responded mainly to light, circadian rhythm, phytohormones, and biotic or abiotic stress. Many members exhibited tissue-specific expression patterns and differentially expressed under biotic stresses, which may contribute to the different functional roles of MdCrRLK1Ls under physiological stress and/or pathological conditions. This study provides new insights into the CrRLK1Ls in Malus spp.

     

Contamination of Bananas with Beauvericin and Fusaric Acid Produced by Fusarium oxysporum f. sp. cubense

Background

Fusarium wilt, caused by the fungal pathogen Fusarium oxysporum f. sp. cubense (Foc), is one of the most destructive diseases of banana. Toxins produced by Foc have been proposed to play an important role during the pathogenic process. The objectives of this study were to investigate the contamination of banana with toxins produced by Foc, and to elucidate their role in pathogenesis.

Methodology/Principal Findings

Twenty isolates of Foc representing races 1 and 4 were isolated from diseased bananas in five Chinese provinces. Two toxins were consistently associated with Foc, fusaric acid (FA) and beauvericin (BEA). Cytotoxicity of the two toxins on banana protoplast was determined using the Alamar Blue assay. The virulence of 20 Foc isolates was further tested by inoculating tissue culture banana plantlets, and the contents of toxins determined in banana roots, pseudostems and leaves. Virulence of Foc isolates correlated well with toxin deposition in the host plant. To determine the natural occurrence of the two toxins in banana plants with Fusarium wilt symptoms, samples were collected before harvest from the pseudostems, fruit and leaves from 10 Pisang Awak ‘Guangfen #1’ and 10 Cavendish ‘Brazilian’ plants. Fusaric acid and BEA were detected in all the tissues, including the fruits.

Conclusions/Signficance

The current study provides the first investigation of toxins produced by Foc in banana. The toxins produced by Foc, and their levels of contamination of banana fruits, however, were too low to be of concern to human and animal health. Rather, these toxins appear to contribute to the pathogenicity of the fungus during infection of banana plants.     

苹果和梨抗病相关基因的诱导与表达分析

该研究结合蔷薇科数据库,经多序列比对、表达分析和验证,筛选了苹果和梨抗病反应Marker基因及其检测引物,并以腐烂病抗性资源杜梨和东北山荆子悬浮细胞为材料,经20%腐烂病菌(Vp)代谢物处理,采用实时荧光定量PCR(RT qPCR)分析Marker基因对腐烂病信号响应的表达模式,为苹果、梨抗病反应的快速检测和杜梨抗腐烂病机理的系统研究奠定基础。结果显示：(1)经检索比对共筛选出水杨酸(SA)、茉莉酸(JA)、乙烯(ET)、系统获得型抗性(SAR)反应、病原相关分子模式激发的免疫反应(PTI)、植保素和防御相关等信号的15个Marker基因及其对应引物。(2)各处理cDNA浓度采用100 ng·μL^-1时Cq值均介于18～25,且PCR扩增效率高,表明所选的15个Marker基因的引物均可准确反映抗性反应的激活状况,可作为各自信号通路的Marker基因。(3)与对照相比,Vp代谢物处理后杜梨悬浮细胞中ROS的积累随处理时间的延长呈逐渐显著上升的趋势,并于处理6 h时,ROS信号值达到对照的3.2倍,表明Vp代谢物会激活体内的免疫反应(PTI),进而导致植物体内ROS的爆发。(4)RT qPCR验证分析显示,Vp代谢物处理后,杜梨悬浮细胞中SA、JA、PTI、SAR、R基因、植保素、防御相关等信号通路的Marker基因都呈上调表达趋势,其中,SA、JA和SAR通路的Marker基因ChiV(Chitinase class V)、LOX1(Lipoxygenase 1)和PR4(Pathogenesis Related 4)及防御相关基因PAL1(Phe Ammonia Lyase 1)的表达上调最为明显,最高分别可上升至对照的1718、691、6369和1072倍,表明杜梨受到Vp代谢物胁迫时,主要激活了植物体内的SA、JA、SAR和防御相关信号通路的基因,进而能够抵御病原的进一步入侵。研究发现,SA、JA、SAR和防御反应等信号参与了杜梨对腐烂病胁迫的响应,进而提高其抗病性。     

Effects of Shading on the Synthesis of Volatile Organic Compounds in ‘Marselan’ Grape Berries (Vitis vinifera L.)

Journal of Plant Growth Regulation - Light is a vital environmental factor that can affect the synthesis of volatile organic compounds (VOCs) in grape berries. However, the mechanism through which...     

大肠杆菌磷酸甘油酸脱氢酶突变体的构建及抗反馈抑制效应

磷酸甘油酸脱氢酶(D-3-phosphoglycerate dehydrogenase,PGDH,EC 1.1.1.95)为L-丝氨酸合成途径的关键酶,其编码基因为ser A,其活性受到合成产物L-丝氨酸的反馈抑制调控。为解除丝氨酸的反馈抑制,采用定点突变技术把编码PGDH酶344位组氨酸或346位天冬氨酸或364位天冬氨酸的密码子定点突变为丙氨酸密码子。改造后的ser AFbr被连到表达载体pT7-7上,并转入大肠杆菌Escherichia coli BL21(DE3)中进行表达,破壁回收粗酶液,通过DEAE阴离子柱纯化PGDH突变体,并对其酶活性和IC_(50)值进行了测定。结果,野生型PGDH酶IC_(50)值为7μmol/L,而PGDH双突变体N346A/H344A催化活性与野生型相近,在丝氨酸浓度为160 mmol/L时,其酶活仍保持未添加丝氨酸时酶活的96%,基本解除反馈抑制。