基因CfATG6和CfATG14参与调控果生刺盘孢细胞自噬和致病力

【目的】炭疽病是油茶的主要病害,由刺盘孢属的多种真菌引起,其中果生刺盘孢分布范围最广、分离率最高,是油茶炭疽病的主要致病菌。研究自噬相关蛋白CfAtg6和CfAtg14的生物学功能,为进一步揭示果生刺盘孢通过细胞自噬调控致病的分子机制,并为油茶炭疽病的防治提供理论基础。【方法】根据同源重组原理,通过聚乙二醇(polyethylene glycol, PEG)介导的方法,在果生刺盘孢中敲除基因CfATG6和CfATG14,并进一步获得回补菌株ΔCfatg6-C和ΔCfatg14-C。【结果】酵母双杂交试验结果显示,果生刺盘孢蛋白CfAtg6和CfAtg14可能存在互作关系。生物学表型测定结果表明,相较于野生型和回补菌株,突变体ΔCfatg6和ΔCfatg14均表现出营养生长速率显著减慢,附着胞形成率分别只有野生型的5%和18%;突变体ΔCfatg6和ΔCfatg14致病力均极显著减弱,造成的油茶叶片病斑面积少于野生型和回补菌株的1/3;CfATG6和CfATG14基因缺失突变体均丧失转运和降解CfAtg8蛋白的能力,并对细胞壁胁迫更敏感。突变体ΔCfatg6的分生孢子产量显著降低,仅为野生型的20%左右;氧化胁迫试验结果表明,相较于野生型和回补菌株,过氧化氢对突变体的生长抑制率升高10%左右。内质网压力胁迫试验表明,ΔCfatg14对二硫苏糖醇抑制率升高5%以上。【结论】自噬相关基因CfATG6和CfATG14参与调控了果生刺盘孢生长发育、细胞自噬和致病力。     

贝莱斯芽孢杆菌BG-2对厚皮甜瓜贮藏品质及防御酶活性的影响

【背景】厚皮甜瓜白霉病主要由尖孢镰刀菌引起,严重影响厚皮甜瓜品质,从而造成经济损失。【目的】研究贝莱斯芽孢杆菌BG-2对尖孢镰刀菌的抑制作用,以及对采后厚皮甜瓜贮藏品质的影响。【方法】以贝莱斯芽孢杆菌为供试菌株,研究其对2种不同贮藏温度（25℃和4℃）下厚皮甜瓜果实腐烂率、失重率、果肉硬度、可滴定酸、可溶性固形物含量和维生素C含量的影响,同时测定过氧化氢酶（catalase,CAT）、过氧化物酶（peroxidase,POD）和超氧化物歧化酶（superoxide dismutase,SOD）防御酶活性,进而探究Bacillus velezensis BG-2对尖孢镰刀菌的抑制作用及对厚皮甜瓜贮藏品质的影响。【结果】贝莱斯芽孢杆菌BG-2菌悬液能有效抑制尖孢镰刀菌的生长,菌悬液浓度为1×10⁷ CFU/mL时抑菌圈直径为（20.45±0.39） mm,抑菌效价为144.48 mm/mL;同时,B. velezensis BG-2能有效减缓果肉硬度、维生素C含量、可溶性固形物含量和可滴定酸的下降,抑制果实失重和腐烂,能较好地保持果实的品质,抑制防御酶活性的下降。【结论】B. velezensis BG-2能显著抑制尖孢镰刀菌的生长,延缓厚皮甜瓜的后熟,维持采后甜瓜果实较高的品质和防御酶活性,对甜瓜腐烂有较好的防治效果。     

香蕉枯萎病菌中Hog1 MAPK同源基因FoHog1敲除突变体的生物学特性

【目的】研究香蕉枯萎病菌4号生理小种中促分裂原活化蛋白激酶基因FoHog1的结构特点及其功能【方法】通过PCR和RT-PCR的方法获得了FoHog1基因序列并进行生物信息学分析,利用PEG介导的原生质体转化法得到了FoHog1基因缺失突变体,分析敲除突变体与野生型的生物学特性差异【结果】FoHog1基因编码一个含有357个氨基酸的蛋白,该蛋白在不同种镰刀菌中高度保守。通过对敲除突变体的研究发现,该基因缺失后菌丝密度下降,产孢量与菌丝干重明显降低,对乙酸钠和氯化铵的利用率下降,对温度、pH及渗透压等外源胁迫更为敏感。通过致病力实验发现,基因敲除突变体的定殖能力有所降低【结论】尖孢镰刀菌古巴专化型4号生理小种中FoHog1基因参与调控菌丝生长、分生孢子生成、乙酸钠和氯化铵代谢、渗透压胁迫反应及致病相关过程。     

蛋白-O-岩藻糖基转移酶1基因CfPOFUT1在果生炭疽菌中的功能分析

【目的】蛋白-O-岩藻糖基转移酶1 (protein O-fucosyltransferase 1,POFUT1)是催化蛋白质O-岩藻糖基化的关键酶,在动物和人体内被证明调控一系列的生理病理过程,然而POFUT1基因在果生炭疽菌乃至真菌中还未见报道。本研究旨在克隆果生炭疽菌中CfPOFUT1基因,并分析其生物学功能。【方法】利用RT-PCR技术扩增CfPOFUT1的基因并进行生物信息学分析,构建了CfPOFUT1基因的沉默和过表达载体,通过PEG介导法将载体导入原生质体中获得CfPOFUT1基因的沉默和过表达突变体。测定了野生型菌株、CfPOFUT1沉默菌株和过表达菌株在PDA上的菌丝生长、分生孢子产生、萌发与附着胞形成、胁迫应答和致病力、杀菌剂敏感性等生物学表型。【结果】与野生型菌株相比,基因过表达突变体产孢量显著增加,致病力增强,对嘧菌酯敏感性降低,但对多菌灵和咪鲜胺敏感性增强。基因沉默突变体产孢量减少,细胞壁完整性、内质网应激敏感性提高,致病力减弱,对嘧菌酯敏感性提高,但对多菌灵和咪鲜胺敏感性降低。【结论】CfPOFUT1基因参与调控果生炭疽菌分生孢子产量,细胞壁完整性、内质网对应激和药剂敏感性,并对其致病性也具有一定的影响。     

禾谷镰刀菌拮抗菌21-6的鉴定及其抑菌活性测定

【背景】禾谷镰刀菌（Fusarium graminearum）是一种危害小麦生产的重要病原真菌。【目的】筛选对禾谷镰刀菌具有拮抗活性的链霉菌菌株,为该病原的生物防治提供理论基础。【方法】采用稀释涂布法分离链霉菌,利用平板对峙法筛选高活性拮抗菌株;通过形态学、生理生化特征和16S rRNA基因序列分析确定其分类地位;采用生长速率法分析其发酵条件及无菌发酵液的稳定性;并测定该菌株的防病效果和抑菌谱。【结果】筛选到一株对禾谷镰刀菌具有较强抑制作用的链霉菌菌株21-6,抑菌率为75.2%±2.1%。根据形态学、生理生化特征及16S rRNA基因序列分析,将其鉴定为Streptomyces stelliscabiei。菌株21-6在pH为中性条件下的PDB培养基中培养5 d能够产生更好的抑菌效果。无菌发酵液能够抑制禾谷镰刀菌的菌丝生长和孢子萌发过程。无菌发酵液不受高温、胃蛋白酶、胰蛋白酶及蛋白酶K的影响,耐酸但对碱性条件敏感。发酵液对禾谷镰刀菌侵染小麦胚芽鞘具有抑制效果。菌株21-6具有聚酮合酶pks-Ⅰ和pks-Ⅱ基因。此外,该菌株对5种植物病原真菌均具有抑制效果。【结论】链霉菌菌株21-6对禾谷镰刀菌具有较好的生防潜力。     

新生隐球菌一个新的产孢相关蛋白Srp1的鉴定与功能分析

【目的】研究产孢相关蛋白Srp1在新生隐球菌有性产孢和致病性中的作用及机理。【方法】采用基因枪转化技术构建新生隐球菌SRP1基因缺失突变体及其互补菌株,并通过小鼠致病性实验和菌株交配实验检测Srp1在新生隐球菌有性产孢和致病性中的作用。【结果】与野生型菌株相比,srp1Δ突变体小鼠致病性无差异;srp1Δ突变体能够交配并形成双核菌丝,但丧失产生担孢子的能力;初步机理分析表明srp1Δ突变体交配后其减数分裂过程被阻断,从而导致srp1Δ突变体不能产生担孢子。【结论】产孢相关蛋白Srp1不影响新生隐球菌的致病性,但可通过调控减数分裂过程影响新生隐球菌的有性生殖。     

乌头根腐病病原菌的分离与鉴定

【背景】四川江油地区栽培乌头极易发生根腐病,植株染病后枯萎死亡,最终影响药材产量。因发病因素和致病菌多样,乌头根腐病的防治向来困难。【目的】鉴定四川江油地区栽培乌头根腐病病原菌,为病害诊断和防治提供理论基础。【方法】采用组织分离法进行病原菌分离;按照Koch’s法则对分离的病菌进行致病性验证;通过形态学观察和真菌r DNA-ITS序列分析,鉴定病原菌种类。【结果】从具有根腐病症状的乌头根部分离得到47株真菌,其中菌株GF3-3、GF3-6和GF6-1是乌头根腐病的致病菌;通过形态特征结合rDNA-ITS序列分析将菌株GF3-3、GF3-6和GF6-1分别鉴定为Fusariumsolani、F.oxysporum和F.proliferatum。【结论】茄腐镰刀菌(F.solani)、尖孢镰刀菌(F. oxysporum)和层出镰刀菌(F. proliferatum)是乌头根腐病的主要病原菌,其中层出镰刀菌引起乌头患根腐病为首次报道。     

拟康宁木霉T 51菌株对番茄枯萎病的生物防治及其机理研究

尖孢镰刀菌是番茄枯萎病的致病菌,该研究利用拟康宁木霉T 51菌株对尖孢镰刀菌展开对峙培养试验、防治最适温度、酸碱度筛选试验及生物防治效果试验,并测定防治试验中番茄幼苗叶片的生理生化指标和水杨酸、茉莉酸合成和信号途径关键基因表达量,探讨T 51菌株的生物防治机理。结果表明：(1)T 51菌株可显著抑制对峙培养中尖孢镰刀菌生长;随着环境温度和pH的增加,T 51菌株对尖孢镰刀菌的抑制率先升后降,并且在20 ℃、pH 7环境下效果最佳。(2)T 51菌株和尖孢镰刀菌混合孢子液处理番茄幼苗植株无明显的感病症状,植株生长状态与清水对照组无显著差异,枯萎病发病率和病情指数比单施尖孢镰刀菌孢子液处理显著大幅度降低,相对防效为87.5%。(3)与单施尖孢镰刀菌孢子液处理相比,混合孢子液处理番茄幼苗叶片的叶绿素荧光参数最大光化学效率、光化学淬灭系数和表观光合电子传递速率,以及抗氧化酶SOD、POD、CAT活性均显著增加,而非光化学淬灭系数和过氧化氢含量均显著降低。(4)与单施尖孢镰刀菌孢子液处理相比,混合孢子液处理番茄幼苗叶片的内源水杨酸(SA)显著降低,而茉莉酸(JA)含量显著升高,同时SA信号通路上的PR1和TGA2基因表达量均显著下调,JA合成基因LoxD的表达量显著上调。研究认为,拟康宁木霉T 51菌株对尖孢镰刀菌有显著的防治效果,并在20 ℃、pH 7环境下防治效果最佳;T 51菌株可能通过抑制尖孢镰刀菌侵染,增强番茄叶片抗氧化酶活性,提高叶片光合效率,以及调控水杨酸和茉莉酸合成和信号途径关键基因表达,调节内源水杨酸和茉莉酸含量,进而提高番茄植株的枯萎病抗病性。研究结果为番茄抗枯萎病提供了生防途径的理论依据。     

不同浓度壳聚糖对炭黑曲霉和硫色镰刀菌生长和发育的影响

【背景】壳聚糖是广泛存在于甲壳动物的一种多糖，具有广谱的抗真菌活性，但壳聚糖是否影响炭黑曲霉(Aspergillus carbonarius)和硫色镰刀菌(Fusarium sulphureum)生长和发育尚未见报道。【目的】明确不同浓度壳聚糖对A. carbonarius和F. sulphureum生长和发育的影响。【方法】通过在PDA培养基中添加不同浓度壳聚糖，测定两种真菌的菌落直径、生物量和菌丝干重，观察产孢量、孢子萌发和芽管长度，比较抑菌的差异。【结果】壳聚糖处理可显著改变两种真菌的菌落形态，处理浓度越高菌落皱缩和变形越明显；壳聚糖还可以有效抑制两种真菌的菌落生长、菌丝干重和菌丝生物量，抑制效果呈明显的浓度依赖，对F. sulphureum的抑制效果更好。壳聚糖可抑制两种真菌的产孢量、孢子萌发和芽管伸长，处理浓度越高抑制效果越好，对F. sulphureum的抑制效果更为明显。壳聚糖对A. carbonarius和F. sulphureum的EC₅₀值分别为0.12 mg/mL和0.075 mg/mL。【结论】壳聚糖可有效抑制A. carbonarius和F. sulphureum的生长发育，抑制效果呈浓度依赖，F. sulphureum对壳聚糖更为敏感。     

天山大峡谷原始森林黏细菌的分离鉴定及其抗菌活性

【背景】黏细菌是一类具有多细胞群体行为特征的高等原核生物,其对植物病原真菌和细菌的捕食特性使其在植物病害防治方面具有重要的应用潜力。【目的】探究乌鲁木齐天山大峡谷原始森林可培养黏细菌的多样性并分析其抗菌活性,为发掘黏细菌生防菌株奠定基础。【方法】以天山大峡谷原始森林采集的土样和腐木为分离材料,采用兔粪诱导法和被捕食菌诱导法从中分离纯化黏细菌菌株,结合形态学观察、生理生化测定和16S rRNA基因序列分析确定其分类地位,并以6种植物病原真菌[大丽轮枝菌(Verticillium dahliae)、尖孢镰刀菌萎蔫专化型(Fusarium oxysporum f. sp. vasinfectum)、拟轮枝链孢霉(Fusarium verticillioides)、立枯丝核菌(Rhizoctonia solani)、黄色镰刀菌(Fusarium culmorum)、细极链格孢菌(Alternaria tenuissima)]和1种植物病原细菌[梨火疫病菌(Erwinia amylovora)]为靶标菌,通过平板对峙法和菌苔捕食法测定其抗菌活性。【结果】从采集的样品中分离出70株菌株,经纯化后获得36株黏细菌纯培养物。经鉴定隶属于4个属,黏球菌属(Myxococcus) 30株、孢囊杆菌属(Cystobacter) 3株、珊瑚球菌属(Corallococcus) 2株和原囊菌属(Archangium) 1株。抗菌活性分析显示,本研究获得的36株黏细菌至少对2种植物病原真菌有抗菌活性,表现出广谱的抗真菌活性,初步筛选出一株菌株NSE37-1兼具广谱和高效抗真菌活性;供试的15株黏细菌对梨火疫病菌均具有捕食活性,初步筛选出一株对梨火疫病菌具有较强捕食能力的黏细菌菌株NSE25。【结论】天山大峡谷可培养黏细菌资源比较丰富,黏球菌属是该地区可培养黏细菌菌群中的优势菌。分离纯化出的黏细菌菌株均表现出广谱的抗植物病原菌活性,具有进一步研究和开发的潜在价值。     

Foreign exploration for Scirtothrips perseae Nakahara (Thysanoptera: Thripidae) and associated natural enemies on avocado (Persea americana Miller)

Scirtothrips perseae Nakahara was discovered attacking avocados in California, USA, in 1996. Host plant surveys in California indicated that S. perseae has a highly restricted host range with larvae being found only on avocados, while adults were collected from 11 different plant species. As part of a management program for this pest, a “classical” biological control program was initiated and foreign exploration was conducted to delineate the home range of S. perseae, to survey for associated natural enemies and inventory other species of phytophagous thrips on avocados grown in Mexico, Guatemala, Costa Rica, the Dominican Republic, Trinidad, and Brazil. Foreign exploration efforts indicate that S. perseae occurs on avocados grown at high altitudes (>1500 m) from Uruapan in Mexico south to areas around Guatemala City in Guatemala. In Costa Rica, S. perseae is replaced by an undescribed congener as the dominant phytophagous thrips on avocados grown at high altitudes (>1300 m). No species of Scirtothrips were found on avocados in the Dominican Republic, Trinidad, or Brazil. In total, 2136 phytophagous thrips were collected and identified, representing over 47 identified species from at least 19 genera. The significance of these species records is discussed. Of collected material 4% were potential thrips biological control agents. Natural enemies were dominated by six genera of predatory thrips (Aeolothrips, Aleurodothrips, Franklinothrips, Leptothrips, Scolothrips, and Karnyothrips). One genus each of parasitoid (Ceranisus) and predatory mite (Balaustium) were found. Based on the results of our sampling techniques, prospects for the importation of thrips natural enemies for use in a “classical” biological control program in California against S. perseae are not promising.     

Taxonomic status of the species of the green algal genusNeochloris

Komárek has recently reviewed the various species assigned to the green algal genusNeochloris Starr (Chlorococcales, Chlorococcaceae) and removed those with uninucleate vegetative cells to a new genus,Ettlia. Watanabe & Floyd, unaware ofKomárek's work, also reviewed the species ofNeochloris and distributed them among three genera—Neochloris, Chlorococcopsis gen. nov., andParietochloris gen. nov.—on the basis of details of the covering of the zoospore and the arrangement of the basal bodies of the flagellar apparatus. This paper reconciles these two treatments and makes additional recommendations at the ranks of genus, family, order, and class.     

Die GattungKarschia — Bindeglied zwischen bitunicaten Ascomyceten und lecanoralen Flechtenpilzen?

The genusKarschia, in the earlier sense, including saprophytes and parasites on lichens, has been thought to be a non-lichenized parallel genus of the lichen genusBuellia. Modern workers included it on the one hand inBuellia, on the other hand combined it with bitunicate ascomycetes. It is now proved thatKarschia is heterogeneous and contains but superficially similar members both of the genusBuellia of theLecanorales and of typical or masked bitunicateAscomycetes. Therefore, it can not be regarded as a link betweenLecanorales andDothideales. The type species ofKarschia belongs to theDothideales.

     

Systematic significance of mature embryo of bamboos

The mature embryo of seven species belonging to five genera of Indian bamboos is described. In all these the basic pattern of embryo organisation is same: the scutellar and coleoptilar bundles are not separated by an internode, the epiblast is absent, the lower portion of the scutellum and the coleorhiza are separated by a cleft and the margins of embryonic leaves overlap. The features unique to fleshy fruited bamboos are: presence of a massive scutellum, the juxtaposition of plumule and radicle and the occurrence of a bud in the axil of the coleoptile. The fleshy fruit bearing bamboos should be classified into one group, the tribeMelocanneae. Evidence is provided to recognise additional groups in the subfamilyBambusoideae.     

Phylogeny of cardinalfishes (Teleostei: Gobiiformes: Apogonidae) and the evolution of visceral bioluminescence

The cardinalfishes (Apogonidae) are a diverse clade of small, mostly reef-dwelling fishes, for which a variety of morphological data have not yielded a consistent phylogeny. We use DNA sequence to hypothesize phylogenetic relationships within Apogonidae and among apogonids and other acanthomorph families, to examine patterns of evolution including the distribution of a visceral bioluminescence system. In conformance with previous studies, Apogonidae is placed in a clade with Pempheridae, Kurtidae, Leiognathidae, and Gobioidei. The apogonid genus Pseudamia is recovered outside the remainder of the family, not as sister to the superficially similar genus Gymnapogon. Species sampled from the Caribbean and Western Atlantic (Phaeoptyx, Astrapogon, and some Apogon species) form a clade, as do the larger-bodied Glossamia and Cheilodipterus. Incidence of visceral bioluminescence is found scattered throughout the phylogeny, independently for each group in which it is present. Examination of the fine structure of the visceral bioluminescence system through histology shows that light organs exhibit a range of morphologies, with some composed of complex masses of tubules (Siphamia, Pempheris, Parapriacanthus) and others lacking tubules but containing chambers formed by folds of the visceral epithelium (Acropoma, Archamia, Jaydia, and Rhabdamia). Light organs in Siphamia, Acropoma, Pempheris and Parapriacanthus are distinct from but connected to the gut; those in Archamia, Jaydia, and Rhabdamia are simply portions of the intestinal tract, and are little differentiated from the surrounding tissues. The presence or absence of symbiotic luminescent bacteria does not correlate with light organ structure; the tubular light organs of Siphamia and chambered tubes of Acropoma house bacteria, those in Pempheridae and the other Apogonidae do not.     

Biological control of three floating water weeds,<Emphasis Type="Italic">Eichhornia crassipes,Pistia stratiotes</Emphasis>, and <Emphasis Type="Italic">Salviniamolesta</Emphasis> in the Republic of Congo

Since 1999, four specific weevils (Coleoptera, Curculionidae) were released in the Republic of Congo against three exotic floating water weeds: Neochetina eichhorniae Warner and N. bruchi Hustache against water hyacinth, Neohydronomus affinis Hustache against water lettuce, and Cyrtobagous salviniae Calder and Sands against water fern. Recoveries of exotic weevils were made from all 24 release sites except one, and all four species have established and spread (up to 800 km for water hyacinth weevils). Within a few years of releases, control of water fern and water lettuce was such that fishing and navigation could be resumed, while reductions of water hyacinth populations were only beginning.     

A molecular phylogeny of Hebeloma species from Europe

In order to widen the scope of existing phylogenies of the ectomycorrhizal agaric genus Hebeloma a total of 53 new rDNA ITS sequences from that genus was generated, augmented by sequences retrieved from GenBank, and analysed using Bayesian, strict consensus and neighbour joining methods. The lignicolous Hebelomina neerlandica, Gymnopilus penetrans, and two species of Galerina served as outgroup taxa. Anamika indica, as well as representatives of the genera Hymenogaster and Naucoria, were included to test the monophyly of Hebeloma, which is confirmed by the results. Hebeloma, Naucoria, Hymenogaster and Anamika indica cluster in a strongly supported monophyletic hebelomatoid clade. All trees largely reflect the current infrageneric classification within Hebeloma, and divide the genus into mostly well-supported monophyletic groups surrounding H. crustuliniforme, H. velutipes, H. sacchariolens, H. sinapizans, and H. radicosum, with H. sarcophyllum being shown at an independent position; however this is not well supported. The section Indusiata divides with strong support into three groups, the position of the pleurocystidiate Hebeloma cistophilum suggests the possible existence of a third subsection within sect. Indusiata. Subsection Sacchariolentia is raised to the rank of section.