Chib1和PAL5基因在AM真菌Glomus fasciculatus诱导大豆抗线虫病害防御反应中的作用

本研究系统分析了大豆(品种:‘鲁豆4’)接种AM真菌Glomusfasciculatum和胞囊线虫(SCN,Heteroderaglycines)4号生理小种后各处理菌根和线虫侵染率、几丁质酶和苯丙氨酸解氨酶(PAL)活性及几丁质酶基因Chib1和苯丙氨酸解氨酶基因PAL5转录物的动态变化。结果表明,接种SCN对AM真菌的侵染率没有产生显著影响,但先接种AM真菌后接种SCN的大豆根内线虫侵染率明显低于只接种SCN的处理。另外,先接种AM真菌后接种SCN的大豆根内几丁质酶和PAL活性显著提高,活性高峰出现在接种线虫后的第3天。值得注意的是,先接种AM真菌后接种SCN的大豆根内两种基因Chib1和PAL5转录物高峰也出现在接种SCN后的第3天,即AM真菌侵染率快速上升而SCN侵染率快速下降时期。所以Chib1和PAL5基因的表达可能是AM真菌诱导的抗大豆胞囊线虫病害防御反应的一种表现。因此推测Chib1和PAL5直接参与了AM真菌诱导大豆抗胞囊线虫病害的防御反应。     

AM真菌和胞囊线虫对大豆根内酶活性的影响

将‘鲁豆4号’大豆接种丛枝菌根(AM)真菌聚生球囊霉Glomus fasiculatum和大豆胞囊线虫(SCN)Heterodera glycines4号生理小种后,定期测定大豆根系中AM真菌及线虫侵染速率、过氧化物酶(POD)、苯丙氨酸解氨酶(PAL)、β—1,3葡聚糖酶及几丁质酶活性的动态变化。结果表明,接种AM真菌大豆根系中4种酶活性高于对照水平：先接种AM真菌后接种SCN处理根系中POD、PAL及几丁质酶的活性高于只接种SCN的处理,并且酶活性峰值出现的时间均早于或相当于后者。另外,PAL及几丁质酶活性出现高峰时期也正是AM真菌侵染率迅速升高及线虫侵染速率快速下降期。因此,AM真菌先激活了大豆的防御反应,然后使其对SCN的侵染产生快速反应,PAL及几丁质酶在AM真菌诱导的抗、耐线虫病害机制中起重要作用。值得注意的是,先接种AM真菌后接种SCN处理大豆根系中,β—1,3葡聚糖酶活性低于只接种AM真菌的处理。作者认为本试验条件下,该酶在大豆抗SCN病害中的作用表现不明显。     

AM真菌和胞囊线虫对大豆根内酶活性的影响

将‘鲁豆4号’大豆接种丛枝菌根(AM)真菌聚生球囊霉Glomus fasiculatum和大豆胞囊线虫(SCN)Heterodera glycines 4号生理小种后, 定期测定大豆根系中AM真菌及线虫侵染速率、过氧化物酶(POD)、苯丙氨酸解氨酶(PAL)、β-1,3葡聚糖酶及几丁质酶活性的动态变化。结果表明, 接种AM真菌大豆根系中4种酶活性高于对照水平; 先接种AM真菌后接种SCN处理根系中POD、PAL及几丁质酶的活性高于只接种SCN的处理,并且酶活性峰值出现的时间均早于或相当于后者。另外,PAL及几丁质酶活性出现高峰时期也正是AM真菌侵染率迅速升高及线虫侵染速率快速下降期。因此,AM真菌先激活了大豆的防御反应,然后使其对SCN的侵染产生快速反应,PAL及几丁质酶在AM真菌诱导的抗、耐线虫病害机制中起重要作用。值得注意的是,先接种AM真菌后接种SCN处理大豆根系中,β-1,3葡聚糖酶活性低于只接种AM真菌的处理。作者认为本试验条件下,该酶在大豆抗SCN病害中的作用表现不明显。     

AM真菌和胞囊线虫对大豆根内酶活性的影响*

将‘鲁豆4号’大豆接种丛枝菌根(AM)真菌聚生球囊霉Glomus fasiculatum和大豆胞囊线虫(SCN)Heterodera glycines 4号生理小种后, 定期测定大豆根系中AM真菌及线虫侵染速率、过氧化物酶(POD)、苯丙氨酸解氨酶(PAL)、β-1,3葡聚糖酶及几丁质酶活性的动态变化。结果表明, 接种AM真菌大豆根系中4种酶活性高于对照水平; 先接种AM真菌后接种SCN处理根系中POD、PAL及几丁质酶的活性高于只接种SCN的处理,并且酶活性峰值出现的时间均早于或相当于后者。另外,PAL及几丁质酶活性出现高峰时期也正是AM真菌侵染率迅速升高及线虫侵染速率快速下降期。因此,AM真菌先激活了大豆的防御反应,然后使其对SCN的侵染产生快速反应,PAL及几丁质酶在AM真菌诱导的抗、耐线虫病害机制中起重要作用。值得注意的是,先接种AM真菌后接种SCN处理大豆根系中,β-1,3葡聚糖酶活性低于只接种AM真菌的处理。作者认为本试验条件下,该酶在大豆抗SCN病害中的作用表现不明显。     

分根培养系统中AM真菌抑制大豆胞囊线虫病的效应

在分根培养系统中将大豆(Glycine max Merrill)幼苗接种丛枝菌根(Arbuscular mycorrhiza,AM)真菌摩西球囊霉(Glomus mosseae)、幼套球囊霉(G.etunicatum)或/和大豆胞囊线虫(SCN,Heterodera glycines)后,定期测定大豆根系中AM真菌及线虫侵染率、病情指数、过氧化物酶(POD)、苯丙氨酸解氨酶(PAL)、β-1,3-葡聚糖酶及几丁质酶活性的动态变化。结果表明,将大豆胞囊线虫与AM真菌接种于分根培养系统同一室或分别接种于不同室,AM真菌均能显著降低大豆病情指数和线虫侵染速率,且将二者接种同一室处理的效果大于不同室处理;与只接种SCN的处理相比,接种摩西球囊霉和幼套球囊霉3周后在同室接种SCN处理的根围土壤中胞囊数、根上胞囊数和根内线虫数分别降低了47.4%、58.9%、46.6%和50.5%、67.0%、57.5%,表明AM真菌能显著抑制线虫的发育;摩西球囊霉和幼套球囊霉在一定时间段内诱导了大豆根系过氧化物酶、苯丙氨酸解氨酶、β-1,3-葡聚糖酶及几丁质酶的活性。摩西球囊霉和幼套球囊霉能够诱导大豆植株抵抗大豆胞囊线虫的侵染,既能在同一室的根围局部与SCN竞争侵染位点,又能对不同室的根系诱导产生防御性酶,推测摩西球囊霉和幼套球囊霉拮抗SCN的效应既是局部的,也是系统性的。     

两个紧密连锁的小麦苯丙氨酸解氨酶基因的分离与鉴定

利用一个小麦苯丙氨酸解氨酶基因PCR片段为探针,从小麦核DNA基因库中筛选出一个阳性噬菌体克隆,该克隆含有两个高度同源、紧密连锁、转录方向相同的小麦苯丙氨酸解氨酶基因PAL1与PAL2,它们之间的核酸序列同源性。为93％,相距约7kb,利用PAL1特异片段进行Southern分析,表明该基因在小麦基因组中具有多个拷贝。Northern杂交表明,经秆锈菌接种诱导,苯丙氨酸解氨酶基因在一对小麦抗-感近等基因系中差异表达：抗病等基因系中国春-Sr11携带与接种菌无毒性基因P11相对应的抗病基因Sr11,在接种4d后开始诱导表达,8d后表达量更高;而缺少抗病基因的感病系中国春-sr11接种6d后才开始表达,8d后的表达量与抗病系中6d时相当。用秆锈菌诱导物和几丁质寡聚物处理小麦悬浮细胞,均可在2h内激活苯丙氨酸解氨酶基因表达,但真菌诱导物在早期的诱导活性显著高于几丁质寡聚物。从转录水平证实了小麦苯丙氨酸解氨酶基因在秆锈菌诱导的抗性反应中具有重要作用。     

丛枝菌根真菌摩西管柄囊霉侵染增强番茄对机械损伤的响应

植食性昆虫取食会给植物造成机械损伤并激活植物的防御反应,而与有益微生物共生是否可以增强植物对机械损伤的响应对植物抗虫有重要意义.本研究在番茄根系被丛枝菌根真菌摩西管柄囊霉侵染后,研究机械损伤对番茄防御反应的影响.结果表明: 预先接种菌根真菌的番茄叶片受到机械损伤处理(FD)后,叶片苯丙氨酸解氨酶(PAL)、超氧化物歧化酶(SOD)、过氧化物酶(POD)、多酚氧化酶(PPO)和过氧化氢酶(CAT)活性,以及叶片和根系苯丙氨酸解氨酶基因(PAL)和β-1,3-葡聚糖酶基因(PR2)的转录水平均显著高于只进行机械损伤的处理(D)、只接种摩西管柄囊霉的处理(F),以及既未接种菌根菌也未进行机械损伤的健康番茄植株(CK).虽然D和 F处理也可诱导部分酶活性及基因转录水平升高,但FD处理诱导的防御反应更迅速和强烈.表明丛枝菌根真菌侵染可以警备(prime)番茄对机械损伤做出更快速和强烈的响应.     

AM真菌和镰刀菌对西瓜根系几种酶活性的影响*

在温室盆栽条件下研究了丛枝菌根(Arbuscular Mycorrhiza, AM)真菌Glomus versiforme和西瓜枯萎镰刀菌Fusarium oxysporum f.sp. niveum对西瓜根系中过氧化物酶(POD)、苯丙氨酸解氨酶(PAL)、β-1,3-葡聚糖酶和几丁质酶活性的影响。结果表明,接种AM真菌的西瓜根系中4种酶的活性均高于对照,先接种G. versiforme,后接种F. oxysporum f.sp. niveum处理的4种酶的活性均高于只接种F. oxysporum f.sp. niveum 的处理,且酶的活性峰值出现较早。表明接种G. versiforme 能预先诱导这4种酶的产生,提高其活性,从而提高西瓜对F. oxysporum f.sp. niveum侵染的抗性。接种G. versiforme的感枯萎病西瓜品种“郑杂5号”酶的增加幅度大于抗病品种“京欣1号”的接种处理,说明G. versiforme对提高感病西瓜品种酶活性的作用更大。     

AM真菌和镰刀菌对西瓜根系几种酶活性的影响

在温室盆栽条件下研究了丛枝菌根(Arbuscular Mycorrhiza, AM)真菌Glomus versiforme和西瓜枯萎镰刀菌Fusarium oxysporum f.sp. niveum对西瓜根系中过氧化物酶(POD)、苯丙氨酸解氨酶(PAL)、β-1,3-葡聚糖酶和几丁质酶活性的影响。结果表明,接种AM真菌的西瓜根系中4种酶的活性均高于对照,先接种G. versiforme,后接种F. oxysporum f.sp. niveum处理的4种酶的活性均高于只接种F. oxysporum f.sp. niveum 的处理,且酶的活性峰值出现较早。表明接种G. versiforme 能预先诱导这4种酶的产生,提高其活性,从而提高西瓜对F. oxysporum f.sp. niveum侵染的抗性。接种G. versiforme的感枯萎病西瓜品种“郑杂5号”酶的增加幅度大于抗病品种“京欣1号”的接种处理,说明G. versiforme对提高感病西瓜品种酶活性的作用更大。     

AM真菌和镰刀菌对西瓜根系几种酶活性的影响

在温室盆栽条件下研究了丛枝菌根（Arbuscular Mycorrhiza,AM)真菌Glomus versiforme和西瓜枯萎镰刀菌Fusarium oxysporum f.sp.niveum对西瓜根系中过氧化物酶（POD）,苯丙氨酸解氨酶（PAL）,β－1,2－葡聚糖酶和几丁质酶活性的影响。结果表明,接种AM真菌的西瓜根系中4种酶的活性均高于对照,先接种G.versiforme,后接种F.oxysporum f.sp.niveum处理的4种酶的活性均高于只接种F.oxysporum f.sp.niveum的处理,且酶的活性峰值出现较早,表明接种G.versiforme能预先诱导这4种酶的产生,提高其活性,从而提高西瓜对F.oxysporum f.sp.niveum侵染的抗性,接种G.versiforme的感枯萎病西瓜品种“郑杂5号”酶的增加幅度大于抗病品种“京欣1号”的接种处理,说明G.versiforme对提高感病西瓜品种酶活性的作用更大。     

AM fungi might affect the root morphology of maize by increasing indole-3-butyric acid biosynthesis

Inoculation of maize ( Zea mays L.) with the arbuscular mycorrhizal (AM) fungus Glomus intraradices resulted in a distinct root phenotype ca 10 days after inoculation. Although the fresh weight of inoculated and control roots was about the same, the AM-inoculated roots showed a significant increase in the percentage of lateral fine roots. This increase coincided with an increase in free indole-3-butyric acid (IBA) as well as an increase in IBA synthesis. At later time points (31 days after inoculation), the free IBA content was not increased in infected roots; however, the fraction of bound IBA increased compared to controls. The phenotype of mycorrhizal maize roots could be mimicked by IBA applied exogenously to non-mycorrhizal roots. Addition of trifluoro-IBA (TFIBA), an inhibitor of IBA-induced root growth and lateral root induction, simultaneously with IBA resulted in a phenotype resembling that of untreated controls. In roots treated with TFIBA the inoculation with AM fungi did not increase the formation of fine roots. The TFIBA treatment also reduced endogenous free IBA and the AM infection rate in mycorrhizal roots. The results are discussed with respect to a possible role of IBA in the establishment of AM symbiosis.     

Chitinase in roots of mycorrhizal Allium porrum: regulation and localization

Chitinase (EC 3.2.1.14) activity was measured in roots of Allium prorrum L. (leek) during development of a vesicular-arbuscular mycorrhizal symbiosis with Glomus versiforme (Karst.) Berch. During the early stages of infection, between 10 and 20 d after inoculation, the specific activity of chitinase was higher in mycorrhizal roots than in the uninfected controls. However, 60–90 d after inoculation, when the symbiosis was fully established, the mycorrhizal roots contained much less chitinase than control roots. Chitinase was purified from A. porrum roots. An antiserum against beanleaf chitinase was found to cross-react specifically with chitinase in the extracts from non-mycorrhizal and mycorrhizal A. porrum roots. This antiserum was used for the immunocytochemical localization of the enzyme with fluorescent and gold-labelled probes. Chitinase was localized in the vacuoles and in the extracellular spaces of non-mycorrhizal and mycorrhizal roots. There was no immunolabelling on the fungal cell walls in the intercellular or the intracellular phases. It is concluded that the chitin in the fungal walls is inaccessible to plant chitinase. This casts doubts on the possible involvement of this hydrolase in the development of the mycorrhizal fungus. However, fungal penetration does appear to cause a typical defense response in the first stages that is later depressed.     

Soluble and membrane symbiosis-related polypeptides associated with the development of arbuscular mycorrhizas in tomato (Lycopersicon esculentum)

To analyse the effect of arbuscular mycorrhizal (AM) colonization on tomato gene expression, two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) patterns of crude extracts, soluble and membrane proteins of tomato roots, either mycorrhizal and the AM fungus Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe or non-mycorrhizal, have been compared. In the three fractions analysed, AM colonization induced up-regulation with down-regulation of the synthesis of polypeptides already present in tomato roots and induction of some new polypeptides. Separation of root extracts into soluble and membrane fractions allowed us to identify two soluble, and five membrane-bound, newly induced polypeptides in AM roots. Comparison of the protein patterns of AM roots with those of the external mycelium of G. mosseae showed that one of the newly induced polypeptides might correspond to a fungal polypeptide. By using this experimental approach, we have been able to detect 44 polypeptides that are differentially displayed in tomato roots as a consequence of the establishment of the AM symbiosis.     

Improved tolerance of maize plants to salt stress by arbuscular mycorrhiza is related to higher accumulation of soluble sugars in roots

The effect of colonization with the arbuscular mycorrhizal (AM) fungus Glomus mosseae (Nicol. & Gerd.) Gerdemann & Trappe on the growth and physiology of NaCl-stressed maize plants ( Zea mays L. cv. Yedan 13) was examined in the greenhouse. Maize plants were grown in sand with 0 or 100 mM NaCl and at two phosphorus (P) (0.05 and 0.1 mM) levels for 34 days, following 34 days of non-saline pre-treatment. Mycorrhizal plants maintained higher root and shoot dry weights. Concentrations of chlorophyll, P and soluble sugars were higher than in non-mycorrhizal plants under given NaCl and P levels. Sodium concentration in roots or shoots was similar in mycorrhizal and non-mycorrhizal plants. Mycorrhizal plants had higher electrolyte concentrations in roots and lower electrolyte leakage from roots than non-mycorrhizal plants under given NaCl and P levels. Although plants in the low P plus AM fungus treatment and those with high P minus AM fungus had similar P concentrations, the mycorrhizal plants still had higher dry weights, soluble sugars and electrolyte concentrations in roots. Similar relationships were observed regardless of the presence or absence of salt stress. Higher soluble sugars and electrolyte concentrations in mycorrhizal plants suggested a higher osmoregulating capacity of these plants. Alleviation of salt stress of a host plant by AM colonization appears not to be a specific effect. Furthermore, higher requirement for carbohydrates by AM fungi induces higher soluble sugar accumulation in host root tissues, which is independent of improvement in plant P status and enhances resistance to salt-induced osmotic stress in the mycorrhizal plant.     

Effects of liming and mycorrhizal colonization on soil phosphate depletion and phosphate uptake by maize (Zea mays L.) and soybean (Glycine max L.) grown in two tropical acid soils

The effects of liming and inoculation with the arbuscular mycorrhizal fungus, Glomus intraradices Schenck and Smith on the uptake of phosphate (P) by maize (Zea mays L.) and soybean (Glycine max [L.] Merr.) and on depletion of inorganic phosphate fractions in rhizosphere soil (Al-P, Fe-P, and Ca-P) were studied in flat plastic containers using two acid soils, an Oxisol and an Ultisol, from Indonesia. The bulk soil pH was adjusted in both soils to 4.7, 5.6, and 6.4 by liming with different amounts of CaCO₃.In both soils, liming increased shoot dry weight, total root length, and mycorrhizal colonization of roots in the two plant species. Mycorrhizal inoculation significantly increased root dry weight in some cases, but much more markedly increased shoot dry weight and P concentration in shoot and roots, and also the calculated P uptake per unit root length. In the rhizosphere soil of mycorrhizal and non-mycorrhizal plants, the depletion of Al-P, Fe-P, and Ca-P depended in some cases on the soil pH. At all pH levels, the extent of P depletion in the rhizosphere soil was greater in mycorrhizal than in non-mycorrhizal plants. Despite these quantitative differences in exploitation of soil P, mycorrhizal roots used the same inorganic P sources as non-mycorrhizal roots. These results do not suggest that mycorrhizal roots have specific properties for P solubilization. Rather, the efficient P uptake from soil solution by the roots determines the effectiveness of the use of the different soil P sources. The results indicate also that both liming and mycorrhizal colonization are important for enhancing P uptake and plant growth in tropical acid soils.     

Role of arbuscular mycorrhizal symbiosis in root mineral uptake under CaCO3 stress

This study investigated the effects of increasing CaCO(3) concentrations (0, 5, 10, 20?mM) on arbuscular mycorrhizal (AM) symbiosis establishment as well as on chicory root growth and mineral nutrient uptake in a monoxenic system. Although CaCO(3) treatments significantly decreased root growth and altered the symbiosis-related development steps of the AM fungus Rhizophagus irregularis (germination, germination hypha elongation, root colonization rate, extraradical hyphal development, sporulation), the fungus was able to completely fulfill its life cycle. Even when root growth decreased more drastically in mycorrhizal roots than in non-mycorrhizal ones in the presence of high CaCO(3) levels, the AM symbiosis was found to be beneficial for root mineral uptake. Significant increases in P, N, Fe, Zn and Cu concentrations were recorded in the mycorrhizal roots. Whereas acid and alkaline phosphatase enzymatic activities remained constant in mycorrhizal roots, they were affected in non-mycorrhizal roots grown in the presence of CaCO(3) when compared with the control.