Molecular Characterization of Arbuscular mycorrhizal Symbiosis for Defense,Nutrient Absorption andSecondary Metabolism in Plants简

Arbscular mycorrhiza （AM）,a symbiosis between plants and members of fungi Glomeromycota,improves the resistance,nutrition and material metabolism of plant.Arbuscules generated by symbiotic development,is the main site of nutrient exchange and genetic material recombination,resulting in physiological changes and gene expression regulation.AM regulates pathogenesis-related protein （PRs） genes and antioxidant enzyme genes against biotic and abiotic stresses.Nutrient exchange induced by AM is directly involved in uptake,transformation and utilization of nutrient elements in plants.Importantly,transporter genes play an important role in phosphate,nitrogen and carbon acquisition.In AM interactions,phosphate transporter （PT） genes,from both arbuscular mycorrhizal fungi and plant root,are induced and there product promote phosphate acquisition; increasing expression of ammonium transporter （AMT） genes and arginine biosynthesis/degradation enzyme genes is in charge of nitrogen acquisition;and promotion mechanism of carbon acquisition is involved in up-regulation of sugar transporter genes.In addition,secondary metabolites,functioned as signal moleculars and defense compounds,are increased with development of AM symbiont by up-regulating related synthetic genes based on different promotion mechanism.Taken together,molecular regulation of plant and arbuscular mycorrhizal fungi,induced by infection process,stimulate plant nutrient acquisition and resist to biotic/abiotic stress.     

Ascophyllum nodosum Extract and Its Organic Fractions Stimulate Rhizobium Root Nodulation and Growth of Medicago sativa (Alfalfa)

The effects of the seaweed Ascophyllum nodosum extracts (ANE) on nitrogen (N)–fixing nodules and growth of alfalfa plants were studied under greenhouse conditions. The treatment of alfalfa roots increased the number of total nodules per plant with ANE (69%) and organic sub-fractions methanol (20%) and chloroform (35%) at 1 g L^?1 concentration. The number of functional nodules was greater per plant in ANE (36%) and its organic sub-fraction chloroform (105%). Maximum increase in shoot length was observed in ANE-treated plants (42%) and chloroform-treated plants (42%). Root length was longer in the chloroform fraction (15%), whereas the shoot dry-weight accumulation was greater in plants treated with ANE (118%), methanol (85%), and chloroform (85%) than the control. Root dry-weight accumulation increased in plants treated with ANE (118%) and chloroform (69%) compared to the control. Further studies are under way to identify the chemical components in ANE and organic fractions.     

铝胁迫和丛枝菌根真菌对樟树幼苗生长的影响

为了探讨丛枝菌根缓解铝（Al）毒对三峡库区林木胁迫的机理,该文研究了使用Al3+浓度为0、0.5、8和15 mmol/L的酸性Al溶液胁迫10周后,接种和不接种丛枝菌根真菌的樟树幼苗的形态、生物量以及不同器官的磷（P）含量等指标.结果表明,在对照（c(Al 3+)=0 mmol/L）和轻度胁迫（c(Al3+)=0.5 mmol/L）下,植株地上部分和地下部分的形态、生物量和不同器官的P含量等大部分指标,接种的植株显著好于不接种的植株;而在中度胁迫（c(Al3+)=8 mmol/L）和重度胁迫（c(Al3+)=15 mmol/L）下,接种植株的上述指标要略好或接近于不接种的植株.说明接种丛枝菌根赋予植株一定的抗Al毒特性.      

The significant contribution of mycorrhizal fungi and earthworms to maize protection and phytoremediation in Cd-polluted soils

Mycorrhizal fungi and earthworms can individually or interactively influence plant growth and heavy metal uptake. The influence of earthworms and arbuscular mycorrhizal (AM) fungi either alone or in combination on maize (Zea mays L.) growth and cadmium (Cd) uptake was investigated in a calcareous soil artificially spiked with Cd. Soils were contaminated with Cd (10 and 20 mg Cd kg⁻¹), inoculated or un-inoculated with the epigeic earthworm Lumbricus rubellus and two AM fungal species (Rhizophagus irregularis and Funneliformis mosseae) for two months of growth under greenhouse conditions. Generally, earthworms alone increased both shoot P uptake and biomass but decreased shoot Cd concentration and root Cd uptake. AM fungi individually often increased total maize P uptake, declined shoot Cd concentration, and consequently produced higher total biomass. However, R. irregularis enhanced shoot Cd uptake at low Cd level and root Cd uptake at high Cd level. In plants inoculated with F. mosseae species, earthworms increased shoot biomass and Cd uptake, decreased root biomass and Cd uptake at all Cd levels, and increased shoot Cd concentration at low Cd level. In plants colonized by R. irregularis species, however, earthworm addition decreased maize biomass only at high Cd level and root Cd concentration and total maize Cd uptake at both Cd levels. Earthworm activity decreased Cd transfer from the soil to maize roots at low Cd level, but this was counterbalanced in the presence of F. mosseae. Mycorrhizal symbiosis significantly reduced the transfer of Cd from roots to shoots, independence of earthworm effect. Overall, it is concluded that L. rubellus and AM fungi, in particular F. mosseae isolate, improved maize tolerance to Cd toxicity both individually and interactively by increasing plant growth and P nutrition, and restricting Cd transfer to the aboveground biomass. Consequently, the single and interactive effects of the two soil organisms might potentially be important not only in protecting maize plants against Cd toxicity, but also in Cd phytostabilization in soils polluted by this highly toxic metal.     

基于协同-共生视角的茶产业生态圈协调发展实证分析

随着产业结构的调整与优化,产业内各要素逐步由相互竞争的失衡状态向互相依存、协同共生的结构转变。本研究基于协同共生视角,以福建省特色农业产业茶产业为研究对象,研究生产者、消费者和分解者三者关系结构对茶产业生态圈协同发展的影响路径。结果表明：生产者创新能力、消费者需求水平对茶产业生态圈协同进化发展具有显著正向影响;金融服务、平台服务等服务支持对茶产业生态圈协同进化无直接效应,但其通过影响产业共生性来影响茶产业生态圈的协同进化水平,产业共生性在其中扮演完全中介角色。基于此,从提升生产者创新能力、树立消费需求导向、完善服务支持和构建资源利益共享机制等方面提出对策建议。     

Impact of arbuscular mycorrhizal fungi on the growth and expression of gene encoding stress protein – metallothionein BnMT2 in the non‐host crop Brassica napus L.

Arbuscular mycorrhizal (AM) fungi are an important component of the soil biota in most agroecosystems, and their association can directly or indirectly affect the diversity of soil microorganisms, nutrient cycling, and growth of host plants. Since not all crops are symbiotic, we hypothesized that the presence of AM fungi can: (1) inhibit the growth of non‐host plants by resulting in biotic stress, or (2) promote their growth indirectly by increased nutrient mobilization. These hypotheses were tested in the present study on the non‐mycorrhizal crop canola (Brassica napus L.) in the presence and absence of other autochthonous soil microorganisms. The soil was inoculated with a mixture of AM fungi (Acaulospora longula, Glomus geosporum, G. mosseae, Scutellospora calospora) and as a control, a non‐inoculated soil was used. The impact of inoculation on plant growth (biomass production, nutrient concentrations) and expression of the stress protein metallothionein gene BnMT2 was investigated in the shoots. B. napus L. did not form mycorrhizal associations on its roots, but its growth was promoted after inoculation with AM fungi. In the soil with autochthonic microorganisms, growth inhibition after inoculation was observed compared to the control. The concentrations of N, P, K, and S in the shoot were always significantly increased after inoculation with AM fungi. However, this was partly combined with reduced growth and thereby decreased total uptake of nutrients. Expression of BnMT2 in the leaves was increased after inoculation with AM spores at the soil devoid of indigenous microorganisms, but decreased in their presence. The expression of stress proteins (BnMT2) significantly increased with increasing length and biomass of shoots. In conclusion, the inhibition of the non‐host plant B. napus L. following inoculation with AM fungi was confirmed, however, only in combination with autochthonous microorganisms. Growth promotion of B. napus L. in the presence of AM fungi in the absence of autochthonous soil microorganisms suggest that plant growth depression in the presence of AM fungi was based on interactive effects of AM fungi with the autochthonous microorganisms in the soil rather than on a direct impact of the AM fungi.     

蚕豆/玉米间作接种AM真菌和根瘤菌对外源有机磷利用的影响

本研究以植酸钠为有机磷源,利用根系不同分隔方式的盆栽实验研究了蚕豆/玉米问作体系中,接种根瘤菌、AH真菌(Glomus mosseae)和双接种对间作体系利用有机磷的影响.结果表明:接种AM真菌使蚕豆和玉米的根际磷酸酶活性增加,显著提高了蚕豆/玉米间作体系对有机磷的吸收,双接种处理蚕豆和玉米总吸磷量平均比单接AH真菌和根瘤菌平均分别增加了11.7%和90.8%;相对干其它处理,在双接种条件下蚕豆对玉米吸收有机磷的促进作用更显著,不分隔和尼龙网分隔处理玉米的吸磷量比完全分隔处理分别提高43.4%(5.29mg)和17.9%(2.18 mg);在问作体系中同时接种AM真菌和根瘤菌能提高玉米的菌根侵染率,间作产量优势显著高于单接AM真菌和根瘤菌.     

春兰菌根的显微结构观察

应用石蜡切片法,借助于光学显微镜观察春兰无菌组培苗、接菌组培苗的根及野生状态下的新生营养根、老根,结果表明:接菌组培苗的根及野生状态下的新生营养根、老根,其皮层组织细胞内有大量的菌丝结等兰科菌根的典型结构,而无菌组培苗的根则无菌丝、菌丝结等结构.菌根真菌自外皮层薄壁通道细胞侵入根的皮层细胞,春兰菌根是典型的地生兰菌根.     

Nodulation and root growth of forage legumes sown into tall fescue swards

Establishing forage legumes into endophyte‐infected tall fescue (Festuca arundinacae Schreb.) pastures is problematic, especially in well‐established stands. A oversowing field experiment determined if this problem was because of poor nodulation. Four renovation techniques, clipped sward (treatment A), herbicided + rye seeding in the previous autumn (treatment B), herbicided in the autumn and spring (treatment C) and herbicided to suppress the sward (treatment D), were investigated to determine their effect on nodulation and root growth of lucerne (Medicago sativa L.), red clover (Trifolium pratense L.) and white clover (T. repens L.) at 16, 22 and 29 d after sowing the legumes. A pot experiment was also conducted under optimal growth conditions and using the same soil to determine the nodulation and root growth potentials of these legume species. At adequate rhizobial populations (>6 × 10⁴ cfu g^?1 soil), substantial nodulation of all species occurred by 29 d after sowing in treatments C and D, whereas nodulation of clovers was usually reduced in treatment A. Total root lengths for all sampling dates, species and treatments were severely restricted, especially under treatment A. A general correspondence of nodulation with root growth was observed for all species, with high correlations (r ≥ 0·85) between these variables for all legume species and treatments, suggesting that soil moisture, and possibly competition for light, were the limiting factors. These results demonstrate that weak stands of forage legumes, typically found when sown into tall fescue swards, are probably not because of inadequate nodulation. Rather, inhibition of root growth by detrimental physical/chemical conditions or allocation of limited photosynthate to shoots instead of roots is suggested.     

大豆根瘤菌HH103ΩNopAAΩNopD双突变体构建及结瘤能力鉴定

大豆—根瘤菌的共生模式为大豆提供了丰富的氮源。根瘤菌Ⅲ型效应因子是影响共生结瘤的关键信号分子之一,通过对HH103ΩNopAA与HH103ΩNopD的结瘤鉴定表明两个突变体对绥农14和ZYD00006的宿主亲和性不同,而后通过三亲杂交方法在HH103ΩNopAA基础上构建HH103ΩNopAAΩNopD的双突变体。利用绥农14与野生豆ZYD00006对突变体进行结瘤鉴定,HH103ΩNopAAΩNopD的根瘤数与根瘤重与HH103ΩNopAA无显著性差异。而后利用前期收集的100份大豆资源进行结瘤鉴定,分析NopAA与NopD的突变在不同遗传背景下的大豆品种的结瘤特性,绝大多数品种根瘤数明显减少,部分品种根瘤数在接种单突变体与双突变体存在显著差异。该研究为后续解析NopAA与NopD的共生信号传导以及根瘤菌与大豆品种亲和性提供新的思路。同时可以根据基因型的差异,筛选与不同根瘤菌均有较高亲和性的大豆品种,为进一步培育高结瘤、高固氮的大豆品种提供支撑。