Arbuscular mycorrhizal symbiosis facilitates apricot seedling(Prunus sibirica L.)growth and photosynthesis in northwest China

Arbuscular mycorrhizal(AM)fungi can successfully enhance photosynthesis(P_(n))and plants growth in agricultural or grassland ecosystems.However,how the symbionts affect species restoration in sunlight-intensive areas remains largely unexplored.Therefore,this study’s objective was to assess the effect of AM fungi on apricot seedling physiology,within a specific time period,in northwest China.In 2010,an experimental field was established in Shaanxi Province,northwest China.The experimental treatments included two AM fungi inoculation levels(0 or 100 g of AM fungal inoculum per seedling),three shade levels(1900,1100,and 550µmol m^(−2) s^(−1)),and three ages(1,3,and 5 years)of transplantation.We examined growth,Pn,and morphological indicators of apricot(Prunus sibirica L.)seedling performances in 2011,2013,and 2015.The colonization rate in mycorrhizal seedlings with similar amounts of shade is higher than the corresponding controls.The mycorrhizal seedling biomass is significantly higher than the corresponding non-mycorrhizal seedling biomass.Generally,P_(n),stomatal conductance(G_(s)),transpiration rate(T_(r)),and water use efficiency are also significantly higher in the mycorrhizal seedlings.Moreover,mycorrhizal seedlings with light shade(LS)have the highest Pn.WUE is increased in non-mycorrhizal seedlings because of the reduction in T_(r),while T_(r) is increased in mycorrhizal seedlings with shade.There is a significant increase in the N,P,and K fractions detected in roots compared with shoots.This means that LS had apparent benefits for mycorrhizal seedlings.Our results also indicate that AM fungi,combined with LS,exert a positive effect on apricot behavior.

Symbiosis between fungi and the hybrid Cymbidium and its mycorrhizal microstructures

Tissue culture seedlings of the hybrid Cymbidium were inoculated with six different fungal strains, isolated from the roots of different wild terrestrial orchids. About three months later, the average increment of fresh weight of seedlings inoculated with strains CF1, CF3 and CF12 were respectively 130.26%, 345.65% and 153.34% while that of the control was only 88.40%. The differences between the three treatments and the control were statistically significant （α = 0.05）, highlighting the treatment with strain CF3 （α = 0.01）. In addition, the three strains were obtained by re-isolating. Pelotons, regarded as typical structures of orchid mycorrhiza, were also found in the inoculating roots under a microscope. It seems that the strains of CF1, CF3, and CF12 are associated with the hybrid Cymbidium and supplied the orchid with nutrition. It can be confirmed that the three strains are beneficial for the seedlings of this hybrid.

Arbuscular mycorrhizal symbiosis and ecosystem processes: Prospects for future research in tropical soils

Arbuscular mycorrhizal fungi (AMF) are more widely distributed and can associate with a wide range of plant species. AMF are keystone organisms that form an interface between soils and plant roots. They are also sensitive to environmental changes. AMF are important microbial symbioses for plants under conditions of P-limitation. The AMF are crucial for the functioning of terrestrial ecosystems as they form symbiotic interactions with plants. Mycorrhizal fungi are known to influence plant diversity patterns in a variety of ecosystems globally. AMF hyphae form an extensive network in the soil. The length is a common parameter used to quantifying fungal hyphae. The mycelial network of AM fungi extends into the soil volume and greatly increases the surface area for the uptake of immobile nutrients. Also, AM symbioses improve plants tolerance to drought and enhance plants’ tolerance of or resistance to root pathogens. Also, the networks of AM hyphae play a crucial role in the formation of stable soil aggregates and in the building up of a macroporous structure of soil that allows penetration of water and air and thereby prevents erosion. The functioning of AMF symbiosis is mediated by direct and indirect effects of biotic and abiotic factors of the surrounding rhizosphere, the community, and the ecosystem. AMF have great potential in the restoration of disturbed land and low fertility soil. However, despite the importance of AMF to terrestrial ecosystems, little is known about the effects of environmental changes on AMF abundance, activity and the impact of these changes on the ecosystem services. Therefore, it is important to gain a clearer understanding of the effects of environmental changes on the AM fungal species to guide conservation and restoration efforts.

Development of Preparative Chromatography for Proteomic Approach of Mycorrhizal Symbiosis

Although mechanism of symbiosis between arbuscular mycorrhizal fungi (AMF) and host plants has been investigated by genetic analysis, very little knowledge has been obtained because genome analysis of AMF is not perfect yet. Thus, we tried to develop mass purification of proteins using preparative chromatography in order to accelerate roteomic analysis of proteins related to mycorrhizal symbiosis, such as 24 and 53 kDa proteins. In particular, our data showed that 53 kDa proteins would be restrictively expressed when mycorrhizal fungi and host plants were stressed. However, 24 kDa proteins, which appear to be a usable indicator for the existence of various my-corrhizal fungi, were habitually detected in not only AMF but also other mycorrhizal fungi such as ectomycorrhizal fungi (EF). Moreover, we discovered new preparative chromatographical techniques for isolation and mass purification of those proteins. We are convinced that this chromato-graphical technique will greatly contribute to proteomic approach of mycorrhizal symbiosis.

Signaling events during initiation of arbuscular mycorrhizal symbiosis

Under nutrient-limiting conditions, plants will enter into symbiosis with arbuscular mycorrhizal （AM） fungi for the enhancement of mineral nutrient acquisition from the surrounding soil. AM fungi live in close, intracellular association with plant roots where they transfer phosphate and nitrogen to the plant in exchange for carbon. They are obligate fungi, relying on their host as their only carbon source. Much has been discovered in the last decade concerning the signaling events during initiation of the AM symbiosis, including the identification of signaling molecules generated by both partners. This signaling occurs through symbiosis-specific gene products in the host plant, which are indispensable for normal AM development. At the same time, plants have adapted complex mechanisms for avoiding infection by pathogenic fungi, including an innate immune response to general microbial molecules, such as chitin present in fungal cell walls. How it is that AM fungal colonization is maintained without eliciting a defensive response from the host is still uncertain. In this review, we present a summary of the molecular signals and their elicited responses during initiation of the AM symbiosis, including plant immune responses and their suppression.

Screening for differentially expressed genes in Anoectochilus roxburghii (Orchidaceae) during symbiosis with the mycorrhizal fungus Epulorhiza sp.

Mycorrhizal fungi promote the growth and development of plants, including medicinal plants. The mechanisms by which this growth promotion occurs are of theoretical interest and practical importance to agriculture. Here, an endophytic fungus （AR-18） was isolated from roots of the orchid Anoectochilus roxburghii growing in the wild, and identified as Epulorhiza sp. Tissue-cultured seedlings of A. roxburghii were inoculated with AR-l 8 and co-cultured for 60 d. Endotrophic mycorrhiza formed and the growth of A. roxburghii was markedly promoted by the fungus. To identify genes in A. roxburghii that were differentially expressed during the symbiosis with AR-18, we used the differential display reverse transcription polymerase chain reac- tion （DDRT-PCR） method to compare the transcriptomes between seedlings inoculated with the fungus and control seedlings. We amplified 52 DDRT-PCR bands using 15 primer combinations of three anchor primers and five arbitrary primers, and nine bands were re-amplified by double primers. Reverse Northern blot analyses were used to further screen the bands. Five clones were up-regulated in the symbiotic interaction, including genes encoding a uracil phosphoribosyltransferase （UPRTs; EC 2.4.2.9） and a hypothetical protein. One gene encoding an amino acid transmembrane transporter was down-regulated, and one gene encoding a tRNA-Lys （trnK） and a maturase K （matK） pseudogene were expressed only in the inoculated seedlings. The possible roles of the above genes, especially the UPRTs and marK genes, are discussed in relation to the fungal interaction. This study is the first of its type in A. roxburghii.

The RNAome landscape of tomato during arbuscular mycorrhizal symbiosis reveals an evolving RNA layer symbiotic regulatory network

Arbuscular mycorrhizal symbiosis(AMS)is an ancient plant-fungus relationship that is widely distributed in terrestrial plants.The formation of symbiotic structures and bidirectional nutrient exchange requires the regulation of numerous genes.However,the landscape of RNAome during plant AMS involving different types of regulatory RNA is poorly understood.In this study,a combinatorial strategy utilizing multiple sequencing approaches was used to decipher the landscape of RNAome in tomato,an emerging AMS model.The annotation of the tomato genome was improved by a multiple-platform sequencing strategy.A total of 3,174 protein-coding genes were upregulated during AMS,42%of which were alternatively spliced.Comparative-transcriptome analysis revealed that genes from 24 orthogroups were consistently induced by AMS in eight phylogenetically distant angiosperms.Seven additional orthogroups were specifically induced by AMS in all surveyed dicot AMS host plants.However,these orthogroups were absent or not induced in monocots and/or non-AMS hosts,suggesting a continuously evolving AMS-responsive network in addition to a conserved core regulatory module.Additionally,we detected 587 lncRNAs,ten miRNAs,and 146 circRNAs that responded to AMS,which were incorporated to establish a tomato AMSresponsive,competing RNA-responsive endogenous RNA(ceRNA)network.Finally,a tomato symbiotic transcriptome database(TSTD,https://efg.nju.edu.cn/TSTD)was constructed to serve as a resource for deep deciphering of the AMS regulatory network.These results help elucidate the reconfiguration of the tomato RNAome during AMS and suggest a sophisticated and evolving RNA layer responsive network during AMS processes.

Medicago AP2-Domain Transcription Factor WRI5a Is a Master Regulator of Lipid Biosynthesis and Transfer during Mycorrhizal Symbiosis

Most land plants have evolved a mutualistic symbiosis with arbuscular mycorrhiza (AM)fungi that improve nutrient acquisition from the soil.In return,up to 20% of host plant photosynthate is transferred to the mycorrhizal fungus in the form of lipids and sugar.Nutrient exchange must be regulated by both partners in order to maintain a reliable symbiotic relationship.However,the mechanisms underlying the regulation of lipid transfer from the plantto the AM fungus remain elusive.Here,we show that the Medicago truncatula AP2/EREBP transcription factor WRI5a,and likely its two homologs WRI5b/Erfl and WRI5c,are master regulators of AM symbiosis Controlling lipid transfer and periarbuscular membrane formation.We found that WRI5a binds AW-box cis-regulatory elements in the promoters of M.truncatula STR,which encodes a periarbuscular membrane-localized ABC transporter required for lipid transfer from the plant to the AM fungus, and MtPT4,whichr encodes a phosphate transporter required for phosphate transfer from the AM fungus to the plant.The hairy roots of the M.truncatula wti5a mutant and RNAi composite plants displayed impaired arbuscule formation,whereas overexpression of WRI5a resulted in enhanced expression of STR and MtPT4,suggesting that WRI5a regulates bidirectional symbiotic nutrient exchange.Moreover,we found that WRI5a and RAM1(Required for Arbuscular Mycorrhization symbiosis 1),which encodes a GRASdomain transcription factor,regulate each other at the transcriptional level,forming a positive feedback loop for regulatingAM symbiosis.Collectively,our data suggest a role for WRI5a in controlling bidirectional nutrient exchange and periarbuscular membrane formation via the regulation of genes involved in the biosynthesis of fatty acids and phosphate uptake in arbuscule-containing cells.

A Rice GRAS Gene Has an Impact on the Success of Arbuscular Mycorrhizal Colonization

Arbuscular mycorrhiza?(AM) is one of the most spread symbiosis established between 80% of land plants and soil fungi belonging to the Glomeromycota. Molecular determinants involved in the formation of arbuscular mycorrhizas are still poorly understood. It has been demonstrated that in both Legumes and rice plants, several GRAS transcription factors are directly involved in both mycorrhizal signaling and colonization, namely NSP1, NSP2, RAM1, DELLA, DELLA-interacting protein (DIP1) and RAD1. Here, we focused on a rice GRAS protein, named Arbuscular Mycorrhizal 18 (OsAM18), previously identified as specifically expressed in rice mycorrhizal roots, and considered as an AM-specific gene. Phylogenetic analysis revealed that OsAM18 had a peculiar amino acid sequence, which clustered with putative SCARECROW proteins, even though it formed a separate branch. Allelic osma18 mutant displayed a drastic reduction in mycorrhizal colonization in-tensity and in arbuscule abundance, as mirrored by OsPT11 expression level. Non-mycorrhizal osam18 plants displayed a comparable plant development and root apparatus compared with the WT, while mycorrhizal osam18 mutants showed a reduction of plant biomass compared with mycorrhizal WT plants. The results suggest that OsAM18?is a rice protein, which is likely to have an impact not only on the colonization process and AM functionality, but also on the systemic effects of the AM symbiosis.

Transcriptome analysis of the symbiosis-related genes between Funneliformis mosseae and Amorpha fruticosa

Arbuscular mycorrhizal fungi(AMF) can colonize and form associations with the roots of Amorpha fruticosa L.(desert false indigo). Various genes are induced during the symbiotic process. In this study, de novo transcriptome sequencing using RNA-seq was conducted for the first time for a comprehensive analysis of AMF-A. fruticosa symbionts at the transcript level. We obtained 12 G of raw data from illumina sequencing and recovered 115,786 unigenes with an average length of547 bp, among them 41,848 of significance. A total of2460 diffexpression genes were identified, including 1579 down-regulated and 881 up-regulated genes. A threshold for false discovery rate of \ 0.001 and fold change of [ 1 determined significant differences in gene expression.Using these criteria, we screened 285 significant differentially expressed genes, of which 82 were up-regulated and203 down-regulated. The 82 up-regulated genes were classified according to their functions and assigned into seven categories: stress and defense, metabolism, signaling transduction, protein folding and degradation, energy,protein synthesis, and transcription. The 203 down-regulated genes were screened according to fold change [ 2,and 50 highly significant down-regulated genes were obtained related to stress and defense. The results of this study will provide a useful foundation for further investigation on the metabolic characteristics and molecular mechanisms of AMF associations with leguminous woody shrubs.

Effects of microplastic polystyrene,simulated acid rain and arbuscular mycorrhizal fungi on Trifolium repens growth and soil microbial community composition

Microplastic pollution is a global and ubiquitous environmental problem in the oceans as well as in the terrestrial environment.We examined the fate of microplastic polystyrene(MPS)beads in experimental soil in the presence and absence of symbiotic arbuscular mycorrhizal fungi(AMF)and simulated acid rain(SAR)to determine whether the combinations of these three factors altered the growth of white clover Trifolium repens.We found that MPS,SAR,or AMF added singly to soil did not alter T.repens growth or yields.In contrast,MPS and AMF together significantly reduced shoot biomass,while SAR and MPS together significantly reduced soil available phosphorus independent of AMF presence.Microplastic polystyrene,AMF,and SAR together significantly reduced soil NO_(3)^(-)-N.Arbuscular mycorrhizal fungi added singly also enriched the beneficial soil bacteria(genus Solirubrobacter),while MPS combined with AMF significantly enriched the potential plant pathogenic fungus Spiromastix.Arbuscular mycorrhizal fungi inoculation with MPS increased the abundance of soil hydrocarbon degraders independent of the presence of SAR.In addition,the abundance of soil nitrate reducers was increased by MPS,especially in the presence of AMF and SAR.Moreover,SAR alone increased the abundance of soil pathogens within the fungal community including antibiotic producers.These findings indicate that the coexistence of MPS,SAR,and AMF may exacerbate the adverse effects of MPS on soil and plant health.

Responses of arbuscular mycorrhizal fungi to straw return and nitrogen fertilizer reduction in a rainfed maize field

Straw return can be used to reduce fertilizer input and improve agricultural sustainability and soil health.However,how straw return and reduced fertilizer application affect beneficial soil microbes,particularly arbuscular mycorrhizal fungi(AMF),remains poorly understood.Here,we conducted a five-year field experiment in a rainfed maize field on the Loess Plateau of northwestern China.We tested four treatments with straw return combined with four nitrogen(N)application rates,i.e.,100%,80%,60%,and 0%of the common N application rate(225 kg N ha^(-1)year^(-1))in this region,and two reference treatments(full or no N application),with three replicates for each treatment.Mycorrhizal colonization was quantified and AMF communities colonizing maize roots were characterized using Illumina sequencing.Forty virtual taxa(VTs)of AMF were identified in root samples,among which VT113(related to Rhizophagus fasciculatus)and VT156(related to Dominikia gansuensis)were the predominant taxa.Both root length colonization and AMF VT richness were sensitive to N fertilization,but not to straw return;furthermore,both gradually increased with decreasing N application rate.The VT composition of the AMF community was also affected by N fertilization,but not by straw return,and the community variation could be well explained by soil available N and phosphorus concentrations.Additionally,60%,80%,and full N fertilization produced similar maize yields.Thus,our study revealed the response patterns of AMF to straw return and N fertilizer reduction and showed that straw return combined with N fertilizer reduction may be a promising practice to maintain mycorrhizal symbiosis concomitantly with crop productivity.

Arbuscular mycorrhizal fungi regulate plant mineral nutrient uptake and partitioning in iron ore tailings undergoing eco-engineered pedogenesis

Excess available K and Fe in Fe ore tailings with organic matter amendment and water-deficiencies may restrain plant colonization and growth,which hinders the formation of eco-engineered soil from these tailings for sustainable and cost-effective mine site rehabilitation.Arbuscular mycorrhizal(AM)fungi are widely demonstrated to assist plant growth under various unfavorable environments.However,it is still unclear whether AM symbiosis in tailings amended with different types of plant biomass and under different water conditions could overcome the surplus K and Fe stress for plants in Fe ore tailings,and if so,by what mechanisms.Here,host plants(Sorghum sp.Hybrid cv.Silk),either colonized or noncolonized by the AM fungi(Glomus spp.),were cultivated in lucerne hay(LH,C:N ratio of 18)-or sugarcane mulch(SM,C:N ratio of 78)-amended Fe ore tailings under well-watered(55%water-holding capacity(WHC)of tailings)or water-deficient(30%WHC of tailings)conditions.Root mycorrhizal colonization,plant growth,and mineral elemental uptake and partitioning were examined.Results indicated that AM fungal colonization improved plant growth in tailings amended with plant biomass under water-deficient conditions.Arbuscular mycorrhizal fungal colonization enhanced plant mineral element uptake,especially P,both in the LH-and SM-amended tailings regardless of water condition.Additionally,AM symbiosis development restrained the translocation of excess elements(i.e.,K and Fe)from plant roots to shoots,thereby relieving their phytotoxicity.The AM fungal roles in P uptake and excess elemental partitioning were greater in LH-amended tailings than in SM-amended tailings.Water deficiency weakened AM fungal colonization and functions in terms of mineral element uptake and partitioning.These findings highlighted the vital role AM fungi played in regulating plant growth and nutrition status in Fe ore tailings technosol,providing an important basis for involvement of AM fungi in the eco-engineered pedogenesis of Fe ore tailings.

Nutrient Exchange and Regulation in Arbuscular Vlycorrhizal Symbiosis

Most land plants form symbiotic associations with arbuscular mycorrhizal （AM） fungi. These are the most common and widespread terrestrial plant symbioses, which have a global impact on plant mineral nutrition. The establishment of AM symbiosis involves recognition of the two partners and bidirectional transport of different mineral and carbon nutrients through the symbiotic interfaces within the host root cells. Intrigu- ingly, recent discoveries have highlighted that lipids are transferred from the plant host to AM fungus as a major carbon source, in this review, we discuss the transporter-mediated transfer of carbon, nitrogen, phosphate, potassium and sulfate, and present hypotheses pertaining to the potential regulatory mecha- nisms of nutrient exchange in AM symbiosis. Current challenges and future perspectives on AM symbiosis research are also discussed.

High levels of arbuscular mycorrhizal fungus colonization on Medicago truncatula reduces plant suitability as a host for pea aphids (Acyrthosiphon pisum)

This study sheds light on a poorly understood area in insect-plant-microbe interactions,focusing on aphid probing and feeding behavior on plants with varying levels of arbuscular mycorrhizal(AM)fungus root colonization.It investigates a commonly occurring interaction of three species:pea aphid Acyrthosiphon pisum,barrel medic Medicago truncatula,and the AM fungus Rhizophagus irregularis,examining whether aphid-feeding behavior changes when insects feed on plants at different levels of AM fungus colonization(42% and 84% root length colonized).Aphid probing and feeding behavior was monitored throughout 8 h of recording using the electrical penetration graph(EPG)technique,also,foliar nutrient content and plant growth were measured.Summarizing,aphids took longer to reach their 1st sustained phloem ingestion on the 84% AM plants than on the 42% AM plants or on controls.Less aphids showed phloem ingestion on the 84% AM plants relative to the 42% AM plants.Shoots of the 84% AM plants had higher percent carbon(43.7%)relative to controls(40.5%),and the 84% AM plants had reduced percent nitrogen(5.3%)relative to the 42% AM plants(6%).In conclusion,EPG and foliar nutrient data support the hypothesis that modifications in plant anatomy(e.g.,thicker leaves),and poor food quality(reduced nitrogen)in the 84% AM plants contribute to reduced aphid success in locating phloem and ultimately to differences in phloem sap ingestion.This work suggests that M.truncatula plants benefit from AM symbiosis not only because of increased nutrient uptake but also because of reduced susceptibility to aphids.

A LysM Receptor Heteromer Mediates Perception of Arbuscular Mycorrhizal Symbiotic Signal in Rice

Symbiotic microorganisms improve nutrient uptake by plants.To initiate mutualistic symbiosis with arbus-cular mycorrhizal(AM)fungi,plants perceive Myc factors,including lipochitooligosaccharides(LCOs)and short-chain chitooligosaccharides(CO4/CO5),secreted by AM fungi.However,the molecular mechanism of Myc factor perception remains elusive.In this study,we identified a heteromer of LysM receptor-like kinases consisting of OsMYR1/OsLYK2 and OsCERK1 that mediates the perception of AM fungi in rice.CO4 directly binds to OsMYR1,promoting the dimerization and phosphorylation of this receptor complex.Compared with control plants,Osmyr1 and Oscerk1 mutant rice plants are less sensitive to Myc factors and show decreased AM colonization.We engineered transgenic rice by expressing chimeric receptors that respectively replaced the ectodomains of OsMYR1 and OsCERK1 with those from the homologous Nod factor receptors MtNFP and MtL YK3 of Medicago truncatula.Transgenic plants displayed increased cal-cium oscillations in response to Nod factors compared with control rice.Our study provides significant mechanistic insights into AM symbiotic signal perception in rice.Expression of chimeric Nod/Myc recep-tors achieves a potentially important step toward generating cereals that host nitrogen-fixing bacteria.

Suppression of LjBAK1-mediated immunity by SymRK promotes rhizobial infection in Lotus japonicus.

An important question in biology is how organisms can associate with different microbes that pose no threat (commensals), pose a severe threat (pathogens) and those that are beneficial (symbionts). The root nodule symbiosis serves as important model system to address such questions in the context of plant-microbe interactions. It is now generally accepted that rhizobia have the abilities to actively suppress host immune responses during the infection process, analogous to the way in which plant pathogens can evade immune recognition. However, much remains to be elucidated with regard to the mechanisms by which the host recognizes the rhizobia as pathogens and how, subsequently, these pathways are suppressed to allow establishment of the nitrogen fixing symbiosis. In this study, we found that SymRK (Symbiosis Receptor-like Kinase) is required for rhizobial suppression of plant innate immunity in Lotus japonicus. SymRK associates with LjBAK1 (BRASSINOSTEROID INSENSITIVE 1-Associated receptor Kinase 1), a well characterized, positive regulator of plant innate immunity, and directly inhibits LjBAK1 kinase activity. Rhizobial inoculation enhances the association between SymRK and LjBAK1 in planta. LjBAK1 is required to regulate plant innate immunity and plays a negative role in mediating rhizobial infection in L. japonicus. The data indicate that the protein complex of SymRK-LjBAK1 serves as an intersection point between rhizobial symbiotic signaling pathways and innate immunity pathways, which provides an evidence that rhizobia might actively suppress the host's ability to mount a defense response in the legume-rhizobium symbiosis.

利用代谢组学分析红汁乳菇-马尾松菌根苗根系分泌物

为探究红汁乳菇(Lactarius hatsudake)与宿主共生后菌根苗根系分泌物中促进红汁乳菇生长及菌根合成的潜在物质,利用非靶向代谢组(LC-MS/MS)分析红汁乳菇-马尾松菌根苗与马尾松非菌根苗的根系分泌物。结果表明:与马尾松非菌根苗相比,红汁乳菇-马尾松菌根苗根系分泌物在正、负离子模式下的差异代谢物共有352种,其中315种显著上调,37种显著下调;差异代谢物主要分布在代谢途径、抗生素生物合成、赖氨酸降解、次生代谢产物生物合成等28条通路中;差异代谢物2-异丙基苹果酸、磷酸、UDP-N-乙酰葡糖胺、茉莉酸、甲羟戊酸等参与多条代谢通路,可能在红汁乳菇-马尾松菌根形成中起重要作用。选取的9种差异显著代谢物中,1 mg·L^(-1)的D-天冬氨酸、DL-精氨酸、脱硫生物素、脱落酸对红汁乳菇JH5菌丝生长具有促进作用;1 mg·L^(-1)脱硫生物素、烟酸、脱落酸对红汁乳菇-马尾松菌根形成有促进作用。本研究可为红汁乳菇-马尾松菌根苗的高效培育提供参考。

丛枝菌根真菌和根瘤菌与植物共生研究进展

丛枝菌根真菌(AMF)和根瘤菌可以影响植物生产力、微生物群落结构和土壤质量,是生态系统可持续发展的重要驱动因子。在长期的进化过程中,AMF和根瘤菌逐步形成了互惠互利共生关系,充分发挥AMF-根瘤菌-植物共生体的生物固氮和养分吸收等作用,对于减少化学肥料的投入,保障农业可持续发展具有重要意义。但也有研究表明AMF和根瘤菌之间存在相互制约的作用,这可能与环境因素密切相关。因此,需要系统总结AMF-根瘤菌与植物共生相互作用的机理及其影响因素。本研究通过文献梳理以及定性比较分析,阐明了植物根系通过根系分泌物刺激根瘤菌和AMF形成结瘤因子和菌根因子,激活后续信号通路,从而使根瘤菌和AMF与植物建立共生关系的过程和机制;概述了AMF-根瘤菌与植物共生的协同增效和拮抗作用;总结了影响AMF和根瘤菌与植物共生及其相互作用的生物和非生物因素。最后,本研究提出AMF-根瘤菌与植物建立共生关系的作用机理目前还不完全明确,微生物菌肥研发缓慢等问题,并从理论、技术和应用等层面对未来研究的重点方向进行了展望,以期为利用AMF和根瘤菌促进农业可持续发展提供新思路和新方法。

印度梨形孢与杜鹃共生体系建立及提高抗旱性效应

【目的】从印度梨形孢入手,建立印度梨形孢与杜鹃共生体系,为提高现有园林绿化杜鹃的抗旱性提供新思路。【方法】采用国内园林绿地常用锦绣杜鹃品种‘紫蝴蝶’,持续浇灌印度梨形孢菌液6次,共计30天,建立印度梨形孢与杜鹃共生体系,探究定殖印度梨形孢的杜鹃植株形态结构变化,评价印度梨形孢对杜鹃抗旱性的作用及部分相关生理生化指标的变化。【结果】浇灌印度梨形孢菌液4次(第20天)后发现印度梨形孢已逐步定殖于杜鹃根系,浇灌5、6次(第25、30天)后的定殖率分别达91.67%、100%。定殖30天后的杜鹃叶片鲜质量、干质量、叶面积增大,叶片解剖结构的上、下表皮厚度减小,栅栏组织与栅海比增大,叶片结构更紧密,根细胞截面积增大。随着干旱胁迫时间延长,定殖印度梨形孢的杜鹃生长状态较好,干旱胁迫20天后存活率高,叶片相对电导率、脯氨酸含量、丙二醛含量、超氧化物歧化酶活性随干旱时间延长的差异不显著,半致死时间显著延长,受胁迫程度轻,抗旱性显著增强。【结论】锦绣杜鹃能与印度梨形孢建立互利共生关系,从而提高其对干旱胁迫的抗性。印度梨形孢可作为提高园林绿化植物杜鹃抗旱性的一种菌剂进行应用。