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.

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.

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.

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.

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.

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.

A cross-city molecular biogeographic investigation of arbuscular mycorrhizas in Conyza canadensis rhizosphere across native and non-native regions

Introduction:The ecological processes underlying the suppressive impacts of invasive species on native species diversity,both above-and below-ground,in non-native regions are not well understood.We therefore aimed to investigate the cross-city biogeographic patterns of arbuscular mycorrhizal(AM)diversity in Conyza canadensis rhizosphere in native(North American)and non-native(Kashmir Himalayan)regions.Methods:We recovered AMF spores from rhizospheric soils of Conyza in native and non-native ranges,besides doing so from the uninvaded sites in the introduced region.DNA extracted from AMF spores was processed for cloning and PCR-RFLP of SSU rRNA gene to yield the restriction groups(RGs)followed by their sequence analysis to determine the sequence groups(SGs).Results:The results indicated greater diversity of RGs and SGs in Conyza rhizosphere in native than in non-native sites.In the introduced region,however,the AMF diversity was more in uninvaded than in invaded sites.The species composition of AMF varied significantly between native and non-native regions and so also between invaded and uninvaded habitats.Conclusions:Though difference in AMF diversity between Conyza invaded and uninvaded sites may be attributed to invasion,the role of other evolutionary factors seems likely for differences between the native and non-native regions.We suggest that the ecological processes underlying these evolutionary differences in two biogeographic regions,besides the intensity of urbanization,might play some role in these differences.