Symbiotic Fungi Research Articles

An Assessment of the Potential Economic Impacts of the Invasive Polyphagous Shot Hole Borer (Coleoptera: Curculionidae) in South Africa.

Studies addressing the economic impacts of invasive alien species are biased towards ex-post assessments of the costs and benefits of control options, but ex-ante assessments are also required to deal with potentially damaging invaders. The polyphagous shot hole borer Euwallacea fornicatus (Coleoptera: Curculionidae) is a recent and potentially damaging introduction to South Africa. We assessed the potential impact of this beetle by working across economic and biological disciplines and developing a simulation model that included dynamic mutualistic relations between the beetle and its symbiotic fungus. We modeled the potential growth in beetle populations and their effect on the net present cost of damage to natural forests, urban trees, commercial forestry, and the avocado industry over 10 yr. We modeled high, baseline, and low scenarios using discount rates of 8, 6, and 4%, and a plausible range of costs and mortality rates. Models predicted steady growth in the beetle and fungus populations, leading to average declines in tree populations of between 3.5 and 15.5% over 10 yr. The predicted net present cost was 18.45 billion international dollars (Int. $), or about 0.66% of the country's GDP for our baseline scenario ($2.7 billion to $164 billion for low and high scenarios). Most of the costs are for the removal of urban trees that die as a result of the beetle and its fungal symbiont, as has been found in other regions. We conclude that an ex-ante economic assessment system dynamics model can be useful for informing national strategies on invasive alien species management.

Diversity, distribution and ecology of fungal communities present in Antarctic lake sediments uncovered by DNA metabarcoding

We assessed fungal diversity in sediments obtained from four lakes in the South Shetland Islands and James Ross Island, Antarctica, using DNA metabarcoding. We detected 218 amplicon sequence variants (ASVs) dominated by the phyla Ascomycota, Basidiomycota, Mortierellomycota, Mucoromycota and Chytridiomycota. In addition, the rare phyla Aphelidiomycota, Basidiobolomycota, Blastocladiomycota, Monoblepharomycota, Rozellomycota and Zoopagomycota as well as fungal-like Straminopila belonging to the phyla Bacillariophyta and Oomycota were detected. The fungal assemblages were dominated by unknown fungal taxa (Fungal sp. 1 and Fungal sp. 2), followed by Talaromyces rubicundus and Dactylonectria anthuriicola. In general, they displayed high diversity, richness and moderate dominance. Sequences representing saprophytic, pathogenic and symbiotic fungi were detected, including the phytopathogenic fungus D. anthuriicola that was abundant, in the relatively young Soto Lake on Deception Island. The lake sediments studied contained the DNA of rich, diverse and complex fungal communities, including both fungi commonly reported in Antarctica and other taxa considered to be rare. However, as the study was based on the use of environmental DNA, which does not unequivocally confirm the presence of active or viable organisms, further studies using other approaches such as shotgun sequencing are required to elucidate the ecology of fungi in these Antarctic lake sediments.

Dancing with Douglas‐fir: Determinism dominates fungal community assembly processes

Abstract Fungal communities can influence the productivity, composition and survival of trees through cycling nutrients, providing resources and altering pathogens. Thus, shifts in fungal communities could impact forests by altering interactions between trees and their environments. Fungal community composition may be shaped by stochastic and deterministic processes such as dispersal limitation, environmental filtering and partner specificity between trees and fungi. For tree species with large geographical ranges, we expect fungal assembly processes to change with environmental variation across the range of the tree partner. Due to specificity between trees and symbiotic fungi, we expect deterministic to outweigh stochastic processes in root compared with soil fungi. As some tree species have exceptional longevity, we also expected tree age to influence fungal community assembly. We surveyed fungi in four stands of Pseudotsuga menziesii with tree ages up to 800 years along an 1,800 km transect. We sampled roots and soil around 12 P. menziesii in each stand, aged the trees, and sequenced fungal rDNA to determine composition and richness from which we calculated the relative role of deterministic and stochastic assembly processes. We used null models to evaluate the relative importance of deterministic variable and homogenizing selection, and stochastic dispersal limitation, drift and homogenizing dispersal in fungal community assembly. We detected 7,280 amplicon sequence variants with 5,270 associated with soil, 3,887 with roots and 1,877 found across both roots and soils. Deterministic processes dominated root and soil fungal communities at all sites except one where stochastic processes (i.e. dispersal limitation and drift) controlled root fungi. Despite the dominance of determinism in fungal community assembly, the proportion of processes differed by site. Assembly processes did not vary with tree age. Synthesis. Taken together, we suggest that the local environment, water limitation and partner‐preference between trees and their associated fungi, influence fungal community composition across the range of P. menziesii. We conclude that while fungal communities occurring near P. menziesii are dominated by homogenizing selection, the role of neutral processes still has a minor influence on community assembly and may be important in spatially isolated communities and those with strong gradients of fungal diversity.

Microscopy Techniques for Interpreting Fungal Colonization in Mycoheterotrophic Plants Tissues and Symbiotic Germination of Seeds.

Structural botany is an indispensable perspective to fully understand the ecology, physiology, development, and evolution of plants. When researching mycoheterotrophic plants (i.e., plants that obtain carbon from fungi), remarkable aspects of their structural adaptations, the patterns of tissue colonization by fungi, and the morphoanatomy of subterranean organs can enlighten their developmental strategies and their relationships with hyphae, the source of nutrients. Another important role of symbiotic fungi is related to the germination of orchid seeds; all Orchidaceae species are mycoheterotrophic during germination and seedling stage (initial mycoheterotrophy), even the ones that photosynthesize in adult stages. Due to the lack of nutritional reserves in orchid seeds, fungal symbionts are essential to provide substrates and enable germination. Analyzing germination stages by structural perspectives can also answer important questions regarding the fungi interaction with the seeds. Different imaging techniques can be applied to unveil fungi endophytes in plant tissues, as are proposed in this article. Freehand and thin sections of plant organs can be stained and then observed using light microscopy. A fluorochrome conjugated to wheat germ agglutinin can be applied to the fungi and co-incubated with Calcofluor White to highlight plant cell walls in confocal microscopy. In addition, the methodologies of scanning and transmission electron microscopy are detailed for mycoheterotrophic orchids, and the possibilities of applying such protocols in related plants is explored. Symbiotic germination of orchid seeds (i.e., in the presence of mycorrhizal fungi) is described in the protocol in detail, along with possibilities of preparing the structures obtained from different stages of germination for analyses with light, confocal, and electron microscopy.

Small workers are more persistent fighters than soldiers in the highly polymorphic Atta leaf-cutting ants

Social animals often coordinate behavioural activities for the gathering, maintenance and protection of resources. In eusocial insects, morphological and/or behavioural heterogeneity among worker caste allows division of labour and, in some instances, the specialization of individuals in specific tasks. In leaf-cutting ants (genus Atta ), the division of labour is based on body size differences (alloethism), meaning that differently sized workers will likely perform different tasks. Although alloethism is now well understood during foraging and processing of food resources in Atta , the relationship between body size and aggressive response has been poorly investigated, and, so far, it is not well understood how different morphological subcastes are integrated into the defensive strategy. Here, we quantified conspecifc and heterospecific aggression, in a within-colony social context (inside the nest), aiming to test which worker size class (subcaste) exhibits the most aggressive response against non-nestmates (NNMs). Workers were divided into three distinct subcastes, minors, majors and soldiers, and reared in subcolonies containing two individuals of each subcaste, as well as brood and the symbiotic fungus. We found a low probability of aggression towards conspecific NNMs and a high probability towards heterospecific NNMs. Quantification of aggression across subcastes showed that minors directed the most overt physical attacks towards heterospecific NNMs. We suggest that the nest, where minors perform most of their tasks, might constitute a strong social contextual stimulus for them, lowering their response threshold and increasing their aggression towards foreign ants. We also suggest that possible signals (i.e. chemical or mechanical) emitted during interactions involving minors stimulate larger workers to engage in fights, a mechanism that has been demonstrated in other ant species. The integration of size-specific behavioural traits might constitute a very efficient defensive mechanism. • Atta workers show the highest degree of morphological differentiation among ants. • However, the link between body size and aggression is little understood. • We measured aggression towards ant intruders in Atta workers of different size. • We found that the decision to attack an enemy is not related to body size. • Attack persistency, however, is far higher in small than in large workers.

The cytochrome P450s of Leptographium qinlingensis: Gene characteristics, phylogeny, and expression in response to terpenoids

Leptographium qinlingensis is one of the major fungal associates of the Chinese white pine beetle (Dendroctonus armandi) and is an active participant in the large-scale death of Pinus armandi. Beetles and associated fungi have evolved efficient systems for overcoming the toxicity of host defense chemicals, which consist of a multitude of monoterpenes and diterpenes. As fungal cytochromes (CYPs) can detoxify and degrade various xenobiotic compounds, we identified 11 CYPs from L. qinlingensis to analyze their potential function in detoxifying or degrading host chemical defense. These 11 CYPs of L. qinlingensis belong to 6 clans and cluster into 3 clades, clade 2, clade 8 and clade 10, based on their phylogenetic relationships. Moreover, we also analyzed the transcript levels of CYPs following treatment with terpenes or expression in mycelia grown on terpenoids as a carbon source. The results in this paper showed that several CYPs were upregulated after treatment with terpenes or growth on terpenoids as the only carbon source. Our research provides some insight into the function of CYPs from bark beetle symbiotic fungi in the detoxification of pine defense compounds or their relationships with the utilization of terpenoids.

Two previously undescribed phthalides from Talaromyces amestolkiae, a symbiotic fungus of Syngnathus acus

Amestolkins A (1) and B (2), two previously undescribed phthalides sharing the same planar structure of (1, 5-dihydroxyhexyl)-7-hydroxyisobenzofuran-1(3H)-one were isolated from Talaromyces amestolkiae. Their absolute configurations were elucidated by comprehensive analyses of spectroscopic evidences in high-resolution electrospray mass spectra (HRESIMS) and nuclear magnetic resonance (NMR) combined with electronic circular dichroism (ECD) and NMR calculations. 1 and 2 showed anti-neuroinflammatory activity by inhibiting the gene expressions of proinflammatory factors including C-C motif chemokine ligand 2 (CCL-2), tumor necrosis factor-α (TNF-α) and interleukin 6 (IL-6), as well as attenuating the excretion of inducible nitric oxide synthase (iNOS) in BV-2 microglial cells at the concentration of 30 μM.

Rhizosphere and root fungal community of the invasive plant Galinsoga quadriradiata changes along its elevational expansion route

Abstract Fungal communities related to invasive plants may change with an elevational gradient, which may affect the performance and invasiveness of invasive plants. Our recent study revealed that root arbuscular mycorrhizal fungi colonization rate of invasive plant Galinsoga quadriradiata decreased with elevation. However, it is unclear whether it is caused by the changes in the fungal community along elevation. To address this issue, we used high-throughput sequencing techniques, functional groupings and linear statistics to examine how fungal communities in the rhizosphere and roots of G. quadriradiata are changed across the elevation in Qinling and Bashan Mountains, China. Our results revealed that species diversity and composition of the rhizosphere and root fungal communities changed along the elevation. The Shannon–Wiener diversity index in the rhizosphere and roots increased and decreased with elevation, respectively. In contrast, the relative abundance of pathotroph in the rhizosphere decreased while it increased in the roots with elevation. These suggest that, when the invasive plant colonizes into high altitudes, it may not suffer from limited rhizosphere fungal symbionts, but rather the ability of the plant to create and maintain these associations decreases. The invader tends to accumulate more pathogenic fungi in the roots, while the dependence on symbiotic fungi is reduced during expansion into higher elevations. These results highlight that the interactions between invasive plants and fungal community substantially change along elevation, and that belowground interactions may be key in our understanding of how invasive plants derive success in stressful, high-elevation environments.

IMPORTANCE OF BIO FERTILIZERS AS ALTERNATIVE SOIL FERTILITY AMENDMENTS

There is a current interest in agrarian sustainability with soil microorganisms instead of agro-chemicals. Key constraints in the use of bio fertilizers are; inadequate awareness about bio inoculants and lack of promotion network and publicity among the end users. This review discusses current technical information a way of creating awareness in order to promote the use of bio fertilizers. Publon, Google Scholar, Science Direct and Microsoft Academic data bases were used for the review 2021. Research and review articles published from 2019 onwards were considered as current information for the review. The findings of the review are that; both primary and secondary macronutrients can be provided by bio fertilizers. Potential microbes are; free-living nitrogen fixing bacteria and cyanobacteria, symbiotic nitrogen-fixing bacteria and fungi such as mycorrhiza. Other important functions of bacteria are; conferring to plants the ability for salt tolerance, lignin degradation and remediation of heavy metals from the soil. Bio Compost, vermicompost and termite soil with their rich microorganism content can be used as bio fertilizers for soil nutrient increase. In order to reap maximum benefit from bio fertilizers there is need to formulate them in appropriate materials. Apart from addition of nutrients to the soil, bio fertilizers play an important role in plant health, conclusion. This paper has brought to the fore the need to improve rhizosphere management in a sustainable way particularly at this point in time when there are strong indications that it has deteriorated in the face of continued use of chemical fertilizers.

Novel Trichoderma Isolates Alleviate Water Deficit Stress in Susceptible Tomato Genotypes.

Symbiotic fungi in the genus Trichoderma can induce abiotic stress tolerance in crops. The beneficial effects of Trichoderma on water deficit stress are poorly understood and may be isolate-specific. Our objective was to evaluate a collection of Nepalese Trichoderma isolates and their efficacy to improve tomato (Solanum lycopersicum) growth under water deficit. Variable growth in low moisture environments was observed among Trichoderma isolates from Nepal, Ohio, and commercial sources using in vitro assays. The overall performance of the population decreased when cultured under conditions of decreasing matric water potential (0.0, –2.8, –4.8, and –8.5 Ψ). Twelve isolates were selected for evaluation for their potential to elicit drought tolerance in greenhouse-grown ‘Roma Organic’ tomatoes. Plants treated with T. asperelloides-NT33 had higher shoot weight than the non-inoculated control (T0) under water deficit stress conditions. Further, the stress-reducing efficacy of isolates T. asperelloides-NT33, T. asperellum-NT16, T. asperelloides-NT3, and commercial T. harzianum-T22 were tested on tomato genotypes with differing tolerance to drought [‘Roma Organic,’ ‘Jaune Flamme,’ and ‘Punta Banda’]. The water deficit susceptible genotypes ‘Roma Organic’ and ‘Jaune Flamme’ inoculated with isolate NT33 had significantly higher shoot weight (37 and 30% respectively; p < 0.05) compared to the non-inoculated control under water deficit stress conditions. In drought tolerant ‘Punta Banda,’ shoot weight was also significantly greater in NT33 inoculated plants under water deficit stress conditions, but with lower magnitude difference (8%; p < 0.05). Our results demonstrate differences in the ability of Trichoderma isolates to confer tolerance to water deficit in tomato with NT33 potentially relieving stress. Tomato genotypes also play a role in the outcome of interactions with the Trichoderma isolates we tested.

N limit as a switch node between positive and negative plant-soil feedback: A meta-analysis based on the covariant diagnosis of plant growth and soil factors

Mounting evidence has confirmed the existence of plant-soil feedback, a reflection of plant-soil interaction. However, analysis of ecological feedback pathways remains a challenge. In this study, single and mixed plant communities in different soil ecosystems were screened using strict control systems in global ecosystems to identify the positive or negative feedback effects in indicator plants. Furthermore, the plant components and biomass were identified in each pathway. The significantly changed components indicated pathway factors. As negative feedback increased, the InRR (Response Ratio) of soil organic matter, soil total N, microbial alpha diversity and the symbiotic fungi proportion were significantly up-regulated (P < 0.05). In contrast, the stoichiometric ratio (C: N), water content, and the pathogenic bacteria proportion were downregulated (P < 0.05). However, the positive feedback showed the opposite trend. Importantly, N limit as a transform node between positive and negative plant-soil feedback predicted by Akaike information criterion (AIC > 0.8). Therefore, it has become an important evaluation standard for the inter-species relationship and ecological environment changes under the background of global N deposition. Finally, the feedback values of each sampling site were recalculated over the next 20 years, 50 years, and 100 years based on the global temperature rise and changing rainfall patterns. We also found that global warming and extreme rainfall may change the distribution of interspecies relationships on a global scale, with global warming having the greatest recognisable effect and decreasing the negative feedback layout by 21.7% (P < 0.05). Therefore, this work promotes the cognition of relationship of soil environment, microbial abundance and function, plant diversity and plant- soil feedback model. Meanwhile, it is of great significance to protect species diversity and restore environmental degradation.

Symbiont demand guides resource supply: leaf-cutting ants preferentially deliver their harvested fragments to undernourished fungus gardens

Leaf-cutting ants are highly successful herbivores in the Neotropics. They forage large amounts of fresh plant material to nourish a symbiotic fungus that sustains the colony. It is unknown how workers organize the intra-nest distribution of resources, and whether they respond to increasing demands in some fungus gardens by adjusting the amount of delivered resources accordingly. In laboratory experiments, we analyzed the spatial distribution of collected leaf fragments among nest chambers in Acromyrmex ambiguus leaf-cutting ants, and how it changed when one of the fungus gardens experienced undernourishment. Plant fragments were evenly distributed among nest chambers when the fungal symbiont was well nourished. That pattern changed when one of the fungus gardens was undernourished and had a higher leaf demand, resulting in more leaf discs delivered to the undernourished fungus garden over at least 2 days after deprivation. Some ants bypassed nourished gardens to directly deliver their resource to the chamber with higher nutritional demand. We hypothesize that cues arising from that chamber might be used for orientation and/or that informed individuals, presumably stemming from the undernourished chamber, may preferentially orient to them.

Tulasnella can contribute to breakthrough in germination of the medicinal orchid Bletilla striata via producing plant hormones

Bletilla striata (Thund.) Reichb. f. is a perennial herb in the Orchidaceae with both ornamental and medicinal value. Because its seed is so thin without endosperm, it is extremely difficult to germinate under natural conditions. For this study, we first observed the mycorrhizal construction of B. striata, the cortical cells were colonized by a large number of hyphae, with colonization rates ranging from 50% to 70%. Then, the nursery cups were used to bait symbiotic mycorrhizal fungi in native B. striata areas. Subsequently, four strains of Tulasnella were isolated and purified, of which one strain was from two-year-old B. striata (CFE 3) and three strains were from symbiotic germination B. striata (CFE 14, CFE 15, and CFE 25). The symbiotic germination experiment was developed. Germination in the presence of four mycorrhizal fungi showed separately 53% (CFE 3), 53% (CFE 14), 61% (CFE 15) and 67% (CFE 25) germination compared to 39% of control plants in 35 DAI. The results of the growth-promoting experiment demonstrated that CFE 25 could better promote the growth of leaves and roots. The range of seedlings, leaf lengths and main root lengths were significant improved 2.8, 2.4 and 13.6 times, respectively. CFE 15 was more beneficial for the growth of pseudobulbs and fresh weight, which were remarkably enhanced by 1.5 and 5.8 times. Finally, the germination and growth promotion efficiency was significantly related to the hormone content produced by Tulasnella. Our research revealed that the Tulasnella genera fungi from the mycorrhiza of B. striata can promote seed germination and seedling growth via producing plant hormones.

Hardening Blueberry Plants to Face Drought and Cold Events by the Application of Fungal Endophytes

Harsh environmental conditions derived from current climate change trends are among the main challenges for agricultural production worldwide. In the Mediterranean climatic region of central Chile, sudden occurrence of spring cold temperatures in combination with water shortage for irrigation (drought) constitutes a major limitation to highbush blueberry (Vaccinium corymbosum) plantations, as flowering and fruiting stages are highly sensitive. Hardening crops may be achievable by boosting beneficial interactions of plants with microorganisms. Inoculation with symbiotic fungi isolated from plants adapted to extreme environments could be a good strategy, if they are able to maintain functional roles with non-original hosts. Here, we evaluated the effect of two Antarctic fungal endophytes (AFE), Penicillium rubens and P. bialowienzense, on the tolerance of V. corymbosum plants to cold events in combination with drought under controlled conditions. Inoculated and uninoculated plants were exposed for a month to one event of a cold temperature (2 °C/8 h) per week with or without drought and were evaluated in physiological, biochemical, and molecular variables. A complementary set of plants was kept under the same environmental conditions for two additional months to evaluate survival as well as fruit weight and size. There was an overall positive effect of AFE on plant performance in both environmental conditions. Endophyte-inoculated plants exhibited higher gene expression of the Late Embryogenesis Abundant protein (LEA1), higher photochemical efficiency (Fv/Fm), and low oxidative stress (TBARS) than uninoculated counterparts. On the other hand, plant survival was positively affected by the presence of fungal endophytes. Similarly, fruit diameter and fruit fresh weight were improved by fungal inoculation, being this difference higher under well-watered condition. Inoculating plants with fungal endophytes isolated from extreme environments represents a promising alternative for hardening crops. This is especially relevant nowadays since agriculture is confronting great environmental uncertainties and difficulties which could became worse in the near future due to climate change.

Antiparasitic potential of agrochemical fungicides on a non-target aquatic model (Daphnia × Metschnikowia host-parasite system)

Pesticides are a major anthropogenic threat to the biodiversity of freshwater ecosystems, having the potential to affect non-target aquatic organisms and disrupt the processes in which they intervene. Important knowledge gaps have been recognised concerning the ecological effects of synthetic fungicides on non-target symbiotic aquatic fungi and the ecological processes where they intervene. The goal of this work was to assess the influence of three commonly used fungicides (myclobutanil, metalaxyl and cymoxanil), which differ in their mode of action, on a host (the crustacean Daphnia magna) × parasite (the yeast Metschnikowia bicuspidata) experimental model. Using a set of life history experiments, we evaluated the effect of each fungicide on the outcome of this relationship (disease) and on the fitness of both host and parasite. Contrasting results were observed: (i) cymoxanil and metalaxyl were overall innocuous to host and parasite at the tested concentrations, although host reproduction was occasionally reduced in the simultaneous presence of parasite and fungicide; (ii) on the contrary, myclobutanil displayed a clear antifungal effect, decreasing parasite prevalence and alleviating infection signs in the hosts. This antiparasitic effect of myclobutanil was further investigated with a follow-up experiment that manipulated the timing of application of the fungicide, to understand which stage of parasite development was most susceptible: while myclobutanil did not interfere in the early stages of infection, its antifungal activity was clearly observable at a later stage of the disease (by impairing the production of transmission stages of the parasite). More research is needed to understand the broader consequences of this parasite-clearance effect, especially in face of increasing evidence that parasites are ecologically more important than their cryptic nature might suggest.

The Symbiotic Fungus Leucoagaricus gongylophorus (Möller) Singer (Agaricales, Agaricaceae) as a Target Organism to Control Leaf-Cutting Ants.

Simple SummaryThe most used approach to control leaf-cutting ants (which cause damage in agricultural areas) is the application of synthetic chemical compounds that directly affect these insects. But another approach is the use of natural substances that attack the symbiotic fungus responsible for many aspects of the survival of the nest. In this study, we discuss the natural substances already reported in the literature to have fungicidal activity and how they could be applicable as products for the control of leaf-cutting ants.Atta and Acromyrmex are the main genera of leaf-cutting ants present in North and South America, causing extensive damage to agroforestry. Control of the ants requires high handling costs with few effective methods available to decrease the losses. The symbiosis between the leaf-cutting ants and the fungus Leucoagaricus gongylophorus is essential for ant nest survival. Therefore, L. gongylophorus may be a key target in controlling leaf-cutting ants, since its reduction may cause an imbalance in the symbiosis necessary to maintain the nest. Among the options for natural fungal control, plant species are considered important sources of compounds belonging to several classes of natural products that show potential as antifungal agents. This review also presents studies that establish that the antagonist fungi from the Escovopsis and Trichoderma genera effectively reduce the development of L. gongylophorus. The development of nanostructured delivery systems, which have shown advantages over conventional formulations, is suggested for ant control; no commercial nanotechnology-based product has yet been developed, and this appears to be a new approach for future studies.

Effect of symbiotic bee fungus on survival of stingless bee Heterotrigona itama larvae

Effect of symbiotic bee fungus on survival of stingless bee Heterotrigona itama larvae

Distribution patterns of four Termitomyces species cultivated by a fungus-growing termite, Odontotermes formosanus, in Taiwan

Fungus-growing termites inoculate the obligate symbiotic fungus Termitomyces into the fungus comb in their colonies. In this study, Taiwanese Termitomyces species were determined by diagnostic PCR using the metagenome of the body of Odontotermes formosanus (the only host termite living in Taiwan) as a template. Phylogenetic analyses revealed that four different Termitomyces species are cultivated by O. formosanus in Taiwan. Three have previously been registered in the DNA database, but one was first recorded in Taiwan. Only Termitomyces sp. Type C was distributed in all areas investigated in Taiwan, whereas the other three species were distributed regionally. Field observations indicated that the flush period and the number of fruit bodies in each colony varied between species. The distribution patterns of Termitomyces spp. in Taiwan may be related to the Taiwanese climate and/or the fruiting pattern. • Four Termitomyces species establish symbiosis with a fungus-growing termite in Taiwan. • One Termitomyces is first recorded in Taiwan. • Only one species inhabits all of Taiwan, whereas the other is regionally distributed. • Flush period and size of fruit body may affect Termitomyces distribution pattern.

Interaction Analysis of Odorant-Binding Protein 12 from Sirex noctilio and Volatiles from Host Plants and Symbiotic Fungi Based on Molecule Dynamics Simulation

As a quarantine pest of conifer, Sirex noctilio has caused widespread harm around the world. It is expected that the molecular mechanism of protein–ligand binding can be elucidated to carry out the pest control. Through studies of SnocOBP12–ligand hydrophobic binding and dynamics and responsible amino acid residues identification, we got some promising results. SnocOBP12 had a general and excellent affinity for host plant volatiles, and may be a key protein for S. noctilio to find host plants. Among the many odor molecules that are bound to SnocOBP12, (−)-α-cedrene and (E)-β-farnesene from host plants and (−)-globuol from the symbiotic fungi of Sirex noctilio stood out and formed highly stable complexes with SnocOBP12. By the molecular mechanics Poisson–Boltzmann surface area (MM-PBSA) method, the calculated free binding energy of the three complexes was −30.572 ± 0.101 kcal/mol, −28.349 ± 0.119 kcal/mol and −25.244 ± 0.152 kcal/mol, respectively. It was found that the van der Waals energy contributed to the stability of the complexes. Some key amino acid residues were also found: LEU74 and TYR109 were very important for SnocOBP12 to stably bind (−)-α-cedrene, while for (E)-β-farnesene, ILE6, MET10, and LEU74 were very important for the stable binding system. We discovered three potential ligands and analyzed the interaction pattern of the protein with them, this paper provides a favorable molecular basis for optimizing the attractant formulation. Investigation of the binding characteristics in the olfactory system at the molecular level is helpful to understand the behavior of S. noctilio and develop new methods for more effective and environmentally friendly pest control.

Full-Length Transcriptome Sequencing-Based Analysis of Pinus sylvestris var. mongolica in Response to Sirex noctilio Venom

Simple SummarySirex noctilio, as a devastating international forestry quarantine pest whose venom can cause a series of physiological changes in the host plants, such as needle wilting, yellowing, decreased transpiration rate and increased respiration rate, etc. In this study, a full-length reference transcript of Pinus sylvestris var. mongolica was constructed by combining second- and third-generation transcriptome sequencing technologies. We also identified the specific expression genes and transcription factors of P. sylvestris var. mongolica under S. noctilio venom and wounding stress. S. noctilio venom mainly induced the expression of genes related to ROS, GAPDH and GPX, and mechanical damage mainly induced the photosynthesis−related genes. The results provide a better understanding of the molecular regulation of pine trees in response to S. noctilio venom.Sirex noctilio is a major international quarantine pest that recently emerged in northeast China to specifically invade conifers. During female oviposition, venom is injected into the host together with its symbiotic fungus to alter the normal Pinus physiology and weaken or even kill the tree. In China, the Mongolian pine (Pinus sylvestris var. mongolica), an important wind-proof and sand-fixing species, is the unique host of S. noctilio. To explore the interplay between S. noctilio venom and Mongolian pine, we performed a transcriptome comparative analysis of a 10-year-old Mongolian pine after wounding and inoculation with S. noctilio venom. The analysis was performed at 12 h, 24 h and 72 h. PacBio ISO-seq was used and integrated with RNA-seq to construct an accurate full-length transcriptomic database. We obtained 52,963 high-precision unigenes, consisting of 48,654 (91.86%) unigenes that were BLASTed to known sequences in the public database and 4309 unigenes without any annotation information, which were presumed to be new genes. The number of differentially expressed genes (DEGs) increased with the treatment time, and the DEGs were most abundant at 72 h. A total of 706 inoculation-specific DEGs (475 upregulated and 231 downregulated) and 387 wounding-specific DEGs (183 upregulated and 204 downregulated) were identified compared with the control. Under venom stress, we identified 6 DEGs associated with reactive oxygen species (ROS) and 20 resistance genes in Mongolian pine. Overall, 52 transcription factors (TFs) were found under venom stress, 45 of which belonged to the AP2/ERF TF family and were upregulated. A total of 13 genes related to the photosystem, 3 genes related photo-regulation, and 9 TFs were identified under wounding stress. In conclusion, several novel putative genes were found in Mongolian pine by PacBio ISO seq. Meanwhile, we also identified various genes that were resistant to S. noctilio venom, such as GAPDH, GPX, CAT, FL2, CERK1, and HSP83A, etc.