Expression of various biotin-binding proteins in transgenic tobacco confers resistance to potato tuber moth, <Emphasis Type="Italic">Phthorimaea operculella</Emphasis> (Zeller) (fam. Gelechiidae)

The high affinity biotin-binding proteins (BBPs) avidin and streptavidin are established insecticidal agents, effective against a range of insect pests. Earlier work showed that, when expressed in planta, full length avidin and a truncated form of streptavidin are highly insecticidal. More recently, a wide range of BBPs, found in diverse organisms or engineered for various biotechnological applications have been reported. However, their effectiveness as plant-based insecticides has not been established. Here we report in planta expression of three different genes, designed to produce BBP variant proteins in the vacuole. The first was mature full length chicken avidin, the second a circularly permuted dual chain chicken avidin, and the third was an avidin homologue, a native bradavidin from Bradyrhyzobium japonicum. All three proteins were expressed in Nicotiana tabacum (tobacco). The transgenic tobacco lines were healthy, phenotypically normal and, when subjected to bioassay, resistant to the important cosmopolitan pest, potato tuber moth (Phthorimaea operculella) larvae at concentrations of ~50 ppm.     

Cutting Edge: Differential inhibition of TLR signaling pathways by cell-permeable peptides representing BB loops of TLRs

We designed cell-penetrating peptides comprised of the translocating segment of Drosophila antennapedia homeodomain fused with BB loop sequences of TLR2, TLR4, and TLR1/6. TLR2- and TLR4-BB peptides (BBPs) inhibited NF-kappaB translocation and early IL-1beta mRNA expression induced by LPS, and the lipopeptides S-[2,3-bis(palmitoyloxy)-(2-RS)-propyl]-N-palmitoyl-(R)-Cys-Ser-Lys(4)-OH (P3C) and S-[2,3-bis(palmitoyloxy)-(2-RS)-propyl]-Cys-Ser-Lys(4)-OH (P2C). TLR4- and TLR2-BBPs also strongly inhibited LPS-induced activation of ERK. Only TLR2-BBP significantly inhibited ERK activation induced by P3C, which acts via TLR2/1 heterodimers. BBPs did not inhibit activation of ERK induced by P2C, a TLR2/6 agonist. The TLR2-BBP induced weak activation of p38, but not ERK or cytokine mRNA. The TLR1/6-BBP failed to inhibit NF-kappaB or MAPK activation induced by any agonist. Our results suggest that the receptor BBPs selectively affect different TLR signaling pathways, and that the BB loops of TLR1/6 and TLR2 play distinct roles in formation of receptor heterodimers and recruitment of adaptor proteins.     

Principles from community and metapopulation ecology: application to fungal entomopathogens

Fungal entomopathogens are often studied within the context of their use for biological control, yet these natural enemies are also excellent subjects for studies of ecological interactions. Here, we present selected principles from community ecology and discuss these in relation to fungal entomopathogens. We discuss the relevance of apparent competition, food web construction, intraguild predation and density-mediated and trait-mediated indirect effects. Although current knowledge of community interactions involving fungal entomopathogens are limited, fungal entomopathogens can be important, interactive members of communities and the activities of fungal entomopathogens should be evaluated in the context of ecological principles. We also discuss aspects of metapopulation ecology and the application of these principles to fungal entomopathogens. Knowledge of ecological interactions is crucial if we are to understand and predict the effects of fungal entomopathogens on host populations and understand the interactions among fungal entomopathogens and other organisms in the communities in which they occur.     

Back to the future: natural history and the way forward in modern fungal ecology

The growing power and increasing availability of molecular tools for identifying fungi in environmental samples has revolutionized the way that fungal ecologists work. As a result, more people from around the globe have jumped into the fungal community sequencing endeavor. Paradoxically, as these extensive datasets accumulate we are often at a loss for interpretation due to the lack of basic autecology and natural history information for most fungi. As a result we are in danger of learning less and about more and more. I suggest that one way forward in fungal ecology is through a modern version of fungal natural history, with a focus on holistic understanding of individual species and ecosystems, but driven by modern genomic and molecular tools. By combining the extensive data generated through environmental sequencing with an intensive, molecular-based natural history we can create a synergy that will propel fungal ecology forward.     

Relationships of fungal spore concentrations in the air and meteorological factors

High concentrations of airborne fungal spores are associated with human health concerns. Environmental variables, such as temperature and moisture, can influence growth and reproduction in fungi and airborne spore concentrations can fluctuate seasonally. However, we do not understand how long-term changes in climate affect fungal abundance in the air. Here, we sampled annually (at peak season, in September, over a 20-yr period) for airborne fungal spores in two North American cities (New York and Toronto), and related fungal abundance to local variation in climate. We found that at both locations, the total precipitation during the 2- month period prior to sampling (Jul.–Aug.) was negatively related to observed fungal spore concentrations. Considering that climate predictions for these two regions indicate an increase in drought events in summer, we expect airborne fungal concentrations to increase in future years, potentially exacerbating human health concerns.     

Metabarcoding技术在真菌多样性研究中的应用

由于受到气候变化、土地利用变化及环境污染等诸多因素的干扰, 真菌多样性受到不容忽视的威胁, 亟需得到保护。构建物种数据库是实现真菌多样性研究和保护的重要前提。近年来兴起的DNA条形码及metabarcoding技术能够在很大程度上弥补传统鉴定方法的缺陷, 可对真菌物种进行大规模、准确、快速、高效地鉴定。本文梳理了metabarcoding技术在真菌物种多样性评估、真菌多样性影响机制和真菌古生态重建等研究中的应用, 同时强调了metabarcoding技术用于真菌多样性研究尚处于初期阶段, 在构建有效参照数据库、优化实验流程以及升级生物信息学工具等方面仍需要进一步的完善。建议加强真菌分类学家、生态学家以及计算机工具研发工程师之间的合作, 共同解决metabarcoding技术在真菌多样性研究及应用中面临的问题, 为宏观尺度上真菌多样性保护提供更加科学的依据。     

Differences in soil fungal assemblages associated with native and non-native tree species of varying weediness

Here we characterize and compare the diversity of belowground fungal communities of maples (Sapindaceae: Acer) varying in both nativity and weediness, and interpret our findings in the context of multiple non-exclusive theories on tree invasions and fungal associations. We made our fungal community comparisons based on high-throughput Illumina sequencing of the internal transcribed spacer region of fungal ribosomal DNA of soil samples associated with the roots of different species of maple collected from six sites throughout Central Pennsylvania. In our system, we found that weedy species, regardless of nativity, had the greatest soil fungal richness and that the nonnative invasive Norway maple had the highest abundance of mycorrhizal mutualists. Despite that much of the fungal community variability in our system was attributable to inter-site variability, we found that the core fungal communities associated with nonnative tree species were an inclusively larger set that included nearly all of those associated with native trees in addition to many not found with the natives, and the core communities of non-weedy species were largely a subset of those associated with weedy maples. In addition to confirming the strong influence that site variation has on soil fungal communities, our findings are also largely consistent with positive feedback from native fungal communities, possible co-invasion by fungal associates that are only associated with the nonnative trees, and generally add to the growing number of studies that have observed a greater abundance of mutualists associated with invasive trees that interact with arbuscular mycorrhizal fungi.     

Mitogen-activated protein kinase signaling in plant-interacting fungi: distinct messages from conserved messengers

Mitogen-activated protein kinases (MAPKs) are evolutionarily conserved proteins that function as key signal transduction components in fungi, plants, and mammals. During interaction between phytopathogenic fungi and plants, fungal MAPKs help to promote mechanical and/or enzymatic penetration of host tissues, while plant MAPKs are required for activation of plant immunity. However, new insights suggest that MAPK cascades in both organisms do not operate independently but that they mutually contribute to a highly interconnected molecular dialogue between the plant and the fungus. As a result, some pathogenesis-related processes controlled by fungal MAPKs lead to the activation of plant signaling, including the recruitment of plant MAPK cascades. Conversely, plant MAPKs promote defense mechanisms that threaten the survival of fungal cells, leading to a stress response mediated in part by fungal MAPK cascades. In this review, we make use of the genomic data available following completion of whole-genome sequencing projects to analyze the structure of MAPK protein families in 24 fungal taxa, including both plant pathogens and mycorrhizal symbionts. Based on conserved patterns of sequence diversification, we also propose the adoption of a unified fungal MAPK nomenclature derived from that established for the model species Saccharomyces cerevisiae. Finally, we summarize current knowledge of the functions of MAPK cascades in phytopathogenic fungi and highlight the central role played by MAPK signaling during the molecular dialogue between plants and invading fungal pathogens.     

Environmental filtering affects soil fungal community composition more than dispersal limitation at regional scales

The relative importance of dispersal limitation versus environmental filtering for community assembly has received much attention for macroorganisms. These processes have only recently been examined in microbial communities. Instead, microbial dispersal has mostly been measured as community composition change over space (i.e., distance decay). Here we directly examined fungal composition in airborne wind currents and soil fungal communities across a 40 000 km² regional landscape to determine if dispersal limitation or abiotic factors were structuring soil fungal communities. Over this landscape, neither airborne nor soil fungal communities exhibited compositional differences due to geographic distance. Airborne fungal communities shifted temporally while soil fungal communities were correlated with abiotic parameters. These patterns suggest that environmental filtering may have the largest influence on fungal regional community assembly in soils, especially for aerially dispersed fungal taxa. Furthermore, we found evidence that dispersal of fungal spores differs between fungal taxa and can be both a stochastic and deterministic process. The spatial range of soil fungal taxa was correlated with their average regional abundance across all sites, which may imply stochastic dispersal mechanisms. Nevertheless, spore volume was also negatively correlated with spatial range for some species. Smaller volume spores may be adapted to long-range dispersal, or establishment, suggesting that deterministic fungal traits may also influence fungal distributions. Fungal life-history traits may influence their distributions as well. Hypogeous fungal taxa exhibited high local abundance, but small spatial ranges, while epigeous fungal taxa had lower local abundance, but larger spatial ranges. This study is the first, to our knowledge, to directly sample air dispersal and soil fungal communities simultaneously across a regional landscape. We provide some of the first evidence that soil fungal communities are mostly assembled through environmental filtering and experience little dispersal limitation.     

中国丝状真菌次级代谢分子调控研究进展

在目前已知的具有生物活性的微生物次级代谢物中约有50%是由丝状真菌产生的,其中包括人们所熟知的青霉素、环孢菌素A以及洛伐他汀等。鉴于丝状真菌次级代谢物在农业、医药和工业上的重要价值,它们的生物合成及其分子调控一直备受关注。丝状真菌次级代谢物的生物合成是一个复杂的过程,一般涉及多步酶学反应,该过程往往受到不同水平的调控。深入了解丝状真菌次级代谢的分子调控机制,可以为其产量的提高、新骨架化合物的发掘以及隐性次级代谢物的激活奠定重要的理论基础。本文以丝状真菌次级代谢分子调控为主线,重点介绍近40年来我国科研工作者在该领域取得的研究进展,并对这一领域未来的发展进行展望。     

Measuring diversity of endophytic fungi in leaf fragments: does size matter?

Endophytic fungi inhabit living plant tissues without causing disease symptoms. Although abundant, the extent of their contribution to fungal biodiversity remains unclear. Since endophytic fungi are poorly known, especially in the tropics, current estimates of fungal species are probably conservative. Here we tested strategies for sampling endophytic fungi in tropical plants. We compared the number of fungi isolated from 400 mm2 leaf pieces that were divided into increasingly small fragments. Leaf pieces were surface-sterilized, cut into fragments and plated on culture media. For a given area, cutting leaf pieces into smaller fragments significantly increased the number of fungal morphospecies recovered. There was a strong linear relationship between size of fragments and number of fungi isolated. By extrapolation, an estimated 16 +/- 3 fungi could be recovered from a 2 x 2 cm leaf piece, using infinitely small fragments. This represents a large part of the fungal diversity estimated to exist in leaf endophytes in a population. We conclude that reducing the size and increasing the number of leaf fragments will increase the number of fungal species isolated. This strategy will help to estimate real values of endophytic fungal diversity.     

New insights on the development of fungal vaccines: from immunity to recent challenges

Fungal infections are emerging as a major problem in part due to high mortality associated with systemic infections, especially in the case of immunocompromised patients. With the development of new treatments for diseases such as cancer and the acquired immune deficiency syndrome pandemic, the number of immunosuppressed patients has increased and, as a consequence, also the number of invasive fungal infections has increased. Several studies have proposed new strategies for the development of effective fungal vaccines. In addition, better understanding of how the immune system works against fungal pathogens has improved the further development of these new vaccination strategies. As a result, some fungal vaccines have advanced through clinical trials. However, there are still many challenges that prevent the clinical development of fungal vaccines that can efficiently immunise subjects at risk of developing invasive fungal infections. In this review, we will discuss these new vaccination strategies and the challenges that they present. In the future with proper investments, fungal vaccines may soon become a reality.     

Genetic engineering of crop plants for fungal resistance: role of antifungal genes

Fungal diseases damage crop plants and affect agricultural production. Transgenic plants have been produced by inserting antifungal genes to confer resistance against fungal pathogens. Genes of fungal cell wall-degrading enzymes, such as chitinase and glucanase, are frequently used to produce fungal-resistant transgenic crop plants. In this review, we summarize the details of various transformation studies to develop fungal resistance in crop plants.     

High spatial resolution analysis of fungal cell biochemistry--bridging the analytical gap using synchrotron FTIR spectromicroscopy.

Fungi impact humans and the environment in many ways, for good and ill. Some fungi support the growth of terrestrial plants or are used in biotechnology, and yet others are established or emerging pathogens. In some cases, the same organism may play different roles depending on the context or the circumstance. A better understanding of the relationship between fungal biochemical composition as related to the fungal growth environment is essential if we are to support or control their activities. Synchrotron FTIR (sFTIR) spectromicroscopy of fungal hyphae is a major new tool for exploring cell composition at a high spatial resolution. Brilliant synchrotron light is essential for this analysis due to the small size of fungal hyphae. sFTIR biochemical characterization of subcellular variation in hyphal composition will allow detailed exploration of fungal responses to experimental treatments and to environmental factors.     

The Ascomycetes MAT locus: its evolution, structure and regulation

Invasive fungal infections of the respiratory tract are a major cause of serious morbidity and mortality especially in immunocompromised patients due to neutropenia, corticosteroids, or hematologic malignancy. The role of imaging is very important in the management of patients with fungal infections and chest x-ray is still the most used exploration. Nevertheless, new approaches recommend the systematic use of computed tomography scan for early documentation of invasive fungal infection. Combination of clinical setting with recognition of radiological pattern is the best approach to pulmonary fungal diseases. The following is a review of the imaging features of different invasive fungal infections we can face in our daily practice.     

High spatial resolution analysis of fungal cell biochemistry – bridging the analytical gap using synchrotron FTIR spectromicroscopy

Fungi impact humans and the environment in many ways, for good and ill. Some fungi support the growth of terrestrial plants or are used in biotechnology, and yet others are established or emerging pathogens. In some cases, the same organism may play different roles depending on the context or the circumstance. A better understanding of the relationship between fungal biochemical composition as related to the fungal growth environment is essential if we are to support or control their activities. Synchrotron FTIR (sFTIR) spectromicroscopy of fungal hyphae is a major new tool for exploring cell composition at a high spatial resolution. Brilliant synchrotron light is essential for this analysis due to the small size of fungal hyphae. sFTIR biochemical characterization of subcellular variation in hyphal composition will allow detailed exploration of fungal responses to experimental treatments and to environmental factors.     

Invasive fungal infections in solid organ transplant recipients

Invasive fungal infections are a major problem in solid organ transplant (SOT) recipients. Overall, the most common fungal infection in SOT is candidiasis, followed by aspergillosis and cryptococcosis, except in lung transplant recipients, where aspergillosis is most common. Development of invasive disease hinges on the interplay between host factors (e.g., integrity of anatomical barriers, innate and acquired immunity) and fungal factors (e.g., exposure, virulence and resistance to prophylaxis). In this article, we describe the epidemiology and clinical features of the most common fungal infections in organ transplantation. Within this context, we review recent advances in diagnostic modalities and antifungal chemotherapy, and their impact on evolving prophylaxis and treatment paradigms.     

Fungal Smn and Spf30 homologues are mainly present in filamentous fungi and genomes with many introns: implications for spinal muscular atrophy

Spinal muscular atrophy is an important rare genetic disease characterized by the loss of motor neurons, where the main gene responsible is smn1. Orthologous genes have only been characterized in a single fungal genome: Schizosaccharomyces pombe. We have searched for putative SMN orthologues in publically available fungal genomes, finding that they are predominately present in filamentous fungi. SMN binding partners and the SPF30 SMN paralogue, which are all involved in mRNA splicing, were found to be present in a similar but non-identical subset of fungal genomes. The Saccharomycces cerevisiae yeast genome contains neither smn1 orthologues nor paralogues and it has been suggested that this might be related to the low number of introns in this yeast. Here we have tested this hypothesis by looking at other fungal genomes. Significantly, we find that fungal genomes with high numbers of introns also possess an SMN orthologue or at least its paralogue, SPF30.     

Arbuscular mycorrhizal fungi (Glomeromycota) harbour ancient fungal tubulin genes that resemble those of the chytrids (Chytridiomycota)

The genes encoding alpha- and beta-tubulins have been widely sampled in most major fungal phyla and they are useful tools for fungal phylogeny. Here, we report the first isolation of alpha-tubulin sequences from arbuscular mycorrhizal fungi (AMF). In parallel, AMF beta-tubulins were sampled and analysed to identify the presence of paralogs of this gene. The AMF alpha-tubulin amino acid phylogeny was congruent with the results previously reported for AMF beta-tubulins and showed that AMF tubulins group together at a basal position in the fungal clade and showed high sequence similarities with members of the Chytridiomycota. This is in contrast with phylogenies for other regions of the AMF genome. The amount and nature of substitutions are consistent with an ancient divergence of both orthologs and paralogs of AMF tubulins. At the amino acid level, however, AMF tubulins have hardly evolved from those of the chytrids. This is remarkable given that these two groups are ancient and the monophyletic Glomeromycota probably diverged from basal fungal ancestors at least 500 million years ago. The specific primers we designed for the AMF tubulins, together with the high molecular variation we found among the AMF species we analysed, make AMF tubulin sequences potentially useful for AMF identification purposes.