Molecular evidence for host-adapted races of the fungal endophyte Epichloë bromicola after presumed host shifts

Abstract.— Host shifts of plant‐feeding insects and parasites promote adaptational changes that may result in the formation of host races, an assumed intermediate stage in sympatric speciation. Here, we report on genetically differentiated and host‐adapted races of the fungal endophyte Epichloë bromicola, which presumably emerged after a shift from the grass Bromus erectus to other Bromus hosts. Fungi of the genus Epichloë (Ascomycota) and related anamorphs of Neotyphodium are widespread endophytes of cool‐season grasses. Sexually reproducing strains sterilize the host by formation of external fruiting structures (stromata), whereas asexual strains are asymptomatic and transmitted via seeds. In E. bromicola, strains infecting B. erectus are sexual, and strains from two woodland species, B. benekenii and B. ramosus, are asexual and seed transmitted. Analyses of amplified fragment length polymorphism fingerprinting and of intron sequences of the tub2 and tef1 genes of 26 isolates from the three Bromus hosts collected at natural sites in Switzerland and nearby France demonstrated that isolates are genetically differentiated according to their host, indicating that E. bromicola does not form a single, randomly mating population. Phylogenetic analyses of sequence data did not unambiguously resolve the exact origin of asexual E. bromicola strains, but it is likely they arose from within sexual populations on B. erectus. Incongruence of trees derived from different genes may have resulted from recombination at some time in the recent history of host strains. Reciprocal inoculations of host plant seedlings showed that asexual isolates from B. benekenii and B. ramosus were incapable of infecting B. erectus, whereas the sexual isolates from B. erectus retained the assumed ancestral trait of broad compatibility with Bromus host seedlings. Because all isolates were interfertile in experimental crosses, asexual strains may not be considered independent biological species. We suggest that isolates infecting B. benekenii and B. ramosus represent long‐standing host races or incipient species that emerged after host shifts and that may evolve through host‐mediated reproductive isolation toward independent species.     

Mixed inoculation alters infection success of strains of the endophyte Epichloë bromicola on its grass host Bromus erectus

Within-host competition in multiply infected hosts is considered an important component of host-parasite interactions, but experimental studies on the dynamics of multiple infections are still rare. We measured the infection frequencies of four strains of the fungal endophyte Epichloë bromicola on two genotypes of its host plant Bromus erectus after single- and double-strain inoculation. Double-strain inoculations resulted in fewer double, but more single, infections than expected on the basis of infection frequencies in single-strain inoculations. In most cases, only one of the two strains established an infection, and strains differed in their overall competitive ability. This pattern resembles the mutual exclusion scenarios in some theoretical models of parasite evolution. In addition, competitive ability varied with host genotype, which may represent a mechanism for the coexistence of strains in a population. Hence, considering the genetic variation in both host and parasite may be important for a better understanding of within-host dynamics and their role in epidemiology or (co)evolution.     

Effects of the endophyte Epichloë coenophiala on the root microbial community and growth performance of tall fescue in different saline-alkali soils

Soil salinization is detrimental to plant growth and yield in agroecosystems worldwide. Epichloë endophytes, a class of clavicipitaceous fungi, enhance the resistance of host plants to saline-alkali stress. This study explored the effects of the systemic fungal endophyte Epichloë coenophiala on the root microbial community and growth performance of tall fescue (Lolium arundinaceum) growing under different saline-alkali stress conditions. Structural equation modeling (SEM) was conducted to analyze the direct and indirect effects (mediated by root microbial community diversity and soil properties) of the endophyte on the growth of tall fescue under saline-alkali stress. The endophyte-infected plants produced higher shoot and root biomass compared to endophyte-free plants under saline-alkali stress (200 and 400 mM). Endophyte infection increased the fungal community diversity and altered its composition in the roots, decreasing the relative abundance of Ascomycota and increasing that of Glomeromycota. Furthermore, endophyte infection decreased the bacterial community diversity and the relative abundance of dominant Proteobacteria. SEM showed that endophyte infection increased the shoot and root biomass under saline-alkali stress (200 and 400 mM) by increasing the arbuscular mycorrhizal fungal diversity in the roots, and soil total nitrogen and phosphorus concentrations. Therefore, it is important to examine aboveground microbes as factors influencing plant growth in saline-alkali stress by affecting belowground microbes and soil chemical properties.     

Effect of Epichloë fungal endophyte symbiosis on tall fescue to cope with flooding-derived oxygen-limited conditions depends on the host genotype

Plant and Soil - There is little information about the role of fungal endophytes on plant performance under oxygen-limited conditions. This study aimed to investigate the effect of Epichloë...     

Epichloë endophyte affects the root colonization pattern of belowground symbionts in a wild grass

Plants host multiple symbionts that interact with each other affecting plant performance and regulating their establishment. Here, we analyzed how the association with Epichloë endophytes affects belowground colonization by Dark Septate Endophytes (DSE) and arbuscular mycorrhizal fungi (AMF) in the grass Bromus auleticus. Epichloë-symbiotic (E+) and Epichloë-non symbiotic (E−) plants were sampled from a long-term experimental plot and colonization structures were analyzed in the roots. We also examined the influence of Epichloë exudates on the in vitro growth of DSE Microdochium bolleyi isolated from roots. Epichloë symbiosis increased AMF colonization, although differences were not significant. Despite the lack of differences in total DSE colonization, in concordance with in vitro findings, a higher significant abundance of microsclerotia was observed in E+ plants. A negative correlation between total mycorrhizal and DSE was found. Our findings show a more uniform root colonization pattern in E+ plants, suggesting a root symbiosis modulating role.     

The effects of carbohydrate supply and host genetic background on Epichloë endophyte and alkaloid concentrations in perennial ryegrass

The ecological effects of novel grass–endophyte associations used in agriculture have not been widely studied. Previous studies of asexual Epichloë-infected Lolium perenne suggest that endophyte concentration is altered in high sugar grasses (HSGs) selectively bred to produce higher concentrations of water-soluble carbohydrates relative to conventional cultivars. We investigated whether differences are due to the effects of altered carbohydrates, or genetic background, by growing multiple cultivars in both high-sugar trait expression and non-expression conditions (using light/temperature treatments). Endophyte and alkaloid concentrations were measured in three HSG and three NSG (normal-sugar grass) cultivars infected with Lp19 or AR37 endophyte strains. Low molecular weight (LMW) carbohydrates had a small effect, explaining <6% of the variation in endophyte concentration. Endophyte concentrations were strongly dependent on plant genotype and fungal strain, with the highest concentrations seen in Lp19, suggesting that the interaction is highly dependent on genetic compatibility. Changes in endophyte concentration due to altered environmental variables and genetic compatibility may have consequences for persistence, toxicity, and invasive potential of endophyte-infected plants.     

The formation of vesicles in the developmental cycle of the nodular endophyte of Hippophaë rhamnoides L.

Summary The mature vesicle of the Hippophaë rhamnoides root nodule endophyte is spherical, approximately 3–4 m in diameter and exhibits a high degree of apparently random septation. Electron micrographs are presented which show that this vesicular form in the endophytic development within the host cell originates as a swelling of the hyphal tip. The young vesicle is non-septate and in general attains a minimum diameter of 3 m before septation becomes evident. The number of septa then increases with vesicle maturity.     

Infection by the systemic fungus Epichloë glyceriae alters clonal growth of its grass host,Glyceria striata

Parasites and pathogens are hypothesized to change host growth, reproduction and/or behaviour to increase their own transmission. However, studies which clearly demonstrate that parasites or pathogens are directly responsible for changes in hosts are lacking. We previously found that infection by the systemic fungus Epichloë glyceriae was associated with greater clonal growth by its host, Glyceria striata. Whether greater clonal growth resulted directly from pathogen infection or indirectly from increased likelihood of infection for host genotypes with greater clonal growth could not be determined because only naturally infected and uninfected plants were used. In this study, we decoupled infection and host genotype to evaluate the role of pathogen infection on host development and clonal growth. We found that total biomass production did not differ for clones of the same genotype, but infected clones allocated more biomass to clonal growth. Disinfected clones had more tillers and a greater proportion of their biomass in the mother ramet. Infected clones produced fewer tillers but significantly more and longer stolons than disinfected clones. These results support the hypothesis that pathogen infection directly alters host development. Parasite alteration of clonal growth patterns might be advantageous to the persistence and spread of host plants in some ecological conditions.     

Effect of the fungal endophyte Epichloë bromicola on polyamines in wild barley (Hordeum brevisubulatum) under salt stress

Plant and Soil - The endophytic fungus Epichloë bromicola forms mutualistic symbiotic associations with wild barley (Hordeum brevisubulatum) in the saline-alkali areas of northwestern China....     

A comparative life cycle assessment of the sugarcane value chain in the province of Tucumán (Argentina) considering different technology levels

Purpose

The purpose of this work is to quantify the environmental impact of the sugarcane industry in Tucumán (Argentina) through the life cycle analysis (LCA). The distinctive feature is the consideration of different technology levels (TLs) in the agricultural stage: high (HTL), medium (MTL), and low (LTL).

Methods

The scope of the study covers the agricultural and industrial stages through a “from cradle to gate” approach (from sugarcane cultivation until production of finished products: sugar and alcohol). The system is divided into Agriculture, Sugar Factory, and Distillery. Data used for the inventory are mainly provided by local experts, sugarcane growers, and processing companies. The characteristics of each TL are taken from a regional classification. For the impact assessment, the CML 2001 model (nine impact categories) is used.

Results and discussion

Regardless of the TL, in most of the impact categories, an important contribution attributable to the use of synthetic agrochemicals is evident. As for the comparison among TLs, the ethanol produced with HTL has less impact values than the ones produced with MTL and LTL in seven categories. These results can be mainly explained by the better cultural yields obtained with HTL, and to the fact that sugarcane is not burnt before harvesting in HTL as it is in MTL and LTL.

Conclusions

This study explores the implications of using different TLs for the agricultural tasks on the sugarcane supply chain in Tucumán, which is characterized by a vertically nonintegrated productive scheme. If practices associated to HTL are implemented, a reduction of the environmental impact is observed in most categories. It is necessary to compare these results with economic and social implications to ensure sustainability of the sugarcane value chain.

     

Protein composition of different stages in the life cycle of Ulva mutabilis,Føyn

Summary Soluble protein, about 15% of the total cellular protein, was extracted from different stages in the haplodiplontic life cycle of Ulva mutabilis. The electrophoretic band pattern of the protein extracts from the haploid gametophyte and the diploid sporophyte were found to be the same, except for one slow moving band present in the gametophyte, but lacking in the diploid sporophyte. This band was also missing in the extract from the haploid parthenosporophyte, but is seen in the extract from the zoospores. It was found that the synthesis of the protein in this band occurred during most of the preparation period preceding meiosis. The band is not seen in extracts from gametes, and it is inferred that this protein is broken down during the period preceding the mitotic gametangial division in the gametophyte. So far the protein making up this band behaves as should be required for a factor determining the shift in generation during the life cycle.     

Increasing the lifetime of products by nanomaterial inclusions—life cycle energy implications

The International Journal of Life Cycle Assessment - Typically, the high energy required to manufacture nanomaterials is weighed against the benefits transferred to a product. Adequately...     

The methodology and results of using life cycle assessment to measure and reduce the greenhouse gas emissions footprint of “Major Events” at the University of Arizona

Purpose

In 2012 and 2013, the University of Arizona’s Office of Sustainability conducted environmental life cycle assessments of two Homecoming events that drew 60,000 attendees each. Based on reviews of published literature, this is the first time that a process-based life cycle assessment has been conducted for an event of this size. This study contributes to the small but growing field of research using life cycle assessment to track the environmental impacts of events.

Methods

The assessments at The University of Arizona considered the environmental impact of food, materials, waste, travel, and lodging. The effects of these components of Homecoming weekend were evaluated in terms of nine different categories. However, this paper focuses on greenhouse gas emissions. The data collection process for these assessments was completed by student observers and supplemented with information provided by university departments, event organizers, and survey responses from attendees. Data were analyzed using SimaPro Life Cycle Assessment software and using data from the EcoInvent database. Based on the results of the 2012 study, initiatives were put into place for 2013 that were designed to reduce the environmental impact of the subsequent Homecoming event.

Results and discussion

The results show that the total impact of Homecoming 2012 was an estimated 2400 metric tons of CO₂-eq, whereas the impact of Homecoming 2013 was an estimated 1900 metric tons of CO₂-eq, a 19 % decrease year over year. Data were analyzed in terms of carbon dioxide emissions in both years. Travel made up the majority of the environmental impact (82.04 % in 2012 and 77.77 % in 2013), followed by accommodations (17.5 % in 2012 and 19.31 % in 2013), with energy, materials, and food having almost negligible impacts (0.46 % in 2012 and 2.92 % in 2013). While there had been noticeable changes in the measured impact of food and energy between 2012 and 2013, the significant impact of travel overshadowed all other impact categories in terms of greenhouse gas emissions, making these changes less noticeable. Analysis of each of these categories of impact helped to establish best practices for mitigating the impact of events on a category-by-category basis.

Conclusions

This study introduces a framework for assessing impacts of a large university event while also highlighting ways to reduce impacts. The initiatives implemented in 2013 to reduce impacts of large-scale events can be informative to others working to reduce emissions at large events. Additional recommendations to reduce impacts of large events are provided.

     

Epichloë endophyte affects the ability of powdery mildew (Blumeria graminis) to colonise drunken horse grass (Achnatherum inebrians)

The effect of the systemic seed-borne endophyte Epichloë gansuensis on the colonization by Blumeria graminis, the cause of powdery mildew disease, and the growth of the host grass Achnatherum inebrians, was studied under four soil water conditions. Infection incidence, disease lesion parameters, disease index, biomass production and growth parameters of the grass with and without the fungal endophyte were measured and counted after a period of disease. There was a significantly (P < 0.05) higher disease incidence and disease index for endophyte-free (E−) compared to endophyte-infected (E+) plants under different drought stresses. The presence of the endophyte significantly positively affected all of the host grass growth factors. The results of the present study demonstrate that the presence of the Epichloë endophyte reduced the ability of B. graminis to colonise A. inebrians and also conferred enhanced host plant growth at all soil water conditions tested.     

The effects of Epichloë endophytes on the growth and competitiveness of Achnatherum sibiricum are mediated by soil microbe diversity

季节性干旱驱动亚热带森林的碳积累 本研究旨在表明处于南亚热带的鼎湖山生物圈保护区的干旱频率和强度正在增加,并说明季节性干旱对亚热带森林碳积累的影响。这是为了应对全球气候变化导致的干旱加剧所带来的威胁开展的一项研究。我们使干旱指数(标准化降水指数、标准降水蒸散发指数、降水距平百分率及自校准帕尔默干旱指数)准确确定干旱期和降水量增加期。此后,将2003至2014年(12年)监测采集的实测涡动通量和土壤含水量数据在干旱期和湿润期之间进行比较,以确定干旱对生态系统碳积累的影响。在本研究所选择的12年期间,干旱的发生时间约占比20%,最强干旱事件和严重程度发生于2012至2013年。研究期间的年平均降水量和气温分别为1404.57 ± 43.2 mm和22.65 ± 0.1 °C,与30年记录(1990–2020)相比较,年降水量减少量可达523 mm,而气温则增加了2.55 °C。与全球针对大多数森林生态系统研究所发表的数据呈相反趋势,处于中国南亚热带区域的鼎湖山生物圈保护区在60%的干旱期内所监测的森林生态系统记录到显著的碳积累趋势,说明季节性干旱驱动了森林的碳积累。     

NMR study of hydrogen exchange during the B-Z transition of a DNA duplex induced by the Zα domains of yatapoxvirus E3L

The Yaba-like disease viruses (YLDV) are members of the Yatapoxvirus family and have double-stranded DNA genomes. The E3L protein, which is essential for pathogenesis in the vaccinia virus, consists of two domains: an N-terminal Z-DNA binding domain and a C-terminal RNA binding domain. The crystal structure of the E3L orthologue of YLDV (yabZα_E3L) bound to Z-DNA revealed that the overall structure of yabZα_E3L and its interaction with Z-DNA are very similar to those of hZα_ADAR1. Here we have performed NMR hydrogen exchange experiments on the complexes between yabZα_E3L and d(CGCGCG)₂ with a variety of protein-to-DNA molar ratios. This study revealed that yabZα_E3L could efficiently change the B-form helix of the d(CGCGCG)₂ to left-handed Z-DNA via the active-mono B-Z transition pathway like hZα_ADAR1.