Browsing by Subject "DEFENSE"

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  • Cui, Fuqiang; Wenwu, Wu; Wang, Kai; Zhang, Yuan; Zhubing, Hu; Brosche, Mikael; Liu, Shenkui; Overmyer, Kirk (2019)
    Prevailing evidence indicates that abscisic acid (ABA) negatively influences immunity to the fungal pathogen Botrytis cinerea in most but not all cases. ABA is required for cuticle biosynthesis, and cuticle permeability enhances immunity to Botrytis via unknown mechanisms. This complex web of responses obscures the role of ABA in Botrytis immunity. Here, we addressed the relationships between ABA sensitivity, cuticle permeability, and Botrytis immunity in the Arabidopsis thaliana ABA-hypersensitive mutants protein phosphatase2c quadruple mutant (pp2c-q) and enhanced response to aba1 (era1-2). Neither pp2c-q nor era1-2 exhibited phenotypes predicted by the known roles of ABA; conversely, era1-2 had a permeable cuticle and was Botrytis resistant. We employed RNA-seq analysis in cuticle-permeable mutants of differing ABA sensitivities and identified a core set of constitutively activated genes involved in Botrytis immunity and susceptibility to biotrophs, independent of ABA signaling. Furthermore, botrytis susceptible1 (bos1), a mutant with deregulated cell death and enhanced ABA sensitivity, suppressed the Botrytis immunity of cuticle permeable mutants, and this effect was linearly correlated with the extent of spread of wound-induced cell death in bos1. Overall, our data demonstrate that Botrytis immunity conferred by cuticle permeability can be genetically uncoupled from PP2C-regulated ABA sensitivity, but requires negative regulation of a parallel ABA-dependent cell-death pathway.
  • Kimura, Sachie; Hunter, Kerri; Vaahtera, Lauri; Tran, Cuong; Citterico, Matteo; Vaattovaara, Aleksia; Rokka, Anne; Stolze, Sara Christina; Harzen, Anne; Meißner, Lena; Wilkens, Maya Melina Tabea; Hamann, Thorsten; Toyoga, Masatsugu; Nakagami, Hirofumi; Wrzaczek, Michael (2020)
    Reactive oxygen species (ROS) are important messengers in eukaryotic organisms and their production is tightly controlled. Active extracellular ROS production by NADPH oxidases in plants is triggered by receptor-like protein kinase (RLK)-dependent signaling networks. Here we show that the cysteine-rich RLK CRK2 kinase activity is required for plant growth and CRK2 exists in a preformed complex with the NADPH oxidase RBOHD in Arabidopsis. Functional CRK2 is required for the full elicitor-induced ROS burst and consequently the crk2 mutant is impaired in defense against the bacterial pathogen Pseudomonas syringae pv. tomato DC3000. Our work demonstrates that CRK2 regulates plant innate immunity. We identified in vitro CRK2-dependent phosphorylation sites in the C-terminal region of RBOHD. Phosphorylation of S703 RBOHD is enhanced upon flg22 treatment and substitution of S703 with alanine reduced ROS production in Arabidopsis. Phylogenetic analysis suggests that phospho-sites in C-terminal region of RBOHD are conserved throughout the plant lineage and between animals and plants. We propose that regulation of NADPH oxidase activity by phosphorylation of the C-terminal region might be an ancient mechanism and that CRK2 is an important element in regulating MAMP-triggered ROS production.
  • Safronov, Omid; Kreuzwieser, Juergen; Haberer, Georg; Alyousif, Mohamed S.; Schulze, Waltraud; Al-Harbi, Naif; Arab, Leila; Ache, Peter; Stempfl, Thomas; Kruse, Joerg; Mayer, Klaus X.; Hedrich, Rainer; Rennenberg, Heinz; Salojarvi, Jarkko; Kangasjarvi, Jaakko (2017)
    Plants adapt to the environment by either long-term genome evolution or by acclimatization processes where the cellular processes and metabolism of the plant are adjusted within the existing potential in the genome. Here we studied the adaptation strategies in date palm, Phoenix dactylifera, under mild heat, drought and combined heat and drought by transcriptomic and metabolomic profiling. In transcriptomics data, combined heat and drought resembled heat response, whereas in metabolomics data it was more similar to drought. In both conditions, soluble carbohydrates, such as fucose, and glucose derivatives, were increased, suggesting a switch to carbohydrate metabolism and cell wall biogenesis. This result is consistent with the evidence from transcriptomics and cis-motif analysis. In addition, transcriptomics data showed transcriptional activation of genes related to reactive oxygen species in all three conditions (drought, heat, and combined heat and drought), suggesting increased activity of enzymatic antioxidant systems in cytosol, chloroplast and peroxisome. Finally, the genes that were differentially expressed in heat and combined heat and drought stresses were significantly enriched for circadian and diurnal rhythm motifs, suggesting new stress avoidance strategies.
  • Kovalchuk, Andriy; Zeng, Zhen; Ghimire, Rajendra P.; Kivimäenpää, Minna; Raffaello, Tommaso; Liu, Mengxia; Mukrimin, Mukrimin; Kasanen, Risto Aarne Olavi; Sun, Hui; Julkunen-Tiitto, Riitta; Holopainen, Jarmo K.; Asiegbu, Frederick Obioma (2019)
    BackgroundRoot and butt rot of conifer trees caused by fungi belonging to the Heterobasidion annosum species complex is one of the most economically important fungal diseases in commercial conifer plantations throughout the Northern hemisphere. We investigated the interactions between Heterobasidion fungi and their host by conducting dual RNA-seq and chemical analysis on Norway spruce trees naturally infected by Heterobasidion spp. We analyzed host and pathogen transcriptome and phenolic and terpenoid contents of the spruce trees.ResultsPresented results emphasize the role of the phenylpropanoid and flavonoid pathways in the chemical defense of Norway spruce trees. Accumulation of lignans was observed in trees displaying symptoms of wood decay. A number of candidate genes with a predicted role in the higher level regulation of spruce defense responses were identified. Our data indicate a possible role of abscisic acid (ABA) signaling in the spruce defense against Heterobasidion infection. Fungal transcripts corresponding to genes encoding carbohydrate- and lignin-degrading enzymes, secondary metabolism genes and effector-like genes were expressed during the host colonization.ConclusionsOur results provide additional insight into defense strategies employed by Norway spruce trees against Heterobasidion infection. The potential applications of the identified candidate genes as markers for higher resistance against root and butt rot deserve further evaluation.
  • Huang, Weini; Traulsen, Arne; Werner, Benjamin; Hiltunen, Teppo; Becks, Lutz (2017)
    Trade-offs play an important role in evolution. Without trade-offs, evolution would maximize fitness of all traits leading to a "master of all traits". The shape of trade-offs has been shown to determine evolutionary trajectories and is often assumed to be static and independent of the actual evolutionary process. Here we propose that coevolution leads to a dynamical trade-off. We test this hypothesis in a microbial predator-prey system and show that the bacterial growth-defense trade-off changes from concave to convex, i.e., defense is effective and cheap initially, but gets costly when predators coevolve. We further explore the impact of such dynamical trade-offs by a novel mathematical model incorporating de novo mutations for both species. Predator and prey populations diversify rapidly leading to higher prey diversity when the trade-off is concave (cheap). Coevolution results in more convex (costly) trade-offs and lower prey diversity compared to the scenario where only the prey evolves.
  • Woestmann, Luisa; Kvist, Jouni Antero; Saastamoinen, Marjo Anna Kaarina (2017)
    Flight represents a key trait in most insects, being energetically extremely demanding, yet often necessary for foraging and reproduction. Additionally, dispersal via flight is especially important for species living in fragmented landscapes. Even though, based on life-history theory, a negative relationship may be expected between flight and immunity, a number of previous studies have indicated flight to induce an increased immune response. In this study, we assessed whether induced immunity (i.e. immune gene expression) in response to 15-min forced flight treatment impacts individual survival of bacterial infection in the Glanville fritillary butterfly (Melitaea cinxia). We were able to confirm previous findings of flight-induced immune gene expression, but still observed substantially stronger effects on both gene expression levels and life span due to bacterial infection compared to flight treatment. Even though gene expression levels of some immunity-related genes were elevated due to flight, these individuals did not show increased survival of bacterial infection, indicating that flight-induced immune activation does not completely protect them from the negative effects of bacterial infection. Finally, an interaction between flight and immune treatment indicated a potential trade-off: flight treatment increased immune gene expression in naive individuals only, whereas in infected individuals no increase in immune gene expression was induced by flight. Our results suggest that the up-regulation of immune genes upon flight is based on a general stress response rather than reflecting an adaptive response to cope with potential infections during flight or in new habitats.
  • Mariotti, Lorenzo; Huarancca Reyes, Thais; Ramos-Diaz, Jose Martin; Jouppila, Kirsi; Guglielminetti, Lorenzo (2021)
    Increased ultraviolet-B (UV-B) due to global change can affect plant development and metabolism. Quinoa tolerates extreme conditions including high UV levels. However, the physiological mechanisms behind its abiotic stress tolerance are unclear, especially those related to UV-B. We previously demonstrated that 9.12 kJ m−2 d−1 may induce UV-B-specific signaling while 18.24 kJ m−2 d−1 promotes a UV-B-independent response. Here, we explored the effects of these UV-B doses on hormonal regulation linked to plant morphology and defense among diverse varieties. Changes in fluorescence parameters of photosystem II, flavonoids and hormones (indoleacetic acid (IAA), jasmonic acid (JA), abscisic acid (ABA) and salicylic acid (SA)) were surveyed under controlled conditions. Here, we showed that the sensitivity to short acute UV-B doses in varieties from different habitats is influenced by their parental lines and breeding time. UV-B sensitivity does not necessarily correlate with quinoa’s geographical distribution. The role of flavonoids in the UV-B response seems to be different depending on varieties. Moreover, we found that the extent of changes in JA and SA correlate with UV-B tolerance, while the increase of ABA was mainly related to UV-B stress.
  • Pimentel, Andre C.; Beraldo, Camila S.; Cogni, Rodrigo (2021)
    Host shifts, when a cross-species transmission of a pathogen can lead to successful infections, are the main cause of emerging infectious diseases, such as COVID-19. A complex challenge faced by the scientific community is to address the factors that determine whether the cross-species transmissions will result in spillover or sustained onwards infections. Here we review recent literature and present a perspective on current approaches we are using to understand the mechanisms underlying host shifts. We highlight the usefulness of the interactions between Drosophila species and viruses as an ideal study model. Additionally, we discuss how cross-infection experiments - when pathogens from a natural reservoir are intentionally injected in novel host species-can test the effect cross-species transmissions may have on the fitness of virus and host, and how the host phylogeny may influence this response. We also discuss experiments evaluating how cooccurrence with other viruses or the presence of the endosymbiont bacteria Wolbachia may affect the performance of new viruses in a novel host. Finally, we discuss the need of surveys of virus diversity in natural populations using next-generation sequencing technologies. In the long term, these approaches can contribute to a better understanding of the basic biology of host shifts.
  • Tang, Jiaxin; Chen, Yang; She, Guozhen; Xu, Yang; Sha, Kewei; Wang, Xin; Wang, Yi; Zhang, Zhenhua; Hui, Pan (2021)
    Google Scholar has been a widely used platform for academic performance evaluation and citation analysis. The issue about the mis-configuration of author profiles may seriously damage the reliability of the data, and thus affect the accuracy of analysis. Therefore, it is important to detect the mis-configured author profiles. Dealing with this issue is challenging because the scale of the dataset is large and manual annotation is time-consuming and relatively subjective. In this paper, we first collect a dataset of Google Scholar's author profiles in the field of computer science and compare the mis-configured author profiles with the reliable ones. Then, we propose an integrated model that utilizes machine learning and node embedding to automatically detect mis-configured author profiles. Additionally, we conduct two application case studies based on the data of Google Scholar, i.e., outstanding scholar searching and university ranking, to demonstrate how the improved dataset after filtering out the mis-configured author profiles will change the results. The two case studies validate the importance and meaningfulness of the detection of mis-configured author profiles.
  • Fuchs, Siiri-Anna; Sundström, Liselotte; Bos, Nick; Stucki, Dimitri; Freitak, Dalial (2018)
    Parental immune experience can enhance offspring defence mechanisms towards prevalent pathogens in the surrounding environment. This process of inherited resistance from one generation to another is known as trans-generational immune priming (TGIP) in invertebrates. In sedentary and dense insect societies, such as ant colonies, TGIP can influence colony survival and fitness upon pathogen outbreaks. However, TGIP appears to depend on species and environmental stressors and therefore can vary in intensity, as well as in the molecular mechanisms leading to resistance. Here, we stimulated the immune system of queens of the ant Formica fusca (LINNAEUS, 1758) by wounding or injecting dead conidia of the entomopathogenic fungus Beauveria bassiana (BALS.-CRIV.) VUILL. (1912). The offspring were subsequently infected with B. bassiana, and the effect of this priming on survival was evaluated. Furthermore, we investigated whether immune challenge of the mother queen induces changes in the expression of immunity-related genes in queens themselves and their brood. We combined this information with measurements of offspring size and number. Larvae produced by untreated queens had a significantly higher mortality after infection with B. bassiana, whereas those produced by immune-primed queens survived no worse than unexposed ones. Adult worker offspring from sham-control mothers showed a protective effect of queen treatment, consistent with transgenerational immune priming. Thus, the effects of queen priming appear to manifest themselves slightly differently in larval and adult offspring. No differences were detected in offspring number or size, but immune gene expression levels showed changes, both in queens and their offspring.
  • Wang, Kai; Sipilä, Timo Petteri; Overmyer, Kirk Loren (2016)
    The genetic model plant Arabidopsis thaliana (arabidopsis) has been instrumental to recent advances in our understanding of the molecular function of the plant immune system. However, this work has not yet included plant associated and phytopathogenic yeasts largely due to a lack of yeast species known to interact with arabidopsis. The plant phylloplane is a significant habitat for neutral-residents, plant-growth and health-promoting species, and latent-pathogenic species. However, yeast phylloplane residents of arabidopsis remain underexplored. To address this, resident yeasts from the phyllosphere of wild arabidopsis collected in field conditions have been isolated and characterized. A total of 95 yeast strains representing 23 species in 9 genera were discovered, including potentially psychrophilic and pathogenic strains. Physiological characterization revealed thermotolerance profiles, sensitivity to the arabidopsis phytoalexin camalexin, the production of indolic compounds, and the ability to activate auxin responses in planta. These results indicate a rich diversity of yeasts present in the arabidopsis phylloplane and have created culture resources and information useful in the development of model systems for arabidopsis-yeast interactions.
  • Zhang, Sheng; Tang, Duoteng; Korpelainen, Helena; Li, Chunyang (2019)
    Dioecious trees have evolved sex-specific adaptation strategies to cope with inorganic phosphorus (Pi) limitation. Yet, little is known about the effects of Pi limitation on plant metabolism, particularly in dioecious woody plants. To identify potential gender-specific metabolites appearing in response to Pi limitation in poplars, we studied the metabolic and ionomic responses in the roots and leaves of Populus cathayana Rehd males and females exposed to a 60-day period of Pi deficiency. Besides significant decreases in phosphorus contents in both Pi-deficient roots and leaves, the calcium level decreased significantly and the sulfur content increased significantly in Pi-deficient male roots, while the zinc and ferrum contents increased significantly in Pi-deficient female roots. Inorganic P deficiency caused a smaller change in the abscisic acid content, but a significant increase in the jasmonic acid content was detected in both leaves and roots. Salicylic acid significantly decreased under Pi deficiency in male leaves and female roots. Changes were found in phospholipids and phosphorylated metabolites (e.g., fructose-6-phosphate, glycerol-3-phosphate, glucose-6-phosphate, phosphoric acid and inositol-1-phosphate) in roots and leaves. Both P. cathayana males and females relied on inorganic pyrophosphate-dependent but not on Pi-dependent glycolysis under Pi-deficient conditions. Sex-specific metabolites in leaves were primarily in the category of primary metabolites (e.g., amino acids), while in roots primarily in the category of secondary metabolites (e.g., organic acids) and sugars. The metabolome analysis revealed that sexually different pathways occurred mainly in amino acid metabolism, and the tissue-related differences were in the shikimate pathway and glycolysis. We observed changes in carbon flow, reduced root biomass and increased amino acid contents in P. cathayana males but not in females, which indicated that males have adopted an energy-saving strategy to adapt to Pi deficiency. Thus, this study provides new insights into sex-specific metabolic responses to Pi deficiency.
  • Tanigaki, Yusuke; Ito, Kenji; Obuchi, Yoshiyuki; Kosaka, Akiko; Yamato, Katsuyuki T.; Okanami, Masahiro; Lehtonen, Mikko T.; Valkonen, Jari P. T.; Akita, Motomu (2014)
  • Hämäläinen, Liisa; Mappes, Johanna; Thorogood, Rose; Valkonen, Janne K.; Karttunen, Kaijamari; Salmi, Tuuli; Rowlanda, Hannah M. (2020)
    Many prey species contain defensive chemicals that are described as tasting bitter. Bitter taste perception is, therefore, assumed to be important when predators are learning about prey defenses. However, it is not known how individuals differ in their response to bitter taste, and how this influences their foraging decisions. We conducted taste perception assays in which wild-caught great tits (Parus major) were given water with increasing concentrations of bitter-tasting chloroquine diphosphate until they showed an aversive response to bitter taste. This response threshold was found to vary considerably among individuals, ranging from chloroquine concentrations of 0.01 mmol/L to 8 mmol/L. We next investigated whether the response threshold influenced the consumption of defended prey during avoidance learning by presenting birds with novel palatable and defended prey in a random sequence until they refused to attack defended prey. We predicted that individuals with taste response thresholds at lower concentrations would consume fewer defended prey before rejecting them, but found that the response threshold had no effect on the birds' foraging choices. Instead, willingness to consume defended prey was influenced by the birds' body condition. This effect was age- and sex-dependent, with adult males attacking more of the defended prey when their body condition was poor, whereas body condition did not have an effect on the foraging choices of juveniles and females. Together, our results suggest that even though taste perception might be important for recognizing prey toxicity, other factors, such as predators' energetic state, drive the decisions to consume chemically defended prey. Lay Summary: Individual differences in predators' bitter taste perception do not influence the consumption of chemically defended prey. Many prey species have bitter-tasting defenses that generate aversive responses in predators. We show that great tits vary in their response to bitter taste, but this does not influence the number of novel defended prey they attack during avoidance learning. This suggests that other factors, such as the current physiological state, have a larger impact on predators' foraging decisions.
  • Sipari, Nina; Lihavainen, Jenna; Shapiguzov, Alexey; Kangasjärvi, Jaakko; Keinänen, Markku (2020)
    Rcd1 (radical-induced cell death1) is an Arabidopsis thaliana mutant, which exhibits high tolerance to paraquat [methyl viologen (MV)], herbicide that interrupts photosynthetic electron transport chain causing the formation of superoxide and inhibiting NADPH production in the chloroplast. To understand the biochemical mechanisms of MV resistance and the role of RCD1 in oxidative stress responses, we performed metabolite profiling of wild type (Col-0) and rcd1 plants in light, after MV exposure and after prolonged darkness. The function of RCD1 has been extensively studied at transcriptomic and biochemical level, but comprehensive metabolite profiling of rcd1 mutant has not been conducted until now. The mutant plants exhibited very different metabolic features from the wild type under light conditions implying enhanced glycolytic activity, altered nitrogen and nucleotide metabolism. In light conditions, superoxide production was elevated in rcd1, but no metabolic markers of oxidative stress were detected. Elevated senescence-associated metabolite marker levels in rcd1 at early developmental stage were in line with its early-senescing phenotype and possible mitochondrial dysfunction. After MV exposure, a marked decline in the levels of glycolytic and TCA cycle intermediates in Col-0 suggested severe plastidic oxidative stress and inhibition of photosynthesis and respiration, whereas in rcd1 the results indicated sustained photosynthesis and respiration and induction of energy salvaging pathways. The accumulation of oxidative stress markers in both plant lines indicated that MV-resistance in rcd1 derived from the altered regulation of cellular metabolism and not from the restricted delivery of MV into the cells or chloroplasts. Considering the evidence from metabolomic, transcriptomic and biochemical studies, we propose that RCD1 has a negative effect on reductive metabolism and rerouting of the energy production pathways. Thus, the altered, highly active reductive metabolism, energy salvaging pathways and redox transfer between cellular compartments in rcd1 could be sufficient to avoid the negative effects of MV-induced toxicity.
  • Durian, Guido; Rahikainen, Moona; Vuorinen, Katariina; Gollan, Peter J.; Brosche, Mikael; Salojarvi, Jarkko; Glawischnig, Erich; Winter, Zsófia; Li, Shengchun; Noctor, Graham; Aro, Eva-Mari; Kangasjärvi, Jaakko; Overmyer, Kirk; Burow, Meike; Kangasjärvi, Saijaliisa (2020)
    Plants optimize their growth and survival through highly integrated regulatory networks that coordinate defensive measures and developmental transitions in response to environmental cues. Protein phosphatase 2A (PP2A) is a key signaling component that controls stress reactions and growth at different stages of plant development, and the PP2A regulatory subunit PP2A-B'gamma is required for negative regulation of pathogenesis responses and for maintenance of cell homeostasis in short-day conditions. Here, we report molecular mechanisms by which PP2A-B'gamma regulates Botrytis cinerea resistance and leaf senescence in Arabidopsis (Arabidopsis thaliana). We extend the molecular functionality of PP2A-B'gamma to a protein kinase-phosphatase interaction with the defense-associated calcium-dependent protein kinase CPK1 and present indications this interaction may function to control CPK1 activity. In presenescent leaf tissues, PP2A-B'gamma is also required to negatively control the expression of salicylic acid-related defense genes, which have recently proven vital in plant resistance to necrotrophic fungal pathogens. In addition, we find the premature leaf yellowing of pp2a-b'gamma depends on salicylic acid biosynthesis via SALICYLIC ACID INDUCTION DEFICIENT2 and bears the hallmarks of developmental leaf senescence. We propose PP2A-B'gamma age-dependently controls salicylic acid-related signaling in plant immunity and developmental leaf senescence.
  • Raffaello, Tommaso; Asiegbu, Fred O. (2017)
    The basidiomycete Heterobasidion annosum sensu lato (s. l.) is considered to be one of the most destructive conifer pathogens in the temperate forests of the northern hemisphere. H. annosum is characterized by a dual fungal lifestyle. The fungus grows necrotrophically on living plant cells and saprotrophically on dead wood material. In this study, we screened the H. annosum genome for small secreted proteins (HaSSPs) that could potentially be involved in promoting necrotrophic growth during the fungal infection process. The final list included 58 HaSSPs that lacked predictable protein domains. The transient expression of HaSSP encoding genes revealed the ability of 8 HaSSPs to induce cell chlorosis and cell death in Nicotiana benthamiana. In particular, one protein (HaSSP30) could induce a rapid, strong, and consistent cell death within 2 days post-infiltration. HaSSP30 also increased the transcription of host-defence-related genes in N. benthamiana, which suggested a necrotrophic-specific immune response. This is the first line of evidence demonstrating that the H. annosum genome encodes HaSSPs with the capability to induce plant cell death in a non-host plant.
  • Stucki, Dimitri; Freitak, Dalial; Bos, Nick; Sundstrom, Liselotte (2019)
    Organisms are simultaneously exposed to multiple stresses, which requires regulation of the resistance to each stress. Starvation is one of the most severe stresses organisms encounter, yet nutritional state is also one of the most crucial conditions on which other stress resistances depend. Concomitantly, organisms often deploy lower immune defenses when deprived of resources. This indicates that the investment into starvation resistance and immune defenses is likely to be subject to trade-offs. Here, we investigated the impact of starvation and oral exposure to bacteria on survival and gene expression in the ant Formica exsecta. Of the three bacteria used in this study, only Serratia marcescens increased the mortality of the ants, whereas exposure to Escherichia coli and Pseudomonas entomophila alleviated the effects of starvation. Both exposure to bacteria and starvation induced changes in gene expression, but in different directions depending on the species of bacteria used, as well as on the nutritional state of the ants.
  • Tamura, Mako; Tanabe, Minatsu; Valkonen, Jari P. T.; Akita, Motomu (2019)
    Mosses are ecologically important plants also used for greening, gardening, and decorative purposes. Knowledge of the microbial flora associated with mosses is expected to be important for control and preservation of global and local environments. However, the moss-associated microbial flora is often poorly known. Moss-associated fungi and bacteria may promote plant growth and pest control, but they may be alternative hosts for pathogens of vascular plants. In this study, the fungus Sclerotinia delphinii was identified for the first time as a pathogen that causes severe damage to Sunagoke moss (Racomitrium japonicum). This moss is used for greening roofs and walls of buildings in urban environments owing to its notable tolerance of environmental stresses. Inoculation with the S. delphinii strain SR1 of the mono- and dicotyledonous seed plants Hordeum vulgare, Brassica rapa var. pekinensis, Lactuca sativa, and Spinacia oleracea, in addition to the liverwort Marchantia polymorpha and the moss Physcomitrella patens, showed that the fungus has a wide host range. Colonization with SR1 progressed more rapidly in non-vascular than in vascular plant species. Studies with P. patens under controlled conditions showed that SR1 secreted a fluid during colonization. Treatment with the secretion induced production of reactive oxygen species in the moss. Endogenous peroxidase partially inhibited SR1 colonization of P. patens. A bacterial isolate, most likely Bacillus amyloliquefaciens, that coexists with R. japonicum was antagonistic to SR1 growth. Taken together, the present results suggest that fungal colonization of mosses may be prevented by a peroxidase secreted by the moss and an antagonistic bacterium coexisting in the moss habitat. The findings suggest that there is potential to apply biological control measures for protection of mosses against fungal pathogens.
  • Rosa, Elena; van Nouhuys, Saskya; Saastamoinen, Marjo (2017)
    Aggregation can confer advantages in animal foraging, defense, and thermoregulation. There is a tight connection between the evolution of insect sociality and a highly effective immune system, presumably to inhibit rapid disease spread in a crowded environment. This connection is less evident for animals that spend only part of their life cycle in a social environment, such as noneusocial gregarious insects. Our aim was to elucidate the effects of group living by the gregarious larvae of the Glanville fritillary butterfly with respect to individual performance, immunity, and susceptibility to a parasitoid. We were also interested in the role of family relative to common postdiapause environment in shaping life-history traits. Larvae were reared at high or low density and then exposed to the pupal parasitoid wasp Pteromalus apum, either in presence or absence of a previous immune challenge that was used to measure the encapsulation immune response. Surviving adult butterflies were further tested for immunity. The wasp offspring from successfully parasitized butterfly pupae were counted and their brood sex ratios assessed. Larvae reared at high density grew larger and faster than those at low density. Despite high mortality due to parasitism, survival was greater among individuals with high pupal immunity in both density treatments. Moreover, butterfly pupae reared at high density were able to kill a larger fraction of individuals in the parasitoid broods, although this did not increase survival of the host. Finally, a larger proportion of variation observed in most of the traits was explained by butterfly family than by common postdiapause rearing environment, except for adult survival and immunity, for which this pattern was reversed. This gregarious butterfly clearly benefits from high conspecific density in terms of developmental performance and its ability to fight a parasitoid. These positive effects may be driven by cooperative interactions during feeding.