Welcome to IMC 2018 International Mycological Congress
Conference Calendar

 

Displaying One Session

Symposia
Location
202 B+C 2nd Floor
Date
07/21/2018
Time
08:30 AM - 10:30 AM
Symposia

Microbial competition within the context of entomopathogenic fungi and infection of their insect hosts

Session Number
S35
Location
202 B+C 2nd Floor, Puerto Rico Convention Center, San Juan, Puerto Rico
Date
07/21/2018
Time
08:30 AM - 10:30 AM
Presentation Number
S35-1
Authors
  • N. Keyhani

Abstract

Abstract

Ascomycete (Hypocrealean) insect pathogenic fungi, including Metarhizium and Beauveria sp. are capapble of infecting and killing a wide range of insect host insects. These fungi are able to overcome the formidable array of insect defenses that include the cuticle waxy-layer and various levels of insect humoral and innate immune systems. In order to complete its life-cycle the fungus must sporulate on the insect cadaver to produce the next generation of fungal cells, and development on the dead insect has been recognized as an important and discrete part of the infection stage. One hitherto unexplored aspect of the infection process, however, are the roles insect associated as well as other environmental microbes may play in affecting the infection process. Competing (antagonistic) and/or assisting (i.e. facilitating infection) microbes may be present on the insect cuticle surface, within the insect gut, and potentially in specialized insect microbe hosting structures. Endogenous insect microbes that can impact insect (immune) defenses may also be found within cells, and include a wide array of facultative and/or obligate exo- and endo-symbionts. These microbes contribute critical functions to their insect hosts including providing essential compounds, mediating development, facilitating nutrient acquisition, and potentially proving defense against other microbes; the latter via production of antimicrobial compounds. In turn, there is accumulating evidence that insect pathogenic fungi can exploit or suppressing host microbes via mechanisms including the production of antimicrobial compounds whose expression is controlled as part of the developmental program in the insect cadaver. The insect microbiome and its interactions with fungal insect pathogens represents a new frontier that add to the complexity of the environmental interactions that occur and can provide explanations for why there are such large discrepancies between laboratory and field assays, where often the former are very successful whereas the latter are not. In addition, cues for the production of a set of fungal secondary metabolites likely involves competitive interactions with other microbes for completion of the fungal life-cycle on the insect cadaver.
Collapse
Symposia

Contribution of nematophagous Hirsutella spp. in the suppressive soil of soybean cyst nematode

Session Number
S35
Location
202 B+C 2nd Floor, Puerto Rico Convention Center, San Juan, Puerto Rico
Date
07/21/2018
Time
08:30 AM - 10:30 AM
Presentation Number
S35-2
Authors
  • X. Liu
  • M. Xiang
  • S. Chen

Abstract

Abstract

Soybean cyst nematode (SCN), Heterodera glycines, is a devastating pest of the soybean (Glycine max) worldwide. Continuously monoculturing soybean generally resulted in SCN suppressiveness which has been reported in a number of locations. We have conducted the studies on SCN suppressive soils for more than two decades. Hirsutella rhossiliensis and H. minnesotensis have been found to be the dominant parasites of SCN juveniles in the USA and China respectively. Both Hirsutella species have been demonstrated to correspond to the SCN suppressiveness in suppressive soils. OWVT-1, a strain of H. rhossiliensis isolated from the suppressive soil in a field in Waseca, Minnesota, USA, has resulted in more than 90% control efficiency for SCN in greenhouse trial and has showed a density dependent parasitism with SCN density. However, field trial by inoculation of Hirsutella species into the soils did not obtain stable suppression of SCN. Recently, a comparative analysis of microbiomes in suppressive soil and conducive soil has revealed that more microbes are involved in the SCN-suppressive soil. The detail analysis showed that a bacteria in Chitinophaga specifically responded to the SCN suppressiveness. Based on our study, we hypothesize that both Hirsutella spp. as key biocontrol agents (characterized by dominant parasites and density-dependent parasitism) and Chitinophaga spp. as the functional microbes are contributed to the SCN suppressive soil. Comprehensive understanding of suppressive soils can provide novel strategies for successful control of soil-borne disease.

Collapse
Symposia

Ergot alkaloids in bioactive Metarhizium species

Session Number
S35
Location
202 B+C 2nd Floor, Puerto Rico Convention Center, San Juan, Puerto Rico
Date
07/21/2018
Time
08:30 AM - 10:30 AM
Presentation Number
S35-3
Authors
  • C. Leadmon
  • J. Tyo
  • A. Macias
  • M. Kasson
  • D. Panaccione

Abstract

Abstract

Ergot alkaloids are important agricultural and pharmaceutical chemicals. Publicly available genomic sequence data indicate that fungi in the genus Metarhizium have the capacity to produce lysergic acid-derived ergot alkaloids; however, the accumulation of ergot alkaloids in these fungi has not been experimentally demonstrated. Metarhizium species colonize soil, roots of many plants, and insects. Because of these properties, some Metarhizium species are used as biocontrol agents. We investigated Metarhizium species grown under different conditions for accumulation of ergot alkaloids by high performance liquid chromatography (HPLC) with fluorescence detection. Metarhizium anisopliae and Metarhizium flavoviride were cultured saprotrophically on three different media: corn meal agar, malt extract agar, and sucrose yeast extract agar. Accumulation of ergot alkaloids varied by medium and fungus. Metarhizium flavoviride did not accumulate ergot alkaloids on any of these culture media. Metarhizium anisopliae accumulated large quantities of the ergot alkaloids lysergic acid α-hydroxyethylamide (LAH), ergine, ergonovine and chanoclavine-I on sucrose yeast extract agar, lesser quantities on malt extract agar, and none on corn meal agar. The identities of the alkaloids were confirmed by mass spectrometry. Interestingly, M. anisopliae secreted over 80% of its alkaloid yield into the medium, whereas the ergot alkaloids of most ergot alkaloid-producing fungi are retained in their hyphae. Metarhizium robertsii and M. brunneum were cultured only on sucrose yeast extract agar; M. brunneum produced the same profile of ergot alkaloids as M. anisopliae, but ergot alkaloids were not detected in saprotrophically cultured M. robertsii. We also investigated the accumulation of ergot alkaloids under the ecologically relevant conditions of mutualistic growth on plant roots and parasitic growth in infected insects. We inoculated roots of corn (Zea mays), bean (Phaseolus vulgaris), and Medicago truncatula with M. anisopliae and M. flavoviride, and no ergot alkaloids were produced by either fungus on any of the plants. Larvae of the insect Galleria mellonella were inoculated with spore suspensions of M. anisopliae, M. flavoviride, M. brunneum, and M. robertsii. Each of the four species produced ergot alkaloids in infected larvae. The mean concentration of LAH (the most abundantly accumulating ergot alkaloid) in M. anisopliae-infected larvae was 154 μM, a concentration that was 300-fold greater than the concentration observed in sucrose yeast extract medium. The data demonstrate that several Metarhizium species have the ability to produce ergot alkaloids of the lysergic acid amide class and that production of ergot alkaloids is tightly regulated and associated with insect colonization.

Collapse
Symposia

Metarhizium and plants: the symbiosis is mutual

Session Number
S35
Location
202 B+C 2nd Floor, Puerto Rico Convention Center, San Juan, Puerto Rico
Date
07/21/2018
Time
08:30 AM - 10:30 AM
Presentation Number
S35-4
Authors
  • R. St. Leger
  • B. Lovett

Abstract

Abstract

First discovered on insect cadavers, Metarhizium spp. are best known as insect killing fungi; however, the ability of these fungi to form epiphytic interactions with plant roots likely contributes to their abundance in soils world-wide. Genomic and molecular techniques have revealed that the early ancestors of the genus Metarhizium were plant symbionts, which took on an insect killing lifestyle providing insect-derived nitrogen to the plant in exchange for carbon. This hypothesis has generated a plethora of promising avenues of research investigating commonalities and distinctions between these two lifestyles. These fungi have further demonstrated the capacity to specialize variously with insect and plant hosts. Root colonizing Metarhizium strains are now known to promote plant growth by mechanisms that include killing insects, making nutrients available, increasing stress resistance and producing growth-promoting plant hormones. Field trials have confirmed that the ability to adhere to root surfaces plays an important part in maintaining Metarhizium population size, and that their endophytic and entomopathogenic lifestyles can be decoupled experimentally. The same molecular and genomic tools developed to probe and manipulate Metarhizium spp. to better kill insects are quickly laying the foundation for development of these fungi as comprehensive plant-growth promoters.
Collapse
Symposia

Cordyceps fungi endemic to the caterpillars in Colombia: successful natural pest controls

Session Number
S35
Location
202 B+C 2nd Floor, Puerto Rico Convention Center, San Juan, Puerto Rico
Date
07/21/2018
Time
08:30 AM - 10:30 AM
Presentation Number
S35-5
Authors
  • T. Sanjuan
  • L. Castillo
  • A. Osorio
Symposia

Molecular and chemical strategies employed by insect biocontrol fungi to counteract host immune defenses

Session Number
S35
Location
202 B+C 2nd Floor, Puerto Rico Convention Center, San Juan, Puerto Rico
Date
07/21/2018
Time
08:30 AM - 10:30 AM
Presentation Number
S35-6
Authors
  • C. Wang

Abstract

Abstract

Insect pathogenic fungi such as Metarhizium spp. and Beauveria bassiana have been developed as environmentally friendly biocontrol agents against different insect pests. Phylogenetic analysis revealed that fungal entomopathogenicity is polyphyletic, so similar expansions of insect cuticle degrading proteases and chitinases reflect a convergent evolution during the arms race of fungus-insect interactions. Relative to the advances in understanding fungus-plant interactions, the mechanisms of the molecular pathogenesis of entomopathogenic fungi are rather limitedly understood. In particular, the machinery of effector-mediated inhibition of host immunity has not been well established in fungus-insect interactions. We found that the divergent LysM proteins are present in animal pathogens. By using the insect pathogen B. bassiana as a model, we revealed that two of 12 encoded LysM protein genes are required for full fungal virulence against insect hosts to deregulate insect immune responses and protect fungal cells from chitinase hydrolysis. For M. robertsii, a collagen-like protein can camouflage cell wall components for evading host immunity. In addition, in vivo metabolomics analysis revealed the dynamics of small molecules were produced by both the fungi and insect hosts during fungal invasion of hosts. In particular, the small molecules such as the cyclodepsipeptide destruxins produced by M. robertsii and dibenzoquinone oosporein by B. bassiana could be deployed by the fungus to inhibit host immune responses to facilitate fungal infection. The understanding of fungal molecular pathogenesis can facilitate the development of cost-effective mycoinsecticides.

Collapse