Structure and non-enzymatic light emission of two luciferin precursors isolated from the luminous mushroom Panellus stipticus

The Luminous Fungi of Japan

Luminous fungi have long attracted public attention in Japan, from old folklore and fiction to current tourism, children's toys, games, and picture books. At present, 25 species of luminous fungi have been discovered in Japan, which correspond to approximately one-fourth of the globally recognized species. This species richness is arguably due to the abundant presence of mycophiles looking to find new mushroom species and a tradition of night-time activities, such as firefly watching, in Japan. Bioluminescence, a field of bioscience focused on luminous organisms, has long been studied by many Japanese researchers, including the biochemistry and chemistry of luminous fungi. A Japanese Nobel Prize winner, Osamu Shimomura (1928-2018), primarily focused on the bioluminescence system of luminous fungi in the latter part of his life, and total elucidation of the mechanism was finally accomplished by an international research team with representatives from Russia, Brazil, and Japan in 2018. In this review, we focused on multiple aspects related to luminous fungi of Japan, including myth, taxonomy, and modern sciences.

Identification of hispidin as a bioluminescent active compound and its recycling biosynthesis in the luminous fungal fruiting body

Luminous mushrooms glow continuously by recycling the fungal luciferin presursor, hispidin.

Evaluation of the ecotoxicity of pollutants with bioluminescent microorganisms

This chapter deals with the use of bioluminescent microorganisms in environmental monitoring, particularly in the assessment of the ecotoxicity of pollutants. Toxicity bioassays based on bioluminescent microorganisms are an interesting complement to classical toxicity assays, providing easiness of use, rapid response, mass production, and cost effectiveness. A description of the characteristics and main environmental applications in ecotoxicity testing of naturally bioluminescent microorganisms, covering bacteria and eukaryotes such as fungi and dinoglagellates, is reported in this chapter. The main features and applications of a wide variety of recombinant bioluminescent microorganisms, both prokaryotic and eukaryotic, are also summarized and critically considered. Quantitative structure-activity relationship models and hormesis are two important concepts in ecotoxicology; bioluminescent microorganisms have played a pivotal role in their development. As pollutants usually occur in complex mixtures in the environment, the use of both natural and recombinant bioluminescent microorganisms to assess mixture toxicity has been discussed. The main information has been summarized in tables, allowing quick consultation of the variety of luminescent organisms, bioluminescence gene systems, commercially available bioluminescent tests, environmental applications, and relevant references.

Secrets of the subterranean pathosystem of Armillaria

Armillaria root disease affects fruit and nut crops, timber trees and ornamentals in boreal, temperate and tropical regions of the world. The causal pathogens are members of the genus Armillaria (Basidiomycota, Physalacriaceae). This review summarizes the state of knowledge and highlights recent advances in Armillaria research.

TAXONOMY

Armillaria includes more than 40 morphological species. However, the identification and delineation of species on the basis of morphological characters are problematic, resulting in many species being undetected. Implementation of the biological species' concept and DNA sequence comparisons in the contemporary taxonomy of Armillaria have led to the discovery of a number of new species that are not linked to described morphological species.

HOST RANGE

Armillaria exhibits a range of symbioses with both plants and fungi. As plant pathogens, Armillaria species have broad host ranges, infecting mostly woody species. Armillaria can also colonize orchids Galeola and Gastrodia but, in this case, the fungus is the host and the plant is the parasite. Similar to its contrasting relationships with plants, Armillaria acts as either host or parasite in its interactions with other fungi. Disease control: Recent research on post-infection controls has revealed promising alternatives to the former pre-plant eradication attempts with soil fumigants, which are now being regulated more heavily or banned outright because of their negative effects on the environment. New study tools for genetic manipulation of the pathogen and characterization of the molecular basis of the host response will greatly advance the development of resistant rootstocks in a new stage of research. The depth of the research, regardless of whether traditional or genomic approaches are used, will depend on a clear understanding of where the different propagules of Armillaria attack a root system, which of the pathogen's diverse biolymer-degrading enzymes and secondary metabolites facilitate infection, and how the course of infection differs between resistant and susceptible hosts.

Bioluminescence characteristics of a tropical terrestrial fungus (Basidiomycetes)

Freshly collected samples of luminous mycelium of a terrestrial fungus from Panama were investigated for their bioluminescence characteristics. Taxonomic identification of fungal species could not be determined because of the lack of fruiting bodies. Fluorescence excited by 380 nm illumination had an emission spectrum with a main peak at 480 nm and additional chlorophyll peaks related to the wood substrate. Bioluminescence appeared as a continuous glow that did not show any diel variation. The light production was sensitive to temperature and decreased with temperatures higher or lower than ambient. Bioluminescence intensity was sensitive to hydration, increasing by a factor of 400 immediately after exposure to water and increasing by a factor of 1 million after several hours. This increase may have occurred through dilution of superoxide dismutase, which is a suppressive factor of bioluminescence in fungus tissue. The mycelium typically transports nutritive substances back to the fruiting body. The function of luminescent mycelium may be to increase the intensity of light from the fungus and more effectively attract nocturnal insects and other animals that serve as disseminating vectors for fungal spores.

Bioluminescence

Bioluminescence has evolved independently many times; thus the responsible genes are unrelated in bacteria, unicellular algae, coelenterates, beetles, fishes, and others. Chemically, all involve exergonic reactions of molecular oxygen with different substrates (luciferins) and enzymes (luciferases), resulting in photons of visible light (approximately 50 kcal). In addition to the structure of luciferan, several factors determine the color of the emissions, such as the amino acid sequence of the luciferase (as in beetles, for example) or the presence of accessory proteins, notably GFP, discovered in coelenterates and now used as a reporter of gene expression and a cellular marker. The mechanisms used to control the intensity and kinetics of luminescence, often emitted as flashes, also vary. Bioluminescence is credited with the discovery of how some bacteria, luminous or not, sense their density and regulate specific genes by chemical communication, as in the fascinating example of symbiosis between luminous bacteria and squid.