Lampteromyces bioluminescence--1. Identification of riboflavin as the light emitter in the mushroom L. japonicus

Cloning and Expression Analysis of Bioluminescence Genes in Omphalotus guepiniiformis Reveal Stress-Dependent Regulation of Bioluminescence

Bioluminescence is a type of chemiluminescence that arises from a luciferase-catalyzed oxidation reaction of luciferin. Molecular biology and comparative genomics have recently elucidated the genes involved in fungal bioluminescence and the evolutionary history of their clusters. However, most studies on fungal bioluminescence have been limited to observing the changes in light intensity under various conditions. To understand the molecular basis of bioluminescent responses in Omphalotus guepiniiformis under different environmental conditions, we cloned and sequenced the genes of hispidin synthase, hispidin-3-hydroxylase, and luciferase enzymes, which are pivotal in the fungal bioluminescence pathway. Each gene showed high sequence similarity to that of other luminous fungal species. Furthermore, we investigated their transcriptional changes in response to abiotic stresses. Wound stress enhanced the bioluminescence intensity by increasing the expression of bioluminescence pathway genes, while temperature stress suppressed the bioluminescence intensity via the non-transcriptional pathway. Our data suggested that O. guepiniiformis regulates bioluminescence to respond differentially to specific environmental stresses. To our knowledge, this is the first study on fungal bioluminescence at the gene expression level. Further studies are required to address the biological and ecological meaning of different bioluminescence responses in changing environments, and O. quepiniiformis could be a potential model species.

De novo genome assembly of the bioluminescent mushroom Omphalotus guepiniiformis reveals an Omphalotus-specific lineage of the luciferase gene block

Omphalotus guepiniiformis, a bioluminescent mushroom species, is a source of the potentially valuable anticancer chemical. To provide genome information, we de novo assembled the high-quality O. guepiniiformis genome using two Next-Generation sequencing techniques, PacBio and Illumina sequencing. Our draft O. guepiniiformis genome comprises 42.5 Mbp of sequence with only 80 contigs and an N50 sequence length of over 1 Mbp. There were 15,554 predicted coding genes, and 7693 genes were functionally annotated with Gene Ontology terms. We performed a genomic study focusing on mushroom bioluminescent pathway cluster genes by comparing 17 luminescent and 23 non-luminescent Agaricales species belonging to 23 genera. Synteny analysis of genomic regions near the luminescent pathway cluster genes inferred that the Omphalotus lineage was genus-specific. In summary, our de novo assembled O. guepiniiformis genome provides significant biological insights into this organism, including the evolution of the luciferase gene block, and forms the basis for future analyses.

Identification of possible light emitters in the gills of a bioluminescent fungus Mycena chlorophos

The pileus of Mycena chlorophos actively, spontaneously, and continuously emits green light. Molecular mechanisms underlying this bioluminescence remain unclear. We investigated light emitters in the pileus of M. chlorophos to determine the underlying mechanisms. High-performance liquid chromatography-fluorescence-photodiode array-mass detection analyses showed that actively luminescent gills in the pileus exclusively and abundantly possessed riboflavin, riboflavin 5'-monophosphate, and flavin adenine dinucleotide as green-fluorescent components. These components were localized in the bioluminescent region of the gills at the microscopic level. Fluorescence spectra of these green-fluorescent components and the gills were identical with the spectrum of gill bioluminescence (maximum emission wavelength, 525 nm). Thus, our results indicated that the possible light emitters in the pileus of M. chlorophos were riboflavin, riboflavin 5'-monophosphate, and/or flavin adenine dinucleotide. Copyright © 2016 John Wiley & Sons, Ltd.

Extraction and purification of a luminiferous substance from the luminous mushroom Mycena chlorophos

Bioluminescence has attracted considerable attention in the area of biophysics, primarily because the phenomenon can fundamentally be interpreted as the conversion of chemical to light energy. Although the molecular mechanisms underlying luminescence have been studied extensively in fireflies and bacteria, few studies have been undertaken in luminous fungi. This relative lack of information is likely due to the absence of a common and species-specific reaction-type in the luminous fungi examined to date. We recently succeeded in extracting, for the first time, a luminiferous substance from the fungus Mycena chlorophos. The substance was purified and characterized according to its chemical and optical properties. It is hoped that this information will facilitate the clarification of a novel molecular mechanism in fungal bioluminescence systems.

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

The chemical structure of two luciferin precursors PS-A and PS-B, isolated from the luminous mushroom Panellus stipticus, were determined as 1-O-decanoylpanal (2) and 1-O-dodecanoylpanal (3), respectively. Both PS-A and PS-B were converted into chemiluminescent luciferins by treatment with 50 mmol/l methylamine in a pH 3.5 buffer solution containing an anionic surfactant Tergitol 4 at 25-35 degrees C. The luciferins emitted chemiluminescence in a pH 7-8 buffer solution containing a cationic surfactant in the presence of O2 and O2-.

Dyakia bioluminescence--1. Bioluminescence and fluorescence spectra of the land snail, D. striata

The luminescent land snail Dyakia striata displayed a bioluminescence spectrum with a maximum wavelength of 515 nm. A green fluorescent substance extracted from the photogenic organ of an adult snail had a similar wavelength maximum but its fluorescence spectrum differed from that of flavin chromophore substances involved in light emission in some other luminescent organisms.