The origin of bioluminescence

Evolution of bioluminescence in Anthozoa with emphasis on Octocorallia

Bioluminescence is a widespread phenomenon that has evolved multiple times across the tree of life, converging among diverse fauna and habitat types. The ubiquity of bioluminescence, particularly in marine environments where it is commonly used for communication and defense, highlights the adaptive value of this trait, though the evolutionary origins and timing of emergence remain elusive for a majority of luminous organisms. Anthozoan cnidarians are a diverse group of animals with numerous bioluminescent species found throughout the world's oceans, from shallow waters to the light-limited deep sea where bioluminescence is particularly prominent. This study documents the presence of bioluminescent Anthozoa across depth and explores the diversity and evolutionary origins of bioluminescence among Octocorallia-a major anthozoan group of marine luminous organisms. Using a phylogenomic approach and ancestral state reconstruction, we provide evidence for a single origin of bioluminescence in Octocorallia and infer the age of occurrence to around the Cambrian era, approximately 540 Ma-setting a new record for the earliest timing of emergence of bioluminescence in the marine environment. Our results further suggest this trait was largely maintained in descendants of a deep-water ancestor and bioluminescent capabilities may have facilitated anthozoan diversification in the deep sea.

Bioluminescence and Photoreception in Unicellular Organisms: Light-Signalling in a Bio-Communication Perspective

Bioluminescence, the emission of light catalysed by luciferases, has evolved in many taxa from bacteria to vertebrates and is predominant in the marine environment. It is now well established that in animals possessing a nervous system capable of integrating light stimuli, bioluminescence triggers various behavioural responses and plays a role in intra- or interspecific visual communication. The function of light emission in unicellular organisms is less clear and it is currently thought that it has evolved in an ecological framework, to be perceived by visual animals. For example, while it is thought that bioluminescence allows bacteria to be ingested by zooplankton or fish, providing them with favourable conditions for growth and dispersal, the luminous flashes emitted by dinoflagellates may have evolved as an anti-predation system against copepods. In this short review, we re-examine this paradigm in light of recent findings in microorganism photoreception, signal integration and complex behaviours. Numerous studies show that on the one hand, bacteria and protists, whether autotrophs or heterotrophs, possess a variety of photoreceptors capable of perceiving and integrating light stimuli of different wavelengths. Single-cell light-perception produces responses ranging from phototaxis to more complex behaviours. On the other hand, there is growing evidence that unicellular prokaryotes and eukaryotes can perform complex tasks ranging from habituation and decision-making to associative learning, despite lacking a nervous system. Here, we focus our analysis on two taxa, bacteria and dinoflagellates, whose bioluminescence is well studied. We propose the hypothesis that similar to visual animals, the interplay between light-emission and reception could play multiple roles in intra- and interspecific communication and participate in complex behaviour in the unicellular world.

Multi-level convergence of complex traits and the evolution of bioluminescence

Evolutionary convergence provides natural opportunities to investigate how, when, and why novel traits evolve. Many convergent traits are complex, highlighting the importance of explicitly considering convergence at different levels of biological organization, or 'multi-level convergent evolution'. To investigate multi-level convergent evolution, we propose a holistic and hierarchical framework that emphasizes breaking down traits into several functional modules. We begin by identifying long-standing questions on the origins of complexity and the diverse evolutionary processes underlying phenotypic convergence to discuss how they can be addressed by examining convergent systems. We argue that bioluminescence, a complex trait that evolved dozens of times through either novel mechanisms or conserved toolkits, is particularly well suited for these studies. We present an updated estimate of at least 94 independent origins of bioluminescence across the tree of life, which we calculated by reviewing and summarizing all estimates of independent origins. Then, we use our framework to review the biology, chemistry, and evolution of bioluminescence, and for each biological level identify questions that arise from our systematic review. We focus on luminous organisms that use the shared luciferin substrates coelenterazine or vargulin to produce light because these organisms convergently evolved bioluminescent proteins that use the same luciferins to produce bioluminescence. Evolutionary convergence does not necessarily extend across biological levels, as exemplified by cases of conservation and disparity in biological functions, organs, cells, and molecules associated with bioluminescence systems. Investigating differences across bioluminescent organisms will address fundamental questions on predictability and contingency in convergent evolution. Lastly, we highlight unexplored areas of bioluminescence research and advances in sequencing and chemical techniques useful for developing bioluminescence as a model system for studying multi-level convergent evolution.

BIOPHOTONS IN RADIOBIOLOGY: INHIBITORS, COMMUNICATORS AND REACTORS

Radiation-induced bystander effects refer to the production of signals from irradiated cells which induce responses in unirradiated, or bystander, cells. There has been a recent resurgence of interest in low-energy photon biology. This is due to concerns about health effects, increased use of biophoton imaging techniques, and the fact that biophotons can act as a bystander signal. This review discusses the history of light signaling in biology and potential mechanisms involved in the generation and transduction of signaling mechanisms. The role of photons in signaling in the animal and plant kingdoms is also reviewed. Finally, the potential to harness these mechanisms in radiation protection or therapy is discussed with emphasis on promising future directions for research.

Symbiont evolution during the free-living phase can improve host colonization

For micro-organisms cycling between free-living and host-associated stages, where reproduction occurs in both of these lifestyles, an interesting inquiry is whether evolution during the free-living stage can be positively pleiotropic to microbial fitness in a host environment. To address this topic, the squid host Euprymna tasmanica and the marine bioluminescent bacterium Vibrio fischeri were utilized. Microbial ecological diversification in static liquid microcosms was used to simulate symbiont evolution during the free-living stage. Thirteen genetically distinct V. fischeri strains from a broad diversity of ecological sources (e.g. squid light organs, fish light organs and seawater) were examined to see if the results were reproducible in many different genetic settings. Genetic backgrounds that are closely related can be predisposed to considerable differences in how they respond to similar selection pressures. For all strains examined, new mutations with striking and facilitating effects on host colonization arose quickly during microbial evolution in the free-living stage, regardless of the ecological context under consideration for a strain’s genetic background. Microbial evolution outside a host environment promoted host range expansion, improved host colonization for a micro-organism, and diminished the negative correlation between biofilm formation and motility.

The dark and bright sides of an enzyme: a three dimensional structure of the N-terminal domain of Zophobas morio luciferase-like enzyme, inferences on the biological function and origin of oxygenase/luciferase activity

Beetle luciferases, the enzymes responsible for bioluminescence, are special cases of CoA-ligases which have acquired a novel oxygenase activity, offering elegant models to investigate the structural origin of novel catalytic functions in enzymes. What the original function of their ancestors was, and how the new oxygenase function emerged leading to bioluminescence remains unclear. To address these questions, we solved the crystal structure of a recently cloned Malpighian luciferase-like enzyme of unknown function from Zophobas morio mealworms, which displays weak luminescence with ATP and the xenobiotic firefly d-luciferin. The three dimensional structure of the N-terminal domain showed the expected general fold of CoA-ligases, with a unique carboxylic substrate binding pocket, permitting the binding and CoA-thioesterification activity with a broad range of carboxylic substrates, including short-, medium-chain and aromatic acids, indicating a generalist function consistent with a xenobiotic-ligase. The thioesterification activity with l-luciferin, but not with the d-enantiomer, confirms that the oxygenase activity emerged from a stereoselective impediment of the thioesterification reaction with the latter, favoring the alternative chemiluminescence oxidative reaction. The structure and site-directed mutagenesis support the involvement of the main-chain amide carbonyl of the invariant glycine G323 as the catalytic base for luciferin C4 proton abstraction during the oxygenase activity in this enzyme and in beetle luciferases (G343).

Roles of biogenic amines in regulating bioluminescence in the Australian glowworm Arachnocampa flava

The glowworm Arachnocampa flava is a carnivorous fly larva (Diptera) that uses light to attract prey into its web. The light organ is derived from cells of the Malpighian tubules, representing a bioluminescence system that is unique to the genus. Bioluminescence is modulated through the night although light levels change quite slowly compared with the flashing of the better-known fireflies (Coleoptera). The existing model for the neural regulation of bioluminescence in Arachnocampa, based on use of anaesthetics and ligations, is that bioluminescence is actively repressed during the non-glowing phase and the repression is partially released during the bioluminescence phase. The effect of the anaesthetic, carbon dioxide, on the isolated light organ from the present study indicates that the repression is at least partially mediated at the light organ itself rather than less directly through the central nervous system. Blocking of neural signals from the central nervous system through ligation leads to uncontrolled release of bioluminescence but light is emitted at relatively low levels compared with under anaesthesia. Candidate biogenic amines were introduced by several methods: feeding prey items injected with test solution, injecting the whole larva, injecting a ligated section containing the light organ or bathing the isolated light organ in test solution. Using these methods, dopamine, serotonin and tyramine do not affect bioluminescence output. Exposure to elevated levels of octopamine via feeding, injection or bathing of the isolated light organ indicates that it is involved in the regulation of repression. Administration of the octopamine antagonists phentolamine or mianserin results in very high bioluminescence output levels, similar to the effect of anaesthetics, but only mianserin acts directly on the light organ.

The origin of luciferase activity in Zophobas mealworm AMP/CoA-ligase (protoluciferase): luciferin stereoselectivity as a switch for the oxygenase activity

Beetle luciferases evolved from AMP/CoA-ligases. However, it is unclear how the new luciferase activity evolved. In order to clarify this question, we compared the luminescence and catalytic properties of a recently cloned luciferase-like enzyme from Zophobas mealworm, an AMP/CoA-ligase displaying weak luminescence activity, with those of cloned luciferases from the three main families of luminescent beetles: Phrixthrix hirtus railroad worm; Pyrearinus termitilluminans click beetle and Photinus pyralis firefly. The catalytic constant of the mealworm enzyme was 2-4 orders of magnitude lower than that of beetle luciferases, but 3 orders of magnitude above the non-catalyzed chemiluminescence of luciferyl-adenylate in buffer. Studies with D- and L-luciferin and their adenylates show that the luminescence reaction of the luciferase-like enzyme and beetle luciferases are stereoselective for D-luciferin and its adenylate, and that the selectivity is determined mainly at the adenylation step. Modelling studies showed that the luciferin binding site cavity of this enzyme is smaller and more hydrophobic than that of beetle luciferases. Therefore Zophobas mealworm enzyme displays true luciferase activity, keeping the attributes of an ancient protoluciferase. These results suggest that stereoselectivity for D-luciferin may have been a key event for the origin of oxygenase/luciferase activity in AMP/CoA-ligases, and that efficient luciferase activity may have further evolved mainly by increasing the catalytic constant of the oxidative reaction and the quantum yield of bioluminescence.

Differential effects of relaxation techniques on ultraweak photon emission

BACKGROUND

Evidence has accumulated favoring the possible role of oxidative stress in the pathogenesis of many chronic diseases. Meditation is utilized as an adjunct to conventional medical treatment for several clinical conditions. A few studies suggest a role of long-term meditation in the control of the free-radical metabolism. Many techniques for recording reactive oxygen species (ROS) have been made available. However, most are invasive and none are applicable to all conditions. Attention has recently been drawn to spontaneous ultraweak photon emission (UPE). However, the application of this method in meditation studies is very limited.

OBJECTIVE

The present study recorded spontaneous UPE at multiple anatomic locations of subjects with long-term experience in transcendental meditation (TM) and compared this with a group that practiced other meditation techniques (OMT) and with subjects having no meditation experience.

METHODS

The study examined the anatomic pattern of UPE of 20 subjects practicing TM, compared to 20 subjects practicing OMT, and 20 control subjects with no experience in meditation. Subjects were men who were reported to be healthy and nonsmokers. Meditation was not practiced on the day prior to recording. UPE was recorded in a dark room, using a highly sensitive, cooled photomultiplier system designed for manipulation in three directions. The protocol for the multisite registration of UPE included recording 12 anatomic locations, including the anterior torso, head, neck, and hands.

RESULTS

Data demonstrated emission intensities in the TM and OMT groups that were 27% and 17% lower, respectively, compared to the control group. The decrease was recorded at all anatomic locations. The percent emission contribution of each location to total emission was very similar for the three groups.

CONCLUSIONS

Data supported the hypothesis that persistent meditation resulted in decreased UPE. However, the determination of oxidation levels as the source of group differences needs to be verified further to confirm our hypothesis.

Fire?y luciferin as antioxidant and light emitter: the evolution of insect bioluminescence

Insects are the main group with luminescent species among terrestrial animals. In this paper, we report that fire fly luciferin is endowed with antioxidant properties against oxidative and nitrosative stress. The luciferin reduces linoleate peroxidation in acellular tests and increases the viability of mammalian cells exposed to the oxidant tert-butyl hydroperoxide. Dehydrorhodamine-based tests indicate that fire fly luciferin also scavenges peroxynitrite, whereas parallel tests on cells showed a marked protection of cells subjected to the peroxynitrite generator SIN-1. Together, these results suggest that fire fly luciferin's antioxidant properties could help photocytes coping with the hyperoxidant conditions to which they are submitted during luminous emissions. These data could also suggest that the evolutionary foundation of the bioluminescent system could have been the luciferin, and not the luciferase, first serving as a scavenger of oxidants toxic to the cells, then as a light emitting substrate for luciferase precursors. Similarities with the evolutionary scenario proposed for marine bioluminescent organisms relying on coelenterazine suggest that the surprisingly high success rate observed in the independent emergence of bioluminescent animals could reflect the ease of transformation of antioxidant mechanisms into light-producing systems.

Daily variations of antioxidant enzyme and luciferase activities in the luminescent click-beetle Pyrearinus termitilluminans: cooperation against oxygen toxicity

Several lines of investigation have suggested an interplay between bioluminescence (BL) and oxyradical metabolism, mainly in bacteria and beetles. Although not yet confirmed, luminescent beetles seem to be challenged daily by oxidative conditions imposed by higher oxygen absorption necessary to enhance light emission for courtship (adult lampyrids and elaterids) and prey attraction (e.g. Pyrearinus termitilluminans larvae). This work reports the activities of luciferase, superoxide dismutase (SOD), catalase and dehydroascorbate reductase (DHAR) and total glutathione content at different times of the day in the bright prothorax and dim abdomen of larval Pyrearinus termitilluminans (Coleoptera: Elateridae), investigating a possible adjuvant role for luciferase in oxygen detoxification. Luciferase activity in the prothorax was shown to peak at 7 p.m., which is the time when P. termitilluminans larvae light up for prey attraction. In their habitat, P. termitilluminans larvae emit light until 8.30 p.m. However, at 8 p.m., prothorax luciferase activity achieved basal levels and total glutathione content declined to the daily lowest value, possibly resulting from hyperoxidative conditions during this time. Significant increases in the activities of total SOD (28%) and catalase (37%) were observed in the prothorax at 9 p.m., which should minimize the extent of damage from this potentially hazardous period. Prothorax total SOD (42% higher than daily average) and abdomen CuZnSOD (41%) and catalase (95%) activities showed extra peaks at 7-10 a.m., and abdomen DHAR activity was maximal (37%) earlier (4-7 a.m.). These morning increases in antioxidant enzyme activities may be associated with biological events other than bioluminescence, e.g. intense physical activity for digging tunnels and/or digestion of captured preys. These data suggest that oxyradical pathway and bioluminescence are coordinated, especially in the prothorax, to minimize the oxidative stress imposed by higher irrigation of the photocytes with O(2) when P. termitilluminans larvae emit light.

Measurement of oxygen partial pressure, its control during hypoxia and hyperoxia, and its effect upon light emission in a bioluminescent elaterid larva

This study investigates the respiratory physiology of bioluminescent larvae of Pyrearinus termitilluminans in relation to their tolerance to hypoxia and hyperoxia and to the supply of oxygen for bioluminescence. The partial pressure of oxygen (P(O2)) was measured within the bioluminescent prothorax by in vivo electron paramagnetic resonance (EPR) oximetry following acclimation of larvae to hypoxic, normoxic and hyperoxic (normobaric) atmospheres and during periods of bioluminescence (during normoxia). The P(O2) in the prothorax during exposure to an external P(O2) of 15.2, 160 and 760 mmHg was 10.3+/−2.6, 134+/−0.9 and 725+/−73 mmHg respectively (mean +/− s.d., N=5; 1 mmHg=0.1333 kPa). Oxygen supply to the larvae via gas exchange through the spiracles, measured by determining the rate of water loss, was also studied in the above atmospheres and was found not to be dependent upon P(O2). The data indicated that there is little to no active control of extracellular tissue P(O2) within the prothorax of these larvae. The reduction in prothorax P(O2) observed during either attack-response-provoked bioluminescence or sustained feeding-related bioluminescence in a normoxic atmosphere was variable, but fell within the range 10–25 mmHg. The effect of hypoxic atmospheres on bioluminescence was measured to estimate the intracellular P(O2) within the photocytes of the prothorax. Above a threshold value of 50–80 mmHg, bioluminescence was unaffected by P(O2). Below this threshold, an approximately linear relationship between P(O2) and bioluminescence was observed. Taken together with the extracellular P(O2) measurements, this suggests that control of P(O2) within the photocyte may occur. This work establishes that EPR oximetry is a valuable technique for long-term measurement of tissue P(O2) in insects and can provide valuable insights into their respiratory physiology. It also raises questions regarding the hypothesis that bioluminescence can have a significant antioxidative effect by reduction of prothorax P(O2)through oxygen consumption.

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.

Bioluminescence as a possible auxiliary oxygen detoxifying mechanism in elaterid larvae

This work examines the hypothesis that beetle bioluminescent reactions may primarily have evolved to provide an auxiliary O2 detoxifying mechanism. The activities of antioxidant enzymes and of luciferase in the prothorax (bright) and abdomen (dim) of luminous larval Pyrearinus termitilluminans (Coleoptera: Elateridae) were measured after previous challenge with either hyperoxia, hypoxia, or the firefly luciferase inhibitor luciferin 6'-methyl ether (LME). Upon exposure to pure O2 for 72 h, the prothorax activities of total superoxide dismutase (SOD) and catalase were found to increase by 85% and 50%, respectively. Concomitantly, levels of luciferase and luciferin increased 80% and 50%. Assays of thiobarbituric acid reactive substances (TBARS) showed significantly augmented lipid peroxidation only in the abdomen (30%) where levels of antioxidant enzymes and especially luciferase are low. In contrast, exposure to hypoxia (2% O2) led to significant increases in prothorax citrate synthase (85%), succinate dehydrogenase (25%), and lactate dehydrogenase (30%) activities, but not in luciferase or antioxidant enzyme levels. LME administration alone decreased luciferase activities 20% but did not alter prothorax SOD activity. Prothorax SOD activity was increased by concomitant LME and hyperoxia treatments (30%), along with higher levels of TBARS (25%) and protein reactive carbonyl groups (50%). Altogether these data suggest that in elaterids, bioluminescence and reactions catalyzed by antioxidant enzymes may cooperate to minimize oxidative stress.

Light organ symbioses in fishes

Most bioluminescent fishes are self-luminescent, but a substantial minority of bioluminescent teleosts produce light that is due to symbiotic luminous bacteria housed in elaborate light organs. The majority of symbiotically bioluminescent fishes (ten families in five orders) harbors common free-living species of marine luminous bacteria: Photobacterium phosphoreum, P. leiognathi, and P. fischeri (= Vibrio fischeri). Others, associated with the beryciform family Anomalopidae and nine families in the lophiiform suborder Ceratioidei, have apparently obligate symbionts that have recently been identified by small subunit (16S) rRNA analysis as new groups within the genus Vibrio. This article summarizes what is currently known about relationships between light organ symbionts and their hosts, including characteristics of light organ environments, physiology of light organ symbionts, and the evolution of light organ symbionts and their associations.

Stress-induced photon emission from perturbed organisms

This paper reviews an ultraweak luminescent response of selected biological systems (lower and higher plants, insects and spermatozoa) to certain kinds of detrimental mechanical, temperature, chemical and photochemical stress and to lethal factors. The enhancing effect of white light and formaldehyde on the ultraweak luminescence of yeast and spermatozoa cells is described for the first time. An increase in the percentage of long wavelengths (lambda > 600 nm) with an increase in reaction time, and a significant influence of the suspending medium on the ultraweak luminescence, were observed. The vitality and motility of bull spermatozoa and the vitality of yeast cells were drastically decreased by treatment with white light, water, formaldehyde and iron-ions. Successive irradiation of intact bull spermatozoa cells with white light caused an increase in the intensity of delayed luminescence. An attempt has been undertaken to find stochastic models of non-stationary photon emission. The quasi-relaxation descending stage of non-stationary processes can be modeled as the Integrated Moving Average process IMA (0, 1, 1), and memory and transfer functions can describe the degree of perturbation in the yeast Saccharomyces cerevisiae. The relation of the ultraweak luminescence response to perturbations of homeostasis is discussed in the framework of biochemical and physical models.

Evolutionary origins of bacterial bioluminescence

In bacteria, most genes required for the bioluminescence phenotype are contained in lux operons. Sequence alignments of several lux gene products show the existence of at least two groups of paralogous products. The alpha- and beta-subunits of bacterial luciferase and the non-fluorescent flavoprotein are paralogous, and two antennae proteins (lumazine protein and yellow fluorescence protein) are paralogous with riboflavin synthetase. Models describing the evolution of these paralogous proteins are suggested, as well as a postulate for the identity of the gene encoding a protobioluminescent luciferase.

Borrowed proteins in bacterial bioluminescence

A library of Photobacterium phosphoreum DNA was screened in lambda 2001 for the lumazine protein gene, using two degenerate 17-mer oligonucleotide probes that were deduced from a partial protein primary sequence. The lumazine protein gene was localized to a 3.4-kilobase BamHI/EcoRI fragment in one clone. The fragment contained an open reading frame, encoding a 189-residue protein, that had a predicted amino acid sequence that concurred with the partial sequence determined for lumazine protein. Considerable sequence similarity was detected between lumazine protein, the yellow fluorescence protein from Vibrio fischeri, and the alpha subunit of riboflavin synthetase (EC 2.5.1.9). A highly conserved sequence in lumazine protein corresponds to the proposed lumazine binding sites in the alpha subunit of riboflavin synthetase. Several secondary structure programs predict the conformation of this site in lumazine protein to be a beta-sheet. A minimal model with three interactions between the ligand and this beta-sheet structure is proposed, which is consistent with the results of NMR and ligand binding studies.

Luminescence research and its relation to ultraweak cell radiation

The fundamental laws of photochemistry and the essential results of experimental research on ultraweak cell radiation are presented. By comparing all the facts it can be concluded that the phenomena discussed may arise from a variety of possible reactions and sources. Recombination reactions of certain radicals actually do release sufficient energy to generate UV-photons of the intensity under consideration. On the other hand, stimulated emission cannot be excluded in view of the distinct deviation of the radiation field from thermal equilibrium. There exist, however, various other candidates, such as direct emitters like flavins, indoles, porphyrins, carbonyl derivatives and aromatic compounds, and molecular oxygen and its various species, as well as collective molecular interactions, e.g. dimole or exciplex transitions, triplet-triplet annihilation, collective hydrolysis, electric field effects in membranes, etc. Careful biochemical and biophysical experiments are still necessary to find answers to all the questions that remain; not only individual problems have to be solved, but it is important to keep in mind the interrelationships between certain reactions.

Microsomal chemiluminescence of benzo[a]pyrene-7,8-dihydrodiol and its synthetic analogues trans- and cis-1-methoxyvinylpyrene

The cis- and trans-methoxyvinylpyrene (MVP) analogues of benzo[a]pyrene-7,8-dihydrodiol (7,8-diol) produce specific microsomal chemiluminescence comparable to that produced from 7,8-diol in Aroclor-induced rat liver microsome preparations. The chemiluminescence quantum yields, emission spectra, and the concentration and the temporal kinetics of these three substrates have been examined. Radiolabelled 7,8-diol and t-MVP exhibit significant covalent binding (more than 14%) to microsomal protein when metabolized enzymatically. The extreme quenching of the dioxetane chemiluminescence by both microsomes and phosphatidylcholine, as a model phospholipid, implies that despite the low quantum yield (approx. 10(-8) photons per substrate molecule) for microsomal chemiluminescence of these substrates, a significant fraction of their microsomal oxygenations may proceed via a dioxetane pathway.

Biological diversity, chemical mechanisms, and the evolutionary origins of bioluminescent systems

A diversity of organisms are endowed with the ability to emit light, and to display and control it in a variety of ways. Most of the luciferins (substrates) of the various phylogenetically distant systems fall into unrelated chemical classes, and, based on still limited data, the luciferases (enzymes) and reaction mechanisms are distinctly different. Based on its diversity and phylogenetic distribution, it is estimated that bioluminescence may have arisen independently as many as 30 times in the course of evolution. However, there are several examples of cross-phyletic similarities among the substrates; some of these may be accounted for nutritionally, but in other cases they may have evolved independently.

Ecology of Colors of Firefly Bioluminescence

Dark-active North American fireflies emit green bioluminescence and dusk-active species emit yellow, in general. Yellow light and yellow visual spectral sensitivity may be adaptations to increase the signal-to-noise (that is, foliage-reflected ambient light) ratio for sexual signaling during twilight. The peaks of the electroretinogram visual spectral sensitivities of four species tested, two dark- and two dusk-active, correspond with the peak of their bioluminescent emissions.

Hydroperoxide-induced chemiluminescence of the perfused lung

Light-emission of the perfused lung is induced by t-butyl hydroperoxide, giving chemiluminescence yields that oscillate between 800 and 1500 counts/s depending on the site and position of the lung. The response of the perfused lung to infusion with different hydroperoxides gives a pattern similar to that observed with the liver microsomal fraction; ethyl hydroperoxide shows a much higher chemiluminescence yield than the tertiary (t-butyl and cumene)hydroperoxides. Alveolar oedema affected the light-emission of the perfused lung depending on the time at which oedema developed, decreasing light emission on infusion of hydroperoxide in the oedematous lung and increasing it when oedema appeared after the maximal chemiluminescence yield was already achieved. Paraquat, administered in vivo, augmented light-emission by approximately 2-fold. The effect of paraquat was a time-dependent process. Lung chemiluminescence, compared with liver chemiluminescence, needed higher hydroperoxide concentration to induce light-emission.

Low-level chemiluminescence of bovine heart submitochondrial particles

Submitochondrial particles from bovine heart mitochondria showed low-level chemiluminescence when supplemented with organic hydroperoxides. Chemiluminescence seems to measure integratively radical reactions involved in lipid peroxidation and related processes. Maximal light-emission was about 1500 counts/s and was reached 2-10min after addition of hydroperoxides. Ethyl hydroperoxide, cumene hydroperoxide and t-butyl hydroperoxide were effective in that order. Antimycin and rotenone increased chemiluminescence by 50-60%; addition of substrates, NADH and succinate did not produce marked changes in the observed chemiluminescence. Cyanide inhibited chemiluminescence; half-maximal inhibitory effect was obtained with 0.03mm-cyanide and the inhibition was competitive with respect to t-butyl hydroperoxide. Externally added cytochrome c (10-20mum) had a marked stimulatory effect on chemiluminescence, namely a 12-fold increase in light-emission of antimycin-inhibited submitochondrial particles. Stimulation of hydroperoxide-induced chemiluminescence of submitochondrial particles by cytochrome c was matched by a burst of O(2) consumption. O(2) is believed to participate in the chain radical reactions that lead to lipid peroxidation. Superoxide anion seems to be involved in the chemiluminescence reactions as long as light-emission was 50-60% inhibitible by superoxide dismutase. Singlet-oxygen quenchers, e.g. beta-carotene and 1,4-diazabicyclo[2,2,2]-octane, affected light-emission. beta-Carotene was effective either when incorporated into the membranes or added to the cuvette. The present paper suggests that singlet molecular oxygen is mainly responsible for the light-emission in the hydroperoxide-supplemented submitochondrial particles.

Organ chemiluminescence: noninvasive assay for oxidative radical reactions

In situ and perfused rat livers showed a spontaneous chemiluminescence of 7-12 counts/sec . cm2 (corresponding to 7-12 x 10(3) photons/sec . cm2); chemiluminescence was increased up to 30 times by infusion of exogenous hydroperoxides. The chemiluminescence of the perfused liver was oxygen dependent. Ethyl, t-butyl, and cumene hydroperoxides were almost equally effective in inducing light emission in the perfused liver. Glutathione release and chemiluminescence showed a parallel increase upon hydroperoxide supply to the perfused liver. A partial spectral analysis of the chemiluminescence of the perfused liver showed a predominance of red-light-emitting species, presumably arising from the singlet oxygen dimol-emission peaks. Many side reactions derived from the complex free radical sequence of lipid peroxidation could afford the chemistry leading to light emission, which represents only about 10(-14) of the utilization of peroxide.