TEMPERATURE AND MYCOCHROME SYSTEM IN NEAR-UV LIGHT INDUCIBLE AND BLUE LIGHT REVERSIBLE PHOTOINDUCTION OF CONIDIATION IN Alternaria tomato*

Abstract— When dark-grown colonies were exposed to near-UV light, conidiophore formation was induced, and conidia developed during a subsequent dark period. Simultaneous exposure to near-UV and blue light inhibited induction of conidiation. The inductive effect of near-UV light irradiation was greatly enhanced by treating colonies with low temperatures for 4 h during the 2nd-6th hour of incubation in the dark following inductive irradiation: the enhancement was greatest at 21^°C. The extent of inhibition by blue light increased with the temperature between 10 and 28^°C. This diminution by low temperature was greatest when colonies previously kept at a low temperature were exposed to inductive irradiation: the longer the duration between inductive irradiation and temperature treatment, the lower the diminution. Higher fluences of blue light were required to suppress conidial induction at lower temperature. Thus, it is evident that the inductive effect of near-UV light irradiation on conidiation and the suppressive effect of blue light irradiation are each responsive to different temperatures applied at different times.     

MYCOCHROME SYSTEM AND CONIDIAL DEVELOPMENT IN CERTAIN FUNGI IMPERFECTI

Abstract. A photoreceptor system, “mycochrome”, is involved in a blue and near UV reversible photo-reaction which in turn plays an important role in the photocontrol of conidial development in Alternaria tomato, Botrytis cinerea and Helminthosporium oryzae. Conidial development was controlled by alternating exposures to blue and near UV light with the final response being determined by the final light received. When the final light was near UV a conidium developed; when it was blue, conidiation was inhibited and a “sterile” conidiophore was formed. The effects of the two lights were alternatively reversible. Blue and near UV reversible photoreaction was also found in a light-minus-dark difference spectrum of an intracellular particulate fraction isolated from dark-grown mycelia of A. tomato, and two pigments, P_B (blue absorbing type) and P_NUV (near UV absorbing type), were contained in that photoreaction. P_B was tightly bound to the particulate fraction and P_NUV was either soluble in the cytoplasm or very loosely bound to the particulate fraction. Blue and near UV reversible photoreaction occurred only under the coexistence of P_B and P_NUV. That is, a dip in the near UV region and peak absorbance in the blue region was induced by irradiation with near UV light; however, both conditions were partially dissipated with a subsequent irradiation of blue light. These absorbance changes were revers-ibly repeated by alternating doses of blue and near UV light. When molecular oxygen was introduced after exposure to near UV light, peak absorbance in the blue region rapidly disappeared, and these absorbance changes were repeatedly reversible. Similar results were obtained by treatment with sodium hydrosulfite and molecular oxygen. Thus, it was concluded that the mycochrome system suggested in photo-conidiation was consistent with certain active substances showing blue and near UV reversible absorbance changes and caused by photooxidation reduction reaction.     

CORRELATION BETWEEN ABSORBANCE CHANGES AND A PHYSIOLOGICAL RESPONSE INDUCED BY BLUE LIGHT IN NEUROSPORA

Abstract— Absorbance changes due to the photoreduction of a b -type cytochrome are associated with many biological blue light-controlled processes. Evidence is presented for their causal relationship with the perception of light which induced conidia formation under conditions of starvation in Neurospora crassa mutant albino band, but not with light-induced phase shifts of conidiation bands.     

RHYTHMS IN BLUE-LIGHT-INDUCED CONIDIATION OF WILD TYPE AND A MUTANT STRAIN OF Trichoderma harzianum

Abstract— Trichoderma harzianum normally requires light for conidiation. Conidiation of colonies grown in continuous light does not appear to be rhythmic, but sharp banding patterns are formed under light/dark cycles. A single pulse of blue light produces a sharp band of conidia that forms where the growing edge of the mycelia is located at the time when the light is given. A period of about 24 h is required following the light pulse to produce mature conidia. During this time colonies are insensitive to further induction by light. The fluence required to produce 50% saturation varies by a factor of about 3 depending on when the pulse is given. This change of sensitivity is rhythmic with a period length of approximately 27 h when grown on medium containing deoxycholate.
The pattern of conidiation in a mutant strain (B119), which is able to form conidia in the dark, is rhythmic and the period length is dependent on the composition of the medium. Addition of deoxycholate to the medium increased the interval between dark bands from 12 to 24 h. The rhythmic banding is suppressed in constant light and a double banding pattern is produced in light/dark cycles. A pulse of blue light induces a band of conidia in this mutant, as in the wild type, but it also delays the reappearance of the dark banding pattern. The extent of this delay depends on when the pulse is given and, although the period length of the dark conidiation rhythm is affected by deoxycholate, the effect of blue light on its phase is not. Of the various rhythmic responses of Trichoderma studied here. the delay in reappearance of the dark banding pattern in B119 is the most promising for further detailed studies, for example of wavelength and temperature dependence.     

ROSEOFLAVIN INHIBITION OF PHOTOCONIDIATION IN A Trichoderma RIBOFLAVIN AUXOTROPH: INDIRECT EVIDENCE FOR FLAVIN REQUIREMENT for PHOTOREACTIONS

Roseoflavin, an analog known to compete with riboflavin in Lactobacillus casei , riboflavin-deficient rats, and fungi, was used to ascertain whether a flavin plays a role as a sensitizing pigment for photomorphogenesis in the fungus Trichoderma . Roseoflavin inhibited blue light induced conidiation of a riboflavin-requiring auxotroph of Trichoderma . Colonies pre-incubated with roseoflavin needed six times more light to saturate conidiation. Roseoflavin did not change the dark rate of conidial development indicating that it interfered only with the photoact. A revertant from the riboflavin auxotroph strain was not inhibited by roseoflavin. Simultaneous addition of 10 μ M riboflavin prevented inhibition by 6.4 μ M roseoflavin. Thus, roseoflavin inhibition is probably specific, possibly replacing riboflavin or one of its metabolites in the light reactions. There was no detectable shift in the action spectrum towards the green where roseoflavin absorbs; thus it did not replace a flavin as an efficient photoreceptor.     

Growth under Visible Light Increases Conidia and Mucilage Production and Tolerance to UV‐B Radiation in the Plant Pathogenic Fungus Colletotrichum acutatum

Light conditions can influence fungal development. Some spectral wavebands can induce conidial production, whereas others can kill the conidia, reducing the population size and limiting dispersal. The plant pathogenic fungus Colletotrichum acutatum causes anthracnose in several crops. During the asexual stage on the host plant, Colletototrichum produces acervuli with abundant mucilage‐embedded conidia. These conidia are responsible for fungal dispersal and host infection. This study examined the effect of visible light during C. acutatum growth on the production of conidia and mucilage and also on the UV tolerance of these conidia. Conidial tolerance to an environmentally realistic UV irradiance was determined both in conidia surrounded by mucilage on sporulating colonies and in conidial suspension. Exposures to visible light during fungal growth increased production of conidia and mucilage as well as conidial tolerance to UV. Colonies exposed to light produced 1.7 times more conidia than colonies grown in continuous darkness. The UV tolerances of conidia produced under light were at least two times higher than conidia produced in the dark. Conidia embedded in the mucilage on sporulating colonies were more tolerant of UV than conidia in suspension that were washed free of mucilage. Conidial tolerance to UV radiation varied among five selected isolates.     

The opposed effect of 5-azacytidine and light on the development of reproductive structures in Neurospora crassa

Blue light inhibits the formation of asexual cycle spores (conidia) and stimulates the development of the sexual (female) reproductive structures (protoperithecia) in the nitrogen-starved mycelium of Neurospora crassa. The DNA methylation inhibitor, 5-azacytidine (3-300 microM), opposed the effect of light by suppressing the protoperithecia formation and stimulating a conidiation. The addition of 300 microM 5-azacytidine inhibited protoperithecia formation in the dark-cultivated mycelium by about two orders of magnitude and activated conidiation in the light-exposed mycelium by almost three orders of magnitude. Both in the dark-cultivated and the irradiated mycelium treated with various 5-azacytidine concentrations, the yield of conidia and protoperithecia demonstrated an inverse relationship. We suggest that DNA methylation and blue light are involved in the organism's selection of sexual or asexual reproductive cycle.     

Photoreception and Phototropism in Phycomyces: Antagonistic Interactions between Far-UV, Blue, and Red Light

Abstract— Phototropism of the sporangiophore of the fungus Phycomyces is mediated by UV and blue light. Classical phototropism action spectra with maxima near 280, 370 and 450 nm indicate a flavin-like photoreceptor. Blue light mediates positive phototropism while far-UV light mediates negative phototropism. To better understand the mode of interaction of far-UV with blue light we performed phototropism experiments in which sporangio-phores were placed for 4 h between sources of 280 and 454 nm light coming from opposite directions. The fluence rates of the far-UV were chosen such that unilateral light alone elicited 90° of negative bending. For blue light, moderate fluence rates were applied that elicited about 40° bending. Under conditions of bilateral irradiation the blue light substantially reduced the far-UV elicited phototropism. In the presence of tonic red light the antagonism between far-UV and blue light was greatly reduced. Red light, which by itself is phototropically ineffective, also reduced phototropic bending elicited by either far-UV or blue light. These observations are taken as indications for the existence of a red light-absorbing intermediate of the blue-light receptor. Because the far-UV/ blue-light antagonism disappeared almost completely in the presence of tonic red light, the antagonism may occur at the level of this receptor intermediate.     

INDUCTION OF UMUC+ GENE EXPRESSION IN Escherichia coli IRRADIATED BY NEAR ULTRAVIOLET LIGHT

Abstract— The induction of umu + gene expression caused by irradiation with near ultraviolet light (BLB; black light blue) was studied in Escherichia coli K-12 strains with special reference to the effects of SOS repair deficiencies. The umuC + gene expression was measured as the enzymic activity of (J-galactosidase which is regulated by the promoter of the umuC + operon carried in a plasmid DNA carrying a promoter of umuC* operon, a umuD + gene and a umuC +- lacZ + gene fusion. A high induction of the umuC + gene expression was observed in the uvrA cells in the case of BLB or UV irradiation as compared with the parental wild-type cells. Caffeine inhibited the induction of the umuC* gene expression due to BLB or UV irradiation in both strains. There was very little induction in lexA and recA mutants. In contrast with UV irradiation, there was no killing of cells by BLB irradiation in any strain (wild, uvrA, lexA and recA). Possible implications of the present experimental results were discussed.     

CHANGES IN cAMP AND cGMP CONCENTRATION, BIREFRINGENT FIBRILS AND CONTRACTILE ACTIVITY ACCOMPANYING UV AND BLUE LIGHT PHOTOAVOIDANCE IN PLASMODIA OF AN ALBINO STRAIN OF Physarum polycephalum

Abstract— Photoavoidance by plasmodia of an albino strain of Physarum polycephalum was studied. When the organism was irradiated locally, the protoplasm moved away from the irradiated region. The action spectrum for this avoidance showed three peaks at about 260, 370 and 460 nm. The organism was about one hundred times as sensitive to far UV as to near UV and blue light, and high intensity far-UV caused the gelation of the protoplasm. Irradiation with UV or blue light increased the mean level or the amplitude of oscillation in intracellular cAMP and cGMP concentrations. Upon UV irradiation, birefringent fibrils, presumably microfilaments of F-actin, became thick and numerous, and the plasmodial strand generated a strong tensile force. It is postulated that UV or blue light brings about an increased concentration of cyclic nucleotides which leads to an enhanced local development of contractile fibrils which squeeze protoplasmic sol from the area, resulting in photoavoidance.     

Photoinduction of albino-3 gene expression in Neurospora crassa conidia.

The synthesis of carotenoids is induced by blue light in Neurospora crassa mycelia, while in conidia (the vegetative spores) the accumulation of carotenoids also occurs in the dark. The expression of the albino-3 (al-3) gene (coding for the carotenogenic enzyme geranyl-geranyl pyrophosphate synthetase) in isolated conidia was analysed. The level of al-3 mRNA was shown to be increased in light-induced wild type (wt) conidia. This light response was elicited by blue light and was under the control of the white collar-1 (wc-1) and white collar-2 (wc-2) gene products. This indicates that the blue-light photoreceptor and the light transduction pathway which activate al-3 gene expression in mycelia are probably the same as in conidia.     

Conidial pigmentation is important to tolerance against solar-simulated radiation in the entomopathogenic fungus Metarhizium anisopliae

The importance of conidial pigmentation to solar UV radiation tolerance in the entomopathogenic fungus Metarhizium anisopliae var. anisopliae, was estimated by comparing the effects of exposure to simulated solar UV radiation on the wild-type parent strain U.S. Department of Agriculture (USDA)-Agricultural Research Service (ARS) Collection of Entomopathogenic Fungal Cultures (ARSEF) 23, which has dark green conidia, and three groups of color mutants with yellow, purple and white conidia. The comparisons included inactivation levels and the kinetics of germination of conidia exposed or not exposed to simulated solar UV radiation. In addition to significantly inactivating the conidia of different mutants, exposure to radiation delayed for several hours the germination of surviving conidia of the wild type and all mutants. In general, mutants with white conidia were more sensitive to simulated solar UV radiation than mutants with purple conidia, which were more sensitive than mutants with yellow conidia, which in turn were more sensitive than the green wild strain. A significant variation in tolerance to simulated solar radiation was observed among mutants within each color group, particularly among mutants with yellow conidia. Revertants with green conidia, DWR 179 and DWR 176, were obtained from the very sensitive UV mutants DWR 148 (yellow conidia) and DWR 149 (purple conidia), respectively. These revertants had levels of tolerance to simulated solar UV radiation similar to those of the wild-type ARSEF 23. This observation is strong evidence of the importance of green conidial pigmentation for tolerance to simulated solar UV radiation, a factor that could be manipulated to produce M. anisopliae strains with more tolerance to solar UV radiation.     

8-METHOXYPSORALEN-PHOTOINDUCED DNA CROSSLINKS AS DETERMINED IN YEAST BY ALKALINE STEP ELUTION UNDER DIFFERENT REIRRADIATION CONDITIONS. RELATION WITH GENETIC EFFECTS

Abstract— DNA damage induced by 8-methoxypsoralen (8-MOP) plus near UV light (UVA) was analyzed in diploid yeast using the alkaline step elution technique. The presence of 8-MOP and UVA induced DNA interstrand cross-links was revealed by the increase of DNA retained on elution filters as compared to untreated controls. The fraction of DNA retained on filters increased linearly with UVA dose. The amount of cross-links was estimated from the fraction of DNA retained on filters using a dose of -radiation leading to a number of DNA strand breaks at least equivalent to the number of 8-MOP induced photoadducts.
When 8-MOP treated cells were exposed to monochromatic light, 365 nm light induced monoadducts and cross-links whereas 405 nm light induced only monoadducts. When submitting 8-MOP plus 405 nm light treated cells to 365 nm irradiation, after removal of unbound 8-MOP by washing, a portion of 8-MOP plus 405 nm light induced monoadducts was converted into cross-links. The amount of monoadducts transformed into cross-links was dependent on the dose of 365 nm irradiation up to a maximum likely to correspond to the number of suitably positioned furan-side monoadducts that could be converted into biadducts. When 8-MOP plus 365 nm light treated cells were reirradiated with 365 nm light, following the same protocol, the maximum level of cross-linking obtainable in yeast was lower than that obtained with 8-MOP in a 405 nm plus 365 nm reirradiation protocol.
In the presence of 8-MOP single exposures to 405 nm light were found to be only slightly genotoxic. However, when followed by second exposures to 365 nm light, a dose-dependent increase in genetic effects, i.e. mutation and gene conversion, was observed in parallel to the induction of DNA crosslinks. These results stress again the prominent role of DNA cross-links in the genotoxicity of 8-MOP.     

Photostimulation of conidiation in mutants of Neurospora crassa

Various mutants of Neurospora crassa were screened for light-stimulated conidiation which is a blue light effect and, at least in strain albino-band, is mediated by the flavoprotein nitrate reductase (NR). NR- mutants showed practically no photoconidiation under standard conditions. However, in fusion products of nit-1 (diaphorase activity present, terminal activity missing) plus nit-3 (terminal activity present, diaphorase activity missing), NR activities and photoconidiation were partially restored. Mutants with altered light sensitivities, such as white collar WC-1 and light-insensitive lis-2 and lis-3, had normal NR activities and their conidiation was promoted by light, whereas WC-2 and lis-1 responded only slightly. These two mutants showed low NR activities especially when grown on solid medium which might be the cause of their blindness. Experiments with NR- mutants indicated that nitrite reductase might also act as a blue light photoreceptor.     

Photodynamic Inactivation of Conidia of the Fungi Metarhizium anisopliae and Aspergillus nidulans with Methylene Blue and Toluidine Blue

Antimicrobial photodynamic treatment (PDT) is a promising method that can be used to control localized mycoses or kill fungi in the environment. A major objective of the current study was to compare the conidial photosensitization of two fungal species (Metarhizium anisopliae and Aspergillus nidulans) with methylene blue (MB) and toluidine blue (TBO) under different incubation and light conditions. Parameters examined were media, photosensitizer (PS) concentration and light source. PDT with MB and TBO resulted in an incomplete inactivation of the conidia of both fungal species. Conidial inactivation reached up to 99.7%, but none of the treatments was sufficient to achieve a 100% fungicidal effect using either MB or TBO. PDT delayed the germination of the surviving conidia. Washing the conidia to remove unbound PS before light exposure drastically reduced the photosensitization of A. nidulans. The reduction was much smaller in M. anisopliae conidia, indicating that the conidia of the two species interact differently with MB and TBO. Conidia of green and yellow M. anisopliae mutants were less affected by PDT than mutants with white and violet conidia. In contrast to what occurred in PBS, photosensitization of M. anisopliae and A. nidulans conidia was not observed when PDT was performed in potato dextrose media.     

聚酰胺-胺树形分子对胶带上油潜指纹的显现研究

研究了不同pH值和光源波长条件下,荧光性聚酰胺-胺树形分子(PAMAM)水溶液对胶带粘面上油潜指纹的显现效果.结果显示:PAMAM树形分子水溶液pH值大于7时,指纹残留物被不同程度地溶解,因此显现效果不佳;pH值为4—7时,显现效果较好,处理过的指纹发出明亮的蓝色荧光,指纹纹路完整、特征明显,且与基底的对比度较高;但由于用365 nm紫外光激发时,PAMAM树形分子的蓝色荧光容易受胶带中杂质蓝色荧光的影响,因此对比度仅为28.8%左右;采用其它波段的可见光或者复合白光作为光源后,有效规避了胶带中杂质的同色系荧光干扰,指纹对比度可提高至90%,并且避免了紫外光使用过程中对人体的伤害.PAMAM树形分子水溶液是一种环保的、具有潜在应用价值的识别胶带粘面上油潜指纹的优良显现材料.     

Polykaryon formation using a swollen conidium of Trichoderma reesei

The cellulolytic fungus, Trichoderma has oval and mononucleate conidia. When these conidia are incubated in a liquid medium, they begin to swell and their shape becomes spherical followed by an increase in inner space. In such swollen conidia, it is possible to produce a larger autopolyploid nucleus using a mitotic arrester compared with the case of the original conidia. In this study, polykaryon formation was attempted using these swollen conidia. Dried mature green conidia of Trichoderma reesei QM6a (IFO 31326) were incubated in Mandel's medium in order to swell. The swollen conidia were treated with a mitotic arrester, colchicine, for autopolyploidization. After autopolyploidization, polykary on formation was carried out using the swollen conidia. After the treatment, multiple smaller nuclei whose diameter was almost the same as that of the original strain were generated from an autopolyploid nucleus in a swollen conidium. A cellulase hyperproducer without decrease in growth rate could be selected using such swollen conidia.     

Rat lens glycolysis after in vivo exposure to narrow band UV or blue light radiation

UV radiation and short wavelength visible light are known to damage various tissues in the eye. This paper investigates the effect on rat lens glycolysis after in vivo exposure with 90 kJ m⁻² narrow band UV radiation (UVB, 300 nm) and 90 kJ m⁻² blue light (435 nm) radiation. After exposure, all lenses were incubated in Medium 199. Samples of culture medium were withdrawn after 2, 4, 6 h and 5, 10, 20 h in two UVB studies and after 5, 10 and 20 h in a blue light study. Lactate is the major end product of lens glycolysis. Lactate was determined with a modified enzymatic-photometric method. Intralenticular lactate was determined in one UVB experiment. In the UVB experiments we found a lower lactate production in the exposed lenses 2–6 h after exposure. There was an accumulation of lactate inside UVB-exposed lenses after 6 h incubation compared with their contralateral lenses. No significant effect on lactate production was observed in the blue light experiment. Conclusions. UVB induced a reversible inhibition of glycolysis. UVB also induced an accumulation of lactate inside the lens. Blue light tended to increase glycolysis.     

NITRATE REDUCTASE—A KEY ENZYME IN BLUE LIGHT-PROMOTED CONIDIATION AND ABSORBANCE CHANGE OF NEUROSPORA

Abstract— Neurospora , when starved for several hours, can be stimulated by blue light to conidiate and also shows a blue light-inducible, flavin-mediated absorbance change near 425 nm due to photoreduc-tion of a h-type cytochrome. Under the same physiological conditions, nitrate reductase activity (NADPH-dependent nitrate reduction) decreases and the activity of its small subunit (methylviologen-to-nitrate reductase activity) increases. The increased activity is membrane associated (plasma membrane and mitochondria). The methylviologen-to-nitrate activity increase can also be brought about by treating mycelium briefly with diluted acetone. It is, therefore, interpreted as change within the nitrate reductase molecule (configuration change or separation of subunits with changed exposure of active sites). After acetone treatment the blue light-induced absorbance change can be observed immediately in the mycelium. Nitrate reductase with its flavin and protoheme prosthetic groups seems to be involved in both events, the induction of conidiation and in the described absorbance change.     

DNA SINGLE-STRAND LESIONS DUE TO ''SUNLIGHT'' AND UV LIGHT: A COMPARISON OF THEIR INDUCTION IN CHINESE HAMSTER AND HUMAN CELLS, AND THEIR FATE IN CHINESE HAMSTER CELLS

Abstract— It has been shown that the lethal properties of germicidal UV light (254 nm) and sunlight-simulating near UV light are qualitatively different (Elkind et al ., 1978). Further to compare these two radiations, the induction of single-strand DNA breaks (i.e. frank breaks plus alkali-labile lesions) was measured in two cell lines. Equal numbers of breaks in Chinese hamster cells require a dose of UV 5.5% of a near UV dose but in HeLa cells a UV dose of 7.6% of a near-UV dose is required. The rate of break production by these radiations is about 1/10-th of that due to X-rays when a comparison is made on an equal killing dose basis. The inventory of breaks in Chinese hamster cells was also followed and was found to be characteristically different for UV compared to near UV light. These data indicate that significant differences exist, at a molecular level, in the effects produced by ultraviolet and sunlight-simulating light, and further emphasize the need for caution in attempting to extrapolate from observed molecular or biological effects due to the former to those to be expected from the latter.