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The patterns of sclerotial development in Botrytis cinerea were studied under controlled enviromental conditions capable of inducing sclerotial formation. Two types of sclerotial development were distinguished. Terminal type of sclerotia was induced by mounting a cover-glass on the tips of vegetative hyphae for a definite period of time. On the other hand, lateral type of sclerotia was induced in a narrow region of the mycelia produced at the beginning of high-temperature treatment by exposing to a temporary high-temperature. Thus, in Botrytis cinerea which has been previously grouped into a former of terminal type of sclerotia, there also exists the lateral type of sclerotial development.

When the fruitfly, Drosophila melanogaster, was reared on media deficient in carotenoids and retinoids, the level of 3-hydroxyretinal (the chromophore of fly rhodopsin) in the retina decreased to less than 1% compared with normal flies. The level of 3-hydroxyretinal increased markedly in flies that were given a diet supplemented with retinoids or carotenoids. The retinas of flies fed on all-trans retinoids and maintained in the dark predominantly contained the all-trans form of 3-hydroxyretinal, and showed no increase in the level of either the 11-cis isomer or the visual pigment. Subsequent illumination of the flies converted substantial amounts of all-trans 3-hydroxyretinal to its 11-cis isomer. The action spectrum of the conversion by illumination showed the optimum wavelength to be approximately 420 nm, which is significantly greater than the absorption maximum of free, all-trans 3-hydroxyretinal. Flies that were fed on carotenoids showed a rapid increase of the levels of 11-cis 3-hydroxyretinal and of visual pigment in the absence of light.

Further studies have been made on the blue and near ultraviolet-reversible photoreaction in a cell-free system of the fungus Alternaria tomato, prepared by two-layer sucrose density gradient centrifugation. A light-minus-dark difference spectrum of the supernatant fraction showed a dip in the near ultraviolet region, mainly at 280 nm, when irradiated with near ultraviolet light which could not be reversed by following the initial irradiation with blue light. The difference spectrum of the dialyzed particulate fraction, located in the 68% sucrose band, showed a peak absorbance in the blue region, mainly at 400 nm, when irradiated with near ultraviolet light, and also could not be reversed by blue light. When the particulate fraction plus the supernatant fraction was irradiated with near ultraviolet light, the increment rate of peak absorbance in the blue region increased compared to that of the particulate fraction lacking the supernatant, and both peak absorbance in the blue region and the dip in the near ultraviolet region were reversed by irradiation with blue light following the application of near ultraviolet light. Thus, it was concluded that two photoresponsive systems are involved in blue and near ultraviolet reversible photoreaction on an intracellular particulate fraction.

Photosporulation of Alternaria tomato was very little influenced by polyoxin at concentrations below 10 μg/ml, although hyphae and conidia were morphologically affected. The hyphae grown in the presence of polyoxin were easily disrupted.

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Effects of blue and near ultraviolet lights on the lateral-type sclerotial development in Botrytis cinerea were studied.When a developing sclerotial primordium at a stage from 2 (i.e. swelled hyphae) to 3 (i.e. club-shaped hyphae) was exposed to blue light for 12-24hr, sclerotial development was inhibited. The outgrowth of club-shaped hyphae from swelled ones and further branching of club-shaped hyphae were suppressed and these sclerotial initials de-differentiated into “sterile” hyphae with sharply pointed and shrivelled tips. The inhibitory effect of blue light on the primordia at a stage from 2 to 3 could not be reversed by near ultraviolet light.On the other hand, when a sclerotial primordium at a stage from 1 to 3 was exposed to near ultraviolet light for a short time, the formation of conidiophores was induced on that primordium. Sclerotial development was inhibited by the predominance of conidiation over the sclerotial primordia at a stage from 1 to 2. The sclerotial development after stage 3 was no longer influenced by irradiation with near ultraviolet light, and continued normally.Thus, both blue and near ultraviolet lights inhibited the lateral-type sclerotial development at a definite stage of sclerotial formation, though the effects of these lights were different from each other.

書誌情報のみ, Bibliographic data Only

書誌情報のみ, Bibliographic data Only

書誌情報のみ, Bibliographic data Only

書誌情報のみ, Bibliographic data Only

書誌情報のみ, Bibliographic data Only

In the sporulation of Alternaria tomato, conidiophores are induced by near ultraviolet irradiation but not by darkness, and the conidia develop only when the irradiation is followed by a period of darkness. Conidial development is suppressed by a short exposure to blue light at a definite time during the dark period following the inductive irradiation. The suppression of conidial development by blue light can be reversed by exposure to near ultraviolet light immediately following the blue light irradiation. This reversion is reversibly suppressed by a further exposure to blue light immediately following near ultraviolet irradiation. Thus, at least two stages are involved in the sporulation of A. tomato, the first being a photochemical stage necessary for the induction of conidiophores, and the second essential for the conidial development which proceeds only in the absence of exposure to the blue region of the spectrum. Moreover, conidial development can be controlled by alternating doses of blue and near ultraviolet light, and the subsequent response depends upon the last kind of radiation given. It is concluded that a new pigment system, which we have named “Mycochrome”, is involved in the blue and near ultraviolet reversible photoreaction, and that this compound plays an important role in the photocontrol of conidial development in this fungus.

The effect of light on conidial development of a nonphotoinduced isolate of Helminthosporium oryzae was investigated. Near-ultraviolet light was not required for conidiophore induction, but conidial development was suppressed by blue light applied at a definite stage of conidiophore development, and the conidiophores were dedifferentiated into longer, slender aerial hyphae. Furthermore, the effect of blue light could be reversed by immediate exposure to near-ultraviolet light and the effects of these two spectral regions were alternatively reversible.Thus, it is concluded that a photosensitive system, called mycochrome, is involved in the conidial development of this fungus.

SUMMARY: The effect of the blue and near ultraviolet reversible photoreaction on conidial development in Botrytis cinerea was studied by observing microscopically selected conidiophores. Conidiophore development was divided into six stages: when the developing conidiophores from stage 2 (i.e. a mature conidiophore) to stage 5 (i.e. a conidiophore with conidium initial) were exposed to blue light for a short time, conidiation was suppressed; the conidiophores already formed de-differentiated to ‘sterile’ conidiophores with sharply pointed tips. The suppression of conidial development by blue light could be reversed by subsequent exposure to near ultraviolet light, and conidia then developed normally. This mycochrome system functioned reciprocally within the range of identified conidiophore developmental stages and near ultraviolet light acted only at the same developmental stage as was inhibited by blue light.