The effect of light on the permeability of a myxomycete

Daniel, John W.; Eustace, John C.

doi:10.1016/0014-5793(72)80604-5

Cited by 9 publications

(1 citation statement)

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“…polycephalum plasmodia was reported by Daniel (15) and later was found (24) to be sensitive to gramicidin S. From their experiments the authors concluded that light mediates a H+/K' exchange. Our experiments with the white mutant strain clearly indicate that the effect of light on the extracellular pH of microplasmodial suspensions is not caused by H+ transport and is quantitatively explained by the decreased production ofan acid.…”

Section: Discussionmentioning

confidence: 87%

Blue-light receptor in a white mutant of Physarum polycephalum mediates inhibition of spherulation and regulation of glucose metabolism.

Schreckenbach¹,

Walckhoff²,

Verfuerth³

1981

Proc. Natl. Acad. Sci. U.S.A.

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Blue light induces sporulation ofPhysarum polycephalum macroplasmodia and reversibly inhibits spherulation (sclerotization) of microplasmodia. Illuminated microplasmodia have an abnormal appearance. The photobiological responses of the plasmodia appear to be unaffected by the absence of yellow pigment in the white mutant strain used. Illumination of microplasmodial suspensions with blue light (Am,, -465 nm) results also in an early effect on glucose metabolism: glucose consumption is reversibly inhibited. By using radioactive glucose it was shown that the main products formed are a water-insoluble glucan and the disaccharide trehalose. Inhibition of glucose consumption in the light results in decreased production of these two compounds. Illumination of microplasmodial suspensions also causes a reversible effect on the pH of the medium which is interpreted as a decreased production of a yet unidentified acid from glucose. The action spectrum of the light-induced pH response shows maxima near 390, 465, and 485 nm. It resembles the absorption spectrum of a flavoprotein and confirms the existence of a blue-light receptor in P. polycephalum microplasmodia.white mutant strain of P. polycephalum. Spectroscopic and chromatographic analyses of extracts of white plasmodia have revealed that, within the limit of detection (<<0.1%) the cells contain none of the typical yellow pigments present in the wild type (6). The light induction ofsporulation ofthe white plasmodia, however, appears to be completely unaffected by the absence ofyellow pigment.We assume that the photoreceptor responsible for the induction ofsporulation is present in microplasmodia as well as in macroplasmodia. Here we report on the existence of a blue-light receptor in microplasmodia of the white strain. This pigment cannot mediate the induction ofsporulation in microplasmodia but it inhibits spherulation, a process that can be regarded as the alternative pathway of differentiation. It is further shown that illumination with blue light has an early effect on glucose metabolism.Starving macroplasmodia of the diploid yellow-pigmented myxomycete Physarum polycephalum display two alternative pathways of differentiation. In the dark they undergo conversion to resistant encysted structures (sclerotia) which, upon addition ofnutrients, revert into plasmodia. In the light, irreversible differentiation into fruiting bodies (sporangia) is induced which is followed by meiosis and allows the initiation of a new life cycle. Germination of the spores liberates mononucleated haploid amoeba which generate a plasmodium by sexual fusion (for reviews see refs. 1-3).Microplasmodia of P. polycephalum that are cultured in suspension rather than in surface culture also differentiate into encysted structures (microsclerotia or spherules) when they are incubated under starvation conditions. Illumination of starving microplasmodia, however, does not result in the formation of spores, a process that apparently requires a dry environment.The action spectrum of the light indu...

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Section: Discussionmentioning

confidence: 87%