ISSN:
1432-2048
Keywords:
Key words: Blue-light receptor
;
Flavin
;
Light-induced absorbance changes
;
Phototropism mutants
;
Phycomyces
;
Red-light receptor
;
Semiquinone
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract. Light-induced absorbance changes (LIACs), which are associated with early photochemical events of blue-light transduction, were detected in growing zones of Phycomyces sporangiophores. The novel LIACs meet all the essential requirements for a spectrophotometric photoreceptor assay which was previously unavailaible for blue-light receptors (cryptochromes). In-vivo absorption spectra of growing zones were derived from reflection spectra which were measured with a novel rapid-scan spectrophotometer. To detect photoreceptor-associated absorbance changes white mutants were employed which lack the interfering bulk pigment β-carotene. Blue and white light, not however red light, induced in these strains absorbance changes near 460–490 and 600–620 nm. The LIACs were absent in light-insensitive mutants with defects in the genes madA, madB and madC. Because these genes affect photosensory adaptation and the blue-light receptor itself, the novel in-vivo LIACs must be associated with photochemical events which occur early in the transduction chain. The spectral characteristics of the LIACs are in accordance with a blue- and red-light absorbing flavosemiquinone which is generated upon light absorption by an oxidized flavin receptor. It is proposed that the flavosemiquinone functions itself as photoreceptor which mediates several red-light responses of Phycomyces.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s004250050559
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