title: Characterization of the eyespot regions of "blind" Chlamydomonas mutants after restoration of photophobic responses.
abstract: Chlamydomonas reinhardtii exhibits photophobic and positive and negative phototactic responses that can be defined for cell populations using computerized cell tracking and motion analysis. Mutants CC-2359 and FN68 are pigment deficient mutants that are blocked in carotenoid synthesis and lack these photo responses. In particular, neither mutant exhibits flash-induced photophobic responses to visible light stimuli to which wild-type gametic cells exhibit a strong response, with several behavioral stages. Upon addition of all-trans retinal to these mutants, the photophobic responses are restored with minor quantitative differences from wild-type populations. Using both light and electron microscopy, we have compared the ultrastructural characteristics of wild-type C. reinhardtii to those of both mutants. As previously described, wild-type cells contain an eyespot consisting of 2-4 layers of pigmented granules encased within thylakoid membranes, located between the distal extremities of the flagellar root. This structure is also visible as an orange-red spot in light microscopy. The photoreceptor is thought to be concentrated in the plasma membrane above the eyespot. The mutant, CC-2359, lacks this eyespot as seen by both light and electron microscopy, even when the photophobic response has been restored. FN68-like mutants studied earlier by Morel-Laurens and Feinlieb and others contain an eyespot which can be seen only by electron microscopy. In FN-68, the eyespot generally has the same dimensions as in wt cells, differing mainly in pigment granule appearance.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, New York 10461.
authors.forename: M A
authors.initials: MA
authors.lastname: Lawson
authors.forename: P
authors.initials: P
authors.lastname: Satir
mesh_terms: D000818:Animals; D016825:Chlamydomonas reinhardtii / Q000235:genetics / Q000502:physiology* / Q000648:ultrastructure; D009154:Mutation / Q000502:physiology; D017956:Photoreceptor Cells, Invertebrate / Q000648:ultrastructure*; D018524:Phototropism / Q000187:drug effects / Q000235:genetics*; D012172:Retinaldehyde / Q000494:pharmacology
chemical_list: D012172:Retinaldehyde