title: The heme-binding protein SOUL3 of Chlamydomonas reinhardtii influences size and position of the eyespot.
abstract: The flagellated green alga Chlamydomonas reinhardtii has a primitive visual system, the eyespot. It is situated at the cells equator and allows the cell to phototax. In a previous proteomic analysis of the eyespot, the SOUL3 protein was identified among 202 proteins. Here, we investigate the properties and functions of SOUL3. Heterologously expressed SOUL3 is able to bind specifically to hemin. In C. reinhardtii, SOUL3 is expressed at a constant level over the diurnal cycle, but forms protein complexes that differ in size during day and night phases. SOUL3 is primarily localized in the eyespot and it is situated in the pigment globule layer thereof. This is in contrast to the channelrhodopsin photoreceptors, which are localized in the plasma membrane region of the eyespot. Knockdown lines with a significantly reduced SOUL3 level are characterized by mislocalized eyespots, a decreased eyespot size, and alterations in phototactic behavior. Mislocalizations were either anterior or posterior and did not affect association with acetylated microtubules of the daughter four-membered rootlet. Our data suggest that SOUL3 is involved in the organization and placement of the eyespot within the cell.
authors.affiliation: Institute of General Botany and Plant Physiology, Friedrich Schiller University Jena, 07743 Jena, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Schulze
authors.forename: Sandra
authors.initials: S
authors.lastname: Schreiber
authors.forename: Dobromir
authors.initials: D
authors.lastname: Iliev
authors.forename: Jens
authors.initials: J
authors.lastname: Boesger
authors.forename: Jessica
authors.initials: J
authors.lastname: Trippens
authors.forename: Georg
authors.initials: G
authors.lastname: Kreimer
authors.forename: Maria
authors.initials: M
authors.lastname: Mittag
mesh_terms: D020418:Algal Proteins / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D016825:Chlamydomonas reinhardtii / Q000033:anatomy & histology* / Q000235:genetics / Q000378:metabolism*; D002940:Circadian Rhythm; D055785:Gene Knockdown Techniques; D000081062:Heme-Binding Proteins; D006420:Hemeproteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics
chemical_list: D020418:Algal Proteins; D002352:Carrier Proteins; D000081062:Heme-Binding Proteins; D006420:Hemeproteins