title: Gametogenesis in the Chlamydomonas reinhardtii minus mating type is controlled by two genes, MID and MTD1.
abstract: In the unicellular algae Chlamydomonas reinhardtii, the plus and minus mating types are controlled by a complex locus, MT, where the dominant MID gene in the MT(-) locus has been shown to be necessary for expression of minus-specific gamete-specific genes in response to nitrogen depletion. We report studies on MID expression patterns during gametogenesis and on a second gene unique to the MT(-) locus, MTD1. Vegetative cells express basal levels of MID. An early activation of MID transcription after nitrogen removal, and its sequence similarity to plant RWP-RK proteins involved in nitrogen-responsive processes, suggest that Mid conformation/activity may be nitrogen sensitive. A second stage of MID upregulation correlates with the acquisition of mating ability in minus gametes. Knockdown of MTD1 by RNAi in minus strains results in a failure to differentiate into gametes of either mating type after nitrogen deprivation. We propose that intermediate Mid levels are sufficient to activate MTD1 transcription and to repress plus gamete-specific genes and that MTD1 expression in turn allows the threshold-level MID expression needed to turn on minus gamete-specific genes. We further propose that an MTD1-equivalent system, utilizing at least one gene product encoded in the MT(+) locus, is operant during plus gametogenesis.
authors: Department of Biology, Washington University, St. Louis, Missouri 63130, USA.
authors: Huawen
authors: H
authors: Lin
authors: Ursula W
authors: UW
authors: Goodenough
mesh_terms: D020418:Algal Proteins / Q000235:genetics*; D000818:Animals; D015152:Blotting, Northern; D018929:Cell Culture Techniques; D016825:Chlamydomonas reinhardtii / Q000145:classification / Q000166:cytology / Q000235:genetics / Q000502:physiology*; D003433:Crosses, Genetic; D017931:DNA Primers; D005718:Gametogenesis / Q000235:genetics*; D005786:Gene Expression Regulation; D005799:Genes, Dominant; D008562:Membrane Glycoproteins / Q000235:genetics*; D010802:Phylogeny; D012313:RNA / Q000235:genetics / Q000302:isolation & purification; D012097:Repressor Proteins / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012260:Ribonucleases / Q000378:metabolism; D015534:Trans-Activators / Q000235:genetics*; D015854:Up-Regulation
chemical_list: D020418:Algal Proteins; D017931:DNA Primers; D008562:Membrane Glycoproteins; D012097:Repressor Proteins; D015534:Trans-Activators; D012313:RNA; D012260:Ribonucleases