Flagellar Adhesion between mt+ and mt− Chlamydomonas Gametes Regulates Phosphorylation of the mt+-specific Homeodomain Protein GSP1

Wilson, Nedra F.; O’Connell, Joe; Lu, Min; Snell, William J.

doi:10.1074/jbc.274.48.34383

Cited by 22 publications

(25 citation statements)

References 31 publications

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“…Freshly harvested cells were resuspended in buffer (10 mm Tris, pH 7.0, 1 mm NaCl) containing proteinase inhibitors (Sigma) and flash frozen in liquid nitrogen for .1 hr (Wilson et al 1999). An equal amount of boiling 23 SDS gel-loading buffer was added to the frozen samples and the samples were boiled immediately for 5 min.…”

Section: Methodsmentioning

confidence: 99%

Gametogenesis in the Chlamydomonas reinhardtii minus Mating Type Is Controlled by Two Genes, MID and MTD1

Lin

Goodenough

2007

Genetics

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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 À 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 À 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 gametespecific 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 1 locus, is operant during plus gametogenesis.C HLAMYDOMONAS reinhardtii is a flagellated unicellular green alga that has two mating types, plus and minus, determined by the mating type (MT ) loci (MT 1 and MT À ). The center of this $1-Mb locus of recombinational suppression carries translocations and inversions and is called the rearranged (R) domain (Ferris and Goodenough 1994). Both housekeeping and sex-limited genes are found in this region (Ferris et al. 2002), similar to mating-type loci and sex chromosomes in other organisms (Graves 2006). Six unique regions (a-f ) are found within the R domain, three (ac) specific to MT 1 and three (d-f ) specific to MT À . Four genes have been identified in these regions: MTA1 (MT locus, region a) in a, FUS1 (fusion) in c, MTD1 (MT locus, region d) in d, and MID (minus dominance) in f (Ferris et al. 2002). The two MT À -specific genes are the focus of this study.In response to nitrogen starvation, haploid vegetative Chlamydomonas cells differentiate into gametes. Gametes of opposite mating type are able to agglutinate and fuse to form zygotes (Harris 1989). Occasionally, heterozygous mt 1 /mt À diploids form after mating, resume vegetative growth, and differentiate as gametes with N-starvation. The fact that these diploids always mate as minus indicates that minus is dominant to plus (Harris 1989), a phenomenon found to be controlled by the MID gene (Galloway and Goodenough 1985). MID encodes a transcription factor in the RWP-RK family that also includes several proteins in higher plants that are suggested to exert their function during nitrogen limitation (Schauser et al. 1999(Schauser et al. , 2005Borisov et al. 2003).Previous studies revealed that MID is necessary and sufficient to convert wild-type ...

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Section: Methodsmentioning

confidence: 99%

Gametogenesis in the Chlamydomonas reinhardtii minus Mating Type Is Controlled by Two Genes, MID and MTD1

Lin

Goodenough

2007

Genetics

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“…The fusion of opposite mating type gametes initiates the diploid phase of the Chlamydomonas life cycle. Regarding the genetic mechanism underlying the full program of zygote development, GSP1 originating from plus gametes and GSM1 originating from minus gametes both contribute to zygote development, including the resorption of flagella, fusion of nuclei and chloroplasts, destruction of minus gamete G-chloroplast DNA, and secretion of a resistant cell wall (Wilson et al 1999). Earlier studies showed that the ectopic expression of GSP1 in minus gametes or of GSM1 in plus gametes can switch the zygotic differentiation programme on, and the resulting zygotes could undergo a normal meiosis (Zhao et al 2001, Lee et al 2008.…”

Section: A Molecular Perspective On Fertility Genetic Controlmentioning

confidence: 99%

Seaweed reproductive biology: environmental and genetic controls

et al. 2017

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Knowledge of life cycle progression and reproduction of seaweeds transcends pure academic interest. Successful and sustainable seaweed exploitation and domestication will indeed require excellent control of the factors controlling growth and reproduction. The relative dominance of the ploidy-phases and their respective morphologies, however, display tremendous diversity. Consequently, the ecological and endogenous factors controlling life cycles are likely to be equally varied. A vast number of research papers addressing theoretical, ecological and physiological aspects of reproduction have been published over the years. Here, we review the current knowledge on reproductive strategies, trade-offs of reproductive effort in natural populations, and the environmental and endogenous factors controlling reproduction. Given that the majority of ecophysiological studies predate the "-omics" era, we examine the extent to which this knowledge of reproduction has been, or can be, applied to further our knowledge of life cycle control in seaweeds.

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“…In some experiments sample buffer was used at a final concentration of 2ϫ. The samples were subjected to electrophoresis in 9% acrylamide (15,30) minislab gels at 30 mA in buffer containing 25 mM Tris, 192 mM glycine, 0.1% SDS and then transferred for immunoblot analysis (see below). Typically 15-30 g of protein was loaded in each lane.…”

Section: Cells and Cell Culture-chlamydomonas Reinhardtii Strains 21grmentioning

confidence: 99%

“…The increased cellular levels of cAMP also induce additional events in the cell body, including regulated secretion of molecules required for release and degradation of the extracellular matrix (cell wall), activation of fusion organelles called mating structures on the apical ends of the interacting cells between their sets of flagella, and phosphorylation of an mtϩ gametespecific homeodomain protein, GSP1 (14,15). Adhesion and fusion of the mating structures on the mtϩ and mtϪ gametes are followed by complete merging of the two cell bodies.…”

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Regulated Targeting of a Protein Kinase into an Intact Flagellum

Pan

Snell

2000

Journal of Biological Chemistry

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In the green alga Chlamydomonas reinhardtii flagellar adhesion between gametes of opposite mating types leads to rapid cellular changes, events collectively termed gamete activation, that prepare the gametes for cell-cell fusion. As is true for gametes of most organisms, the cellular and molecular mechanisms that underlie gamete activation are poorly understood. Here we report on the regulated movement of a newly identified protein kinase, Chlamydomonas aurora/Ipl1p-like protein kinase (CALK), from the cell body to the flagella during gamete activation. CALK encodes a protein of 769 amino acids and is the newest member of the aurora/ Ipl1p protein kinase family. Immunoblotting with an anti-CALK antibody showed that CALK was present as a 78/80-kDa doublet in vegetative cells and unactivated gametes of both mating types and was localized primarily in cell bodies. In cells undergoing fertilization, the 78-kDa CALK was rapidly targeted to the flagella, and within 5 min after mixing gametes of opposite mating types, the level of CALK in the flagella began to approach levels normally found in the cell body. Protein synthesis was not required for targeting, indicating that the translocated CALK and the cellular molecules required for its movement are present in unactivated gametes. CALK was also translocated to the flagella during flagellar adhesion of nonfusing mutant gametes, demonstrating that cell fusion was not required for movement. Finally, the requirement for flagellar adhesion could be bypassed; incubation of cells of a single mating type in dibutyryl cAMP led to CALK translocation to flagella in gametes but not vegetative cells. These experiments document a new event in gamete activation in Chlamydomonas and reveal the existence of a mechanism for regulated translocation of molecules into an intact flagellum.Cell-cell interactions leading to fusion between gametes of opposite sexes during fertilization are complex processes that involve dramatic changes in each of the interacting gametes. In most multicellular organisms, interactions between adhesion molecules/receptors on the sperm plasma membrane and ligands on the egg surface activate poorly understood signaling pathways that bring about transformation of the sperm into a fusion competent, activated gamete (1). For example, the sperm surface is remodeled as a consequence of the acrosome reaction, an event that accompanies gamete activation, and previously existing adhesion molecules are mobilized to new sites on the sperm (2-4). The molecular mechanisms that underlie and regulate signal transduction and movement of molecules between different gamete compartments during gamete activation largely are unknown (2).As in multicellular organisms, gamete activation and fertilization in the unicellular green alga Chlamydomonas (5) depend on adhesion-induced signaling pathways and intercompartmental communication. At the completion of gametogenesis, during which asexually growing mtϩ and mtϪ vegetative cells differentiate into sexually competent cells, the resultin...

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Flagellar Adhesion between mt+ and mt− Chlamydomonas Gametes Regulates Phosphorylation of the mt+-specific Homeodomain Protein GSP1

Cited by 22 publications

References 31 publications

Gametogenesis in the Chlamydomonas reinhardtii minus Mating Type Is Controlled by Two Genes, MID and MTD1

Gametogenesis in the Chlamydomonas reinhardtii minus Mating Type Is Controlled by Two Genes, MID and MTD1

Seaweed reproductive biology: environmental and genetic controls

Regulated Targeting of a Protein Kinase into an Intact Flagellum

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