1
|
Ma Y, Yan G, Zhang J, Xiong J, Miao W. Cip1, a CDK regulator, determines heterothallic mating or homothallic selfing in a protist. Proc Natl Acad Sci U S A 2024; 121:e2315531121. [PMID: 38498704 PMCID: PMC10990102 DOI: 10.1073/pnas.2315531121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2023] [Accepted: 02/20/2024] [Indexed: 03/20/2024] Open
Abstract
Mating type (sex) plays a crucial role in regulating sexual reproduction in most extant eukaryotes. One of the functions of mating types is ensuring self-incompatibility to some extent, thereby promoting genetic diversity. However, heterothallic mating is not always the best mating strategy. For example, in low-density populations or specific environments, such as parasitic ones, species may need to increase the ratio of potential mating partners. Consequently, many species allow homothallic selfing (i.e., self-fertility or intraclonal mating). Throughout the extensive evolutionary history of species, changes in environmental conditions have influenced mating strategies back and forth. However, the mechanisms through which mating-type recognition regulates sexual reproduction and the dynamics of mating strategy throughout evolution remain poorly understood. In this study, we show that the Cip1 protein is responsible for coupling sexual reproduction initiation to mating-type recognition in the protozoal eukaryote Tetrahymena thermophila. Deletion of the Cip1 protein leads to the loss of the selfing-avoidance function of mating-type recognition, resulting in selfing without mating-type recognition. Further experiments revealed that Cip1 is a regulatory subunit of the Cdk19-Cyc9 complex, which controls the initiation of sexual reproduction. These results reveal a mechanism that regulates the choice between mating and selfing. This mechanism also contributes to the debate about the ancestral state of sexual reproduction.
Collapse
Affiliation(s)
- Yang Ma
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan430072, China
| | - Guanxiong Yan
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan430072, China
| | - Jing Zhang
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan430072, China
| | - Jie Xiong
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan430072, China
- Key Laboratory of Breeding Biotechnology and Sustainable Aquaculture, Chinese Academy of Sciences, Wuhan430072, China
| | - Wei Miao
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan430072, China
- College of Advanced Agricultural Sciences, University of Chinese Academy of Sciences, Beijing100049, China
- Key laboratory of Lake and Watershed Science for Water Security, Chinese Academy of Sciences, Nanjing210000, China
- Institute of Hydrobiology, Hubei Hongshan Laboratory, Wuhan430000, China
| |
Collapse
|
2
|
Liu L, Huang Y, Song H, Luo M, Dong Z. α-Pheromone Precursor Protein Foc4-PP1 Is Essential for the Full Virulence of Fusarium oxysporum f. sp. cubense Tropical Race 4. J Fungi (Basel) 2023; 9:jof9030365. [PMID: 36983533 PMCID: PMC10057649 DOI: 10.3390/jof9030365] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2023] [Revised: 03/06/2023] [Accepted: 03/12/2023] [Indexed: 03/19/2023] Open
Abstract
Fusarium oxysporum f. sp. cubense (Foc), which causes Fusarium wilt of bananas, is considered one of the most destructive fungal pathogens of banana crops worldwide. During infection, Foc secretes many different proteins which promote its colonization of plant tissues. Although F. oxysporum has no sexual cycle, it has been reported to secrete an α-pheromone, which acts as a growth regulator, chemoattractant, and quorum-sensing signaling molecule; and to encode a putative protein with the hallmarks of fungal α-pheromone precursors. In this study, we identified an ortholog of the α-pheromone precursor gene, Foc4-PP1, in Foc tropical race 4 (TR4), and showed that it was necessary for the growth and virulence of Foc TR4. Foc4-PP1 deletion from the Foc TR4 genome resulted in decreased fungal growth, increased sensitivity to oxidative stress and cell-wall-damaging agents, and attenuation of pathogen virulence towards banana plantlets. Subcellular localization analysis revealed that Foc4-PP1 was concentrated in the nuclei and cytoplasm of Nicotiana benthamiana cells, where it could suppress BAX-induced programmed cell death. In conclusion, these findings suggest that Foc4-PP1 contributes to Foc TR4 virulence by promoting hyphal growth and abiotic stress resistance and inhibiting the immune defense responses of host plants.
Collapse
Affiliation(s)
- Lu Liu
- Innovative Institute for Plant Health/Key Laboratory of Green Prevention and Control on Fruits and Vegetables in South China, Ministry of Agriculture and Rural Affairs, Zhongkai University of Agriculture and Engineering, Guangzhou 510225, China
| | - Yinghua Huang
- Innovative Institute for Plant Health/Key Laboratory of Green Prevention and Control on Fruits and Vegetables in South China, Ministry of Agriculture and Rural Affairs, Zhongkai University of Agriculture and Engineering, Guangzhou 510225, China
- Guangdong Agribusiness Tropical Crop Science Institute, Maoming 525100, China
| | - Handa Song
- Innovative Institute for Plant Health/Key Laboratory of Green Prevention and Control on Fruits and Vegetables in South China, Ministry of Agriculture and Rural Affairs, Zhongkai University of Agriculture and Engineering, Guangzhou 510225, China
- Correspondence: (H.S.); (Z.D.); Tel.: +86-02089003192 (H.S. & Z.D.)
| | - Mei Luo
- Innovative Institute for Plant Health/Key Laboratory of Green Prevention and Control on Fruits and Vegetables in South China, Ministry of Agriculture and Rural Affairs, Zhongkai University of Agriculture and Engineering, Guangzhou 510225, China
| | - Zhangyong Dong
- Innovative Institute for Plant Health/Key Laboratory of Green Prevention and Control on Fruits and Vegetables in South China, Ministry of Agriculture and Rural Affairs, Zhongkai University of Agriculture and Engineering, Guangzhou 510225, China
- Correspondence: (H.S.); (Z.D.); Tel.: +86-02089003192 (H.S. & Z.D.)
| |
Collapse
|
3
|
A focus on yeast mating: From pheromone signaling to cell-cell fusion. Semin Cell Dev Biol 2023; 133:83-95. [PMID: 35148940 DOI: 10.1016/j.semcdb.2022.02.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Revised: 01/31/2022] [Accepted: 02/02/2022] [Indexed: 12/14/2022]
Abstract
Cells live in a chemical environment and are able to orient towards chemical cues. Unicellular haploid fungal cells communicate by secreting pheromones to reproduce sexually. In the yeast models Saccharomyces cerevisiae and Schizosaccharomyces pombe, pheromonal communication activates similar pathways composed of cognate G-protein-coupled receptors and downstream small GTPase Cdc42 and MAP kinase cascades. Local pheromone release and sensing, at a mobile surface polarity patch, underlie spatial gradient interpretation to form pairs between two cells of distinct mating types. Concentration of secretion at the point of cell-cell contact then leads to local cell wall digestion for cell fusion, forming a diploid zygote that prevents further fusion attempts. A number of asymmetries between mating types may promote efficiency of the system. In this review, we present our current knowledge of pheromone signaling in the two model yeasts, with an emphasis on how cells decode the pheromone signal spatially and ultimately fuse together. Though overall pathway architectures are similar in the two species, their large evolutionary distance allows to explore how conceptually similar solutions to a general biological problem can arise from divergent molecular components.
Collapse
|
4
|
Seike T, Niki H. Pheromone Response and Mating Behavior in Fission Yeast. Microbiol Mol Biol Rev 2022; 86:e0013022. [PMID: 36468849 PMCID: PMC9769774 DOI: 10.1128/mmbr.00130-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Most ascomycete fungi, including the fission yeast Schizosaccharomyces pombe, secrete two peptidyl mating pheromones: C-terminally modified and unmodified peptides. S. pombe has two mating types, plus and minus, which secrete two different pheromones, P-factor (unmodified) and M-factor (modified), respectively. These pheromones are specifically recognized by receptors on the cell surface of cells of opposite mating types, which trigger a pheromone response. Recognition between pheromones and their corresponding receptors is important for mate discrimination; therefore, genetic changes in pheromone or receptor genes affect mate recognition and cause reproductive isolation that limits gene flow between populations. Such genetic variation in recognition via the pheromone/receptor system may drive speciation. Our recent studies reported that two pheromone receptors in S. pombe might have different stringencies in pheromone recognition. In this review, we focus on the molecular mechanism of pheromone response and mating behavior, emphasizing pheromone diversification and its impact on reproductive isolation in S. pombe and closely related fission yeast species. We speculate that the "asymmetric" system might allow flexible adaptation to pheromone mutational changes while maintaining stringent recognition of mating partners. The loss of pheromone activity results in the extinction of an organism's lineage. Therefore, genetic changes in pheromones and their receptors may occur gradually and/or coincidently before speciation. Our findings suggest that the M-factor plays an important role in partner discrimination, whereas P-factor communication allows flexible adaptation to create variations in S. pombe. Our inferences provide new insights into the evolutionary mechanisms underlying pheromone diversification.
Collapse
Affiliation(s)
- Taisuke Seike
- Department of Bioinformatic Engineering, Graduate School of Information Science and Technology, Osaka University, Suita, Osaka, Japan
| | - Hironori Niki
- Microbial Physiology Laboratory, Department of Gene Function and Phenomics, National Institute of Genetics, Mishima, Shizuoka, Japan
| |
Collapse
|
5
|
Jacobs KC, Gladfelter AS, Lew DJ. Targeted secretion: Myosin V delivers vesicles through formin condensates. Curr Biol 2022; 32:R1228-R1231. [PMID: 36347230 DOI: 10.1016/j.cub.2022.10.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Secretory vesicles are often delivered to very specific targets, like pre-synaptic terminals or cell tips, to focus exocytosis. New work suggests that a biomolecular condensate focuses actin filaments that deliver incoming vesicles through the condensate to the plasma membrane.
Collapse
Affiliation(s)
- Katherine C Jacobs
- Department of Genetics and Human Genetics Institute of New Jersey, Rutgers University, Piscataway, NJ 08854, USA
| | - Amy S Gladfelter
- Biology Department, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Daniel J Lew
- Department of Pharmacology and Cancer Biology, Duke University, Durham, NC 27705, USA.
| |
Collapse
|
6
|
Billault-Chaumartin I, Muriel O, Michon L, Martin SG. Condensation of the fusion focus by the intrinsically disordered region of the formin Fus1 is essential for cell-cell fusion. Curr Biol 2022; 32:4752-4761.e10. [PMID: 36202103 PMCID: PMC9671092 DOI: 10.1016/j.cub.2022.09.026] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Revised: 08/18/2022] [Accepted: 09/13/2022] [Indexed: 11/06/2022]
Abstract
Secretory vesicle clusters transported on actin filaments by myosin V motors for local secretion underlie various cellular processes, such as neurotransmitter release at neuronal synapses,1 hyphal steering in filamentous fungi,2,3 and local cell wall digestion preceding the fusion of yeast gametes.4 During fission yeast Schizosaccharomyces pombe gamete fusion, the actin fusion focus assembled by the formin Fus1 concentrates secretory vesicles carrying cell wall digestive enzymes.5,6,7 The position and coalescence of the vesicle focus are controlled by local signaling and actin-binding proteins to prevent inappropriate cell wall digestion that would cause lysis,6,8,9,10 but the mechanisms of focusing have been elusive. Here, we show that the regulatory N terminus of Fus1 contains an intrinsically disordered region (IDR) that mediates Fus1 condensation in vivo and forms dense assemblies that exclude ribosomes. Fus1 lacking its IDR fails to concentrate in a tight focus and causes cell lysis during attempted cell fusion. Remarkably, the replacement of Fus1 IDR with a heterologous low-complexity region that forms molecular condensates fully restores Fus1 focusing and function. By contrast, the replacement of Fus1 IDR with a domain that forms more stable oligomers restores focusing but poorly supports cell fusion, suggesting that condensation is tuned to yield a selectively permeable structure. We propose that condensation of actin structures by an IDR may be a general mechanism for actin network organization and the selective local concentration of secretory vesicles.
Collapse
Affiliation(s)
- Ingrid Billault-Chaumartin
- Department of Fundamental Microbiology, Faculty of Biology and Medicine, University of Lausanne, Biophore Building, 1015 Lausanne, Switzerland
| | - Olivia Muriel
- Department of Fundamental Microbiology, Faculty of Biology and Medicine, University of Lausanne, Biophore Building, 1015 Lausanne, Switzerland
| | - Laetitia Michon
- Department of Fundamental Microbiology, Faculty of Biology and Medicine, University of Lausanne, Biophore Building, 1015 Lausanne, Switzerland
| | - Sophie G Martin
- Department of Fundamental Microbiology, Faculty of Biology and Medicine, University of Lausanne, Biophore Building, 1015 Lausanne, Switzerland.
| |
Collapse
|
7
|
Jacobs KC, Gorman O, Lew DJ. Mechanism of commitment to a mating partner in Saccharomyces cerevisiae. Mol Biol Cell 2022; 33:ar112. [PMID: 35947501 DOI: 10.1091/mbc.e22-02-0043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Many cells detect and follow gradients of chemical signals to perform their functions. Yeast cells use gradients of extracellular pheromones to locate mating partners, providing a tractable model to understand how cells decode the spatial information in gradients. To mate, yeast cells must orient polarity toward the mating partner. Polarity sites are mobile, exploring the cell cortex until they reach the proper position, where they stop moving and "commit" to the partner. A simple model to explain commitment posits that a high concentration of pheromone is only detected upon alignment of partner cells' polarity sites, and causes polarity site movement to stop. Here we explore how yeast cells respond to partners that make different amounts of pheromone. Commitment was surprisingly robust to varying pheromone levels, ruling out the simple model. We also tested whether adaptive pathways were responsible for the robustness of commitment, but our results show that cells lacking those pathways were still able to accommodate changes in pheromone. To explain this robustness, we suggest that the steep pheromone gradients near each mating partner's polarity site trap the polarity site in place.
Collapse
Affiliation(s)
- Katherine C Jacobs
- Department of Pharmacology and Cancer Biology, Duke University, Durham, NC 27708
| | - Olivia Gorman
- Department of Pharmacology and Cancer Biology, Duke University, Durham, NC 27708
| | - Daniel J Lew
- Department of Pharmacology and Cancer Biology, Duke University, Durham, NC 27708
| |
Collapse
|
8
|
Abstract
Fungi exhibit an enormous variety of morphologies, including yeast colonies, hyphal mycelia, and elaborate fruiting bodies. This diversity arises through a combination of polar growth, cell division, and cell fusion. Because fungal cells are nonmotile and surrounded by a protective cell wall that is essential for cell integrity, potential fusion partners must grow toward each other until they touch and then degrade the intervening cell walls without impacting cell integrity. Here, we review recent progress on understanding how fungi overcome these challenges. Extracellular chemoattractants, including small peptide pheromones, mediate communication between potential fusion partners, promoting the local activation of core cell polarity regulators to orient polar growth and cell wall degradation. However, in crowded environments, pheromone gradients can be complex and potentially confusing, raising the question of how cells can effectively find their partners. Recent findings suggest that the cell polarity circuit exhibits searching behavior that can respond to pheromone cues through a remarkably flexible and effective strategy called exploratory polarization.
Collapse
|
9
|
Wei M, Dhanasekaran S, Yang Q, Ngolong Ngea GL, Godana EA, Zhang H. Degradation and stress response mechanism of Cryptococcus podzolicus Y3 on ochratoxin A at the transcriptional level. Lebensm Wiss Technol 2022. [DOI: 10.1016/j.lwt.2021.113061] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
|
10
|
Muriel O, Michon L, Kukulski W, Martin SG. Ultrastructural plasma membrane asymmetries in tension and curvature promote yeast cell fusion. J Cell Biol 2021; 220:e202103142. [PMID: 34382996 PMCID: PMC8366684 DOI: 10.1083/jcb.202103142] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Revised: 07/15/2021] [Accepted: 07/26/2021] [Indexed: 12/24/2022] Open
Abstract
Cell-cell fusion is central for sexual reproduction, and generally involves gametes of different shapes and sizes. In walled fission yeast Schizosaccharomyces pombe, the fusion of h+ and h- isogametes requires the fusion focus, an actin structure that concentrates glucanase-containing vesicles for cell wall digestion. Here, we present a quantitative correlative light and electron microscopy (CLEM) tomographic dataset of the fusion site, which reveals the fusion focus ultrastructure. Unexpectedly, gametes show marked asymmetries: a taut, convex plasma membrane of h- cells progressively protrudes into a more slack, wavy plasma membrane of h+ cells. Asymmetries are relaxed upon fusion, with observations of ramified fusion pores. h+ cells have a higher exo-/endocytosis ratio than h- cells, and local reduction in exocytosis strongly diminishes membrane waviness. Reciprocally, turgor pressure reduction specifically in h- cells impedes their protrusions into h+ cells and delays cell fusion. We hypothesize that asymmetric membrane conformations, due to differential turgor pressure and exocytosis/endocytosis ratios between mating types, favor cell-cell fusion.
Collapse
Affiliation(s)
- Olivia Muriel
- Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland
| | - Laetitia Michon
- Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland
| | - Wanda Kukulski
- Medical Research Council Laboratory of Molecular Biology, Cambridge, UK
| | - Sophie G. Martin
- Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland
| |
Collapse
|
11
|
Vještica A, Bérard M, Liu G, Merlini L, Nkosi PJ, Martin SG. Cell cycle-dependent and independent mating blocks ensure fungal zygote survival and ploidy maintenance. PLoS Biol 2021; 19:e3001067. [PMID: 33406066 PMCID: PMC7815208 DOI: 10.1371/journal.pbio.3001067] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2020] [Revised: 01/19/2021] [Accepted: 12/22/2020] [Indexed: 12/22/2022] Open
Abstract
To ensure genome stability, sexually reproducing organisms require that mating brings together exactly 2 haploid gametes and that meiosis occurs only in diploid zygotes. In the fission yeast Schizosaccharomyces pombe, fertilization triggers the Mei3-Pat1-Mei2 signaling cascade, which represses subsequent mating and initiates meiosis. Here, we establish a degron system to specifically degrade proteins postfusion and demonstrate that mating blocks not only safeguard zygote ploidy but also prevent lysis caused by aberrant fusion attempts. Using long-term imaging and flow-cytometry approaches, we identify previously unrecognized and independent roles for Mei3 and Mei2 in zygotes. We show that Mei3 promotes premeiotic S-phase independently of Mei2 and that cell cycle progression is both necessary and sufficient to reduce zygotic mating behaviors. Mei2 not only imposes the meiotic program and promotes the meiotic cycle, but also blocks mating behaviors independently of Mei3 and cell cycle progression. Thus, we find that fungi preserve zygote ploidy and survival by at least 2 mechanisms where the zygotic fate imposed by Mei2 and the cell cycle reentry triggered by Mei3 synergize to prevent zygotic mating. During sexual reproduction, fertilization must happen between exactly two gametes to ensure genome stability. This study shows that two mechanisms – establishment of zygotic fate and re-entry to the cell cycle – combine to prevent fission yeast zygotes fusing with further gametes.
Collapse
Affiliation(s)
- Aleksandar Vještica
- Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland
- * E-mail: (AV); (SGM)
| | - Melvin Bérard
- Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland
| | - Gaowen Liu
- Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland
| | - Laura Merlini
- Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland
| | - Pedro Junior Nkosi
- Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland
| | - Sophie G. Martin
- Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland
- * E-mail: (AV); (SGM)
| |
Collapse
|
12
|
Unisexual reproduction promotes competition for mating partners in the global human fungal pathogen Cryptococcus deneoformans. PLoS Genet 2019; 15:e1008394. [PMID: 31536509 PMCID: PMC6772093 DOI: 10.1371/journal.pgen.1008394] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Revised: 10/01/2019] [Accepted: 08/29/2019] [Indexed: 12/22/2022] Open
Abstract
Courtship is pivotal for successful mating. However, courtship is challenging for the Cryptococcus neoformans species complex, comprised of opportunistic fungal pathogens, as the majority of isolates are α mating type. In the absence of mating partners of the opposite mating type, C. deneoformans can undergo unisexual reproduction, during which a yeast-to-hyphal morphological transition occurs. Hyphal growth during unisexual reproduction is a quantitative trait, which reflects a strain's ability to undergo unisexual reproduction. In this study, we determined whether unisexual reproduction confers an ecological benefit by promoting foraging for mating partners. Through competitive mating assays using strains with different abilities to produce hyphae, we showed that unisexual reproduction potential did not enhance competition for mating partners of the same mating type, but when cells of the opposite mating type were present, cells with enhanced hyphal growth were more competitive for mating partners of either the same or opposite mating type. Enhanced mating competition was also observed in a strain with increased hyphal production that lacks the mating repressor gene GPA3, which contributes to the pheromone response. Hyphal growth in unisexual strains also enables contact between adjacent colonies and enhances mating efficiency during mating confrontation assays. The pheromone response pathway activation positively correlated with unisexual reproduction hyphal growth during bisexual mating and exogenous pheromone promoted bisexual cell fusion. Despite the benefit in competing for mating partners, unisexual reproduction conferred a fitness cost. Taken together, these findings suggest C. deneoformans employs hyphal growth to facilitate contact between colonies at long distances and utilizes pheromone sensing to enhance mating competition.
Collapse
|
13
|
Billault-Chaumartin I, Martin SG. Capping Protein Insulates Arp2/3-Assembled Actin Patches from Formins. Curr Biol 2019; 29:3165-3176.e6. [PMID: 31495586 PMCID: PMC6864609 DOI: 10.1016/j.cub.2019.07.088] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Revised: 07/04/2019] [Accepted: 07/30/2019] [Indexed: 12/13/2022]
Abstract
How actin structures of distinct identities and functions coexist within the same environment is a critical self-organization question. Fission yeast cells have a simple actin cytoskeleton made of four structures: Arp2/3 assembles actin patches around endocytic pits, and the formins For3, Cdc12, and Fus1 assemble actin cables, the cytokinetic ring during division, and the fusion focus during sexual reproduction, respectively. The focus concentrates the delivery of hydrolases by myosin V to digest the cell wall for cell fusion. We discovered that cells lacking capping protein (CP), a heterodimer that blocks barbed-end dynamics and associates with actin patches, exhibit a delay in fusion. Consistent with CP-formin competition for barbed-end binding, Fus1, F-actin, and the linear filament marker tropomyosin hyper-accumulate at the fusion focus in cells lacking CP. CP deletion also rescues the fusion defect of a mutation in the Fus1 knob region. However, myosin V and exocytic cargoes are reduced at the fusion focus and diverted to ectopic foci, which underlies the fusion defect. Remarkably, the ectopic foci coincide with Arp2/3-assembled actin patches, which now contain low levels of Fus1. We further show that CP localization to actin patches is required to prevent the formation of ectopic foci and promote efficient cell fusion. During mitotic growth, actin patches lacking CP similarly display a dual identity, as they accumulate the formins For3 and Cdc12, normally absent from patches, and are co-decorated by the linear filament-binding protein tropomyosin and the patch marker fimbrin. Thus, CP serves to protect Arp2/3-nucleated structures from formin activity.
Collapse
Affiliation(s)
- Ingrid Billault-Chaumartin
- Department of Fundamental Microbiology, Faculty of Biology and Medicine, University of Lausanne, 1015 Lausanne, Switzerland
| | - Sophie G Martin
- Department of Fundamental Microbiology, Faculty of Biology and Medicine, University of Lausanne, 1015 Lausanne, Switzerland.
| |
Collapse
|
14
|
Seike T, Maekawa H, Nakamura T, Shimoda C. The asymmetric chemical structures of two mating pheromones reflect their differential roles in mating of fission yeast. J Cell Sci 2019; 132:jcs.230722. [PMID: 31186279 DOI: 10.1242/jcs.230722] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Accepted: 06/03/2019] [Indexed: 02/01/2023] Open
Abstract
In the fission yeast Schizosaccharomyces pombe, the mating reaction is controlled by two mating pheromones, M-factor and P-factor, secreted by M- and P-type cells, respectively. M-factor is a C-terminally farnesylated lipid peptide, whereas P-factor is a simple peptide. To examine whether this chemical asymmetry in the two pheromones is essential for conjugation, we constructed a mating system in which either pheromone can stimulate both M- and P-cells, and examined whether the resulting autocrine strains can mate. Autocrine M-cells responding to M-factor successfully mated with P-factor-lacking P-cells, indicating that P-factor is not essential for conjugation; by contrast, autocrine P-cells responding to P-factor were unable to mate with M-factor-lacking M-cells. The sterility of the autocrine P-cells was completely restored by expressing the M-factor receptor. These observations indicate that the different chemical characteristics of the two types of pheromone, a lipid and a simple peptide, are not essential; however, a lipid peptide might be required for successful mating. Our findings allow us to propose a model of the differential roles of M-factor and P-factor in conjugation of S. pombeThis article has an associated First Person interview with the first author of the paper.
Collapse
Affiliation(s)
- Taisuke Seike
- Microbial Genetics Laboratory, Genetic Strains Research Center, National Institute of Genetics, 1111 Yata, Mishima, Shizuoka 411-8540, Japan
| | - Hiromi Maekawa
- Yeast Genetic Resources Laboratory, Graduate School of Engineering, Osaka University, 1-6 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Taro Nakamura
- Department of Biology, Graduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan
| | - Chikashi Shimoda
- Department of Biology, Graduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan
| |
Collapse
|
15
|
Martin SG. Molecular mechanisms of chemotropism and cell fusion in unicellular fungi. J Cell Sci 2019; 132:132/11/jcs230706. [PMID: 31152053 DOI: 10.1242/jcs.230706] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
In all eukaryotic phyla, cell fusion is important for many aspects of life, from sexual reproduction to tissue formation. Fungal cells fuse during mating to form the zygote, and during vegetative growth to connect mycelia. Prior to fusion, cells first detect gradients of pheromonal chemoattractants that are released by their partner and polarize growth in their direction. Upon pairing, cells digest their cell wall at the site of contact and merge their plasma membrane. In this Review, I discuss recent work on the chemotropic response of the yeast models Saccharomyces cerevisiae and Schizosaccharomyces pombe, which has led to a novel model of gradient sensing: the cell builds a motile cortical polarized patch, which acts as site of communication where pheromones are released and sensed. Initial patch dynamics serve to correct its position and align it with the gradient from the partner cell. Furthermore, I highlight the transition from cell wall expansion during growth to cell wall digestion, which is imposed by physical and signaling changes owing to hyperpolarization that is induced by cell proximity. To conclude, I discuss mechanisms of membrane fusion, whose characterization remains a major challenge for the future.
Collapse
Affiliation(s)
- Sophie G Martin
- Department of Fundamental Microbiology, University of Lausanne, 1015 Lausanne, Switzerland
| |
Collapse
|
16
|
Autocrine pheromone signalling regulates community behaviour in the fungal pathogen Fusarium oxysporum. Nat Microbiol 2019; 4:1443-1449. [PMID: 31133754 DOI: 10.1038/s41564-019-0456-z] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Accepted: 04/12/2019] [Indexed: 11/09/2022]
Abstract
Autocrine self-signalling via secreted peptides and cognate receptors regulates cell development in eukaryotes and is conserved from protozoans to mammals1,2. In contrast, secreted peptides from higher fungi have been traditionally associated with paracrine non-self-signalling during sexual reproduction3. For example, cells of the model fungus Saccharomyces cerevisiae fall into two distinct mating types (MAT), which produce either a- or α-pheromone and the cognate receptors Ste2 or Ste3, respectively4. Inappropriate autocrine pheromone signalling (APS) during mating is prevented by downregulation of the self-pheromone receptor4,5 and by a-type cell-specific cleavage of α-pheromone through the protease Bar1 (refs. 6-8). While APS can be artificially induced by manipulation of the pheromone secrete-and-sense circuit7,9-11, its natural occurrence in ascomycete fungi has not been described. Here, we show that Fusarium oxysporum-a devastating plant pathogen that lacks a known sexual cycle12-co-expresses both pheromone-receptor pairs, resulting in autocrine regulation of developmental programmes other than mating. We found that unisexual populations of MAT1-1 cells (α-type idiomorphs13) secrete and sense both a- and α-pheromone, and that their perception requires the cognate receptors and conserved elements of the cell wall integrity mitogen-activated protein kinase cascade. We further show that F. oxysporum uses APS to regulate spore germination in a cell-density-dependent manner, whereby the α-Ste2 interaction leads to repression of conidial germination while the a-Ste3 interaction relieves repression. Our results reveal the existence of a regulatory function for peptide pheromones in the quorum-sensing-mediated control of fungal development.
Collapse
|
17
|
Seike T, Shimoda C, Niki H. Asymmetric diversification of mating pheromones in fission yeast. PLoS Biol 2019; 17:e3000101. [PMID: 30668560 PMCID: PMC6342294 DOI: 10.1371/journal.pbio.3000101] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Accepted: 12/19/2018] [Indexed: 01/25/2023] Open
Abstract
In fungi, mating between partners depends on the molecular recognition of two peptidyl mating pheromones by their respective receptors. The fission yeast Schizosaccharomyces pombe (Sp) has two mating types, Plus (P) and Minus (M). The mating pheromones P-factor and M-factor, secreted by P and M cells, are recognized by the receptors mating type auxiliary minus 2 (Mam2) and mating type auxiliary plus 3 (Map3), respectively. Our recent study demonstrated that a few mutations in both M-factor and Map3 can trigger reproductive isolation in S. pombe. Here, we explored the mechanism underlying reproductive isolation through genetic changes of pheromones/receptors in nature. We investigated the diversity of genes encoding the pheromones and their receptor in 150 wild S. pombe strains. Whereas the amino acid sequences of M-factor and Map3 were completely conserved, those of P-factor and Mam2 were very diverse. In addition, the P-factor gene contained varying numbers of tandem repeats of P-factor (4–8 repeats). By exploring the recognition specificity of pheromones between S. pombe and its close relative Schizosaccharomyces octosporus (So), we found that So-M-factor did not have an effect on S. pombe P cells, but So-P-factor had a partial effect on S. pombe M cells. Thus, recognition of M-factor seems to be stringent, whereas that of P-factor is relatively relaxed. We speculate that asymmetric diversification of the two pheromones might be facilitated by the distinctly different specificities of the two receptors. Our findings suggest that M-factor communication plays an important role in defining the species, whereas P-factor communication is able to undergo a certain degree of flexible adaptation–perhaps as a first step toward prezygotic isolation in S. pombe. An asymmetric pheromone/receptor system in the fission yeast Schizosaccharomyces pombe might allow flexible adaptation of pheromones to mutational changes while maintaining stringent recognition for mating partners, perhaps as a first step toward prezygotic mating isolation. The emergence of a new species might occur when two groups can no longer mate. Although such reproductive isolation is considered a key evolutionary process, the mechanisms by which it actually occurs have been confined to conjecture. The two sexes (Plus [P] and Minus [M]) of S. pombe each secrete a pheromone (P-factor and M-factor), which binds to a corresponding receptor (mating type auxiliary minus 2 [Mam2] and mating type auxiliary plus 3 [Map3]) on cells of the opposite sex. The interaction between a pheromone and its receptor is essential for successful mating. Here, we explored conservation of the mating pheromone communication system among 150 wild S. pombe strains of different geographical origins and the closely related species S. octosporus. We found that 1) the M-factor/Map3 interaction was completely conserved, whereas the P-factor/Mam2 interaction was very diverse in the strains investigated, and 2) most of the P-factor variants were functional across species. Thus, we have revealed an asymmetric pheromone/receptor system in fungal mating: namely, whereas M-factor communication operates extremely stringently, P-factor communication has the flexibility to create variations, perhaps facilitating prezygotic isolation in S. pombe.
Collapse
Affiliation(s)
- Taisuke Seike
- Genetics Strains Research Center, National Institute of Genetics, Mishima, Shizuoka, Japan
- * E-mail:
| | - Chikashi Shimoda
- Graduate School of Science, Osaka City University, Sumiyoshi-ku, Osaka, Japan
| | - Hironori Niki
- Genetics Strains Research Center, National Institute of Genetics, Mishima, Shizuoka, Japan
| |
Collapse
|
18
|
Hall AE, Rose MD. Cell fusion in yeast is negatively regulated by components of the cell wall integrity pathway. Mol Biol Cell 2018; 30:441-452. [PMID: 30586320 PMCID: PMC6594448 DOI: 10.1091/mbc.e18-04-0236] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
During mating, Saccharomyces cerevisiae cells must degrade the intervening cell wall to allow fusion of the partners. Because improper timing or location of cell wall degradation would cause lysis, the initiation of cell fusion must be highly regulated. Here, we find that yeast cell fusion is negatively regulated by components of the cell wall integrity (CWI) pathway. Loss of the cell wall sensor, MID2, specifically causes “mating-induced death” after pheromone exposure. Mating-induced death is suppressed by mutations in cell fusion genes (FUS1, FUS2, RVS161, CDC42), implying that mid2Δ cells die from premature fusion without a partner. Consistent with premature fusion, mid2Δ shmoos had thinner cell walls and lysed at the shmoo tip. Normally, Cdc42p colocalizes with Fus2p to form a focus only when mating cells are in contact (prezygotes) and colocalization is required for cell fusion. However, Cdc42p was aberrantly colocalized with Fus2p to form a focus in mid2Δ shmoos. A hyperactive allele of the CWI kinase Pkc1p (PKC1*) caused decreased cell fusion and Cdc42p localization in prezygotes. In shmoos, PKC1* increased Cdc42p localization; however, it was not colocalized with Fus2p or associated with cell death. We conclude that Mid2p and Pkc1p negatively regulate cell fusion via Cdc42p and Fus2p.
Collapse
Affiliation(s)
- Allison E Hall
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544
| | - Mark D Rose
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544.,Department of Biology, Georgetown University, Washington, DC 20057
| |
Collapse
|
19
|
Gallo Castro D, Martin SG. Differential GAP requirement for Cdc42-GTP polarization during proliferation and sexual reproduction. J Cell Biol 2018; 217:4215-4229. [PMID: 30279276 PMCID: PMC6279383 DOI: 10.1083/jcb.201806016] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2018] [Revised: 09/06/2018] [Accepted: 09/21/2018] [Indexed: 12/13/2022] Open
Abstract
The formation of a local zone of Cdc42 GTPase activity, which governs cell polarization in many cell types, requires not only local activation but also switch-off mechanisms. In this study, we identify Rga3, a paralog of Rga4, as a novel Cdc42 GTPase-activating protein (GAP) in the fission yeast Schizosaccharomyces pombe Contrary to Rga4, Rga3 localizes with Cdc42-GTP to sites of polarity. Rga3 is dispensable for cell polarization during mitotic growth, but it limits the lifetime of unstable Cdc42-GTP patches that underlie cell pairing during sexual reproduction, masking a partly compensatory patch-wandering motion. In consequence, cells lacking rga3 hyperpolarize and lose out in mating competition. Rga3 synergizes with the Cdc42 GAPs Rga4 and Rga6 to restrict Cdc42-GTP zone sizes during mitotic growth. Surprisingly, triple-mutant cells, which are almost fully round, retain pheromone-dependent dynamic polarization of Cdc42-GTP, extend a polarized projection, and mate. Thus, the requirement for Cdc42-GTP hydrolysis by GAPs is distinct during polarization by intrinsic or extrinsic cues.
Collapse
Affiliation(s)
- Daniela Gallo Castro
- Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland
| | - Sophie G Martin
- Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland
| |
Collapse
|
20
|
Khalili B, Merlini L, Vincenzetti V, Martin SG, Vavylonis D. Exploration and stabilization of Ras1 mating zone: A mechanism with positive and negative feedbacks. PLoS Comput Biol 2018; 14:e1006317. [PMID: 30028833 PMCID: PMC6070293 DOI: 10.1371/journal.pcbi.1006317] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Revised: 08/01/2018] [Accepted: 06/21/2018] [Indexed: 02/07/2023] Open
Abstract
In mating fission yeast cells, sensing and response to extracellular pheromone concentrations occurs through an exploratory Cdc42 patch that stochastically samples the cell cortex before stabilizing towards a mating partner. Active Ras1 (Ras1-GTP), an upstream regulator of Cdc42, and Gap1, the GTPase-activating protein for Ras1, localize at the patch. We developed a reaction-diffusion model of Ras1 patch appearance and disappearance with a positive feedback by a Guanine nucleotide Exchange Factor (GEF) and Gap1 inhibition. The model is based on new estimates of Ras1-GDP, Ras1-GTP and Gap1 diffusion coefficients and rates of cytoplasmic exchange studied by FRAP. The model reproduces exploratory patch behavior and lack of Ras1 patch in cells lacking Gap1. Transition to a stable patch can occur by change of Gap1 rates constants or local increase of the positive feedback rate constants. The model predicts that the patch size and number of patches depend on the strength of positive and negative feedbacks. Measurements of Ras1 patch size and number in cells overexpressing the Ras1 GEF or Gap1 are consistent with the model. Unicellular fission yeasts mate by fusing with partners of the opposite mating type. Each pair member grows towards its selected partner that signals its presence through secreted pheromone. The process of partner selection occurs through an exploratory patch (containing activated signaling protein Cdc42 and upstream regulator Ras1) that assembles and disassembles on the cell cortex, stabilizing in regions of higher opposite pheromone concentration. We present a computational model of the molecular mechanisms driving the dynamical pattern of patch exploration and stabilization. The model is based on reaction and diffusion along the curved cell membrane, with diffusion coefficients measured experimentally. In the model, a positive Ras1 activation feedback loop generates a patch containing most of the activating protein (Ras1 GEF). The fast diffusing inhibitor Gap1 that is recruited locally from the cytoplasm spreads on the cell membrane, limiting patch size and causing its decay. Spontaneous reinitiation of Ras1 activation elsewhere on the cortex provides a mechanism for exploration. Transition of the system’s behavior to that of a single stable patch is possible upon simulated pheromone sensing. The computational model provides predictions for the number of patches and patch size dependence on parameters that we tested experimentally.
Collapse
Affiliation(s)
- Bita Khalili
- Department of Physics, Lehigh University, Bethlehem, Pennsylvania, United States of America
- Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland
| | - Laura Merlini
- Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland
| | - Vincent Vincenzetti
- Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland
| | - Sophie G. Martin
- Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland
| | - Dimitrios Vavylonis
- Department of Physics, Lehigh University, Bethlehem, Pennsylvania, United States of America
- * E-mail:
| |
Collapse
|
21
|
Serrano A, Illgen J, Brandt U, Thieme N, Letz A, Lichius A, Read ND, Fleißner A. Spatio-temporal MAPK dynamics mediate cell behavior coordination during fungal somatic cell fusion. J Cell Sci 2018; 131:jcs.213462. [PMID: 29592970 DOI: 10.1242/jcs.213462] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Accepted: 03/20/2018] [Indexed: 01/17/2023] Open
Abstract
Mitogen-activated protein kinases (MAPKs) are conserved regulators of proliferation, differentiation and adaptation in eukaryotic cells. Their activity often involves changes in their subcellular localization, indicating an important role for these spatio-temporal dynamics in signal transmission. A striking model illustrating these dynamics is somatic cell fusion in Neurospora crassa Germinating spores of this fungus rapidly alternate between signal sending and receiving, thereby establishing a cell-cell dialog, which involves the alternating membrane recruitment of the MAPK MAK-2 in both fusion partners. Here, we show that the dynamic translocation of MAK-2 is essential for coordinating the behavior of the fusion partners before physical contact. The activation and function of the kinase strongly correlate with its subcellular localization, indicating a crucial contribution of the MAPK dynamics in establishing regulatory feedback loops, which establish the oscillatory signaling mode. In addition, we provide evidence that MAK-2 not only contributes to cell-cell communication, but also mediates cell-cell fusion. The MAK-2 dynamics significantly differ between these two processes, suggesting a role for the MAPK in switching of the cellular program between communication and fusion.
Collapse
Affiliation(s)
- Antonio Serrano
- Institut für Genetik, Technische Universität Braunschweig, Spielmannstraße 7, 38106 Braunschweig, Germany
| | - Julia Illgen
- Institut für Genetik, Technische Universität Braunschweig, Spielmannstraße 7, 38106 Braunschweig, Germany
| | - Ulrike Brandt
- Institut für Genetik, Technische Universität Braunschweig, Spielmannstraße 7, 38106 Braunschweig, Germany
| | - Nils Thieme
- Institut für Genetik, Technische Universität Braunschweig, Spielmannstraße 7, 38106 Braunschweig, Germany
| | - Anja Letz
- Institut für Genetik, Technische Universität Braunschweig, Spielmannstraße 7, 38106 Braunschweig, Germany
| | - Alexander Lichius
- Institute of Microbiology, University of Innsbruck, 6020 Innsbruck, Austria
| | - Nick D Read
- Manchester Fungal Infection Group, Division of Infection, Immunity and Respiratory Medicine, University of Manchester, Manchester M13 9NT, UK
| | - André Fleißner
- Institut für Genetik, Technische Universität Braunschweig, Spielmannstraße 7, 38106 Braunschweig, Germany
| |
Collapse
|
22
|
Giese W, Milicic G, Schröder A, Klipp E. Spatial modeling of the membrane-cytosolic interface in protein kinase signal transduction. PLoS Comput Biol 2018; 14:e1006075. [PMID: 29630597 PMCID: PMC5908195 DOI: 10.1371/journal.pcbi.1006075] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2017] [Revised: 04/19/2018] [Accepted: 03/07/2018] [Indexed: 02/06/2023] Open
Abstract
The spatial architecture of signaling pathways and the interaction with cell size and morphology are complex, but little understood. With the advances of single cell imaging and single cell biology, it becomes crucial to understand intracellular processes in time and space. Activation of cell surface receptors often triggers a signaling cascade including the activation of membrane-attached and cytosolic signaling components, which eventually transmit the signal to the cell nucleus. Signaling proteins can form steep gradients in the cytosol, which cause strong cell size dependence. We show that the kinetics at the membrane-cytosolic interface and the ratio of cell membrane area to the enclosed cytosolic volume change the behavior of signaling cascades significantly. We suggest an estimate of average concentration for arbitrary cell shapes depending on the cell volume and cell surface area. The normalized variance, known from image analysis, is suggested as an alternative measure to quantify the deviation from the average concentration. A mathematical analysis of signal transduction in time and space is presented, providing analytical solutions for different spatial arrangements of linear signaling cascades. Quantification of signaling time scales reveals that signal propagation is faster at the membrane than at the nucleus, while this time difference decreases with the number of signaling components in the cytosol. Our investigations are complemented by numerical simulations of non-linear cascades with feedback and asymmetric cell shapes. We conclude that intracellular signal propagation is highly dependent on cell geometry and, thereby, conveys information on cell size and shape to the nucleus.
Collapse
Affiliation(s)
- Wolfgang Giese
- Mathematical Cell Physiology, Max Delbrück Center for Molecular Medicine, Berlin, Germany
| | - Gregor Milicic
- Department of Mathematics, University of Salzburg, Salzburg, Austria
| | - Andreas Schröder
- Department of Mathematics, University of Salzburg, Salzburg, Austria
| | - Edda Klipp
- Theoretische Biophysik, Humboldt-Universität zu Berlin, Berlin, Germany
- * E-mail:
| |
Collapse
|
23
|
Merlini L, Khalili B, Dudin O, Michon L, Vincenzetti V, Martin SG. Inhibition of Ras activity coordinates cell fusion with cell-cell contact during yeast mating. J Cell Biol 2018; 217:1467-1483. [PMID: 29453312 PMCID: PMC5881505 DOI: 10.1083/jcb.201708195] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Revised: 01/08/2018] [Accepted: 01/24/2018] [Indexed: 02/07/2023] Open
Abstract
In the fission yeast Schizosaccharomyces pombe, pheromone signaling engages a signaling pathway composed of a G protein-coupled receptor, Ras, and a mitogen-activated protein kinase (MAPK) cascade that triggers sexual differentiation and gamete fusion. Cell-cell fusion requires local cell wall digestion, which relies on an initially dynamic actin fusion focus that becomes stabilized upon local enrichment of the signaling cascade on the structure. We constructed a live-reporter of active Ras1 (Ras1-guanosine triphosphate [GTP]) that shows Ras activity at polarity sites peaking on the fusion structure before fusion. Remarkably, constitutive Ras1 activation promoted fusion focus stabilization and fusion attempts irrespective of cell pairing, leading to cell lysis. Ras1 activity was restricted by the guanosine triphosphatase-activating protein Gap1, which was itself recruited to sites of Ras1-GTP and was essential to block untimely fusion attempts. We propose that negative feedback control of Ras activity restrains the MAPK signal and couples fusion with cell-cell engagement.
Collapse
Affiliation(s)
- Laura Merlini
- Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland
| | - Bita Khalili
- Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland.,Department of Physics, Lehigh University, Bethlehem, PA
| | - Omaya Dudin
- Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland
| | - Laetitia Michon
- Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland
| | - Vincent Vincenzetti
- Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland
| | - Sophie G Martin
- Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland
| |
Collapse
|
24
|
Bembenek JN, Meshik X, Tsarouhas V. Meeting report - Cellular dynamics: membrane-cytoskeleton interface. J Cell Sci 2017; 130:2775-2779. [PMID: 29360626 DOI: 10.1242/jcs.208660] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The first ever 'Cellular Dynamics' meeting on the membrane-cytoskeleton interface took place in Southbridge, MA on May 21-24, 2017 and was co-organized by Michael Way, Elizabeth Chen, Margaret Gardel and Jennifer Lippincott-Schwarz. Investigators from around the world studying a broad range of related topics shared their insights into the function and regulation of the cytoskeleton and membrane compartments. This provided great opportunities to learn about key questions in various cellular processes, from the basic organization and operation of the cell to higher-order interactions in adhesion, migration, metastasis, division and immune cell interactions in different model organisms. This unique and diverse mix of research interests created a stimulating and educational meeting that will hopefully continue to be a successful meeting for years to come.
Collapse
Affiliation(s)
- Joshua N Bembenek
- Department of Biochemistry & Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA
| | - Xenia Meshik
- Department of Anesthesiology, Washington University in St. Louis School of Medicine, St. Louis, MO 63110, USA
| | - Vasilios Tsarouhas
- Department of Molecular Biosciences, Stockholm University, Stockholm, Sweden
| |
Collapse
|
25
|
Dudin O, Merlini L, Bendezú FO, Groux R, Vincenzetti V, Martin SG. A systematic screen for morphological abnormalities during fission yeast sexual reproduction identifies a mechanism of actin aster formation for cell fusion. PLoS Genet 2017; 13:e1006721. [PMID: 28410370 PMCID: PMC5409535 DOI: 10.1371/journal.pgen.1006721] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Revised: 04/28/2017] [Accepted: 03/29/2017] [Indexed: 01/15/2023] Open
Abstract
In non-motile fungi, sexual reproduction relies on strong morphogenetic changes in response to pheromone signaling. We report here on a systematic screen for morphological abnormalities of the mating process in fission yeast Schizosaccharomyces pombe. We derived a homothallic (self-fertile) collection of viable deletions, which, upon visual screening, revealed a plethora of phenotypes affecting all stages of the mating process, including cell polarization, cell fusion and sporulation. Cell fusion relies on the formation of the fusion focus, an aster-like F-actin structure that is marked by strong local accumulation of the myosin V Myo52, which concentrates secretion at the fusion site. A secondary screen for fusion-defective mutants identified the myosin V Myo51-associated coiled-coil proteins Rng8 and Rng9 as critical for the coalescence of the fusion focus. Indeed, rng8Δ and rng9Δ mutant cells exhibit multiple stable dots at the cell-cell contact site, instead of the single focus observed in wildtype. Rng8 and Rng9 accumulate on the fusion focus, dependent on Myo51 and tropomyosin Cdc8. A tropomyosin mutant allele, which compromises Rng8/9 localization but not actin binding, similarly leads to multiple stable dots instead of a single focus. By contrast, myo51 deletion does not strongly affect fusion focus coalescence. We propose that focusing of the actin filaments in the fusion aster primarily relies on Rng8/9-dependent cross-linking of tropomyosin-actin filaments.
Collapse
Affiliation(s)
- Omaya Dudin
- Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland
| | - Laura Merlini
- Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland
| | - Felipe O. Bendezú
- Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland
| | - Raphaël Groux
- Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland
| | - Vincent Vincenzetti
- Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland
| | - Sophie G. Martin
- Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland
- * E-mail:
| |
Collapse
|
26
|
A Design Principle for an Autonomous Post-translational Pattern Formation. Cell Rep 2017; 19:863-874. [DOI: 10.1016/j.celrep.2017.03.081] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2016] [Revised: 01/22/2017] [Accepted: 03/30/2017] [Indexed: 12/12/2022] Open
|