1
|
Thorn HI, Guruceaga X, Martin-Vicente A, Nywening AV, Xie J, Ge W, Fortwendel JR. MOB-mediated regulation of septation initiation network (SIN) signaling is required for echinocandin-induced hyperseptation in Aspergillus fumigatus. mSphere 2024; 9:e0069523. [PMID: 38349166 DOI: 10.1128/msphere.00695-23] [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: 11/10/2023] [Accepted: 01/17/2024] [Indexed: 03/27/2024] Open
Abstract
Aspergillus fumigatus is a major invasive mold pathogen and the most frequent etiologic agent of invasive aspergillosis. The currently available treatments for invasive aspergillosis are limited in both number and efficacy. Our recent work has uncovered that the β-glucan synthase inhibitors, the echinocandins, are fungicidal against strains of A. fumigatus with defects in septation initiation network (SIN) kinase activity. These drugs are known to be fungistatic against strains with normal septation. Surprisingly, SIN kinase mutant strains also failed to invade lung tissue and were significantly less virulent in immunosuppressed mouse models. Inhibiting septation in filamentous fungi is therefore an exciting therapeutic prospect to both reduce virulence and improve current antifungal therapy. However, the SIN remains understudied in pathogenic fungi. To address this knowledge gap, we characterized the putative regulatory components of the A. fumigatus SIN. These included the GTPase, SpgA, it's two-component GTPase-activating protein, ByrA/BubA, and the kinase activators, SepM and MobA. Deletion of spgA, byrA, or bubA resulted in no overt septation or echinocandin susceptibility phenotypes. In contrast, our data show that deletion of sepM or mobA largely phenocopies disruption of their SIN kinase binding partners, sepL and sidB, respectively. Reduced septum formation, echinocandin hypersusceptibility, and reduced virulence were generated by loss of either gene. These findings provide strong supporting evidence that septa are essential not only for withstanding the cell wall disrupting effects of echinocandins but are also critical for the establishment of invasive disease. Therefore, pharmacological SIN inhibition may be an exciting strategy for future antifungal drug development.IMPORTANCESepta are important structural determinants of echinocandin susceptibility and tissue invasive growth for the ubiquitous fungal pathogen Aspergillus fumigatus. Components of the septation machinery therefore represent promising novel antifungal targets to improve echinocandin activity and reduce virulence. However, little is known about septation regulation in A. fumigatus. Here, we characterize the predicted regulatory components of the A. fumigatus septation initiation network. We show that the kinase activators SepM and MobA are vital for proper septation and echinocandin resistance, with MobA playing an essential role. Null mutants of mobA displayed significantly reduced virulence in a mouse model, underscoring the importance of this pathway for A. fumigatus pathogenesis.
Collapse
Affiliation(s)
- Harrison I Thorn
- Graduate Program in Pharmaceutical Sciences, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee, USA
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee, USA
| | - Xabier Guruceaga
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee, USA
| | - Adela Martin-Vicente
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee, USA
| | - Ashley V Nywening
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee, USA
- Integrated Program in Biomedical Sciences, College of Graduate Health Sciences, University of Tennessee Health Science Center, Memphis, Tennessee, USA
- Department of Microbiology, Immunology, and Biochemistry, College of Medicine, University of Tennessee Health Science Center, Memphis, Tennessee, USA
| | - Jinhong Xie
- Graduate Program in Pharmaceutical Sciences, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee, USA
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee, USA
| | - Wenbo Ge
- Department of Pharmacy and Pharmaceutical Sciences, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Jarrod R Fortwendel
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee, USA
- Department of Microbiology, Immunology, and Biochemistry, College of Medicine, University of Tennessee Health Science Center, Memphis, Tennessee, USA
| |
Collapse
|
2
|
Zhang J, Qiu R, Bieger BD, Oakley CE, Oakley BR, Egan MJ, Xiang X. Aspergillus SUMOylation mutants exhibit chromosome segregation defects including chromatin bridges. Genetics 2023; 225:iyad169. [PMID: 37724751 PMCID: PMC10697819 DOI: 10.1093/genetics/iyad169] [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: 08/01/2023] [Revised: 08/29/2023] [Accepted: 09/07/2023] [Indexed: 09/21/2023] Open
Abstract
Functions of protein SUMOylation remain incompletely understood in different cell types. Via forward genetics, here we identified ubaBQ247*, a loss-of-function mutation in a SUMO activation enzyme UbaB in the filamentous fungus Aspergillus nidulans. The ubaBQ247*, ΔubaB, and ΔsumO mutants all produce abnormal chromatin bridges, indicating the importance of SUMOylation in the completion of chromosome segregation. The bridges are enclosed by nuclear membrane containing peripheral nuclear pore complex proteins that normally get dispersed during mitosis, and the bridges are also surrounded by cytoplasmic microtubules typical of interphase cells. Time-lapse sequences further indicate that most bridges persist through interphase prior to the next mitosis, and anaphase chromosome segregation can produce new bridges that persist into the next interphase. When the first mitosis happens at a higher temperature of 42°C, SUMOylation deficiency produces not only chromatin bridges but also many abnormally shaped single nuclei that fail to divide. UbaB-GFP localizes to interphase nuclei just like the previously studied SumO-GFP, but the nuclear signals disappear during mitosis when the nuclear pores are partially open, and the signals reappear after mitosis. The nuclear localization is consistent with many SUMO targets being nuclear proteins. Finally, although the budding yeast SUMOylation machinery interacts with LIS1, a protein critical for dynein activation, loss of SUMOylation does not cause any obvious defect in dynein-mediated transport of nuclei and early endosomes, indicating that SUMOylation is unnecessary for dynein activation in A. nidulans.
Collapse
Affiliation(s)
- Jun Zhang
- Department of Biochemistry and Molecular Biology, The Uniformed Services University of the Health Sciences-F. Edward Hébert School of Medicine, Bethesda, MD 20814, USA
| | - Rongde Qiu
- Department of Biochemistry and Molecular Biology, The Uniformed Services University of the Health Sciences-F. Edward Hébert School of Medicine, Bethesda, MD 20814, USA
| | - Baronger D Bieger
- Department of Entomology and Plant Pathology, University of Arkansas Systems Division of Agriculture, Fayetteville, AR 72701, USA
| | - C Elizabeth Oakley
- Department of Molecular Biosciences, University of Kansas, Lawrence, KS 66045, USA
| | - Berl R Oakley
- Department of Molecular Biosciences, University of Kansas, Lawrence, KS 66045, USA
| | - Martin J Egan
- Department of Entomology and Plant Pathology, University of Arkansas Systems Division of Agriculture, Fayetteville, AR 72701, USA
| | - Xin Xiang
- Department of Biochemistry and Molecular Biology, The Uniformed Services University of the Health Sciences-F. Edward Hébert School of Medicine, Bethesda, MD 20814, USA
| |
Collapse
|
3
|
Zhang J, Qiu R, Bieger BD, Oakley CE, Oakley BR, Egan MJ, Xiang X. Aspergillus SUMOylation mutants have normal dynein function but exhibit chromatin bridges. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.16.537086. [PMID: 37131833 PMCID: PMC10153134 DOI: 10.1101/2023.04.16.537086] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Functions of protein SUMOylation remain incompletely understood in different cell types. The budding yeast SUMOylation machinery interacts with LIS1, a protein critical for dynein activation, but dynein-pathway components were not identified as SUMO-targets in the filamentous fungus Aspergillus nidulans. Via A. nidulans forward genetics, here we identified ubaBQ247*, a loss-of-function mutation in a SUMO-activation enzyme UbaB. Colonies of the ubaBQ247*, ΔubaB and ΔsumO mutants looked similar and less healthy than the wild-type colony. In these mutants, about 10% of nuclei are connected by abnormal chromatin bridges, indicating the importance of SUMOylation in the completion of chromosome segregation. Nuclei connected by chromatin bridges are mostly in interphase, suggesting that these bridges do not prevent cell-cycle progression. UbaB-GFP localizes to interphase nuclei just like the previously studied SumO-GFP, but the nuclear signals disappear during mitosis when the nuclear pores are partially open, and the signals reappear after mitosis. The nuclear localization is consistent with many SUMO-targets being nuclear proteins, for example, topoisomerase II whose SUMOylation defect gives rise to chromatin bridges in mammalian cells. Unlike in mammalian cells, however, loss of SUMOylation in A. nidulans does not apparently affect the metaphase-to-anaphase transition, further highlighting differences in the requirements of SUMOylation in different cell types. Finally, loss of UbaB or SumO does not affect dynein- and LIS1-mediated early-endosome transport, indicating that SUMOylation is unnecessary for dynein or LIS1 function in A. nidulans.
Collapse
Affiliation(s)
- Jun Zhang
- Department of Biochemistry and Molecular Biology, The Uniformed Services University of the Health Sciences- F. Edward Hébert School of Medicine, Bethesda, Maryland 20814, USA
| | - Rongde Qiu
- Department of Biochemistry and Molecular Biology, The Uniformed Services University of the Health Sciences- F. Edward Hébert School of Medicine, Bethesda, Maryland 20814, USA
| | - Baronger D. Bieger
- Department of Entomology and Plant Pathology, University of Arkansas Systems Division of Agriculture, Fayetteville, AR, USA
| | - C. Elizabeth Oakley
- Department of Molecular Biosciences, University of Kansas, Lawrence, KS, USA
| | - Berl R. Oakley
- Department of Molecular Biosciences, University of Kansas, Lawrence, KS, USA
| | - Martin J. Egan
- Department of Entomology and Plant Pathology, University of Arkansas Systems Division of Agriculture, Fayetteville, AR, USA
| | - Xin Xiang
- Department of Biochemistry and Molecular Biology, The Uniformed Services University of the Health Sciences- F. Edward Hébert School of Medicine, Bethesda, Maryland 20814, USA
| |
Collapse
|
4
|
Miao P, Mao X, Chen S, Abubakar YS, Li Y, Zheng W, Zhou J, Wang Z, Zheng H. The mitotic exit mediated by small GTPase Tem1 is essential for the pathogenicity of Fusarium graminearum. PLoS Pathog 2023; 19:e1011255. [PMID: 36928713 PMCID: PMC10047555 DOI: 10.1371/journal.ppat.1011255] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Revised: 03/28/2023] [Accepted: 02/28/2023] [Indexed: 03/18/2023] Open
Abstract
The mitotic exit is a key step in cell cycle, but the mechanism of mitotic exit network in the wheat head blight fungus Fusarium graminearum remains unclear. F. graminearum infects wheat spikelets and colonizes the entire head by growing through the rachis node at the bottom of each spikelet. In this study, we found that a small GTPase FgTem1 plays an important role in F. graminearum pathogenicity and functions in regulating the formation of infection structures and invasive hyphal growth on wheat spikelets and wheat coleoptiles, but plays only little roles in vegetative growth and conidiation of the phytopathogen. FgTem1 localizes to both the inner nuclear periphery and the spindle pole bodies, and negatively regulates mitotic exit in F. graminearum. Furthermore, the regulatory mechanisms of FgTem1 have been further investigated by high-throughput co-immunoprecipitation and genetic strategies. The septins FgCdc10 and FgCdc11 were demonstrated to interact with the dominant negative form of FgTem1, and FgCdc11 was found to regulate the localization of FgTem1. The cell cycle arrest protein FgBub2-FgBfa1 complex was shown to act as the GTPase-activating protein (GAP) for FgTem1. We further demonstrated that a direct interaction exists between FgBub2 and FgBfa1 which crucially promotes conidiation, pathogenicity and DON production, and negatively regulates septum formation and nuclear division in F. graminearum. Deletions of FgBUB2 and FgBFA1 genes caused fewer perithecia and immature asci formations, and dramatically down-regulated trichothecene biosynthesis (TRI) gene expressions. Double deletion of FgBUB2/FgBFA1 genes showed that FgBUB2 and FgBFA1 have little functional redundancy in F. graminearum. In summary, we systemically demonstrated that FgTem1 and its GAP FgBub2-FgBfa1 complex are required for fungal development and pathogenicity in F. graminearum.
Collapse
Affiliation(s)
- Pengfei Miao
- Fujian Key Laboratory on Conservation and Sustainable Utilization of Marine Biodiversity, Fuzhou Institute of Oceanography, College of Geography and Oceanography, Minjiang University, Fuzhou, China
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Xuzhao Mao
- Fujian Key Laboratory on Conservation and Sustainable Utilization of Marine Biodiversity, Fuzhou Institute of Oceanography, College of Geography and Oceanography, Minjiang University, Fuzhou, China
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Shuang Chen
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Yakubu Saddeeq Abubakar
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Fujian Agriculture and Forestry University, Fuzhou, China
- Department of Biochemistry, Faculty of Life Sciences, Ahmadu Bello University, Zaria, Nigeria
| | - Yulong Li
- Fujian Key Laboratory on Conservation and Sustainable Utilization of Marine Biodiversity, Fuzhou Institute of Oceanography, College of Geography and Oceanography, Minjiang University, Fuzhou, China
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Wenhui Zheng
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Jie Zhou
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Zonghua Wang
- Fujian Key Laboratory on Conservation and Sustainable Utilization of Marine Biodiversity, Fuzhou Institute of Oceanography, College of Geography and Oceanography, Minjiang University, Fuzhou, China
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Huawei Zheng
- Fujian Key Laboratory on Conservation and Sustainable Utilization of Marine Biodiversity, Fuzhou Institute of Oceanography, College of Geography and Oceanography, Minjiang University, Fuzhou, China
- * E-mail:
| |
Collapse
|
5
|
McCartney B, Dudin O. Cellularization across eukaryotes: Conserved mechanisms and novel strategies. Curr Opin Cell Biol 2023; 80:102157. [PMID: 36857882 DOI: 10.1016/j.ceb.2023.102157] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Revised: 01/27/2023] [Accepted: 01/31/2023] [Indexed: 03/02/2023]
Abstract
Many eukaryotes form multinucleated cells during their development. Some cells persist as such during their lifetime, others choose to cleave each nucleus individually using a specialized cytokinetic process known as cellularization. What is cellularization and how is it achieved across the eukaryotic tree of life? Are there common pathways among all species supporting a shared ancestry, or are there key differences, suggesting independent evolutionary paths? In this review, we discuss common strategies and key mechanistic differences in how cellularization is executed across vastly divergent eukaryotic species. We present a number of novel methods and non-model organisms that may provide important insight into the evolutionary origins of cellularization.
Collapse
Affiliation(s)
- Brooke McCartney
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA 15213, USA.
| | - Omaya Dudin
- Swiss Institute for Experimental Cancer Research, School of Life Sciences, Swiss Federal Institute of Technology (EPFL), Lausanne, Switzerland.
| |
Collapse
|
6
|
SIN-like Pathway Kinases Regulate the End of Mitosis in the Methylotrophic Yeast Ogataea polymorpha. Cells 2022; 11:cells11091519. [PMID: 35563825 PMCID: PMC9105162 DOI: 10.3390/cells11091519] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Revised: 04/21/2022] [Accepted: 04/25/2022] [Indexed: 02/01/2023] Open
Abstract
The mitotic exit network (MEN) is a conserved signalling pathway essential for the termination of mitosis in the budding yeast Saccharomyces cerevisiae. All MEN components are highly conserved in the methylotrophic budding yeast Ogataea polymorpha, except for Cdc15 kinase. Instead, we identified two essential kinases OpHcd1 and OpHcd2 (homologue candidate of ScCdc15) that are homologous to SpSid1 and SpCdc7, respectively, components of the septation initiation network (SIN) of the fission yeast Schizosaccharomyces pombe. Conditional mutants for OpHCD1 and OpHCD2 exhibited significant delay in late anaphase and defective cell separation, suggesting that both genes have roles in mitotic exit and cytokinesis. Unlike Cdc15 in S. cerevisiae, the association of OpHcd1 and OpHcd2 with the yeast centrosomes (named spindle pole bodies, SPBs) is restricted to the SPB in the mother cell body. SPB localisation of OpHcd2 is regulated by the status of OpTem1 GTPase, while OpHcd1 requires the polo-like kinase OpCdc5 as well as active Tem1 to ensure the coordination of mitotic exit (ME) signalling and cell cycle progression. Our study suggests that the divergence of molecular mechanisms to control the ME-signalling pathway as well as the loss of Sid1/Hcd1 kinase in the MEN occurred relatively recently during the evolution of budding yeast.
Collapse
|
7
|
Xu Y, Liu L, Chen Z, Tian X, Chu J. The arthrospore-related gene Acaxl2 is involved in cephalosporin C production in industrial Acremonium chrysogenum by the regulatory factors AcFKH1 and CPCR1. J Biotechnol 2021; 347:26-39. [PMID: 34954288 DOI: 10.1016/j.jbiotec.2021.12.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Revised: 12/17/2021] [Accepted: 12/20/2021] [Indexed: 11/20/2022]
Abstract
Cephalosporin C (CPC) production is often accompanied by a typical morphological differentiation of Acremonium chrysogenum, involving the fragmentation of its hyphae into arthrospores. The type I integral plasma membrane protein Axl2 is a central component of the bud site selection system (BSSS), which was identified as the regulatory factor involved in the hyphal septation process and arthrospore formation. Using CRISPR/Cas9 technology and homologous recombination (HR), we inserted an egfp donor DNA sequence into the Acaxl2 locus, causing the generation of the deletion strain Ac-ΔAcaxl2::eGFP from Acremonium chrysogenum FC3-5-23, the industrial producer of CPC. The mycelial morphology of the deletion strain Ac-ΔAcaxl2::eGFP was mainly composed of arthrospores with a characteristic diameter of 2-8 μm, which increased from 75% at 48h to 90% at 72h post culture and were maintained until the end of the fermentation process. However, the deletion strain showed accelerated production of CPC, and the final titer was 5573μg/ml, which was nearly three times higher than that of the control strain FC3-5-23. The up-regulation of genes related to the biosynthesis gene cluster in Ac-ΔAcaxl2::eGFP, especially the "late" genes, was one reason why its CPC production was higher than that of the original strain. Furthermore, compared with FC3-5-23, the more significant increase of genes involved in the BSSS (Acbud3 and Acbud4) in Ac-ΔAcaxl2::eGFP in the late stage of fermentation, may be responsible for this increase in arthrospore formation. Similarily, the transcription of the regulatory factors AcFKH1 and CPCR1 were also markedly increased at this time and may be the factors responsible for the regulation of CPC synthesis. These results indicated that Acaxl2 plays an important role in both arthrospore formation and CPC production, strongly implicating these regulatory factors as having pivotal links between mycelial morphology and secondary metabolite production in high-yielding A. chrysogenum. To the opposite, the axl2 gene knockout of wild strain CGMCC 3.3795 did not significantly influence the CPC production, which reflected the complexity of the secondary metabolic process and the differences in the function of axl2 gene in high- and low-yielding strains.
Collapse
Affiliation(s)
- Yan Xu
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Ling Liu
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Zhen Chen
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Xiwei Tian
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Ju Chu
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China.
| |
Collapse
|
8
|
Souza ACO, Martin-Vicente A, Nywening AV, Ge W, Lowes DJ, Peters BM, Fortwendel JR. Loss of Septation Initiation Network (SIN) kinases blocks tissue invasion and unlocks echinocandin cidal activity against Aspergillus fumigatus. PLoS Pathog 2021; 17:e1009806. [PMID: 34370772 PMCID: PMC8376064 DOI: 10.1371/journal.ppat.1009806] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Revised: 08/19/2021] [Accepted: 07/16/2021] [Indexed: 11/18/2022] Open
Abstract
Although considered effective treatment for many yeast fungi, the therapeutic efficacy of the echinocandin class of antifungals for invasive aspergillosis (IA) is limited. Recent studies suggest intense kinase- and phosphatase-mediated echinocandin adaptation in A. fumigatus. To identify A. fumigatus protein kinases required for survival under echinocandin stress, we employed CRISPR/Cas9-mediated gene targeting to generate a protein kinase disruption mutant library in a wild type genetic background. Cell wall and echinocandin stress screening of the 118 disruption mutants comprising the library identified only five protein kinase disruption mutants displaying greater than 4-fold decreased echinocandin minimum effective concentrations (MEC) compared to the parental strain. Two of these mutated genes, the previously uncharacterized A. fumigatus sepL and sidB genes, were predicted to encode protein kinases functioning as core components of the Septation Initiation Network (SIN), a tripartite kinase cascade that is necessary for septation in fungi. As the A. fumigatus SIN is completely uncharacterized, we sought to explore these network components as effectors of echinocandin stress survival. Our data show that mutation of any single SIN kinase gene caused complete loss of hyphal septation and increased susceptibility to cell wall stress, as well as widespread hyphal damage and loss of viability in response to echinocandin stress. Strikingly, mutation of each SIN kinase gene also resulted in a profound loss of virulence characterized by lack of tissue invasive growth. Through the deletion of multiple novel regulators of hyphal septation, we show that the non-invasive growth phenotype is not SIN-kinase dependent, but likely due to hyphal septation deficiency. Finally, we also find that echinocandin therapy is highly effective at eliminating residual tissue burden in mice infected with an aseptate strain of A. fumigatus. Together, our findings suggest that inhibitors of septation could enhance echinocandin-mediated killing while simultaneously limiting the invasive potential of A. fumigatus hyphae.
Collapse
Affiliation(s)
- Ana Camila Oliveira Souza
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee, United States of America
| | - Adela Martin-Vicente
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee, United States of America
| | - Ashley V. Nywening
- Integrated Program in Biomedical Sciences, College of Graduate Health Sciences, University of Tennessee Health Science Center, Memphis, Tennessee, United States of America
| | - Wenbo Ge
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee, United States of America
| | - David J. Lowes
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee, United States of America
| | - Brian M. Peters
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee, United States of America
- Department of Microbiology, Immunology, and Biochemistry, College of Medicine, University of Tennessee Health Science Center, Memphis, Tennessee, United States of America
| | - Jarrod R. Fortwendel
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee, United States of America
- Department of Microbiology, Immunology, and Biochemistry, College of Medicine, University of Tennessee Health Science Center, Memphis, Tennessee, United States of America
- * E-mail:
| |
Collapse
|
9
|
Tsumura R, Sawada K, Kunitake E, Sumitani JI, Kawaguchi T, Tani S. A component of the septation initiation network complex, AaSepM, is involved in multiple cellulose-responsive signaling pathways in Aspergillus aculeatus. Appl Microbiol Biotechnol 2021; 105:1535-1546. [PMID: 33481069 DOI: 10.1007/s00253-021-11110-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Revised: 12/22/2020] [Accepted: 01/11/2021] [Indexed: 11/29/2022]
Abstract
Various carbohydrate-active enzymes in Aspergillus are produced in response to physiological inducers, which is regulated at the transcriptional level. To elucidate the induction mechanisms in Aspergillus, we screened for new regulators involved in cellulose-responsive induction from approximately 10,000 Aspergillus aculeatus T-DNA-inserted mutants. We constructed the T-DNA-inserted mutant library using the host strain harboring the orotidine 5'-monophosphate decarboxylase gene (pyrG) under the control of the FIII-avicelase gene (cbhI) promoter. Thus, candidate mutants deficient in cellulose-responsive induction were positively screened via counter selection against 5-fluoroorotic acid (5-FOA). Among less than two hundred 5-FOA-resistant mutants, one mutant that the T-DNA inserted into the AasepM locus reduced the cbhI expression in response to cellulose. Since AaSepM is similar to Schizosaccharomyces pombe Cdc14p (E-value, 2e-20; identities, 33%), which is a component of the septation initiation network (SIN)-complex, we constructed an AasepM deletion mutant (ΔAasepM). We analyzed the expression of cellulase and xylanase genes in response to cellulose, septation, and conidiation in ΔAasepM. The AasepM deletion leads to delayed septation and decreased formation of the conidium chain in A. aculeatus but does not affect hyphal growth on minimal media. We also confirmed AaSepM's involvement in multiple cellulose-responsive signaling pathways of cellulase and xylanase genes under the control of the ManR-dependent, XlnR-dependent, and ManR- and XlnR-independent signaling pathways. KEY POINTS : • A new regulator for cellulolytic gene expression has been identified. • AaSepM is involved in septation and conidiation in A. aculeatus. • AasepM is involved in multiple cellulose-responsive signaling pathways.
Collapse
Affiliation(s)
- Ryosuke Tsumura
- Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-1 Gakuen-cho, Sakai, 599-8531, Japan
| | - Kazumi Sawada
- Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-1 Gakuen-cho, Sakai, 599-8531, Japan
| | - Emi Kunitake
- Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-1 Gakuen-cho, Sakai, 599-8531, Japan.,Graduate School of Bioresources, Mie University, 1577 Kurimamachiya-cho, Tsu, 514-8507, Japan
| | - Jun-Ichi Sumitani
- Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-1 Gakuen-cho, Sakai, 599-8531, Japan
| | - Takashi Kawaguchi
- Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-1 Gakuen-cho, Sakai, 599-8531, Japan
| | - Shuji Tani
- Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-1 Gakuen-cho, Sakai, 599-8531, Japan.
| |
Collapse
|
10
|
Plaza V, Silva-Moreno E, Castillo L. Breakpoint: Cell Wall and Glycoproteins and their Crucial Role in the Phytopathogenic Fungi Infection. Curr Protein Pept Sci 2021; 21:227-244. [PMID: 31490745 DOI: 10.2174/1389203720666190906165111] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Revised: 08/02/2019] [Accepted: 08/17/2019] [Indexed: 01/09/2023]
Abstract
The cell wall that surrounds fungal cells is essential for their survival, provides protection against physical and chemical stresses, and plays relevant roles during infection. In general, the fungal cell wall is composed of an outer layer of glycoprotein and an inner skeletal layer of β-glucans or α- glucans and chitin. Chitin synthase genes have been shown to be important for septum formation, cell division and virulence. In the same way, chitin can act as a potent elicitor to activate defense response in several plant species; however, the fungi can convert chitin to chitosan during plant infection to evade plant defense mechanisms. Moreover, α-1,3-Glucan, a non-degradable polysaccharide in plants, represents a key feature in fungal cell walls formed in plants and plays a protective role for this fungus against plant lytic enzymes. A similar case is with β-1,3- and β-1,6-glucan which are essential for infection, structure rigidity and pathogenicity during fungal infection. Cell wall glycoproteins are also vital to fungi. They have been associated with conidial separation, the increase of chitin in conidial cell walls, germination, appressorium formation, as well as osmotic and cell wall stress and virulence; however, the specific roles of glycoproteins in filamentous fungi remain unknown. Fungi that can respond to environmental stimuli distinguish these signals and relay them through intracellular signaling pathways to change the cell wall composition. They play a crucial role in appressorium formation and penetration, and release cell wall degrading enzymes, which determine the outcome of the interaction with the host. In this review, we highlight the interaction of phypatophogen cell wall and signaling pathways with its host and their contribution to fungal pathogenesis.
Collapse
Affiliation(s)
- Verónica Plaza
- Laboratorio de Biología Molecular y Bioquímica, Departamento de Biología, Universidad de La Serena, La Serena, Chile
| | - Evelyn Silva-Moreno
- Instituto de Ciencias Biomédicas, Universidad Autónoma de Chile, Temuco, Chile
| | - Luis Castillo
- Laboratorio de Biología Molecular y Bioquímica, Departamento de Biología, Universidad de La Serena, La Serena, Chile
| |
Collapse
|
11
|
Hülle Cells of Aspergillus nidulans with Nuclear Storage and Developmental Backup Functions Are Reminiscent of Multipotent Stem Cells. mBio 2020; 11:mBio.01673-20. [PMID: 32788382 PMCID: PMC7439468 DOI: 10.1128/mbio.01673-20] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Some aspergilli are among the most cosmopolitan and ecologically dominant fungal species. One pillar of their success is their complex life cycle, which creates specialized cell types for versatile dispersal and regenesis. One of these cell types is unique to aspergilli-the Hülle cells. Despite being known for over a century, the biological and ecological roles of Hülle cells remain largely speculative. Previously reported data on in vivo Hülle cell formation and localization have been conflicting. Our quantification reveals that Hülle cells can occur at all locations on hyphae and that they show cellular activity similar to that seen with adjacent hyphae, indicating that they develop as intricate parts of hyphal tissue. In addition, we show that during sexual development associated with two parental strains, the typically multinucleate Hülle cells can inherit nuclei from both parents, indicating that they may serve as genetic backups. We provide an easy, reproducible method to study Hülle cell biology and germination with which we investigate the 90-year-old puzzle of whether and how Hülle cells germinate. We present clear evidence for the germination of Hülle cells, and we show that Hülle cells grow hyphae that develop into a spore-producing colony. Finally, we show that Hülle cell-derived colonies produce conidiospores faster than spore-derived colonies, providing evidence for an as-yet-undescribed developmental shortcut program in Aspergillus nidulans We propose that Hülle cells represent a unique cell type as specialized hypha-derived sexual tissue with a nucleus storage function and may act as fungal backup stem cells under highly destructive conditions.IMPORTANCE The in vivo identification of Hülle cells in cases of aspergillosis infections in animals and humans illustrates their biological relevance and suggests that they might be involved in pathogenicity. It is striking that aspergilli have developed and maintained a multinucleate nurse cell that is presumably energy-intensive to produce and is usually found only in higher eukaryotes. Our findings shed light on how the understudied Hülle cells might contribute to the success of aspergilli by acting not only as nurse cells under detrimental conditions (sexual development) but also as fungal backup stem cells with the capacity to produce genetically diverse spores in an accelerated manner, thereby substantially contributing to survival in response to predator attack or under otherwise severely destructive conditions. Our study solved the 90-year-old puzzle of Hülle cell germination and provides easy, reproducible methods that will facilitate future studies on biological and ecological roles of Hülle cells in aspergilli.
Collapse
|
12
|
Mamun MAA, Katayama T, Cao W, Nakamura S, Maruyama JI. A novel Pezizomycotina-specific protein with gelsolin domains regulates contractile actin ring assembly and constriction in perforated septum formation. Mol Microbiol 2020; 113:964-982. [PMID: 31965663 DOI: 10.1111/mmi.14463] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2019] [Revised: 01/13/2020] [Accepted: 01/13/2020] [Indexed: 12/29/2022]
Abstract
Septum formation in fungi is equivalent to cytokinesis. It differs mechanistically in filamentous ascomycetes (Pezizomycotina) from that of ascomycete yeasts by the retention of a central septal pore in the former group. However, septum formation in both groups is accomplished by contractile actin ring (CAR) assembly and constriction. The specific components regulating septal pore organization during septum formation are poorly understood. In this study, a novel Pezizomycotina-specific actin regulatory protein GlpA containing gelsolin domains was identified using bioinformatics. A glpA deletion mutant exhibited increased distances between septa, abnormal septum morphology and defective regulation of septal pore closure. In glpA deletion mutant hyphae, overaccumulation of actin filament (F-actin) was observed, and the CAR was abnormal with improper assembly and failure in constriction. In wild-type cells, GlpA was found at the septum formation site similarly to the CAR. The N-terminal 329 residues of GlpA are required for its localization to the septum formation site and essential for proper septum formation, while its C-terminal gelsolin domains are required for the regular CAR dynamics during septum formation. Finally, in this study we elucidated a novel Pezizomycotina-specific actin modulating component, which participates in septum formation by regulating the CAR dynamics.
Collapse
Affiliation(s)
| | - Takuya Katayama
- Department of Biotechnology, The University of Tokyo, Tokyo, Japan.,Collaborative Research Institute for Innovative Microbiology, The University of Tokyo, Tokyo, Japan
| | - Wei Cao
- Faculty of Information Networking for Innovation and Design, Department of Information Networking for Innovation and Design, Toyo University, Tokyo, Japan
| | - Shugo Nakamura
- Faculty of Information Networking for Innovation and Design, Department of Information Networking for Innovation and Design, Toyo University, Tokyo, Japan
| | - Jun-Ichi Maruyama
- Department of Biotechnology, The University of Tokyo, Tokyo, Japan.,Collaborative Research Institute for Innovative Microbiology, The University of Tokyo, Tokyo, Japan
| |
Collapse
|
13
|
Raudaskoski M. The central role of septa in the basidiomycete Schizophyllum commune hyphal morphogenesis. Fungal Biol 2019; 123:638-649. [DOI: 10.1016/j.funbio.2019.05.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2019] [Revised: 05/10/2019] [Accepted: 05/13/2019] [Indexed: 11/15/2022]
|
14
|
Fukada F, Kodama S, Nishiuchi T, Kajikawa N, Kubo Y. Plant pathogenic fungi Colletotrichum and Magnaporthe share a common G 1 phase monitoring strategy for proper appressorium development. THE NEW PHYTOLOGIST 2019; 222:1909-1923. [PMID: 30715740 DOI: 10.1111/nph.15728] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2018] [Accepted: 01/24/2019] [Indexed: 06/09/2023]
Abstract
To breach the plant cuticle, many plant pathogenic fungi differentiate specialized infection structures (appressoria). In Colletotrichum orbiculare (cucumber anthracnose fungus), this differentiation requires unique proper G1 /S phase progression, regulated by two-component GTPase activating protein CoBub2/CoBfa1 and GTPase CoTem1. Since their homologues regulate mitotic exit, cytokinesis, or septum formation from yeasts to mammals, we asked whether the BUB2 function in G1 /S progression is specific to plant pathogenic fungi. Colletotrichum higginsianum and Magnaporthe oryzae were genetically analyzed to investigate conservation of BUB2 roles in cell cycle regulation, septum formation, and virulence. Expression profile of cobub2Δ was analyzed using a custom microarray. In bub2 mutants of both fungi, S phase initiation was earlier, and septum formation coordinated with a septation initiation network protein and contractile actin ring was impaired. Earlier G1 /S transition in cobub2Δ results in especially high expression of DNA replication genes and differing regulation of virulence-associated genes that encode proteins such as carbohydrate-active enzymes and small secreted proteins. The virulence of chbub2Δ and mobub2Δ was significantly reduced. Our evidence shows that BUB2 regulation of G1 /S transition and septum formation supports its specific requirement for appressorium development in plant pathogenic fungi.
Collapse
Affiliation(s)
- Fumi Fukada
- Laboratory of Plant Pathology, Life and Environmental Sciences, Graduate School of Kyoto Prefectural University, Sakyo, Kyoto, 606-8522, Japan
| | - Sayo Kodama
- Laboratory of Plant Pathology, Life and Environmental Sciences, Graduate School of Kyoto Prefectural University, Sakyo, Kyoto, 606-8522, Japan
| | - Takumi Nishiuchi
- Division of Functional Genomics, Advanced Science Research Centre, Kanazawa University, Kanazawa, 920-0934, Japan
| | - Naoki Kajikawa
- Laboratory of Plant Pathology, Life and Environmental Sciences, Graduate School of Kyoto Prefectural University, Sakyo, Kyoto, 606-8522, Japan
| | - Yasuyuki Kubo
- Laboratory of Plant Pathology, Life and Environmental Sciences, Graduate School of Kyoto Prefectural University, Sakyo, Kyoto, 606-8522, Japan
| |
Collapse
|
15
|
Zhang Y, Gao X, Manck R, Schmid M, Osmani AH, Osmani SA, Takeshita N, Fischer R. Microtubule-organizing centers of Aspergillus nidulans
are anchored at septa by a disordered protein. Mol Microbiol 2017; 106:285-303. [DOI: 10.1111/mmi.13763] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/03/2017] [Indexed: 01/21/2023]
Affiliation(s)
- Ying Zhang
- Department of Microbiology, Institute for Applied Biosciences; Karlsruhe Institute of Technology (KIT) - South Campus, Fritz-Haber-Weg 4; Karlsruhe D-76131 Germany
| | - Xiaolei Gao
- Department of Microbiology, Institute for Applied Biosciences; Karlsruhe Institute of Technology (KIT) - South Campus, Fritz-Haber-Weg 4; Karlsruhe D-76131 Germany
| | - Raphael Manck
- Department of Microbiology, Institute for Applied Biosciences; Karlsruhe Institute of Technology (KIT) - South Campus, Fritz-Haber-Weg 4; Karlsruhe D-76131 Germany
| | - Marjorie Schmid
- Department of Microbiology, Institute for Applied Biosciences; Karlsruhe Institute of Technology (KIT) - South Campus, Fritz-Haber-Weg 4; Karlsruhe D-76131 Germany
| | - Aysha H. Osmani
- Department of Molecular Genetics; Ohio State University, 105 Biological Sciences Building, 484 W 12th Ave; Columbus OH 43210 USA
| | - Stephen A. Osmani
- Department of Molecular Genetics; Ohio State University, 105 Biological Sciences Building, 484 W 12th Ave; Columbus OH 43210 USA
| | - Norio Takeshita
- Department of Microbiology, Institute for Applied Biosciences; Karlsruhe Institute of Technology (KIT) - South Campus, Fritz-Haber-Weg 4; Karlsruhe D-76131 Germany
- School of Life and Environmental Sciences; University of Tsukuba; Ten-Nou-Dai Tsukuba 305-8572 Japan
| | - Reinhard Fischer
- Department of Microbiology, Institute for Applied Biosciences; Karlsruhe Institute of Technology (KIT) - South Campus, Fritz-Haber-Weg 4; Karlsruhe D-76131 Germany
| |
Collapse
|
16
|
Abstract
Filamentous fungi are a large and ancient clade of microorganisms that occupy a broad range of ecological niches. The success of filamentous fungi is largely due to their elongate hypha, a chain of cells, separated from each other by septa. Hyphae grow by polarized exocytosis at the apex, which allows the fungus to overcome long distances and invade many substrates, including soils and host tissues. Hyphal tip growth is initiated by establishment of a growth site and the subsequent maintenance of the growth axis, with transport of growth supplies, including membranes and proteins, delivered by motors along the cytoskeleton to the hyphal apex. Among the enzymes delivered are cell wall synthases that are exocytosed for local synthesis of the extracellular cell wall. Exocytosis is opposed by endocytic uptake of soluble and membrane-bound material into the cell. The first intracellular compartment in the endocytic pathway is the early endosomes, which emerge to perform essential additional functions as spatial organizers of the hyphal cell. Individual compartments within septated hyphae can communicate with each other via septal pores, which allow passage of cytoplasm or organelles to help differentiation within the mycelium. This article introduces the reader to more detailed aspects of hyphal growth in fungi.
Collapse
|
17
|
Location and functional analysis of the Aspergillus nidulans Aurora kinase confirm mitotic functions and suggest non-mitotic roles. Fungal Genet Biol 2017; 103:1-15. [DOI: 10.1016/j.fgb.2017.03.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2017] [Accepted: 03/12/2017] [Indexed: 11/17/2022]
|
18
|
Schinke J, Kolog Gulko M, Christmann M, Valerius O, Stumpf SK, Stirz M, Braus GH. The DenA/DEN1 Interacting Phosphatase DipA Controls Septa Positioning and Phosphorylation-Dependent Stability of Cytoplasmatic DenA/DEN1 during Fungal Development. PLoS Genet 2016; 12:e1005949. [PMID: 27010942 PMCID: PMC4806917 DOI: 10.1371/journal.pgen.1005949] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Accepted: 03/01/2016] [Indexed: 11/18/2022] Open
Abstract
DenA/DEN1 and the COP9 signalosome (CSN) represent two deneddylases which remove the ubiquitin-like Nedd8 from modified target proteins and are required for distinct fungal developmental programmes. The cellular DenA/DEN1 population is divided into a nuclear and a cytoplasmatic subpopulation which is especially enriched at septa. DenA/DEN1 stability control mechanisms are different for the two cellular subpopulations and depend on different physical interacting proteins and the C-terminal DenA/DEN1 phosphorylation pattern. Nuclear DenA/DEN1 is destabilized during fungal development by five of the eight CSN subunits which target nuclear DenA/DEN1 for degradation. DenA/DEN1 becomes stabilized as a phosphoprotein at S243/S245 during vegetative growth, which is necessary to support further asexual development. After the initial phase of development, the newly identified cytoplasmatic DenA/DEN1 interacting phosphatase DipA and an additional developmental specific C-terminal phosphorylation site at serine S253 destabilize DenA/DEN1. Outside of the nucleus, DipA is co-transported with DenA/DEN1 in the cytoplasm between septa and nuclei. Deletion of dipA resulted in increased DenA/DEN1 stability in a strain which is unresponsive to illumination. The mutant strain is dysregulated in cytokinesis and impaired in asexual development. Our results suggest a dual phosphorylation-dependent DenA/DEN1 stability control with stabilizing and destabilizing modifications and physical interaction partner proteins which function as control points in the nucleus and the cytoplasm.
Collapse
Affiliation(s)
- Josua Schinke
- Department of Molecular Microbiology and Genetics, Göttingen Center for Molecular Biosciences (GZMB), and Georg-August-University, Göttingen, Germany
| | - Miriam Kolog Gulko
- Department of Molecular Microbiology and Genetics, Göttingen Center for Molecular Biosciences (GZMB), and Georg-August-University, Göttingen, Germany
| | - Martin Christmann
- Department of Molecular Microbiology and Genetics, Göttingen Center for Molecular Biosciences (GZMB), and Georg-August-University, Göttingen, Germany
| | - Oliver Valerius
- Department of Molecular Microbiology and Genetics, Göttingen Center for Molecular Biosciences (GZMB), and Georg-August-University, Göttingen, Germany
| | - Sina Kristin Stumpf
- Department of Molecular Microbiology and Genetics, Göttingen Center for Molecular Biosciences (GZMB), and Georg-August-University, Göttingen, Germany
| | - Margarita Stirz
- Department of Molecular Microbiology and Genetics, Göttingen Center for Molecular Biosciences (GZMB), and Georg-August-University, Göttingen, Germany
| | - Gerhard H. Braus
- Department of Molecular Microbiology and Genetics, Göttingen Center for Molecular Biosciences (GZMB), and Georg-August-University, Göttingen, Germany
- * E-mail:
| |
Collapse
|
19
|
Fukada F, Kubo Y. Colletotrichum orbiculare Regulates Cell Cycle G1/S Progression via a Two-Component GAP and a GTPase to Establish Plant Infection. THE PLANT CELL 2015; 27:2530-44. [PMID: 26320225 PMCID: PMC4815103 DOI: 10.1105/tpc.15.00179] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Revised: 06/30/2015] [Accepted: 08/10/2015] [Indexed: 05/23/2023]
Abstract
Morphogenesis in filamentous fungi depends on appropriate cell cycle progression. Here, we report that cells of the cucumber anthracnose fungus Colletotrichum orbiculare regulate G1/S progression via a two-component GAP, consisting of Budding-uninhibited-by-benomyl-2 (Bub2) and Byr-four-alike-1 (Bfa1) as well as its GTPase Termination-of-M-phase-1 (Tem1) to establish successful infection. In a random insertional mutagenesis screen of infection-related morphogenesis, we isolated a homolog of Saccharomyces cerevisiae, BUB2, which encodes a two-component Rab GAP protein that forms a GAP complex with Bfa1p and negatively regulates mitotic exit. Interestingly, disruption of either Co BUB2 or Co BFA1 resulted in earlier onset of nuclear division and decreased the time of phase progression from G1 to S during appressorium development. S. cerevisiae GTPase Tem1p is the downstream target of the Bub2p/Bfa1p GAP complex. Introducing the dominant-negative form of Co Tem1 into Co bub2Δ or Co bfa1Δ complemented the defect in G1/S progression, indicating that Co Bub2/Co Bfa1 regulates G1/S progression via Co Tem1. Based on a pathogenicity assay, we found that Co bub2Δ and Co bfa1Δ reduced pathogenesis by attenuating infection-related morphogenesis and enhancing the plant defense response. Thus, during appressorium development, C. orbiculare Bub2/Bfa1 regulates G1/S progression via Co Tem1, and this regulation is essential to establish plant infection.
Collapse
Affiliation(s)
- Fumi Fukada
- Laboratory of Plant Pathology, Life and Environmental Sciences, Graduate School of Kyoto Prefectural University, Kyoto 606-8522, Japan
| | - Yasuyuki Kubo
- Laboratory of Plant Pathology, Life and Environmental Sciences, Graduate School of Kyoto Prefectural University, Kyoto 606-8522, Japan
| |
Collapse
|
20
|
Edgerton H, Paolillo V, Oakley BR. Spatial regulation of the spindle assembly checkpoint and anaphase-promoting complex in Aspergillus nidulans. Mol Microbiol 2014; 95:442-57. [PMID: 25417844 DOI: 10.1111/mmi.12871] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/13/2014] [Indexed: 11/29/2022]
Abstract
The spindle assembly checkpoint (SAC) plays a critical role in preventing mitotic errors by inhibiting anaphase until all kinetochores are correctly attached to spindle microtubules. In spite of the economic and medical importance of filamentous fungi, relatively little is known about the behavior of SAC proteins in these organisms. In our efforts to understand the role of γ-tubulin in cell cycle regulation, we have created functional fluorescent protein fusions of four SAC proteins in Aspergillus nidulans, the homologs of Mad2, Mps1, Bub1/BubR1 and Bub3. Time-lapse imaging reveals that SAC proteins are in distinct compartments of the cell until early mitosis when they co-localize at the spindle pole body. SAC activity is, thus, spatially regulated in A. nidulans. Likewise, Cdc20, an activator of the anaphase-promoting complex/cyclosome, is excluded from interphase nuclei, but enters nuclei at mitotic onset and accumulates to a higher level in mitotic nuclei than in the surrounding nucleoplasm before leaving in anaphase/telophase. The activity of this critical cell cycle regulatory complex is likely regulated by the location of Cdc20. Finally, the γ-tubulin mutation mipAD159 causes a nuclear-specific failure of nuclear localization of Mps1 and Bub1/R1 but not of Cdc20, Bub3 or Mad2.
Collapse
Affiliation(s)
- Heather Edgerton
- Department of Molecular Biosciences, University of Kansas, 1200 Sunnyside Ave., Lawrence, KS, 66045, USA
| | | | | |
Collapse
|
21
|
Zeng CJT, Kim HR, Vargas Arispuro I, Kim JM, Huang AC, Liu B. Microtubule plus end-tracking proteins play critical roles in directional growth of hyphae by regulating the dynamics of cytoplasmic microtubules in Aspergillus nidulans. Mol Microbiol 2014; 94:506-21. [PMID: 25213466 DOI: 10.1111/mmi.12792] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/07/2014] [Indexed: 12/19/2022]
Abstract
Cytoplasmic microtubules (MTs) serve as a rate-limiting factor for hyphal tip growth in the filamentous fungus Aspergillus nidulans. We hypothesized that this function depended on the MT plus end-tracking proteins (+TIPs) including the EB1 family protein EBA that decorated the MT plus ends undergoing polymerization. The ebAΔ mutation reduced colony growth and the mutant hyphae appeared in an undulating pattern instead of exhibiting unidirectional growth in the control. These phenotypes were enhanced by a mutation in another +TIP gene clipA. EBA was required for plus end-tracking of CLIPA, the Kinesin-7 motor KipA, and the XMAP215 homologue AlpA. In addition, cytoplasmic dynein also depended on EBA to track on most polymerizing MT plus ends, but not for its conspicuous appearance at the MT ends near the hyphal apex. The loss of EBA reduced the number of cytoplasmic MTs and prolonged dwelling times for MTs after reaching the hyphal apex. Finally, we found that colonies were formed in the absence of EBA, CLIPA, and NUDA together, suggesting that they were dispensable for fundamental functions of MTs. This study provided a comprehensive delineation of the relationship among different +TIPs and their contributions to MT dynamics and unidirectional hyphal expansion in filamentous fungi.
Collapse
Affiliation(s)
- Cui J Tracy Zeng
- Department of Plant Biology, University of California, Davis, CA, 95616, USA
| | | | | | | | | | | |
Collapse
|
22
|
Role of Candida albicans Tem1 in mitotic exit and cytokinesis. Fungal Genet Biol 2014; 69:84-95. [PMID: 24973462 DOI: 10.1016/j.fgb.2014.06.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Revised: 06/12/2014] [Accepted: 06/17/2014] [Indexed: 11/20/2022]
Abstract
Candida albicans demonstrates three main growth morphologies: yeast, pseudohyphal and true hyphal forms. Cell separation is distinct in these morphological forms and the process of separation is closely linked to the completion of mitosis and cytokinesis. In Saccharomyces cerevisiae the small GTPase Tem1 is known to initiate the mitotic exit network, a signalling pathway involved in signalling the end of mitosis and initiating cytokinesis and cell separation. Here we have characterised the role of Tem1 in C. albicans, and demonstrate that it is essential for mitotic exit and cytokinesis, and that this essential function is signalled through the kinase Cdc15. Cells depleted of Tem1 displayed highly polarised growth but ultimately failed to both complete cytokinesis and re-enter the cell cycle following nuclear division. Consistent with its role in activating the mitotic exit network Tem1 localises to spindle pole bodies in a cell cycle-dependent manner. Ultimately, the mitotic exit network in C. albicans appears to co-ordinate the sequential processes of mitotic exit, cytokinesis and cell separation.
Collapse
|
23
|
Delgado-Álvarez DL, Bartnicki-García S, Seiler S, Mouriño-Pérez RR. Septum development in Neurospora crassa: the septal actomyosin tangle. PLoS One 2014; 9:e96744. [PMID: 24800890 PMCID: PMC4011870 DOI: 10.1371/journal.pone.0096744] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Accepted: 04/10/2014] [Indexed: 12/05/2022] Open
Abstract
Septum formation in Neurospora crassa was studied by fluorescent tagging of actin, myosin, tropomyosin, formin, fimbrin, BUD-4, and CHS-1. In chronological order, we recognized three septum development stages: 1) septal actomyosin tangle (SAT) assembly, 2) contractile actomyosin ring (CAR) formation, 3) CAR constriction together with plasma membrane ingrowth and cell wall construction. Septation began with the assembly of a conspicuous tangle of cortical actin cables (SAT) in the septation site >5 min before plasma membrane ingrowth. Tropomyosin and myosin were detected as components of the SAT from the outset. The SAT gradually condensed to form a proto-CAR that preceded CAR formation. During septum development, the contractile actomyosin ring remained associated with the advancing edge of the septum. Formin and BUD-4 were recruited during the transition from SAT to CAR and CHS-1 appeared two min before CAR constriction. Actin patches containing fimbrin were observed surrounding the ingrowing septum, an indication of endocytic activity. Although the trigger of SAT assembly remains unclear, the regularity of septation both in space and time gives us reason to believe that the initiation of the septation process is integrated with the mechanisms that control both the cell cycle and the overall growth of hyphae, despite the asynchronous nature of mitosis in N. crassa.
Collapse
Affiliation(s)
- Diego Luis Delgado-Álvarez
- Departamento de Microbiología, Centro de Educación Científica y de Educación Superior de Ensenada, Ensenada, B. C. México
| | - Salomón Bartnicki-García
- Departamento de Microbiología, Centro de Educación Científica y de Educación Superior de Ensenada, Ensenada, B. C. México
| | - Stephan Seiler
- Institute for Biology II – Molecular Plant Physiology, Albert-Ludwigs University Freiburg, Freiburg, Germany
- Freiburg Institute for Advanced Studies (FRIAS), Albert-Ludwigs University Freiburg, Freiburg, Germany
| | - Rosa Reyna Mouriño-Pérez
- Departamento de Microbiología, Centro de Educación Científica y de Educación Superior de Ensenada, Ensenada, B. C. México
- * E-mail:
| |
Collapse
|
24
|
Proper actin ring formation and septum constriction requires coordinated regulation of SIN and MOR pathways through the germinal centre kinase MST-1. PLoS Genet 2014; 10:e1004306. [PMID: 24762679 PMCID: PMC3998894 DOI: 10.1371/journal.pgen.1004306] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Accepted: 02/25/2014] [Indexed: 12/17/2022] Open
Abstract
Nuclear DBF2p-related (NDR) kinases constitute a functionally conserved protein family of eukaryotic regulators that control cell division and polarity. In fungi, they function as effector kinases of the morphogenesis (MOR) and septation initiation (SIN) networks and are activated by pathway-specific germinal centre (GC) kinases. We characterized a third GC kinase, MST-1, that connects both kinase cascades. Genetic and biochemical interactions with SIN components and life cell imaging identify MST-1 as SIN-associated kinase that functions in parallel with the GC kinase SID-1 to activate the SIN-effector kinase DBF-2. SID-1 and MST-1 are both regulated by the upstream SIN kinase CDC-7, yet in an opposite manner. Aberrant cortical actomyosin rings are formed in Δmst-1, which resulted in mis-positioned septa and irregular spirals, indicating that MST-1-dependent regulation of the SIN is required for proper formation and constriction of the septal actomyosin ring. However, MST-1 also interacts with several components of the MOR network and modulates MOR activity at multiple levels. MST-1 functions as promiscuous enzyme and also activates the MOR effector kinase COT-1 through hydrophobic motif phosphorylation. In addition, MST-1 physically interacts with the MOR kinase POD-6, and dimerization of both proteins inactivates the GC kinase hetero-complex. These data specify an antagonistic relationship between the SIN and MOR during septum formation in the filamentous ascomycete model Neurospora crassa that is, at least in part, coordinated through the GC kinase MST-1. The similarity of the SIN and MOR pathways to the animal Hippo and Ndr pathways, respectively, suggests that intensive cross-communication between distinct NDR kinase modules may also be relevant for the homologous NDR kinases of higher eukaryotes. Cytokinesis is a fundamental cellular process essential for cell proliferation of uni- and multicellular organisms. The molecular pathways that regulate cytokinesis are highly complex and involve a large number of components that form elaborate interactive networks. The fungal septation initiation network (SIN) functions as tripartite kinase cascade that connects cell cycle progression with the control of cell division. Mis-regulation of the homologous Hippo pathway in animals results in excessive proliferation and formation of tumors, underscoring the conservation and importance of these kinase networks. A second morphogenesis (MOR) pathway involves homologous components and is controlling cell polarity in fungi and higher eukaryotes. Here we show that the promiscuous functioning Ste20-related kinase MST-1 has a dual role in regulating SIN and MOR network function. Moreover, SIN and MOR coordination through MST-1 can be achieved in an enzyme-independent manner through hetero-dimerization of germinal centre kinases, providing an additional level for activity regulation of signaling networks that is not dependent on phosphate transfer. Given the functional conservation of NDR kinase signaling modules and their regulation, our work may define general mechanisms by which NDR kinase pathway are coordinated in fungi and higher eukaryotes.
Collapse
|
25
|
De Souza CP, Hashmi SB, Osmani AH, Osmani SA. Application of a new dual localization-affinity purification tag reveals novel aspects of protein kinase biology in Aspergillus nidulans. PLoS One 2014; 9:e90911. [PMID: 24599037 PMCID: PMC3944740 DOI: 10.1371/journal.pone.0090911] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Accepted: 02/04/2014] [Indexed: 12/22/2022] Open
Abstract
Filamentous fungi occupy critical environmental niches and have numerous beneficial industrial applications but devastating effects as pathogens and agents of food spoilage. As regulators of essentially all biological processes protein kinases have been intensively studied but how they regulate the often unique biology of filamentous fungi is not completely understood. Significant understanding of filamentous fungal biology has come from the study of the model organism Aspergillus nidulans using a combination of molecular genetics, biochemistry, cell biology and genomic approaches. Here we describe dual localization-affinity purification (DLAP) tags enabling endogenous N or C-terminal protein tagging for localization and biochemical studies in A. nidulans. To establish DLAP tag utility we endogenously tagged 17 protein kinases for analysis by live cell imaging and affinity purification. Proteomic analysis of purifications by mass spectrometry confirmed association of the CotA and NimXCdk1 kinases with known binding partners and verified a predicted interaction of the SldABub1/R1 spindle assembly checkpoint kinase with SldBBub3. We demonstrate that the single TOR kinase of A. nidulans locates to vacuoles and vesicles, suggesting that the function of endomembranes as major TOR cellular hubs is conserved in filamentous fungi. Comparative analysis revealed 7 kinases with mitotic specific locations including An-Cdc7 which unexpectedly located to mitotic spindle pole bodies (SPBs), the first such localization described for this family of DNA replication kinases. We show that the SepH septation kinase locates to SPBs specifically in the basal region of apical cells in a biphasic manner during mitosis and again during septation. This results in gradients of SepH between G1 SPBs which shift along hyphae as each septum forms. We propose that SepH regulates the septation initiation network (SIN) specifically at SPBs in the basal region of G1 cells and that localized gradients of SIN activity promote asymmetric septation.
Collapse
Affiliation(s)
- Colin P. De Souza
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, United States of America
| | - Shahr B. Hashmi
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, United States of America
| | - Aysha H. Osmani
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, United States of America
| | - Stephen A. Osmani
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, United States of America
- * E-mail:
| |
Collapse
|
26
|
Heilig Y, Schmitt K, Seiler S. Phospho-regulation of the Neurospora crassa septation initiation network. PLoS One 2013; 8:e79464. [PMID: 24205386 PMCID: PMC3804505 DOI: 10.1371/journal.pone.0079464] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2013] [Accepted: 09/28/2013] [Indexed: 01/04/2023] Open
Abstract
Proper cell division is essential for growth and development of uni- and multicellular organisms. The fungal septation initiation network (SIN) functions as kinase cascade that connects cell cycle progression with the initiation of cytokinesis. Miss-regulation of the homologous Hippo pathway in animals results in excessive cell proliferation and formation of tumors, underscoring the conservation of both pathways. How SIN proteins interact and transmit signals through the cascade is only beginning to be understood. Moreover, our understanding of septum formation and its regulation in filamentous fungi, which represent the vast majority of the fungal kingdom, is highly fragmentary. We determined that a tripartite kinase cascade, consisting of CDC-7, SID-1 and DBF-2, together with their regulatory subunits CDC-14 and MOB-1, is important for septum formation in the model mold Neurospora crassa. DBF-2 activity and septum formation requires auto-phosphorylation at Ser499 within the activation segment and phosphorylation of Thr671 in the hydrophobic motif by SID-1. Moreover, SID-1-stimulated DBF-2 activity is further enhanced by CDC-7, supporting a stepwise activation mechanism of the tripartite SIN kinase cascade in fungi. However, in contrast to the situation described for unicellular yeasts, the localization of the entire SIN cascade to spindle pole bodies is constitutive and cell cycle independent. Moreover, all SIN proteins except CDC-7 form cortical rings prior to septum initiation and localize to constricting septa. Thus, SIN localization and activity regulation significantly differs in unicellular versus syncytial ascomycete fungi.
Collapse
Affiliation(s)
- Yvonne Heilig
- Institute for Biology II – Molecular Plant Physiology, Albert-Ludwigs University Freiburg, Freiburg, Germany
| | - Kerstin Schmitt
- Institute for Microbiology and Genetics, University of Goettingen, Goettingen, Germany
| | - Stephan Seiler
- Institute for Biology II – Molecular Plant Physiology, Albert-Ludwigs University Freiburg, Freiburg, Germany
- Freiburg Institute for Advanced Studies (FRIAS), Albert-Ludwigs University Freiburg, Freiburg, Germany
- * E-mail:
| |
Collapse
|
27
|
|
28
|
Abstract
The filamentous fungi are an ecologically important group of organisms which also have important industrial applications but devastating effects as pathogens and agents of food spoilage. Protein kinases have been implicated in the regulation of virtually all biological processes but how they regulate filamentous fungal specific processes is not understood. The filamentous fungus Aspergillus nidulans has long been utilized as a powerful molecular genetic system and recent technical advances have made systematic approaches to study large gene sets possible. To enhance A. nidulans functional genomics we have created gene deletion constructs for 9851 genes representing 93.3% of the encoding genome. To illustrate the utility of these constructs, and advance the understanding of fungal kinases, we have systematically generated deletion strains for 128 A. nidulans kinases including expanded groups of 15 histidine kinases, 7 SRPK (serine-arginine protein kinases) kinases and an interesting group of 11 filamentous fungal specific kinases. We defined the terminal phenotype of 23 of the 25 essential kinases by heterokaryon rescue and identified phenotypes for 43 of the 103 non-essential kinases. Uncovered phenotypes ranged from almost no growth for a small number of essential kinases implicated in processes such as ribosomal biosynthesis, to conditional defects in response to cellular stresses. The data provide experimental evidence that previously uncharacterized kinases function in the septation initiation network, the cell wall integrity and the morphogenesis Orb6 kinase signaling pathways, as well as in pathways regulating vesicular trafficking, sexual development and secondary metabolism. Finally, we identify ChkC as a third effector kinase functioning in the cellular response to genotoxic stress. The identification of many previously unknown functions for kinases through the functional analysis of the A. nidulans kinome illustrates the utility of the A. nidulans gene deletion constructs.
Collapse
|
29
|
|
30
|
Zhong G, Wei W, Guan Q, Ma Z, Wei H, Xu X, Zhang S, Lu L. Phosphoribosyl pyrophosphate synthetase, as a suppressor of thesepHmutation inAspergillus nidulans, is required for the proper timing of septation. Mol Microbiol 2012; 86:894-907. [DOI: 10.1111/mmi.12026] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/29/2012] [Indexed: 11/30/2022]
Affiliation(s)
- Guowei Zhong
- Jiangsu Key Laboratory for Microbes and Functional Genomics; Jiangsu Engineering and Technology Research Center for Microbiology; College of Life Sciences; Nanjing Normal University; Nanjing; 210046; China
| | - Wenfan Wei
- Jiangsu Key Laboratory for Microbes and Functional Genomics; Jiangsu Engineering and Technology Research Center for Microbiology; College of Life Sciences; Nanjing Normal University; Nanjing; 210046; China
| | - Qi Guan
- Jiangsu Key Laboratory for Microbes and Functional Genomics; Jiangsu Engineering and Technology Research Center for Microbiology; College of Life Sciences; Nanjing Normal University; Nanjing; 210046; China
| | - Zhaofei Ma
- Jiangsu Key Laboratory for Microbes and Functional Genomics; Jiangsu Engineering and Technology Research Center for Microbiology; College of Life Sciences; Nanjing Normal University; Nanjing; 210046; China
| | - Hua Wei
- Jiangsu Key Laboratory for Microbes and Functional Genomics; Jiangsu Engineering and Technology Research Center for Microbiology; College of Life Sciences; Nanjing Normal University; Nanjing; 210046; China
| | - Xushi Xu
- Jiangsu Key Laboratory for Microbes and Functional Genomics; Jiangsu Engineering and Technology Research Center for Microbiology; College of Life Sciences; Nanjing Normal University; Nanjing; 210046; China
| | - Shizhu Zhang
- Jiangsu Key Laboratory for Microbes and Functional Genomics; Jiangsu Engineering and Technology Research Center for Microbiology; College of Life Sciences; Nanjing Normal University; Nanjing; 210046; China
| | - Ling Lu
- Jiangsu Key Laboratory for Microbes and Functional Genomics; Jiangsu Engineering and Technology Research Center for Microbiology; College of Life Sciences; Nanjing Normal University; Nanjing; 210046; China
| |
Collapse
|
31
|
Johnson AE, McCollum D, Gould KL. Polar opposites: Fine-tuning cytokinesis through SIN asymmetry. Cytoskeleton (Hoboken) 2012; 69:686-99. [PMID: 22786806 PMCID: PMC3478943 DOI: 10.1002/cm.21044] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Accepted: 06/04/2012] [Indexed: 01/10/2023]
Abstract
Mitotic exit and cell division must be spatially and temporally integrated to facilitate equal division of genetic material between daughter cells. In the fission yeast, Schizosaccharomyces pombe, a spindle pole body (SPB) localized signaling cascade termed the septation initiation network (SIN) couples mitotic exit with cytokinesis. The SIN is controlled at many levels to ensure that cytokinesis is executed once per cell cycle and only after cells segregate their DNA. An interesting facet of the SIN is that its activity is asymmetric on the two SPBs during anaphase; however, how and why the SIN is asymmetric has remained elusive. Many key factors controlling SIN asymmetry have now been identified, shedding light on the significance of SIN asymmetry in regulating cytokinesis. In this review, we highlight recent advances in our understanding of SIN regulation, with an emphasis on how SIN asymmetry is achieved and how this aspect of SIN regulation fine-tunes cytokinesis.
Collapse
Affiliation(s)
- Alyssa E Johnson
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, Tennessee, USA
| | | | | |
Collapse
|
32
|
Richthammer C, Enseleit M, Sanchez-Leon E, März S, Heilig Y, Riquelme M, Seiler S. RHO1 and RHO2 share partially overlapping functions in the regulation of cell wall integrity and hyphal polarity in Neurospora crassa. Mol Microbiol 2012; 85:716-33. [DOI: 10.1111/j.1365-2958.2012.08133.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
|
33
|
Taheri-Talesh N, Xiong Y, Oakley BR. The functions of myosin II and myosin V homologs in tip growth and septation in Aspergillus nidulans. PLoS One 2012; 7:e31218. [PMID: 22359575 PMCID: PMC3281053 DOI: 10.1371/journal.pone.0031218] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2011] [Accepted: 01/04/2012] [Indexed: 01/05/2023] Open
Abstract
Because of the industrial and medical importance of members of the fungal genus Aspergillus, there is considerable interest in the functions of cytoskeletal components in growth and secretion in these organisms. We have analyzed the genome of Aspergillus nidulans and found that there are two previously unstudied myosin genes, a myosin II homolog, myoB (product = MyoB) and a myosin V homolog, myoE (product = MyoE). Deletions of either cause significant growth defects. MyoB localizes in strings that coalesce into contractile rings at forming septa. It is critical for septation and normal deposition of chitin but not for hyphal extension. MyoE localizes to the Spitzenkörper and to moving puncta in the cytoplasm. Time-lapse imaging of SynA, a v-SNARE, reveals that in myoE deletion strains vesicles no longer localize to the Spitzenkörper. Tip morphology is slightly abnormal and branching occurs more frequently than in controls. Tip extension is slower than in controls, but because hyphal diameter is greater, growth (increase in volume/time) is only slightly reduced. Concentration of vesicles into the Spitzenkörper before incorporation into the plasma membrane is, thus, not required for hyphal growth but facilitates faster tip extension and a more normal hyphal shape.
Collapse
Affiliation(s)
- Naimeh Taheri-Talesh
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas, United States of America
| | - Yi Xiong
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, United States of America
| | - Berl R. Oakley
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas, United States of America
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, United States of America
- * E-mail:
| |
Collapse
|
34
|
Tales of RAM and MOR: NDR kinase signaling in fungal morphogenesis. Curr Opin Microbiol 2010; 13:663-71. [DOI: 10.1016/j.mib.2010.08.010] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2010] [Accepted: 08/30/2010] [Indexed: 02/04/2023]
|
35
|
Seiler S, Justa-Schuch D. Conserved components, but distinct mechanisms for the placement and assembly of the cell division machinery in unicellular and filamentous ascomycetes. Mol Microbiol 2010; 78:1058-76. [PMID: 21091496 DOI: 10.1111/j.1365-2958.2010.07392.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Cytokinesis is essential for cell proliferation, yet its molecular description is challenging, because >100 conserved proteins must be spatially and temporally co-ordinated. Despite the high importance of a tight co-ordination of cytokinesis with chromosome and organelle segregation, the mechanism for determining the cell division plane is one of the least conserved aspects of cytokinesis in eukaryotic cells. Budding and fission yeast have developed fundamentally distinct mechanisms to ensure proper nuclear segregation. The extent to which these pathways are conserved in multicellular fungi remains unknown. Recent progress indicates common components, but different mechanisms that are required for proper selection of the septation site in the different groups of Ascomycota. Cortical cues are used in yeast- and filament-forming species of the Saccharomycotina clade that are established at the incipient bud site or the hyphal tip respectively. In contrast, septum formation in the filament-forming Pezizomycotina species Aspergillus nidulans and Neurospora crassa seems more closely related to the fission yeast programme in that they may combine mitotic signals with a cell end-based marker system and Rho GTPase signalling. Thus, significant differences in the use and connection of conserved signalling modules become apparent that reflect the phylogenetic relationship of the analysed models.
Collapse
Affiliation(s)
- Stephan Seiler
- Institut für Mikrobiologie und Genetik, Universität Göttingen, Grisebachstr. 8, D-37077 Göttingen, Germany.
| | | |
Collapse
|
36
|
Justa-Schuch D, Heilig Y, Richthammer C, Seiler S. Septum formation is regulated by the RHO4-specific exchange factors BUD3 and RGF3 and by the landmark protein BUD4 in Neurospora crassa. Mol Microbiol 2010; 76:220-35. [PMID: 20199606 DOI: 10.1111/j.1365-2958.2010.07093.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Rho GTPases have multiple, yet poorly defined functions during cytokinesis. By screening a Neurospora crassa knock-out collection for Rho guanine nucleotide exchange factor (GEF) mutants that phenocopy rho-4 defects (i.e. lack of septa, slow growth, abnormal branching and cytoplasmic leakage), we identified two strains defective in homologues of Bud3p and Rgf3 of budding and fission yeast respectively. The function of these proteins as RHO4-specific GEFs was determined by in vitro assays. In vivo microscopy suggested that the two GEFs and their target GTPase act as two independent modules during the selection of the septation site and the actual septation process. Furthermore, we determined that the N. crassa homologue of the anillinrelated protein BUD4 is required for septum initiation and that its deficiency leads to typical rho4 defects. Localization of BUD4 as a cortical ring prior to septation initiation was independent of functional BUD3 or RGF3. These data position BUD4 upstream of both RHO4 functions in the septation process and make BUD4 a prime candidate for a cortical marker protein involved in the selection of future septation sites. The persistence of both BUD proteins and of RHO4 at the septal pore suggests additional functions of these proteins at mature septa.
Collapse
Affiliation(s)
- Daniela Justa-Schuch
- Institut für Mikrobiologie und Genetik, Universität Göttingen, Göttingen, Germany
| | | | | | | |
Collapse
|
37
|
Abstract
The ability of fungi to generate polarized cells with a variety of shapes likely reflects precise temporal and spatial control over the formation of polarity axes. The bud site selection system of Saccharomyces cerevisiae represents the best-understood example of such a morphogenetic regulatory system. However, the extent to which this system is conserved in the highly polarized filamentous fungi remains unknown. Here, we describe the functional characterization and localization of the Aspergillus nidulans homolog of the axial bud site marker Bud3. Our results show that AnBud3 is not required for polarized hyphal growth per se, but is involved in septum formation. In particular, our genetic and biochemical evidence implicates AnBud3 as a guanine nucleotide exchange factor for the GTPase Rho4. Additional results suggest that the AnBud3-Rho4 module acts downstream of the septation initiation network to mediate recruitment of the formin SepA to the site of contractile actin ring assembly. Our observations provide new insight into the signaling pathways that regulate septum formation in filamentous fungi.
Collapse
|
38
|
|