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Aerial Hypha

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Marie A Elliot – One of the best experts on this subject based on the ideXlab platform.

  • Dual amyloid domains promote differential functioning of the chaplin proteins during Streptomyces Aerial morphogenesis
    Proceedings of the National Academy of Sciences of the United States of America, 2011
    Co-Authors: David S Capstick, Ahmad Jomaa, Chistopher Hanke, Joaquin Ortega, Marie A Elliot

    Abstract:

    The chaplin proteins are functional amyloids found in the filamentous Streptomyces bacteria. These secreted proteins are required for the Aerial development of Streptomyces coelicolor, and contribute to an intricate rodlet ultrastructure that decorates the surfaces of Aerial Hyphae and spores. S. coelicolor encodes eight chaplin proteins. Previous studies have revealed that only three of these proteins (ChpC, ChpE, and ChpH) are necessary for promoting Aerial development, and of these three, ChpH is the primary developmental determinant. Here, we show that the model chaplin, ChpH, contains two amyloidogenic domains: one in the N terminus and one in the C terminus of the mature protein. These domains have different polymerization properties as determined using fluorescence spectroscopy, secondary structure analyses, and electron microscopy. We coupled these in vitro assays with in vivo genetic studies to probe the connection between ChpH amyloidogenesis and its biological function. Using mutational analyses, we demonstrated that both N- and C-terminal amyloid domains of ChpH were required for promoting Aerial Hypha formation, while the N-terminal domain was dispensable for assembly of the rodlet ultrastructure. These results suggest that there is a functional differentiation of the dual amyloid domains in the chaplin proteins.

  • function and redundancy of the chaplin cell surface proteins in Aerial Hypha formation rodlet assembly and viability in streptomyces coelicolor
    Journal of Bacteriology, 2008
    Co-Authors: Christina Di Berardo, Marie A Elliot, David S Capstick, Maureen J Bibb, Kim Findlay, Mark J Buttner

    Abstract:

    The chaplins are a family of eight secreted proteins that are critical for raising Aerial Hyphae in Streptomyces coelicolor. These eight chaplins can be separated into two main groups: the long chaplins (ChpA to -C) and the short chaplins (ChpD to -H). The short chaplins can be further subdivided on the basis of their abilities to form intramolecular disulfide bonds: ChpD, -F, -G, and -H contain two Cys residues, while ChpE has none. A “minimal chaplin strain” containing only chpC, chpE, and chpH was constructed and was found to raise a substantial Aerial mycelium. This strain was used to examine the roles of specific chaplins. Within this strain, the Cys-containing ChpH was identified as the major polymerization unit contributing to Aerial Hypha formation and assembly of an intricate rodlet ultrastructure on the Aerial surfaces, and the two Cys residues were determined to be critical for its function. ChpC augmented Aerial Hypha formation and rodlet assembly, likely by anchoring the short chaplins to the cell surface, while ChpE was essential for the viability of wild-type S. coelicolor. Interestingly, the lethal effects of a chpE null mutation could be suppressed by the loss of the other chaplins, the inactivation of the twin arginine translocation (Tat) secretion pathway, or the loss of the rodlins. The gram-positive soil-dwelling streptomycetes have a mycelial growth habit that culminates in the formation of dormant exospores that permit survival under adverse environmental conditions (13). Germinating spores produce one or more germ tubes that grow by tip extension to form a network of branching vegetative Hyphae known as the vegetative mycelium. Antibiotics (and other secondary metabolites) are produced within the vegetative Hyphae, and from this vegetative mycelial network emerge specialized reproductive structures known as Aerial Hyphae. These Aerial Hyphae undergo a number of maturation steps, including a synchronous round of cell division, to differentiate into chains of unigenomic spores. The transition from vegetative growth in an aqueous environment to the emergence of Aerial Hyphae into the air requires significant adaptation of the cell surface: the surfaces of vegetative Hyphae are hydrophilic, while those of Aerial Hyphae and spores are extremely hydrophobic. Three groups of proteins are known to be involved in the modulation of cell surfaces during Aerial Hypha formation in Streptomyces coelicolor: the chaplins, the rodlins, and SapB (reviewed in references 8, 16, and 36). These proteins are thought to collectively function like the fungal hydrophobins, which are important for surface modulation and Aerial growth in the filamentous fungi (reviewed in reference 37). Hydrophobins are small secreted proteins that assemble

  • 24 Multicellular Development in Streptomyces
    Myxobacteria, 2008
    Co-Authors: Marie A Elliot, Mark J Buttner, Justin R. Nodwell

    Abstract:

    The colony structure and life cycle of the grampositive, soil-dwelling bacterium Streptomyces coelicolor provide a fascinating exception to the view of bacteria as simple unicellular microorganisms. Mutations in genes involved in morphogenesis alter colony appearance but do not usually compromise viability. The majority of genes identified as being important for Aerial Hypha formation encode regulatory proteins; however, recent work has resulted in the characterization of two classes of structural molecules that are necessary for Aerial development: the SapB surfactant peptide (specified by the ram gene cluster) and eight chaplin proteins (ChpA through H). It has been found that while Streptomyces has many of the conventional genes that are necessary for these processes to occur, Streptomyces cells are organized very differently from other bacteria and these differences are highly relevant to colony development and spore formation. In Streptomyces, however, DivIVA is an essential protein that does not seem to be associated with cell division but rather is crucial for coordinating cell wall growth. The basic mechanism of Z-ring formation appears to be shared between S. coelicolor and other prokaryotes; however, there are important differences in how Streptomyces employs and executes cell division. Streptomyces has no homologues of the Bacillus subtilis or Escherichia coli MinC or MinD proteins and uses its DivIVA for functions apparently unrelated to cell division.

Klas Flärdh – One of the best experts on this subject based on the ideXlab platform.

  • c-di-GMP signalling and the regulation of developmental transitions in streptomycetes
    Nature Reviews Microbiology, 2015
    Co-Authors: Matthew J. Bush, Klas Flärdh, Natalia Tschowri, Susan Schlimpert, Mark J Buttner

    Abstract:

    The complex life cycle of streptomycetes involves two distinct filamentous cell forms: the growing (or vegetative) Hyphae and the reproductive (or Aerial) Hyphae, which differentiate into long chains of spores. Until recently, little was known about the signalling pathways that regulate the developmental transitions leading to sporulation. In this Review, we discuss important new insights into these pathways that have led to the emergence of a coherent regulatory network, focusing on the erection of Aerial Hyphae and the synchronous cell division event that produces dozens of unigenomic spores. In particular, we highlight the role of cyclic di-GMP (c-di-GMP) in controlling the initiation of development, and the role of the master regulator BldD in mediating c-di-GMP signalling. Streptomycetes have a complex life cycle that involves several regulated developmental transitions. In this Review, Buttner and colleagues discuss the factors that have recently been shown to regulate these transitions, including a novel role for the second messenger c-di-GMP. The erection of reproductive Aerial Hyphae and sporulation septation are the two most striking developmental transitions in the life cycle of filamentous streptomycete bacteria. Recent advances in our understanding of how these developmental transitions are controlled have revealed a coherent regulatory network that now allows us to draw direct connections from specific regulators to the cell biological processes associated with major morphogenetic events. BldD has emerged as a master regulator that oversees the entire regulatory cascade through the repression of a global regulon of ∼170 sporulation genes during vegetative growth. This regulon includes almost all of the genes of the core transcriptional regulatory cascade, as well as genes encoding critical components of the cell division and chromosome segregation machineries required for sporulation. BldD-mediated repression requires the second messenger cyclic di-GMP (c-di-GMP), which binds to BldD as a co-repressor to control the decision to initiate the developmental programme. A high level of c-di-GMP blocks the formation of Aerial Hyphae and spores until a drop in the level of c-di-GMP relieves BldD-mediated repression of the regulatory cascade. To allow Aerial Hyphae to emerge into the air, streptomycetes cover these structures in an extremely hydrophobic sheath, composed of two families of proteins called the chaplins and rodlins. The developmental regulator sigma factor σ^BldN is responsible for activating the expression of all of the chaplin and rodlin genes; σ^BldN is in turn regulated by the transmembrane anti-sigma factor RsbN. Chromosome replication is upregulated in each Aerial Hypha before sporulation septation, leading to a single, long ‘sporogenic cell’ containing 50–100 copies of the chromosome. The developmental regulator AdpA, long known to function as a conventional transcription factor for a large regulon of sporulation genes, also controls developmental chromosome replication by binding to two sites in the 5′ region of the origin of replication ( oriC ). Transcriptional regulation of differentiation is common throughout all living systems, but an extremely unusual feature of sporulation in streptomycetes is that these bacteria have appropriated the only tRNA that can translate TTA codons (the BldA tRNA) for a very specific role as a developmental regulator. This tRNA forms part of a unique positive feedback loop in which AdpA activates transcription of bldA and the BldA tRNA is in turn required for expression of adpA , which has a TTA codon. The cessation of Aerial growth is tightly coordinated with the initiation of sporulation septation, and both these processes are controlled by the transcription factors WhiA and WhiB. During this transition, WhiA directly represses the transcription of filP , encoding a protein that forms part of the polarisome that directs cell wall synthesis at the growing Hyphal tip, and directly activates many key components of the sporulation septation machinery, including ftsK, ftsW and ftsZ . Heterodimer formation between two orphan, atypical response regulators, BldM and WhiI, activates genes required for spore maturation. Although BldM functions as a homodimer during early development, WhiI functions solely as an auxiliary protein to modulate BldM binding specificity and there is no set of genes regulated by a WhiI homodimer.

  • Identification of new developmentally regulated genes involved in Streptomyces coelicolorsporulation
    BMC Microbiology, 2013
    Co-Authors: Paola Salerno, Jessica Persson, Giselda Bucca, Emma Laing, Nora Ausmees, Colin P Smith, Klas Flärdh

    Abstract:

    Background The sporulation of Aerial Hyphae of Streptomyces coelicolor is a complex developmental process. Only a limited number of the genes involved in this intriguing morphological differentiation programme are known, including some key regulatory genes. The aim of this study was to expand our knowledge of the gene repertoire involved in S. coelicolor sporulation. Results We report a DNA microarray-based investigation of developmentally controlled gene expression in S. coelicolor . By comparing global transcription patterns of the wild-type parent and two mutants lacking key regulators of Aerial Hyphal sporulation, we found a total of 114 genes that had significantly different expression in at least one of the two mutants compared to the wild-type during sporulation. A whiA mutant showed the largest effects on gene expression, while only a few genes were specifically affected by whiH mutation. Seven new sporulation loci were investigated in more detail with respect to expression patterns and mutant phenotypes. These included SCO7449-7451 that affect spore pigment biogenesis; SCO1773-1774 that encode an L-alanine dehydrogenase and a regulator-like protein and are required for maturation of spores; SCO3857 that encodes a protein highly similar to a nosiheptide resistance regulator and affects spore maturation; and four additional loci ( SCO4421 , SCO4157 , SCO0934 , SCO1195 ) that show developmental regulation but no overt mutant phenotype. Furthermore, we describe a new promoter-probe vector that takes advantage of the red fluorescent protein mCherry as a reporter of cell type-specific promoter activity. Conclusion Aerial Hyphal sporulation in S. coelicolor is a technically challenging process for global transcriptomic investigations since it occurs only as a small fraction of the colony biomass and is not highly synchronized. Here we show that by comparing a wild-type to mutants lacking regulators that are specifically affecting processes in Aerial Hypha, it is possible to identify previously unknown genes with important roles in sporulation. The transcriptomic data reported here should also serve as a basis for identification of further developmentally important genes in future functional studies.

  • Identification of new developmentally regulated genes involved in Streptomyces coelicolor sporulation.
    BMC Microbiology, 2013
    Co-Authors: Paola Salerno, Jessica Persson, Giselda Bucca, Emma Laing, Nora Ausmees, Colin P Smith, Klas Flärdh

    Abstract:

    Background: The sporulation of Aerial Hyphae of Streptomyces coelicolor is a complex developmental process. Only a limited number of the genes involved in this intriguing morphological differentiation programme are known, including some key regulatory genes. The aim of this study was to expand our knowledge of the gene repertoire involved in S. coelicolor sporulation. Results: We report a DNA microarray-based investigation of developmentally controlled gene expression in S. coelicolor. By comparing global transcription patterns of the wild-type parent and two mutants lacking key regulators of Aerial Hyphal sporulation, we found a total of 114 genes that had significantly different expression in at least one of the two mutants compared to the wild-type during sporulation. A whiA mutant showed the largest effects on gene expression, while only a few genes were specifically affected by whiH mutation. Seven new sporulation loci were investigated in more detail with respect to expression patterns and mutant phenotypes. These included SCO7449-7451 that affect spore pigment biogenesis; SCO1773-1774 that encode an L-alanine dehydrogenase and a regulator-like protein and are required for maturation of spores; SCO3857 that encodes a protein highly similar to a nosiheptide resistance regulator and affects spore maturation; and four additional loci (SCO4421, SCO4157, SCO0934, SCO1195) that show developmental regulation but no overt mutant phenotype. Furthermore, we describe a new promoter-probe vector that takes advantage of the red fluorescent protein mCherry as a reporter of cell type-specific promoter activity. Conclusion: Aerial Hyphal sporulation in S. coelicolor is a technically challenging process for global transcriptomic investigations since it occurs only as a small fraction of the colony biomass and is not highly synchronized. Here we show that by comparing a wild-type to mutants lacking regulators that are specifically affecting processes in Aerial Hypha, it is possible to identify previously unknown genes with important roles in sporulation. The transcriptomic data reported here should also serve as a basis for identification of further developmentally important genes in future functional studies.

Mark J Buttner – One of the best experts on this subject based on the ideXlab platform.

  • c-di-GMP signalling and the regulation of developmental transitions in streptomycetes
    Nature Reviews Microbiology, 2015
    Co-Authors: Matthew J. Bush, Klas Flärdh, Natalia Tschowri, Susan Schlimpert, Mark J Buttner

    Abstract:

    The complex life cycle of streptomycetes involves two distinct filamentous cell forms: the growing (or vegetative) Hyphae and the reproductive (or Aerial) Hyphae, which differentiate into long chains of spores. Until recently, little was known about the signalling pathways that regulate the developmental transitions leading to sporulation. In this Review, we discuss important new insights into these pathways that have led to the emergence of a coherent regulatory network, focusing on the erection of Aerial Hyphae and the synchronous cell division event that produces dozens of unigenomic spores. In particular, we highlight the role of cyclic di-GMP (c-di-GMP) in controlling the initiation of development, and the role of the master regulator BldD in mediating c-di-GMP signalling. Streptomycetes have a complex life cycle that involves several regulated developmental transitions. In this Review, Buttner and colleagues discuss the factors that have recently been shown to regulate these transitions, including a novel role for the second messenger c-di-GMP. The erection of reproductive Aerial Hyphae and sporulation septation are the two most striking developmental transitions in the life cycle of filamentous streptomycete bacteria. Recent advances in our understanding of how these developmental transitions are controlled have revealed a coherent regulatory network that now allows us to draw direct connections from specific regulators to the cell biological processes associated with major morphogenetic events. BldD has emerged as a master regulator that oversees the entire regulatory cascade through the repression of a global regulon of ∼170 sporulation genes during vegetative growth. This regulon includes almost all of the genes of the core transcriptional regulatory cascade, as well as genes encoding critical components of the cell division and chromosome segregation machineries required for sporulation. BldD-mediated repression requires the second messenger cyclic di-GMP (c-di-GMP), which binds to BldD as a co-repressor to control the decision to initiate the developmental programme. A high level of c-di-GMP blocks the formation of Aerial Hyphae and spores until a drop in the level of c-di-GMP relieves BldD-mediated repression of the regulatory cascade. To allow Aerial Hyphae to emerge into the air, streptomycetes cover these structures in an extremely hydrophobic sheath, composed of two families of proteins called the chaplins and rodlins. The developmental regulator sigma factor σ^BldN is responsible for activating the expression of all of the chaplin and rodlin genes; σ^BldN is in turn regulated by the transmembrane anti-sigma factor RsbN. Chromosome replication is upregulated in each Aerial Hypha before sporulation septation, leading to a single, long ‘sporogenic cell’ containing 50–100 copies of the chromosome. The developmental regulator AdpA, long known to function as a conventional transcription factor for a large regulon of sporulation genes, also controls developmental chromosome replication by binding to two sites in the 5′ region of the origin of replication ( oriC ). Transcriptional regulation of differentiation is common throughout all living systems, but an extremely unusual feature of sporulation in streptomycetes is that these bacteria have appropriated the only tRNA that can translate TTA codons (the BldA tRNA) for a very specific role as a developmental regulator. This tRNA forms part of a unique positive feedback loop in which AdpA activates transcription of bldA and the BldA tRNA is in turn required for expression of adpA , which has a TTA codon. The cessation of Aerial growth is tightly coordinated with the initiation of sporulation septation, and both these processes are controlled by the transcription factors WhiA and WhiB. During this transition, WhiA directly represses the transcription of filP , encoding a protein that forms part of the polarisome that directs cell wall synthesis at the growing Hyphal tip, and directly activates many key components of the sporulation septation machinery, including ftsK, ftsW and ftsZ . Heterodimer formation between two orphan, atypical response regulators, BldM and WhiI, activates genes required for spore maturation. Although BldM functions as a homodimer during early development, WhiI functions solely as an auxiliary protein to modulate BldM binding specificity and there is no set of genes regulated by a WhiI homodimer.

  • function and redundancy of the chaplin cell surface proteins in Aerial Hypha formation rodlet assembly and viability in streptomyces coelicolor
    Journal of Bacteriology, 2008
    Co-Authors: Christina Di Berardo, Marie A Elliot, David S Capstick, Maureen J Bibb, Kim Findlay, Mark J Buttner

    Abstract:

    The chaplins are a family of eight secreted proteins that are critical for raising Aerial Hyphae in Streptomyces coelicolor. These eight chaplins can be separated into two main groups: the long chaplins (ChpA to -C) and the short chaplins (ChpD to -H). The short chaplins can be further subdivided on the basis of their abilities to form intramolecular disulfide bonds: ChpD, -F, -G, and -H contain two Cys residues, while ChpE has none. A “minimal chaplin strain” containing only chpC, chpE, and chpH was constructed and was found to raise a substantial Aerial mycelium. This strain was used to examine the roles of specific chaplins. Within this strain, the Cys-containing ChpH was identified as the major polymerization unit contributing to Aerial Hypha formation and assembly of an intricate rodlet ultrastructure on the Aerial surfaces, and the two Cys residues were determined to be critical for its function. ChpC augmented Aerial Hypha formation and rodlet assembly, likely by anchoring the short chaplins to the cell surface, while ChpE was essential for the viability of wild-type S. coelicolor. Interestingly, the lethal effects of a chpE null mutation could be suppressed by the loss of the other chaplins, the inactivation of the twin arginine translocation (Tat) secretion pathway, or the loss of the rodlins. The gram-positive soil-dwelling streptomycetes have a mycelial growth habit that culminates in the formation of dormant exospores that permit survival under adverse environmental conditions (13). Germinating spores produce one or more germ tubes that grow by tip extension to form a network of branching vegetative Hyphae known as the vegetative mycelium. Antibiotics (and other secondary metabolites) are produced within the vegetative Hyphae, and from this vegetative mycelial network emerge specialized reproductive structures known as Aerial Hyphae. These Aerial Hyphae undergo a number of maturation steps, including a synchronous round of cell division, to differentiate into chains of unigenomic spores. The transition from vegetative growth in an aqueous environment to the emergence of Aerial Hyphae into the air requires significant adaptation of the cell surface: the surfaces of vegetative Hyphae are hydrophilic, while those of Aerial Hyphae and spores are extremely hydrophobic. Three groups of proteins are known to be involved in the modulation of cell surfaces during Aerial Hypha formation in Streptomyces coelicolor: the chaplins, the rodlins, and SapB (reviewed in references 8, 16, and 36). These proteins are thought to collectively function like the fungal hydrophobins, which are important for surface modulation and Aerial growth in the filamentous fungi (reviewed in reference 37). Hydrophobins are small secreted proteins that assemble

  • 24 Multicellular Development in Streptomyces
    Myxobacteria, 2008
    Co-Authors: Marie A Elliot, Mark J Buttner, Justin R. Nodwell

    Abstract:

    The colony structure and life cycle of the grampositive, soil-dwelling bacterium Streptomyces coelicolor provide a fascinating exception to the view of bacteria as simple unicellular microorganisms. Mutations in genes involved in morphogenesis alter colony appearance but do not usually compromise viability. The majority of genes identified as being important for Aerial Hypha formation encode regulatory proteins; however, recent work has resulted in the characterization of two classes of structural molecules that are necessary for Aerial development: the SapB surfactant peptide (specified by the ram gene cluster) and eight chaplin proteins (ChpA through H). It has been found that while Streptomyces has many of the conventional genes that are necessary for these processes to occur, Streptomyces cells are organized very differently from other bacteria and these differences are highly relevant to colony development and spore formation. In Streptomyces, however, DivIVA is an essential protein that does not seem to be associated with cell division but rather is crucial for coordinating cell wall growth. The basic mechanism of Z-ring formation appears to be shared between S. coelicolor and other prokaryotes; however, there are important differences in how Streptomyces employs and executes cell division. Streptomyces has no homologues of the Bacillus subtilis or Escherichia coli MinC or MinD proteins and uses its DivIVA for functions apparently unrelated to cell division.