Evidence that asgB encodes a DNA-binding protein essential for growth and development of Myxococcus xanthus

Plamann, Lynda; Davis, John M.; Cantwell, Brian J.; Mayor, Jocelyne

doi:10.1128/jb.176.7.2013-2020.1994

Cited by 63 publications

(60 citation statements)

References 43 publications

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“…The A-signal, which is a mixture of amino acids and peptides (27,36), is thought to act as a cell density signal-an extracellular signal that allows M. xanthus to determine whether there is a sufficiently high concentration of cells present for successful formation of fruiting bodies (26). A DNA sequence analysis of asgB suggests that it encodes a DNA-binding protein, and the proposed function of AsgB is to alter gene expression in response to starvation, resulting in the production of extracellular A-signal (35). Because asgA and asgB mutants are defective in A-signal production and are blocked at the same early stage of development, it is reasonable to speculate that the products of these two genes are involved in a signal transduction pathway that leads to the production of extracellular A-signal.…”

Section: Discussionmentioning

confidence: 99%

“…The DNA sequence across the junction of the KpnI site immediately upstream of asgA was determined to verify that no sequences had been inserted or deleted during the construction or isolation of pDC01. Plasmid pDC01 was introduced into M. xanthus by electroporation (35). Quantitation of ␤-galactosidase during growth and development was performed as described by Kroos et al (22).…”

Section: Methodsmentioning

confidence: 99%

“…LaRossa et al (28) found that the asg mutants continue vegetative growth under conditions of phenylalanine limitation, which suggests that wild-type asg genes are required to respond to starvation conditions. A clue to the function of asgB was provided by an examination of its DNA sequence (35). The deduced 163-amino-acid sequence of AsgB contains a region similar to conserved region 4 of sigma factors.…”

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confidence: 99%

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The Myxococcus xanthus asgA gene encodes a novel signal transduction protein required for multicellular development

Plamann

Cantwell

et al. 1995

J Bacteriol

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The Myxococcus xanthus asgA gene is one of three known genes necessary for the production of extracellular A-signal, a cell density signal required early in fruiting body development. We determined the DNA sequence of asgA. The deduced 385-amino-acid sequence of AsgA was found to contain two domains: one homologous to the receiver domain of response regulators and the other homologous to the transmitter domain of histidine protein kinases. A kanamycin resistance (Km r ) gene was inserted at various positions within or near the asgA gene to determine the null phenotype. Those strains with the Km r gene inserted upstream or downstream of asgA are able to form fruiting bodies, while strains containing the Km r gene inserted within asgA fail to develop. The nature and location of the asgA476 mutation were determined. This mutation causes a leucine-to-proline substitution within a conserved stretch of hydrophobic residues in the N-terminal receiver domain. Cells containing the insertion within asgA and cells containing the asgA476 substitution have similar phenotypes with respect to development, colony color, and expression of an asg-dependent gene. An analysis of expression of a translational asgA-lacZ fusion confirms that asgA is expressed during growth and early development. Finally, we propose that AsgA functions within a signal transduction pathway that is required to sense starvation and to respond with the production of extracellular A-signal.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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confidence: 99%

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The Myxococcus xanthus asgA gene encodes a novel signal transduction protein required for multicellular development

Plamann

Cantwell

et al. 1995

J Bacteriol

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“…pTT1 contained a 2.6-kb BclI fragment from pRS415 (containing lacZ) cloned into the BamHI site in pBGS18. We introduced pTT1 into DK7825 (⍀4469 Tn5lac Tet r ) by electroporation (33) and selected Km r Tet r colonies on CTT agar plates. We confirmed the single-copy integration event at the Tn5lac ⍀4469 site by Southern blotting, using lacZ as the probe.…”

Section: Methodsmentioning

confidence: 99%

nsd, a Locus That Affects theMyxococcus xanthusCellular Response to Nutrient Concentration

2004

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Expression of the previously reported Tn5lac ⍀4469 insertion in Myxococcus xanthus cells is regulated by the starvation response. Interested in learning more about the starvation response, we cloned and sequenced the region containing the insertion. Our analysis shows that the gene fusion is located in an open reading frame that we have designated nsd (nutrient sensing/utilizing defective) and that its expression is driven by a 70 -like promoter. Sequence analysis of the nsd gene product provides no information on the potential structure or function of the encoded protein. In a further effort to learn about the role of nsd in the starvation response, we closely examined the phenotype of cells carrying the nsd::Tn5lac ⍀4469 mutation. Our analysis showed that these cells initiate development on medium that contains nutrients sufficient to sustain vegetative growth of wild-type cells. Furthermore, in liquid media these same nutrient concentrations elicit a severe impairment of growth of nsd cells. The data suggest that the nsd cells launch a starvation response when there are enough nutrients to prevent one. In support of this hypothesis, we found that, when grown in these nutrient concentrations, nsd cells accumulate guanosine tetraphosphate, the cellular starvation signal. Therefore, we propose that nsd is used by cells to respond to available nutrient levels.

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“…The asg genes map to three unlinked loci: asgA, asgB, and asgC (33). The DNA sequences of the asg genes indicate that they encode regulatory proteins required for Asignal production (8,48,50). The absence of any one of these regulators results in arrest at an early stage of development (17,38).…”

Section: Multicellular Development Of Myxococcus Xanthus Is Initiatedmentioning

confidence: 99%

Myxococcus xanthus sasS encodes a sensor histidine kinase required for early developmental gene expression

Yang

Kaplan

1997

J Bacteriol

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Initiation of Myxococcus xanthus multicellular development requires integration of information concerning the cells' nutrient status and density. A gain-of-function mutation, sasB7, that bypasses both the starvation and high cell density requirements for developmental expression of the 4521 reporter gene, maps to the sasS gene. The wild-type sasS gene was cloned and sequenced. This gene is predicted to encode a sensor histidine protein kinase that appears to be a key element in the transduction of starvation and cell density inputs. The sasS null mutants express 4521 at a basal level, form defective fruiting bodies, and exhibit reduced sporulation efficiencies. These data indicate that the wild-type sasS gene product functions as a positive regulator of 4521 expression and participates in M. xanthus development. The N terminus of SasS is predicted to contain two transmembrane domains that would locate the protein to the cytoplasmic membrane. The sasB7 mutation, an E139K missense mutation, maps to the predicted N-terminal periplasmic region. The C terminus of SasS contains all of the conserved residues typical of the sensor histidine protein kinases. SasS is predicted to be the sensor protein in a two-component system that integrates information required for M. xanthus developmental gene expression. Multicellular development of Myxococcus xanthus is initiatedby nutrient limitation and proceeds only if these gram-negative soil bacteria are at high density. More than 10 5 cells aggregate to form an organized mound, termed a fruiting body, inside of which the rod-shaped cells differentiate into environmentally resistant ovoid myxospores. This developmental program ensures the survival of the organism until nutrients are available and the spores can germinate (10, 11).M. xanthus cells sense their nutrient status and density by using two different signals. Nutrient limitation is sensed, at least in part, by a rise in intracellular guanosine penta-and tetraphosphate ([p]ppGpp) levels (55). Cell density is sensed through A signal, a specific subset of amino acids at an extracellular concentration greater than 10 M (36). The A signal is presumably generated when extracellular proteinases degrade the surface proteins of developing cells (35,49). If the cells are at a density greater than about 3 ϫ 10 8 /ml, apparently the concentration of extracellular amino acids and peptides exceeds the critical A-signal threshold concentration (36). The transduction of the starvation and A signals and integration of this information within the first 1 to 2 h of development allow the cells to determine if conditions are appropriate to proceed through the early stages of fruiting body development (15,26).The expression of one class of genes expressed during early development requires independent input from both starvation and A signals (4, 25). The best characterized member of this class is the gene 4521, whose expression is monitored by a Tn5 lac transcriptional fusion, ⍀4521 (31). In wild-type cells 1 to 2 h after starvation at high de...

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Evidence that asgB encodes a DNA-binding protein essential for growth and development of Myxococcus xanthus

Cited by 63 publications

References 43 publications

The Myxococcus xanthus asgA gene encodes a novel signal transduction protein required for multicellular development

The Myxococcus xanthus asgA gene encodes a novel signal transduction protein required for multicellular development

nsd, a Locus That Affects theMyxococcus xanthusCellular Response to Nutrient Concentration

Myxococcus xanthus sasS encodes a sensor histidine kinase required for early developmental gene expression

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