Initiation of the proximodistal axis in insect legs

Much of the cell-cell communication that controls assignment of cell fates during animal development appears to be mediated by extracellular signaling molecules. The formation of the proximodistal (P/D) axis of the legs of flies is controlled by at least two such molecules, a Wnt and a TGFbeta, encoded by the wingless (wg) and decapentaplegic (dpp) genes, respectively. The P/D axis appears to be initiated from the site where cells expressing wg are in close association with those expressing dpp. Support for this hypothesis comes from two sources: classical grafting experiments in cockroaches and ectopic protein expression in Drosophila.

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Defining the expression, production, and signaling roles of specialized metabolites during Bacillus subtilis differentiation

Journal of Bacteriology ◽

10.1128/jb.00337-21 ◽

2021 ◽

Author(s):

Alexi A. Schoenborn ◽

Sarah M. Yannarell ◽

E. Diane Wallace ◽

Haley Clapper ◽

Ilon C. Weinstein ◽

...

Keyword(s):

Bacillus Subtilis ◽

Biofilm Formation ◽

Cell Communication ◽

Signaling Molecules ◽

Interspecies Interactions ◽

Communication Signals ◽

Specialized Metabolites ◽

Growing Body ◽

Antagonistic Potential ◽

Cell Cell

Bacterial specialized (or secondary) metabolites are structurally diverse molecules that mediate intra- and interspecies interactions by altering growth and cellular physiology and differentiation. Bacillus subtilis , a Gram-positive model bacterium commonly used to study biofilm formation and sporulation, has the capacity to produce over ten specialized metabolites. Some of these B. subtilis specialized metabolites have been investigated for their role in facilitating cellular differentiation, only rarely has the behavior of multiple metabolites been simultaneously investigated. In this study, we explored the interconnectivity of differentiation (biofilm and sporulation) and specialized metabolites in B. subtilis . Specifically, we interrogated how development influences specialized metabolites and vice versa. Using the sporulation-inducing medium DSM, we found that the majority of the specialized metabolites examined are expressed and produced during biofilm formation and sporulation. Additionally, we found that six of these metabolites (surfactin, ComX, bacillibactin, bacilysin, subtilosin A, and plipastatin) are necessary signaling molecules for proper progression of B. subtilis differentiation. This study further supports the growing body of work demonstrating that specialized metabolites have essential physiological functions as cell-cell communication signals in bacteria. Importance/Significance Bacterially produced specialized metabolites are frequently studied for their potential use as antibiotics and antifungals. However, a growing body of work has suggested that the antagonistic potential of specialized metabolites is not their only function. Here, using Bacillus subtilis as our model bacterium, we demonstrated that developmental processes such as biofilm formation and sporulation are tightly linked with specialized metabolite gene expression and production. Additionally, under our differentiation-inducing conditions, six out of the nine specialized metabolites investigated behave as intraspecific signals that impact B. subtilis physiology and influence biofilm formation and sporulation. Our work supports the viewpoint that specialized metabolites have a clear role as cell-cell signaling molecules within differentiated populations of bacteria.

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Dialkylresorcinols as bacterial signaling molecules

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1417685112 ◽

2014 ◽

Vol 112 (2) ◽

pp. 572-577 ◽

Cited By ~ 79

Author(s):

Sophie Brameyer ◽

Darko Kresovic ◽

Helge B. Bode ◽

Ralf Heermann

Keyword(s):

Quorum Sensing ◽

Bacterial Species ◽

Cell Communication ◽

Signaling Molecules ◽

Human Pathogen ◽

Human Pathogens ◽

Bacterial Signaling ◽

Sensing Systems ◽

Luxr Homolog ◽

Cell Cell

It is well recognized that bacteria communicate via small diffusible molecules, a process termed quorum sensing. The best understood quorum sensing systems are those that use acylated homoserine lactones (AHLs) for communication. The prototype of those systems consists of a LuxI-like AHL synthase and a cognate LuxR receptor that detects the signal. However, many proteobacteria possess LuxR receptors, yet lack any LuxI-type synthase, and thus these receptors are referred to as LuxR orphans or solos. In addition to the well-known AHLs, little is known about the signaling molecules that are sensed by LuxR solos. Here, we describe a novel cell–cell communication system in the insect and human pathogenPhotorhabdus asymbiotica. We identified the LuxR homolog PauR to sense dialkylresorcinols (DARs) and cyclohexanediones (CHDs) instead of AHLs as signals. The DarABC synthesis pathway produces the molecules, and the entire system emerged as important for virulence. Moreover, we have analyzed more than 90 differentPhotorhabdusstrains by HPLC/MS and showed that these DARs and CHDs are specific to the human pathogenP. asymbiotica. On the basis of genomic evidence, 116 other bacterial species are putative DAR producers, among them many human pathogens. Therefore, we discuss the possibility of DARs as novel and widespread bacterial signaling molecules and show that bacterial cell–cell communication goes far beyond AHL signaling in nature.

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