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. 2000 Aug 1;97(16):9098-103.
doi: 10.1073/pnas.97.16.9098.

Spatial control of cell differentiation in Myxococcus xanthus

B Julien  1 , A D Kaiser, A Garza
Affiliations

Spatial control of cell differentiation in Myxococcus xanthus

B Julien et al. Proc Natl Acad Sci U S A. .

Abstract

Myxococcus xanthus develops species-specific multicellular fruiting bodies. Starting from a uniform mat of cells, some cells enter into nascent fruiting body aggregates, whereas other cells remain outside. The cells within the fruiting body differentiate from rods into spherical, heat-resistant spores, whereas the cells outside the aggregates, called peripheral cells, remain rod-shaped. Early developmentally regulated genes are expressed in peripheral cells as well as by cells in the fruiting bodies. By contrast, late developmental genes are only expressed by cells within the nascent fruiting bodies. The data show that peripheral cells begin to develop, but are unable to express genes that are switched on later than about 6 h after the start of development. All of the genes whose expression is limited to the fruiting body are dependent on C-signaling either directly or indirectly, whereas the genes that are equally expressed in peripheral rods and in fruiting body cells are not. One of the C-signal-dependent and spatially patterned operons is called dev, and the dev operon has been implicated in the process of sporulation. It is proposed that expression of certain genes, including those of the dev operon, is limited to the nascent fruiting body because fruiting body cells engage in a high level of C-signaling. Peripheral cells do less C-signaling than fruiting body cells, because they have a different spatial arrangement and are at lower density. As a consequence, peripheral cells fail to express the late genes necessary for spore differentiation.

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Figures

Figure 1
Figure 1
Spatial localization of dev expression, measured in a dev∷gfp transcriptional fusion strain. (A) Bright field microscopy with phase contrast after 24 h of development of the dev∷gfp strain showing a fruiting body surrounded by peripheral rod cells. An arrow points up to indicate an island of cells; an arrow points down to indicate a single cell. (B) Same microscopic field as in A now using fluorescence. (C) A different dev∷gfp fruiting body that has been flattened under a coverslip to spread out the cells from within the mass, and only fruiting body cells are present in this field. It was photographed at 3× higher magnification than A or B. (D) Fruiting body and adjacent peripheral rods formed by a pilA∷gfp strain photographed in fluorescence mode.
Figure 2
Figure 2
CsgA-protein levels in nascent fruiting bodies and peripheral rods. Fruiting bodies (F.B.) and peripheral rods (P.R.) were isolated from TPM agar plates at 18 h of development as described in Materials and Methods. Protein extracts of each were separated by gel electrophoresis, and the proteins were exposed to CsgA-specific antibody, as described (7). An extract of a csgA mutant strain was similarly treated to test the specificity of the anti-CsgA antibody. The same total amount of protein was loaded into each lane.
Figure 3
Figure 3
The C-signal transduction pathway. Both cells have the same transduction circuit, but for clarity the circuit is shown only in the cell on the right. Evidence for the pathway is described in the text.
See this image and copyright information in PMC

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