|Secondary structure of Pxr sRNA.|
|Domain(s)||Myxococcus xanthus, Stigmatella aurantiaca|
Pxr sRNA is a regulatory RNA which downregulates genes responsible for the formation of fruiting bodies in Myxococcus xanthus. Fruiting bodies are aggregations of myxobacteria formed when nutrients are scarce, the fruiting bodies permit a small number of the aggregated colony to transform into stress-resistant spores.
Pxr exists in two forms: Pxr-L (a long form) and Pxr-S which is shorter. The short form was found to be expressed in cells during growth but is rapidly repressed during starvation. This finding implies that Pxr-S is specifically responsible for inhibiting the fruiting body development during cell growth when nutrients are abundant.
Pxr homologs have only been found in one other taxon, namely Stigmatella aurantiaca. Homologs were not found in any other myxobacteria (such as Sorangium cellulosum or Anaeromyxobacter dehalogenans) which suggests the Pxr RNA gene may have a recent evolutionary origin in the sub-clade Myxococcales.
M. Xanthus obligate cheat and phoenix phenotypes
Several mutations in the Pxr sRNA gene have been observed. The first mutation causes an obligate cheat (OC) phenotype to emerge, these bacteria exploit the fruiting bodies of wild-type M. Xanthus to sporulate more efficiently. This phenotype is thought to be caused by a mutation which prevents the repression of Pxr-S, thereby inhibiting the formation of fruiting bodies indefinitely. If Pxr-S is derived from Pxr-L, it may be that RNAi-like processing elements have been knocked out.
In a laboratory experiment, the OC phenotype out-competed and excluded the wild type, eventually bringing about a population crash when there were not enough wild type bacteria to exploit. After this event, a new phenotype emerged via spontaneous mutation dubbed phoenix (PX). The PX phenotype was developmentally superior to both OC and wt, it was able to sporulate autonomously - without forming fruiting bodies and with high efficiency.
- Yu YT, Yuan X, Velicer GJ (May 2010). "Adaptive evolution of an sRNA that controls Myxococcus development". Science 328 (5981): 993. doi:10.1126/science.1187200. PMC 3027070. PMID 20489016. Retrieved 2010-07-22.
- Kuner JM, Kaiser D (July 1982). "Fruiting body morphogenesis in submerged cultures of Myxococcus xanthus". J. Bacteriol. 151 (1): 458–61. PMC 220259. PMID 6806248. Retrieved 2010-07-22.
- Wireman JW, Dworkin M (February 1977). "Developmentally induced autolysis during fruiting body formation by Myxococcus xanthus". J. Bacteriol. 129 (2): 798–802. PMC 235013. PMID 402359. Retrieved 2010-07-22.
- Schneiker S, Perlova O, Kaiser O et al. (November 2007). "Complete genome sequence of the myxobacterium Sorangium cellulosum". Nat. Biotechnol. 25 (11): 1281–9. doi:10.1038/nbt1354. PMID 17965706.
- Thomas SH, Wagner RD, Arakaki AK et al. (2008). "The mosaic genome of Anaeromyxobacter dehalogenans strain 2CP-C suggests an aerobic common ancestor to the delta-proteobacteria". PLoS ONE 3 (5): e2103. doi:10.1371/journal.pone.0002103. PMC 2330069. PMID 18461135. Retrieved 2010-07-22.
- Fiegna F, Yu YT, Kadam SV, Velicer GJ (May 2006). "Evolution of an obligate social cheater to a superior cooperator". Nature 441 (7091): 310–4. doi:10.1038/nature04677. PMID 16710413.
- Stefani G, Slack FJ (March 2008). "Small non-coding RNAs in animal development". Nat. Rev. Mol. Cell Biol. 9 (3): 219–30. doi:10.1038/nrm2347. PMID 18270516.
- Gottesman S (July 2005). "Micros for microbes: non-coding regulatory RNAs in bacteria". Trends Genet. 21 (7): 399–404. doi:10.1016/j.tig.2005.05.008. PMID 15913835. Retrieved 2010-07-22.
- Chen, IC; Griesenauer, B; Yu, YT; Velicer, GJ (Jan 10, 2014). "A recent evolutionary origin of a bacterial small RNA that controls multicellular fruiting body development.". Molecular Phylogenetics & Evolution 73: 1–9. doi:10.1016/j.ympev.2014.01.001. PMID 24418530.