La Fortezza, M.; Verwilt, J.; Cossey, S.; Eisner, S.; Velicer, G. J.; Yu, Y.-T. N.

Small non-coding RNAs (sRNAs) are essential in regulating gene expression during many biological processes. The myxobacteria gene pxr encodes an sRNA known to block fruiting-body development, an aggregative multicellular process triggered by starvation. Deletion of pxr allows Myxococcus xanthus cells to develop in the presence of nutrients. However, potential Pxr binding targets and most genes regulated by Pxr remain unknown. Here, we found that the absence of pxr expression dramatically alters the temporal dynamics of development, thus suggesting an important new role of this sRNA in myxobacterial ecology. We transcriptionally profiled vegetative cells of M. xanthus strains possessing vs lacking pxr and found that over half of the genes impacted by pxr deletion during growth are linked to development, including known and potentially novel critical regulators. Many other genes are associated with general metabolic processes, which Pxr regulates positively. Our study discovers new phenotypic effects of Pxr regulation of likely ecological importance, identifies the suite of genes this sRNA controls during vegetative growth, reveals a previously unknown developmental regulator and provides new insights into the early molecular regulation of myxobacterial development.