The PKA Swarm

Science Signaling  21 Feb 2012:
Vol. 5, Issue 212, pp. ec57
DOI: 10.1126/scisignal.2002974

Crop destruction by swarms of desert locusts (Schistocerca gregaria) can contribute to famines in Africa, the Middle East, and Asia. Before swarming, desert locusts transform from a solitary to a gregarious form, a phenotypic change that is induced by high population densities or crowding and that requires serotonergic signaling. Whereas solitary locusts avoid each other, gregarious locusts are more active and seek out one another. Protein kinase G (PKG) activity is higher in the brains of gregarious locusts compared with those of solitary locusts, and fruit fly larvae carrying the “rover” allele of forager, which encodes a PKG paralog, move over longer distances for food. However, Ott et al. found that solitary locusts injected with KT5720, an inhibitor of protein kinase A (PKA), showed fewer signs of gregarious behavior after crowding than those injected with KT5823, a PKG inhibitor. Neither inhibitor affected the behavior of locusts that had already experienced crowding and showed gregarious behavior before injection. Gregarious behavior after crowding was reduced in solitary locusts treated with RNA interference (RNAi) directed against the pkac1 gene, which encodes the catalytic C1 subunit of PKA, but not with RNAi against the forager ortholog. In the PKA holoenzyme, the catalytic subunits interact directly with and are inhibited by the regulatory subunits, and treatment of solitary locusts with RNAi against pkar1 (which encodes the regulatory subunits) increased gregarious behavior after crowding. The authors speculate that serotonergic signaling in locusts experiencing high population densities activates PKA to phosphorylate substrates (which have yet to be identified) that elicit the changes in gene expression required for gregarious behavior.

S. R. Ott, H. Verlinden, S. M. Rogers, C. H. Brighton, P. S. Quah, R. K. Vleugels, R. Verdonck, J. Vanden Broeck, Critical role for protein kinase A in the acquisition of gregarious behavior in the desert locust. Proc. Natl. Acad. Sci. U.S.A. 109, E381–E387 (2012). [Abstract] [Full Text]