Differential gene expression of density-dependent phenotypic plasticity in Schistocerca americana (Orthoptera: Acrididae)

The American Birdwing Grasshopper, Schistocerca americana, has been shown to express density-dependent phenotypic plasticity reminiscent of the desert locust, Schistocerca gregaria.  This process, in the extreme form of locust phase polyphenism, is the main driver in the desert locust’s ability to swarm.  S. americana does not swarm and rarely has outbreaks but still shows this trait more so than most other Schistocerca species.  The Schistocerca species that do express density-dependent phenotypic plasticity change from a solitary morph, where they are cryptic in color, and have solitary behavior to a crowded morph where they are conspicuous in color, much more active, and aggregate to each other in response to higher population density.  The first aspect to change in this transition is behavior.  It has been found in the desert locust that protein kinase A is involved in the behavioral transition and when its expression is knocked down, solitarious individuals remain solitarious even after exposure to high density.  I have found highly differential expressed transcripts between the isolated and crowded phase of S. americana.  In this study I quantify the expression level of protein kinase-A(PKA), aromatic-L-amino-acid decarboxylase, and tryptophan-5-monooxygenase between these phases.  This work involves analysis of the time course in which the behavior changes and how the expression levels of these behavior related genes change with the behavior.  This is to inspire more research in revealing the molecular processes behind the density-dependent phenotypic plasticity phenomenon that remains largely unknown for Schistocerca and to investigate what the molecular differences are between swarming and non-swarming species.