Time-course analysis of sensory and brain tissue transcriptomes during phase transitions in the Desert Locust (Schistocerca gregaria)

Density-dependent polyphenism has evolved multiple times in insect taxa, but locusts often embody this phenomenon (Orthoptera: Acrididae). In response to conspecific population density changes, solitary, shy and cryptic grasshoppers can develop into gregarious, swarming, and conspicuous locusts (i.e., gregarization); or revert (i.e., solitarization). Among the 19 species recognized as locusts, phase transitions' mechanical and physiological origins have been extensively studied in the Desert Locust (Schistocerca gregaria). Although the temporal dynamics of gregarization and solitarization differed in S. gregaria, both processes are induced by a combination of sight, smell, and tactile stimulation. Along with mechanosensory-induced developmental changes, striking gene expression changes have been highlighted in the central nervous system at the phase change endpoint. Yet, the cascade of molecular mechanisms underlying the phase transition remains unknown. We propose identifying the gene regulatory network and gene expression changes during the phase transition in lab-reared S. gregaria. For this, we simulated gregarization by exposing solitarious nymphs reared in isolation for two generations to crowded cages with high densities of conspecific individuals (500-700) for a period ranging from 30 min to 72h. Similarly, we simulated solitarization by isolating gregarious nymphs. Following density treatment, we obtained seven tissue transcriptomes at each of the 10-time sampling points (brain and sensory organs). In this talk, we will show insights of the tissue-specific transcriptome sequencing that take advantage of the six new reference chromosome-length Schistocerca genomes (BPRI and USDA). Ultimately, the unraveled regulatory patterns will be compared to locusts and non-locust species.