Base genética del cambio de fase en la langosta del desierto Schistocerca gregaria

Abstract

Locust outbreaks affect near two thirds of the Earth’s dry surface, which requires a great investment in their control and repair of the damage they cause. The transformation of isolated and passive locusts into swarming and active locusts is regulated by a striking case of polyphenism called phase change. Despite the knowledge on some potential modulators of the locust phase change, its integrative genetic regulation is not yet understood. This dissertation studies the transcriptional consecuences of phase change in the desert locust Schistocerca gregaria Forskal by comparing the overall gene expression profile differences between the gregarious and solitarious phases. For this purpose, we first develope mathematical models in order to quantify the degree of locust gregariousness. Following that, we sequence, assemble, analyze and compare the transcripts and their expression profiles from two adult tissues (central nervous system and digestive tube) between the two phases, gregarious and solitarious. We validated the results using qPCR and by comparisons with the data from scientific publications on the phase change both in S. gregaria and in the migratory locust, Locusta migratoria. In addition, as case study, we characterize the copy number of chemosensory proteins (CSPs) in both species, and we found some of them to be linked to the phase change in one or both species. In summary, this thesis updates the study of phase change in S. gregaria with a behavioural tool and high amounts of genetic data. The behavioural models developed will facilitate and standarize the functional study of the effect of an experimental treatment in phase change. Our transcriptomes contribute with a wide set of interesting sequences probably involved in phase change and other set of interesting sequences that might be explorable for targeting locusts. In addition, we find that the gregarious CNS presents the highest number of pathways affected or involved in the phase change. We also identified transcripts from a potential biological control agent: a gregarine. The case study presented here offers an example on how to identify putative genes, their copy number, phylogenetic relationships and expression profiles in the gregarious and solitarious phases, which ultimately leads to revealing the potential association of the concrete transcripts with the phase change.