Author:

Abstract:

Desert locusts (Schistocerca gregaria) and migratory locusts (Locusta migratoria) are closely related species, which display a fascinating type of phenotypic plasticity called phase transition. This means that these locusts can occur in two extreme phenotypes: the solitarious and gregarious phases. In appropriate conditions, locusts in the latter phase can form huge swarms which constitute a serious threat to the agriculture in the hit regions. It has been observed that, in addition to behavioral changes, a range of important physiological processes, such as growth, metabolism and reproduction, are affected during phase transition. Interestingly, studies in other animals have demonstrated that insulin-related peptides are involved in the regulation of these processes. For both L. migratoria and S. gregaria, an insulin-related peptide (IRP) has been purified from brain extracts. Furthermore, the cDNA sequences have been determined, showing that both IRP precursors show the typical evolutionary conserved organization observed for (almost all) known protostomian and deuterostomian insulin-related peptides. Although the physiological relevance of these locust peptides has not yet been studied in great detail, there is evidence for a role in the regulation of the locust reproduction process. Moreover, small neuroproteins resembling the vertebrate insulin-like growth factor binding proteins (IGFBPs) have also been described in locusts. These peptides were initially termed neuroparsins, and there is in vitro evidence that they can interact with the endogenous IRP of locusts. Studies in L. migratoria described the pleiotropic activities of one of these neuroparsins, which was shown to have antigonadotropic, neuritogenic, hypertrehalosemic and antidiuretic effects. Neuroparsin analysis in S. gregaria mainly focussed on their possible involvement in reproduction and phase transition. Because of these pleiotropic activities, neuroparsins have been suggested to be important regulators of locust physiology, something for which they may, or may not, act as modulators of IRP signaling. This lecture will give an overview about IRPs and neuroparsins in locusts, their discovery, expression profiles, functions and possible interactions.