Transcriptome Analysis of the Desert Locust Central Nervous System: Production and Annotation of a Schistocerca gregaria EST Database

Abstract

BackgroundThe desert locust (Schistocerca gregaria) displays a fascinating type of phenotypic plasticity, designated as ‘phase polyphenism’. Depending on environmental conditions, one genome can be translated into two highly divergent phenotypes, termed the solitarious and gregarious (swarming) phase. Although many of the underlying molecular events remain elusive, the central nervous system (CNS) is expected to play a crucial role in the phase transition process. Locusts have also proven to be interesting model organisms in a physiological and neurobiological research context. However, molecular studies in locusts are hampered by the fact that genome/transcriptome sequence information available for this branch of insects is still limited.MethodologyWe have generated 34,672 raw expressed sequence tags (EST) from the CNS of desert locusts in both phases. These ESTs were assembled in 12,709 unique transcript sequences and nearly 4,000 sequences were functionally annotated. Moreover, the obtained S. gregaria EST information is highly complementary to the existing orthopteran transcriptomic data. Since many novel transcripts encode neuronal signaling and signal transduction components, this paper includes an overview of these sequences. Furthermore, several transcripts being differentially represented in solitarious and gregarious locusts were retrieved from this EST database. The findings highlight the involvement of the CNS in the phase transition process and indicate that this novel annotated database may also add to the emerging knowledge of concomitant neuronal signaling and neuroplasticity events.ConclusionsIn summary, we met the need for novel sequence data from desert locust CNS. To our knowledge, we hereby also present the first insect EST database that is derived from the complete CNS. The obtained S. gregaria EST data constitute an important new source of information that will be instrumental in further unraveling the molecular principles of phase polyphenism, in further establishing locusts as valuable research model organisms and in molecular evolutionary and comparative entomology.

Critical role for protein kinase A in the acquisition of gregarious behavior in the desert locust

“…We identified a 1,392-bp contig of the for gene orthologue (36) in an S. gregaria CNS GenBank Expressed Sequence Tags (EST) database (13) and used it as a template to generate a 271-bp dsRNA construct (SI Appendix, Fig. S2).…”

“…That newly acquired and fully consolidated gregarious behaviors are mechanistically distinct also tallies with the finding that 5-HT is elevated only transiently, during the first few hours of crowding (16), and therefore cannot maintain gregariousness in the longer term. Activation of PKA may thus provide the link between a transient 5-HT signal and a later phase of consolidation that entails changes in gene expression (11,13). However, previous studies have demonstrated that, after as much as 24 h of crowding, the newly acquired gregarious state is rapidly lost upon reisolation (51), suggesting a prolonged period after 5-HT levels have decreased during which gregarization is still realized through labile modifications of neuronal properties.…”

“…Partial cDNA sequences of for and pkar1 were identified in an EST database of S. gregaria CNS (13). The partial cDNA sequence of pkac1 was obtained by PCR amplification with degenerate primers and subsequent cloning as described in SI Appendix.…”

“…Knowledge about the extensive differences in gene expression between the fully established phases has increased dramatically in recent years, but the molecular mechanisms that switch between the two extreme phenotypes have yet to be fully established (11)(12)(13). The discovery of a central role for the biogenic amine serotonin [5-hydroxytryptamine (5-HT)] in inducing behavioral gregarization (14) suggests parallels with mechanisms underlying classical forms of neuronal and behavioral plasticity (15).…”

Peptidergic control of food intake and digestion in insects1This review is part of a virtual symposium on recent advances in understanding a variety of complex regulatory processes in insect physiology and endocrinology, including development, metabolism, cold hardiness, food intake and digestion, and diuresis, through the use of omics technologies in the postgenomic era.

“…It was suggested that CRF/DH may regulate satiety and signal the end of the meal in locusts (Gäde and Goldsworthy 2003). Starting from partial precursor sequences found in the S. gregaria EST database (Badisco et al 2011), two full precursor sequences were obtained, each encoding the CRF-like DH as well as one of both long "ovary maturating parsin" (OMP) isoforms (Van Wielendaele et al 2012). The encoded DH proved to be identical to the CRF/DH of L. migratoria (Kay et al 1991;Lehmberg et al 1991).…”