Background: To obtain reliable quantitative RT-PCR data, normalization relative to stable housekeeping genes is required. However, in practice, expression levels of 'typical' housekeeping genes have been found to vary between tissues and under different experimental conditions. To date, validation studies of reference genes in insects are extremely rare and have never been performed in locusts. In this study, putative housekeeping genes were identified in the desert locust, Schistocerca gregaria and two different software programs (geNorm and Normfinder) were applied to assess the stability of thesegenes.

No abstract

No 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.

We report on a comprehensive study of the systemic RNAi-response in the desert locust, Schistocerca gregaria. Upon intra-abdominal injection of dsRNA for two housekeeping genes (alpha-tubulin 1a and gapdh) in the range of pg amounts of dsRNA per mg tissue, a potent reduction of their corresponding mRNA was obtained. Moreover, the observed transcript knockdown significantly increased in at least a 10 days period and eventually resulted in high mortality upon silencing of the alpha-tubulin 1a gene. A more moderate RNAi-response was however observed in the reproductive systems. Analysis of the tissue-dependent transcript level profile of several putative RNAi-genes indicated reduced levels of two genes, namely sg-dicer-2 and sg-argonaute-2, in the reproductive systems. By silencing these components, we confirmed their importance in the RNAi-process and suggest that their expression levels are determinant for tissue-dependent differences in the potency of RNAi in the desert locust.