Abstract
Desert locusts (Schistocerca gregaria) show an extreme form of phenotypic plasticity and can transform between a cryptic solitarious phase and a swarming gregarious phase. The two phases differ extensively in behavior, morphology and physiology but very little is known about the molecular basis of these differences. We used our recently generated Expressed Sequence Tag (EST) database derived from S. gregaria central nervous system (CNS) to design oligonucleotide microarrays and compare the expression of thousands of genes in the CNS of long-term gregarious and solitarious adult desert locusts. This identified 214 differentially expressed genes, of which 40% have been annotated to date. These include genes encoding proteins that are associated with CNS development and modeling, sensory perception, stress response and resistance, and fundamental cellular processes. Our microarray analysis has identified genes whose altered expression may enable locusts of either phase to deal with the different challenges they face. Genes for heat shock proteins and proteins which confer protection from infection were upregulated in gregarious locusts, which may allow them to respond to acute physiological challenges. By contrast the longer-lived solitarious locusts appear to be more strongly protected from the slowly accumulating effects of ageing by an upregulation of genes related to anti-oxidant systems, detoxification and anabolic renewal. Gregarious locusts also had a greater abundance of transcripts for proteins involved in sensory processing and in nervous system development and plasticity. Gregarious locusts live in a more complex sensory environment than solitarious locusts and may require a greater turnover of proteins involved in sensory transduction, and possibly greater neuronal plasticity.
Highlights
Desert locusts (Schistocerca gregaria) are notable for their extreme form of phenotypic plasticity
214 genes out of a total of 20,755 represented on the microarrays were differentially expressed between solitarious and gregarious locusts, 100 of which were more strongly expressed in the gregarious phase and 114 in the solitarious phase
Some 40% of the differentially expressed genes have been annotated to date (Table S1), allowing them to be classified under standard ‘Gene Ontology’ (GO) categories [20] (Figure 2)
Summary
Desert locusts (Schistocerca gregaria) are notable for their extreme form of phenotypic plasticity. Depending upon changes in population density, their genome can generate two markedly different phenotypes, which were thought to be different species when first discovered [1;2] These two extreme phenotypes, called the solitarious and gregarious phases, adapt the locusts to very different lifestyles. In situations where solitarious locusts are unable or unwilling to avoid each other (because of restricted food supply for example), visual, olfactory (pheromonal) and mechanosensory stimuli from other locusts induce behavioral gregarization within just a few hours [5,6,7] This behavioural change leads to a positive feedback cycle in which gregarising locusts are constantly bombarded with stimuli from each other, which consolidates and drives further phenotypic changes
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