Abstract
BackgroundMany insects can develop differential biotypes on variable host plants, but the underlying molecular factors and mechanisms are not well understood. To address this issue, transcriptome profiling analyses were conducted for two biotypes of the cereal aphid, Sitobion avenae (Fabricius), on both original and alternative plants.ResultsComparisons between both biotypes generated 4174 differentially expressed unigenes (DEGs). In their response to host plant shift, 39 DEGs were shared by both biotypes, whereas 126 and 861 DEGs occurred only in biotypes 1 and 3, respectively. MMC (modulated modularity clustering) analyses showed that specific DEGs of biotypes 1 and 3 clustered into five and nine transcriptional modules, respectively. Among these DEGs, defense-related genes underwent intensive expression restructuring in both biotypes. However, biotype 3 was found to have relatively lower gene transcriptional plasticity than biotype 1. Gene enrichment analyses of the abovementioned modules showed functional divergence in defensive DEGs for the two biotypes in response to host transfer. The expression plasticity for some defense related genes was showed to be directly related to fecundity of S. avenae biotypes on both original and alternative plants, suggesting that expression plasticity of key defensive genes could have significant impacts on the adaptive potential and differentiation of S. avenae biotypes on different plants.ConclusionsThe divergence patterns of transcriptional plasticity in defense related genes may play important roles in the phenotypic evolution and differentiation of S. avenae biotypes. Our results can provide insights into the role of gene expression plasticity in the divergence of insect biotypes and adaptive evolution of insect populations.
Highlights
Many insects can develop differential biotypes on variable host plants, but the underlying molecular factors and mechanisms are not well understood
Over 78.62, 82.17, 80.98 and 95.42 million clean reads were respectively found in transcriptome sequencing of aphid samples in the four treatment: Biotype on wheat (AW), Biotype on barley (AB), Biotype feeds on wheat (BW), and Biotype feeds on barley (BB) (Table S1)
The results of the principal component analysis (PCA) showed that the four treatments were clearly separated in the plot, and three biological replicates for each treatment clustered together, indicating all biological replications of each treatment had good repeatability (Fig. S2)
Summary
Many insects can develop differential biotypes on variable host plants, but the underlying molecular factors and mechanisms are not well understood. To address this issue, transcriptome profiling analyses were conducted for two biotypes of the cereal aphid, Sitobion avenae (Fabricius), on both original and alternative plants. Phenotypic plasticity seems to be a common phenomenon for different populations of aphids compared with other insect groups [24,25,26,27] Another possible explanation is that phenotypic plasticity and underlying gene expression plasticity may make aphids highly amenable to development of variable biotypes, but direct evidence is rare
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