Robustness and variability inCaenorhabditis elegansdauer gene expression

Abstract

Both plasticity and robustness are pervasive features of developmental programs. The dauer in Caenorhabditis elegans is an arrested, hypometabolic alternative to the third larval stage of the nematode that undergoes dramatic tissue remodeling and gene expression changes compared to conspecifics that continue development. Dauer arrest can be triggered by several adverse environments or genetic mutations that act as independent and parallel inputs into the larval developmental program and is an example of phenotypic plasticity. However, whether gene expression in dauer larvae induced by different genetic or environmental triggers is invariant or varies depending on their route into dauer has not been examined. Here we use RNA-sequencing to characterize gene expression in dauer larvae induced to arrest development in response to different stimuli. By assessing the variance in the expression of all genes and computing the Spearman's rank-order correlation of gene expression within several Gene Ontologies (GO) and gene networks, we find that the expression patterns of most genes are strongly correlated between the different dauer larvae, suggestive of transcriptional robustness. However, we also find that gene expression in specific defense and metabolic pathways varies widely between dauers. We speculate that the transcriptional robustness of core dauer pathways allows for the buffering of variation in the expression of genes involved in the response to the environment, allowing the different dauers to survive in and exploit different niches.