Stepwise changes in gene expression inducing anhydrobiotic state transition and the gene regulatory network in Polypedilum vanderplanki larvae

The larva of the sleeping chironomid, Polypedilum vanderplanki , is the only insect capable of extreme desiccation tolerance, known as anhydrobiosis. The larvae can survive near-complete desiccation and, upon rehydration, rapidly resume metabolism and return to their normal life cycle. Activation of genes involved in antioxidant activity, protection of biomolecules, and DNA repair is required for desiccation tolerance. In the desiccation-tolerant P. vanderplanki cell line Pv11, the key factors of the regulatory network for these genes are heat shock factor ( Hsf ) and nuclear transcription factor Y subunit C ( NF-YC ). However, how desiccation tolerance is established at the whole-body level remains unknown. To unravel the dynamic response to desiccation at this level, it is necessary to clarify which molecules need to function for desiccation tolerance and when. Here, we newly acquired and analyzed detailed time-series gene expression data to reveal the regulatory mechanisms underlying the transition to an ametabolic state during desiccation. We showed that the acquisition of desiccation tolerance requires the expression of a number of desiccation-inducible genes in a specific order. This order can be explained by a gene regulatory network triggered by nuclear transcription factor Y subunit A ( NF-YA ) and Sine oculis-related homeobox 4 ( Six4 ). To our knowledge, this is the first report that desiccation tolerance is related to stepwise changes in gene expression in response to desiccation. • Desiccation induces differential expression of 78% of all Polypedilum vanderplanki genes. • These desiccation-responsive genes undergo gradual and stepwise expression changes. • Gene regulatory networks started by two transcription factors explain these changes. • Gene expression during desiccation can be divided into six states.