Abstract
ABSTRACTGene duplications play a major evolutionary role by providing raw material for functional innovation. Whole Genome Duplication (WGD), or polyploidization, is a particular case of duplication encompassing the entire genome and has been implicated in evolutionary diversification. In plants, WGD is recognized as a major evolutionary force, and is linked to speciation and the ability to resist periods of stress and of environmental upheaval. In animals, examples of current polyploid species are rarer, but multiple ancient events are known, including the charismatic two rounds (2R) of WGD that occurred during early vertebrate evolution. The conditions favouring the success of polyploid lineages are unclear. One debated hypothesis states that polyploidy is adaptive in the short-term, however this has never been studied in animals.In this study, we investigated the consequences of polyploidy on physiology and stress resistance inCaenorhabditis elegans, where tetraploidy can be artificially constructed. Our results reveal that although tetraploidy reduces fitness by decreasing fertility and lifespan in regular conditions, tetraploid animals exhibit increased resilience under specific stress conditions related to temperature changes. While neotetraploid animals exhibit similar pathogen resistance, their response to heat stress is altered. They exhibit modest improvement in thermotolerance and prolongedhsp(heat shock protein) mRNA induction upon heat shock (HS) accompanied by alteredhsp-16.2nuclear localization upon HS. Most notably, under severe cold stress, gravid neotetraploids animals massively escape cold-induced death, and generate more progeny than diploid animals. These results suggest a potential adaptive value of tetraploidy under cold stress and might help explain recent correlations found between the frequency of extant animal polyploids and regions experiencing recent glaciation and large temperature variation.
Publisher
Cold Spring Harbor Laboratory