GENOMERGE · Role of genome merger and redundancy in plant evolution and adaptation

Role of genome merger and redundancy in plant evolution and adaptation

The goal of the GENOMERGE project (2013-2017) was to analyse the evolutionary consequences of genome merger and duplication (two major evolutionary phenomena in plants). It aims at exploring fundamental and emergent questions in biology, such as the dynamics of nuclear genomes, the creation of new genes and/or evolution of new functions in plants and their associated adaptive impacts in natural populations. Allopolyploidy (hybrid genome duplication) is a major speciation process in plants. Both genome merger (resulting from interspecific hybridization) and polyploidy (whole genome duplication) phenomena can have important but differential effects. Several possible fates are acknowledged for genes duplicated through allopolyploidy (including pseudogenisation, gene loss, neofunctionalization or subfunctionalization). These various evolutionary fates of duplicate genes enhance the potential of polyploid species for functional plasticity and evolutionary novelties, contributing to phenotypic variability and enabling the species to adapt a larger range of environmental conditions. So far, most of the knowledge on these phenomena was gained under experimental conditions but far less on biological systems of ecological interest (in their natural conditions). To fill this gap, we explored the immediate impacts of either hybridization or polyploidy on the evolution of gene expression in recently formed hybrid and allopolyploid species of the salt marsh genus Spartina (Poaceae). Using RNA Seq data obtained from various Spartina species grown in similar natural conditions, we found that an important number of genes were differently transcribed (non-additivity) in the hybrids and the allopolyploid species compared to their parents. Our analyses revealed that the genes differently expressed in the hybrid and allopolyploid species compared to their parental species belonged to growth and reproductive processes as well as to responses to abiotic stresses. Further investigations of these differently transcribed genes are ongoing, with a particular focus on genes potentially associated with morphological and physiological features that have facilitated the rapid expansion of invasive Spartina populations. The results gained through this study will also have important impacts in terms of land management and biological conservation, as Spartina species play an important ecological role in the salt-marsh sedimentary dynamics where they are considered as “ecosystem engineers”. Another aim of this project was to study an important and still underexplored aspect of polyploid evolution, which is the link between polyploid genome dynamics and phenotypic changes that are of ecological and adaptive importance. More specifically, the role of this study was to decipher how gene and genome duplication led to a novel biochemical pathway in some Spartina species, namely the ability to produce an anti-stress and osmo-protectant molecule. By performing RNAseq, biochemical and enzymatic assays in Spartina species presenting a contrasted ability to produce this molecule, we significantly increased our understanding of this novel biochemical pathway and of its genes involved. This project was developed in the perspective of permanent integration of the fellow. This goal was successfully attained in 2014 as the fellow obtained a permanent position as Researcher in the team “Biodiversity and Polyploidy” (INRA Rennes) to work on polyploid genome evolution, in collaboration with the host team.

Data: CORDIS, © European Union