Comparative phylogenomics of lateral gene transfers among grasses

Natural selection acting on the genetic variation existing among individuals within a species is a major driving force in evolution. In multicellular organisms, such as animals and plants, novel genetic variants were assumed until recently to exclusively arise through random mutations in the genetic material passed from parents to offsprings. However, recent years have seen the accumulation of reports of gene transfers between distinct multicellular species in a process called lateral gene transfer (LGT).

LGT can spread functional genes for adaptive traits among distant lineages, and in plants, it has facilitated the colonisation of low-light environments, improved efficiency of photosynthesis in high temperatures, and the ability to thrive on different soil types. LGT can therefore lead to big evolutionary leaps, allowing plants to rapidly evolve beyond their inherent potential.

However, a high frequency of LGT would also suggest that genetic material might 'escape' from GM crops and be transferred to wild species. This could lead to the emergence of superweeds that would decrease crop yields and damage natural ecosystems. The evolutionary importance and frequency of LGT remain largely unknown due to a lack of dedicated efforts and sparse species sampling in previous studies.

In this project, we will establish the importance of LGT for plant evolution by quantifying the phenomenon in various groups and establishing the factors that promote such gene transfers. Firstly, we will scan the genomes of numerous flowering plants capturing the diversity of the group to test the hypothesis that some lineages of plants are more likely to exchange genes than others.

Secondly, we will analyse the LGT in multiple individuals of some grass species, the most important group of flowering plants ecologically and economically. From the distribution of LGT among individuals within each species our innovative approach will calculate the rates of gains of LGT independently from the rates of subsequent losses. This will allow us to test the hypothesis that the rate of random LGT gains is high in all species, but that the rate of subsequent losses varies because of different selection regimes.

Thirdly, we will analyse the variation in the number of LGT donated by diverse grass species to determine whether the probability of being the source of the transfers depends on the evolutionary history, morphological characters or the geographic origin of the species.

Our multidimensional project will provide a precise quantification of the amount of LGT gained and lost through time by diverse groups of plants. In addition, our innovative approach will establish the factors that increase the probability of transferring genes to distant relatives. This fundamental knowledge will be pivotal in establishing the importance of genetic exchanges between species on the ecological and functional diversification of plants, potentially leading to a reappraisal of the tree-of-life nature of evolution in multicellular organisms.

In addition, the identification of the factors that promote LGT among grasses will help estimate the risk of gene escape from GM crops and develop mitigating strategies.