Plants can become less uniform by duplicating their genome

What difference does having more copies of your genome make to the shape of your body? Kali Mattingly and Stephen Hovick have examined how whole genome duplication (WGD) influences the plasticity or changeability of a plant. Their experiments with the model plant Arabidopsis thaliana show that simply duplicating the genome can increase plant plasticity.

A. thaliana is the go-to plant for this kind of experiment as it has a small genome that has been well-studied. Typically it’s a diploid plant, meaning that it has the chromosomes that hold the genes in pairs. Whole genome duplication changes this, so the plant has more copies of chromosomes and is polyploid.

When a plant has more copies of a genome, it can have more versions of a gene to draw upon. These extra copies can be advantageous, allowing the polyploid to exploit territory on the fringe of the parent plant’s range. However, it can be a drawback too. A more plastic plant might not conform to a tight optimum set of characteristics, or phenotype, that the diploid plant has.

Mattingly and Hovick developed two lineages of autotetraploid A. thaliana that they could observe alongside related diploid plants. “Using synthesized autotetraploids allowed us to examine the consequences of WGD alone, independent of other potentially confounding processes that operate on natural polyploids, such as hybridization, drift, or natural selection,” they write.

They subjected the plants to several treatments, varying nutrients and salt in the growing medium to put the plants under different stresses.

“Using inbred synthesized taxa, we found that polyploids were more plastic than their diploid progenitors… for the few differences that were at least marginally significant,” Mattingly and Hovick write. “Though our study was limited to two genotypes and a single species, our findings support the hypothesis that increased plasticity in polyploids is the mechanism by which the genomic effects of WGD scale up into ecological consequences: accelerating adaptation (Baniaga et al., 2020), enhancing niche differentiation (Laport et al., 2013), and spurring speciation (Van de Peer et al., 2017).”

The results show how whole genome duplication can act as a mechanism to increase plant diversification.