Genomic Insights into the Evolution of Plant Defense Strategies

Pathogens can significantly reduce the fitness of their hosts, sometimes even leading to host mortality. However, there is considerable variation between species in how much they invest in disease defense. Evolutionary theory suggests that allocation costs influence this investment, but testing this idea has proven difficult.

Postdoctoral Researcher Michael Giolai and Professor of Plant Biodiversity Anna-Liisa Laine from the University of Helsinki utilized open databases to examine plant defense genes and growth traits across 184 plant species. The research was published in Science.

They observed significant variation in the number of defense genes among plant species, ranging from 44 to 2,256. For instance, asparagus has only 72 resistance genes, whereas one chili variety contains as many as 1,095.

Laine and Giolai also found a negative correlation between defense investment and growth traits in wild plants: the greater the proportion of a plant’s genome allocated to defense genes, the lower its growth potential.

Our study demonstrates the significant role of allocation costs in the generation and maintenance of biodiversity. The findings also shed light on mechanisms that limit the evolution of defense.”

Michael Giolai, Postdoctoral Researcher, University of Helsinki

Allocation costs refer to the trade-off involved in distributing resources across various life functions. For plants, this means that allocating many resources (such as energy and nutrients) to maintain defense mechanisms may reduce the resources available for other functions, like growth.

Essentially, plants must balance their resource use, which can lead to a situation where a strong defense system limits growth potential or vice versa.

The study also included cultivated plants that have been bred for specific traits. In these plants, the negative correlation between growth and defense was not observed, as breeding reduced the natural variation in the genomes of crop plants.

This study highlights the potential of open science. Sequencing the genomes of hundreds of plant species and gathering data on growth traits would be unfeasible for a single research team. The expansion of open data allows for new types of research that enhance our understanding of interspecies variation in various traits.

If we want to understand the mechanisms that maintain interspecies trait variation, a multi-species approach like this is essential. The increasing availability of open data enables entirely new levels of investigation into these questions.”

Anna-Liisa Laine, Professor, Plant Biodiversity, University of Helsinki