A team of researchers led by Portland State biology professor Mitch Cruzan recently received an $855k grant from the National Science Foundation to study mutations within plants' cells and their impact on adaptation and evolution. The research could change our understanding of how plants evolve.
The study will focus on somatic mutations--those that occur in cells not associated with reproduction. Unlike animals, plants can inherit somatic mutations. As Cruzan notes, one might expect that the extra load of somatic mutations accumulating during vegetative growth would result in higher mutation loads in plants compared to animals. That, however, is not the case. Building upon research conducted by PSU Ph.D. student Jamie Schwoch, the team hypothesizes that we do not see increased mutation rates in plants because heretofore unexamined processes remove harmful somatic mutations while retaining those that benefit plants and their offspring.
"One of the main questions we're trying to answer is, how does mutation accumulation differ in plants compared to animals," Cruzan said. "Our preliminary work indicates that there is a filtering process going on, and so another question arises: what are the consequences of this filtering effect? So, as we hypothesize that plants can effectively evolve as they grow, we'd like to know, if that indeed happens, how does that affect seedlings of the next generation."
Cruzan is an evolutionary biologist whose research focuses on adaptation, speciation, hybridization, population genetics, and genetic diversity in rare and common plant species. He and his team use ecological genetics tools to study the genomic interactions between plants and their environments related to evolution and adaptation.
In plants, the cells on the front-line of growth contain the genetic material for vegetation (stems, leaves, tendrils, etc.) and sexual reproduction. It is this combination of genetic information that allows plants to pass on somatic mutations--beneficial or otherwise. To test the hypothesis that plants filter deleterious mutations while retaining beneficial ones, the team will cultivate and study monkeyflowers' vegetative tissue over generations.
"What we've been able to show using simulations is that as cells at the leading edge of plant growth die out, they take mutations with them," Cruzan said. "That leaves the plant with a moderate level of mutations that seem to include the good ones."
Throughout the first-of-its-kind study, the researchers will examine the distribution of somatic mutations in reproductive and vegetative tissues in plants growing under high- and low-stress environments to gauge harmful mutations' turnover rates. Additionally, the team will explore the genetic effects of beneficial mutations and evaluate the impacts of somatic mutations on seedlings' success.
The project is a collaboration between Cruzan and his research team and University of Oregon associate professor Matthew Streisfeld. The study will support graduate and undergraduate research opportunities at PSU.
"This is a unique study," Cruzan said. "If our experiments establish that plants indeed undergo somatic evolution while filtering harmful mutations and that those mutations have consequences for adaptation to novel living conditions, it could change our fundamental understanding of plant evolution and have important applications for the fields of plant breeding, agriculture, and conservation biology."