The study challenges the evolutionary theory that DNA mutations are random

Studying the genome of cress, a small flowering herb, has led to a new understanding of DNA mutations. Credit: Pádraic Flood

A simple roadside grass may hold the key to understanding and predicting DNA mutation, according to new research from the University of California, Davis, and the Max Planck Institute for Developmental Biology in Germany.

The results, published January 12 in the journal temper nature, radically changing our understanding of evolution and could one day help researchers produce better crops or even help humans fight cancer.

Mutations occur when DNA is damaged and left unrepaired, resulting in new diversity. The scientists wanted to know if the mutation was purely random or something deeper. What they found was unexpected.

“We’ve always thought that mutation is essentially random across the genome,” said Gray Munro, associate professor in the Department of Plant Sciences at the University of California, Davis and lead author of the paper. “It turns out that mutation is very non-random and non-random in a way that benefits the plant. It’s a whole new way of thinking about mutations.”

Researchers spent three years sequencing the DNA of hundreds of Arabidopsis thalianaCress, or cress, is a small flowering weed that is considered the “lab rat among plants” due to its relatively small genome of about 120 million base pairs. By comparison, humans have approximately 3 billion base pairs.

“It’s a model organism for genetics,” Munro said.

Lab-grown plants produce many variations

Work began at the Max Planck Institute where researchers grew samples in a protected laboratory environment, allowing plants with defects that might not have survived in nature to survive in a controlled setting.

sequence those hundreds of Arabidopsis thaliana Plants detected more than one million mutations. Within those mutations a nonrandom pattern was detected, contrary to what was expected.

“At first glance, what we found seems to contradict the well-established theory that initial mutations are completely random and that only natural selection determines which mutations are observed in organisms,” said Detlev Weigl, scientific director at the Max Planck Institute and senior author of the study.

Rather than randomly, they found patches of the genome with low mutation rates. In those spots, they were surprised to find an over-representation of essential genes, such as those involved in cell growth and gene expression.

“These are the really important regions of the genome,” Munro said. “The areas that are most biologically important are those that are protected from mutations.”

The regions are also sensitive to the harmful effects of new mutations. “It appears that DNA damage repair is particularly effective in these regions,” Weigel added.

Plants evolved to protect themselves

The scientists found that the way DNA was wrapped around different types of proteins was a good indicator of whether a gene would evolve. “This means we can predict which genes are more susceptible to mutation than others and it gives us a good idea of ​​what’s going on,” Weigl said.

The findings add a surprising twist to Charles Darwin’s theory of evolution by natural selection as they reveal that plants evolved to protect their genes from mutations to ensure survival.

“The plant has developed a way to protect its most important places from mutations,” Weigel said. “This is exciting because we can even use these discoveries to think about how to protect human genes from mutations.”

future uses

Knowing why some regions of the genome mutate more than others could help breeders who rely on genetic diversity to develop better crops. Scientists can also use the information to better predict or develop new treatments for diseases such as cancer that are caused by mutations.

The paper concludes, “Our findings yield a more complete description of the driving forces behind natural variation patterns; they should inspire new avenues for theoretical and empirical research on the role of mutation in evolution.”

The co-authors from UC Davis are Daniel Klebstein, Mariel Linsink and Mary Klein from the Department of Plant Sciences. Researchers from the Carnegie Institution for Science, Stanford University, Westfield State University, Montpellier University, Uppsala University, College of Charleston and South Dakota State University contributed to the research.

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more information:
Detlef Weigel, Mutation bias reflects natural selection in Arabidopsis thaliana, temper nature (2022). DOI: 10.1038/s41586-021-04269-6.

the quote: Study challenges evolutionary theory that DNA mutations are random (2022, January 12) Retrieved January 12, 2022 from

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