Plants fix UV damage to DNA with robust repair system

Scientists have detailed the ability of plants to repair DNA damaged by the sun's ultraviolet rays.

The new study, published this week in the journal Nature Communications, marks the first time scientists have mapped the "nucleotide excision repair" system inside an entire multicellular organism.

The newly mapped system is similar to DNA repair systems found in humans and other animals but is more efficient at repairing active genes.

"These findings advance our understanding of DNA repair mechanisms common among all organisms and may also have practical applications," Ogun Adebali, a postdoctoral researcher at the University of North Carolina, said in a news release.

Unlike humans, plants can't put on sunscreen or take refuge inside. Plus, they need significant amounts of sun to survive -- so they can't avoid DNA damage caused by exposure to the sun's ultraviolet rays. Thus, they require a robust DNA repair system.

The study was made possible by a new analysis technique that allows researchers to sequence the small strands of damaged DNA removed from plant chromosomes during the excision repair process. Scientists can reference the snippets against a healthy plant genome to determine which sections of DNA are under repair.

Scientists used their analysis technique, XR-seq, to identify DNA repair activities happening inside a small, flowering plant called thale cress, Arabidopsis thaliana. The thale cress was exposed to UV radiation inside the lab.

The analysis showed DNA repair happens more efficiently for active genes -- DNA sequences that are actively being translated into RNA and triggering the production of proteins. So-called transcription-coupled repair has previously been documented in mammals and bacteria.

"Here we found that the jump in efficiency for transcription-coupled repair is even more pronounced in plants than it is in animals or bacteria," said postdoctoral researcher Onur Oztas.

When researchers left thale cress samples in the dark, they observed continued DNA-repair activities.

"This implies that excision repair is needed to fix DNA damage from other, unknown factors besides UV," Oztas said. "We'd like to identify and characterize those unknown factors and find out how excision repair fixes the types of damage they cause."

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