New findings detail alternative immune pathways in duckweed species

September 26, 2022

Duckweed—a tiny, invasive subfamily of plants capable of reproducing in a day—could harbor an untapped reserve of pathogenic resistance, according to new research from the lab of Ksenia Krasileva, a professor in the Department of Plant and Microbial Biology.

Unlike most plants that have an “innate immune system” encoded in their DNA, duckweed species lack an important chemical pathway previously thought to be essential for plant health. The new findings, published September 25 in the journal New Phytologist, document a recently expanded set of antimicrobial genes that could improve disease resistance in crops like rice and wheat.

“We knew that wild plants like duckweeds are able to survive in diverse environments and defend against a range of plant diseases,” said the study’s lead author Erin Baggs, a postdoctoral researcher in Krasileva’s lab. “What we didn’t know was how exactly they did that. It’s something that’s still unknown for the majority of plants.”

Baggs and other members of the Krasileva lab infected different duckweed species with known bacterial pathogens that typically afflict tomatoes and pepper and observed them for symptoms. Baggs said species that appeared asymptomatic were thought to potentially possess new sources of disease resistance outside of known immune pathways and were subject to additional study.

Next, they used molecular sequencing to identify which immune pathways were activated after exposure to a pathogen and found that the pathways typically used to trigger a response in crops remained inactive within duckweed. According to Baggs, the alternative gene encoding for potential antimicrobial proteins—which are more abundant in duckweed species than other plants—were commonly activated in duckweed plants.

“Together, the results suggest that duckweed could have previously unknown mechanisms of disease resistance that could be utilized to better protect crops,” she said.

The findings align with one of the main questions explored by researchers in Krasileva’s lab: uncovering how organisms with innate immunity recognize rapidly evolving pathogens. Baggs said the group hopes to build on their understanding of alternative immune pathways in duckweed to work toward engineering improved immune responses in plants.

Co-authors of the study include Krasileva; Meije Tiersma, a former undergraduate researcher who worked closely with Baggs; and Todd Michael and Bradley Abramson, researchers from the Salk Institute for Biological Studies.