Peptide in alfalfa holds promise for increased yields

University of Massachusetts Amherst molecular biologists have found a peptide in alfalfa that may be able to improve crop yields without increased fertilizer.

Alfalfa uses an advanced process for putting nitrogen-fixing bacteria, rhizobia, to work more efficiently on plant roots. The study’s lead author and postdoctoral researcher is Minsoo Kim, who worked along with former undergraduate student Chris Waters and professor Dong Wang of UMass Amherst's biochemistry and molecular biology department, with colleagues at the Noble Foundation in Oklahoma.

Researchers have discovered the pepside DNF4, also known as NCR211, can act as a sort of double agent. DNF4 supports nitrogen-fixing bacteria when inside the plant, but its actions can kill free-living bacteria outside.

"They are no longer wild and able to live outside the plant," he says. "I think of it as analogous to domestication of animals by humans." Wang said, "Bacteria that can no longer proliferate as free-living individuals are a bit like slaves at that point, living to serve the plant."

Wang says a companion study also appearing in Proceedings of the National Academy of Sciences at Brigham Young University recovered a bacterial peptidase capable of degrading host NCR peptides.

"This collection of discoveries demonstrates the evolving nature in controlling bacterial differentiation in classical host-microbe mutualism," Wang and Kim said.

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