Legumes Distinguish Friendly from Pathogenic Bacteria & Fungi Using First Known Exopolysaccharide Receptor; Research Alters Understanding of Carbohydrates As Signaling Molecules

An international team of researchers has discovered how legumes are able to tell helpful and harmful invading bacteria (and fungi) apart. The research has implications for improving the understanding of how other plants, animals, and humans interact with bacteria in their environment and defend themselves against hostile infections. These findings can have profound implications for both agricultural research and medical science. The study, which changes the understanding of carbohydrates as signal molecules, was published online on June 27, 2015 in the leading international journal Nature. The article is titled “A Plant Receptor-Like Kinase Required for Both Bacterial and Fungal Symbiosis.” Legumes form a unique symbiotic relationship with bacteria known as rhizobia, which the the legumes allow to infect their roots. This leads to root nodules being formed in which the bacteria convert nitrogen from the air into ammonia that the plant can use for growth. Exactly how these plants are able to distinguish and welcome compatible rhizobia for this self-fertilizing activity - while halting infection by incompatible bacteria - has been a mystery. Now the researchers at the Centre for Carbohydrate Recognition and Signalling (CARB) from Denmark and New Zealand and their collaborators from the Centre for Complex Carbohydrate Research in Georgia, USA, have determined how legumes perceive and distinguish compatible bacteria based on the exopolysaccharides featured on the invading cells' surfaces. Using an interdisciplinary approach involving plant and microbial genetics, biochemistry, and carbohydrate chemistry, the researchers have identified the first known exopolysaccharide receptor gene, called Epr3.
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