Collaboration between grass seedlings and rhizobacteria to scavenge organic nitrogen in soils

Photo of annual bluegrass seedlings on agarose with 0.01% protein, showing dark brown H2O2 zones around roots of seedlings.
Photo of annual bluegrass seedlings on agarose with 0.01% protein, showing dark brown H2O2 zones around roots of seedlings.

Plants require nitrogen to make proteins, nucleic acids and other biological molecules. It is widely accepted that plants absorb inorganic forms of nitrogen to fill their needs. However, recently it has become clear that plants also have the capacity to absorb organic nitrogen from soils. In a new study published in AoB PLANTS, White et al. describe a new kind of symbiosis involving seed-vectored rhizobacteria and grasses that is targeted at enhancing acquisition of organic nitrogen from soils. The authors propose a diurnal process where during the day roots produce and release hydrogen peroxide that oxidizes microbial exoenzymes around roots; at night hydrogen peroxide production ceases, then roots and symbiotic rhizobacteria secrete proteases that degrade the oxidized proteins to form peptides that are absorbed by roots. The existence of a mechanism for organic nitrogen scavenging in grasses emphasizes the nutritional importance of non-pathogenic microbes that associate with roots. Future applications of this process could result in new methods for the cultivation of crop plants.