Serendipita bescii and nitrogen use efficiency in winter wheat

The Serendipitaceae are a diverse group of fungi in the Basidiomycota that encompass endophytes and lineages with ericoid, orchid and ectomycorrhizal lifestyles. Members of Serendipitaceae exhibit plant growth-promoting abilities in a great variety of plants, demonstrating little or no host specificity. Serendipita vermifera ssp. bescii is the first North American strain of Serendipita, isolated in pure culture from switchgrass (Panicum virgatum L.). The use of winter wheat (Triticum aestivum L.) as a dual-purpose forage and grain crop is important to the agricultural economies of the Southern Great Plains, USA. In this study, we sought to document the physiological responses and dissect the regulation of nitrogen and phosphate metabolism in winter wheat when colonized with S. bescii by using a transcriptomic approach. S. bescii significantly improved root branching and forage biomass in winter wheat under limited nitrogen or phosphate regime. Colonization by S. bescii activated a set of genes involved in modulating both phosphate and nitrogen starvation responses, such as auxin and ethylene-mediated root development, secretion of organic acids, adjustment of cytosolic glycolytic pathways, upregulation of ammonium transporters, and the activation of both autophagic and ubiquitin-proteasome mediated protein degradation pathways, all aimed at overall improvement in acquisition, assimilation and remobilization of these two critical nutrients. Based on transcript level gene regulation and physiological responses to nitrogen or phosphate limitation, we suggest Serendipita bescii has the potential to alleviate the phosphate starvation response and improve nitrogen use efficiency in winter wheat.