Beneficial associations between Brassicaceae plants and fungal endophytes under nutrient-limiting conditions: evolutionary origins and host–symbiont molecular mechanisms

• Published in: Current opinion in plant biology 2018-08, Vol.44, p.145-154
• Main Authors: Hiruma, Kei, Kobae, Yoshihiro, Toju, Hirokazu
• Format: Article
• Language: English
• ISSN: 1369-5266; 1879-0356
• DOI: 10.1016/j.pbi.2018.04.009

•Brassicaceae plants associate with a vast diversity of fungal endophytes.•Several fungal endophytes of Brassicaceae plants transfer phosphorus to hosts.•Trp-derived secondary metabolites in Brassicaceae regulate beneficial interactions with fungal endophytes.•Phosphate availability appears to affect the Trp-derived metabolite pathway. Brassicaceae plants have lost symbiotic interactions with mutualistic mycorrhizal fungi, but, nonmycorrhizal Brassicaceae associate with diverse taxonomic groups of mutualistic root-endophytic fungi. Distantly related fungal endophytes of Brassicaceae plants transfer phosphorus to the hosts and promote plant growth, thereby suggesting that the beneficial function was independently acquired via convergent evolution. These beneficial interactions appear tightly regulated by the tryptophan-derived secondary metabolite pathway, which specifically developed in Brassicaceae. Importantly, phosphate availability and types of colonizing microbes appear to influence the metabolite pathway. Thus, endophytes of Brassicaceae may have evolved to adapt to the Brassicaceae-specific traits. Future comparative functional analyses among well-defined endophytic fungi and their relatives with distinct life strategies and host plants will help understand the mechanisms that establish and maintain beneficial interactions.