Diet of Arbuscular Mycorrhizal Fungi: Bread and Butter?

• Published in: Trends in plant science Vol. 22; no. 8; pp. 652 - 660
• Main Authors: Rich, Mélanie K., Nouri, Eva, Courty, Pierre-Emmanuel, Reinhardt, Didier
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.08.2017; Elsevier BV; Elsevier
• Subjects: arbuscular mycorrhiza; Arbuscular mycorrhizas; Carbohydrate Metabolism; carbon; Carbon - metabolism; Carbon sinks; diet; Environmental Sciences; Fatty-acid synthase; Flowers & plants; Fungi; genes; Glomeromycota; Glomeromycota - physiology; Hexoses; Host plants; Life Sciences; Lipid Metabolism; Lipids; Metabolism; Mycorrhizae - physiology; mycorrhizal fungi; Nutrients; Nutrition; Plant Roots - microbiology; Plants - metabolism; Plants - microbiology; Rhizophagus irregularis; roots; Soil microorganisms; Symbiosis; Vegetal Biology; vesicular arbuscular mycorrhizae; lipids; arbuscular mycorrhiza; glomeromycota; symbiosis; cuticular lipsecretion; fatty-acid synthases; exine formation; H+atpase; phosphate transporter; cuticle development; medicago-truncatula; lotus-japonicus; gene-expression; cassette ABC transporter
• ISSN: 1360-1385; 1878-4372; 1878-4372
• DOI: 10.1016/j.tplants.2017.05.008

Most plants entertain mutualistic interactions known as arbuscular mycorrhiza (AM) with soil fungi (Glomeromycota) which provide them with mineral nutrients in exchange for reduced carbon from the plant. Mycorrhizal roots represent strong carbon sinks in which hexoses are transferred from the plant host to the fungus. However, most of the carbon in AM fungi is stored in the form of lipids. The absence of the type I fatty acid synthase (FAS-I) complex from the AM fungal model species Rhizophagus irregularis suggests that lipids may also have a role in nutrition of the fungal partner. This hypothesis is supported by the concerted induction of host genes involved in lipid metabolism. We explore the possible roles of lipids in the light of recent literature on AM symbiosis. AM fungi receive monosaccharides, in particular glucose, from the plant host. However, the fact that AM fungi lack FAS-I suggests that AM fungi may also receive lipidic nutrients. The coordinated induction in the host of genes involved in fatty acid and lipid biosynthesis provides further support to this idea. Thus, AM fungi may receive a complex diet from their hosts.