Fig. 6: Hypothesised mechanism of carbon transport and allocation from plants to arburscular mycorrhizal fungi.

Illustrated mechanism underpinning hexose and fatty acid biosynthesis and transport in the absence (left hand side) and presence (right hand side) of pests (aphids or plant-parasitic nematodes) that compete for host carbon resources. Critical gene upregulation upon colonisation by AM fungi indicated using red lettering, and decreased gene expression in AM fungal-colonised tissues in the presence of pests is shown in blue. MST MonoSaccharide Transporter, SWEETs Sugars Will Eventually be ExporTed, SuSy Sucrose Synthase, DIS/KASI ß-Ketoacyl-Acyl carrier protein Synthase I, RAM2 Glycerol-3-phosphate acyl transferase, STR1/2 Heterodimeric ABCG transporters. “?” represents hypothesised routes of entry for plant-derived C16:0 fatty acids into fungal cells via protein transporters or diffusion18,63,64.