The Medicago truncatula sucrose transporter family: sugar transport from plant source leaves towards the arbuscular mycorrhizal fungus

摘要: In plants, long distance transport of sugars from photosynthetic source leaves to sink organs comprises different crucial steps depending on the species and organ types. Sucrose, the main carbohydrate for long distance transport is synthesized in the mesophyll and then loaded into the phloem. After long distance transport through the phloem vessels, sucrose is finally unloaded towards sink organs. Alternatively, sugar can also be transferred to non‐plant sinks and plant colonization by heterotrophic organisms increases the sink strength and creates an additional sugar demand for the host plant. These sugar fluxes are coordinated by transport systems. Main sugar transporters in plants comprise sucrose (SUTs) and monosaccharide (MSTs) transporters which constitute key components for carbon partitioning at the whole plant level and in interactions with fungi. Although complete SUTs and MSTs gene families have been identified from the reference Dicot Arabidopsis thaliana and Monocot rice (Oriza sativa), sugar transporter families of the leguminous plant Medicago truncatula, which represents a widely used model for studying plant-fungal interactions in arbuscular mycorrhiza (AM), have not yet been investigated.With the recent completion of the M. truncatula genome sequencing as well as the release of transcriptomic databases, monosaccharide and sucrose transporter families of M. truncatula were identified and now comprise 62 MtMSTs and 6 MtSUTs. I focused on the study of the newly identified MtSUTs at a full family scale; phylogenetic analyses showed that the 6 members of the MtSUT family distributed in all three Dicotyledonous …