Phloem loading in Verbascum phoeniceum L. depends on the synthesis of raffinose-family oligosaccharides.

ABSTRACT: Phloem loading is the initial step in photoassimilate export and the one that creates the driving force for mass flow. It has been proposed that loading occurs symplastically in species that translocate carbohydrate primarily as raffinose family oligosaccharides (RFOs). In these plants, dense fields of plasmodesmata connect bundle sheath cells to specialized companion cells (intermediary cells) in the minor veins. According to the polymer trap model, advanced as a mechanism of symplastic loading, sucrose from the mesophyll diffuses into intermediary cells and is converted there to RFOs. This process keeps the sucrose concentration low and, because of the larger size of the RFOs, prevents back diffusion. To test this model, the RFO pathway was down-regulated in Verbascum phoeniceum L. by su

SUBMITTER: McCaskill A 

PROVIDER: S-EPMC2148338 | biostudies-literature | 2007 Dec

REPOSITORIES: biostudies-literature