Studies on the nutrient uptake by the beet cyst nematodeHeterodera schachtiibyin situmicroinjection of fluorescent probes into the feeding structures inArabidopsis thaliana

SUMMARY A method was developed, which enables substances to be injected into the feeding structure (syncytium) established by Heterodera schachtii in roots of Arabidopsis thaliana . The technique was used to study the uptake of nutrients by the feeding nematode. The fluorescent dye lucifer yellow CH (LYCH) and fluorescence-labelled dextrans of different molecular weights were injected into the thin and translucent roots of A. thaliana . Such roots are a feature of this plant and they provide optimal conditions for microinjection. Injected LYCH was taken up by feeding juveniles and adults, indicated by the staining of the alimentary duct and the digestive system. Fluorescent dextrans of 3, 10 and 20 kDa but not of 40 and 70 kDa were ingested, suggesting that molecules of a maximum Stokes radius of 3·2 to 4·4 nm are taken up. It is likely that the feeding tube, forming the interface between the plant cytosol and the nematode's digestive system, is responsible for this size exclusion effect. The injected fluorescent substances were not detected in plant cells adjacent to the syncytium or in the root vascular elements. Injections into parts of roots which were infested by several nematodes revealed that feeding H. schachtii individuals may share one syncytium.