Sugar transport into nematode induced feeding sites

A group of plant parasitic nematodes, the so-called sedentary nematodes, induce specific feeding structures in roots of host plants from which nutrients are drawn. The induced feeding sites are hypertrophied metabolically highly active structures which cause a strong sink in the infected root. The beet cyst nematode Heterodera schachtii induces a symplastically isolated syncytium incorporating hundreds of modified and fused root cells. Sucrose supply of the syncytia is a critical factor for both maintenance of the syncytium and nematode development. In Arabidopsis thaliana the phloem specific sucrose (Suc) transporter AtSUC2 was shown to be specifically expressed in syncytia induced by H. schachtii. However, silcencing of AtSUC2 did neither inhibit syncytium formation nor nematode development. In silenced plants another Suc transporter gene may have compensated the function of AtSUC2. In fact, AtSUC4 (AtSUT4) was found in a syncytium-specific cDNA library and is therefore a plausible candidate. In the present study we will verify the presence of the AtSUC4 transporter in syncytia and study its role in the sugar supply. Further, we will co-silence AtSUC2 and AtSUC4 with the aid of the RNAi technique under the control of constitutive or syncytium-specific promoters in order to reach a complete interruption of sugar supply. In the produced transgenic plants the effects on local sugar partitioning by sucrose and hexose transporters, syncytium formation and nematode development will be studied with real time PCR. To get insights in the deployed sugar transport mechanisms in another plant family, tomato plants will be studied with Heterodera schachtii and another cyst nematode species (Glododera rostochiensis). In this way, general mechanisms of sugar transport in nematode infected plants will be identified and data for an important crop plants will be produced. The results of the project will on one hand improve knowledge of the physiological basis of nematode-plant interactions and, on the other hand, stimulate similar research for other plant pathogens.

A group of plant parasitic nematodes, the so-called sedentary nematodes, induce specific feeding structures in roots of host plants from which nutrients are drawn. The induced feeding sites are hypertrophied metabolically highly active structures which cause a strong sink in the infected root. The beet cyst nematode Heterodera schachtii induces a symplastically isolated syncytium incorporating hundreds of modified and fused root cells. Sucrose supply of the syncytia is a critical factor for both maintenance of the syncytium and nematode development. In Arabidopsis thaliana the phloem specific sucrose (Suc) transporter AtSUC2 was shown to be specifically expressed in syncytia induced by H. schachtii. However, silcencing of AtSUC2 did neither inhibit syncytium formation nor nematode development. In silenced plants another Suc transporter gene may have compensated the function of AtSUC2. In fact, AtSUC4 (AtSUT4) was found in a syncytium-specific cDNA library and is therefore a plausible candidate. In the present study we will verify the presence of the AtSUC4 transporter in syncytia and study its role in the sugar supply. Further, we will co-silence AtSUC2 and AtSUC4 with the aid of the RNAi technique under the control of constitutive or syncytium-specific promoters in order to reach a complete interruption of sugar supply. In the produced transgenic plants the effects on local sugar partitioning by sucrose and hexose transporters, syncytium formation and nematode development will be studied with real time PCR. To get insights in the deployed sugar transport mechanisms in another plant family, tomato plants will be studied with Heterodera schachtii and another cyst nematode species (Glododera rostochiensis). In this way, general mechanisms of sugar transport in nematode infected plants will be identified and data for an important crop plants will be produced. The results of the project will on one hand improve knowledge of the physiological basis of nematode-plant interactions and, on the other hand, stimulate similar research for other plant pathogens.