Arginine metabolism of Arabidopsis thaliana is modulated by Heterodera schachtii infection

The plant-parasitic cyst nematode Heterodera schachtii induces syncytial feeding structures in the roots of host plants. These syncytia provide all required nutrients, water and solutes to the parasites. Previous studies on the composition of primary metabolites in syncytia revealed significantly increased amino acid levels. However, mainly due to technical limitations, little is known about the role of arginine in plant-nematode interactions. This free amino acid plays a central role in the plant primary metabolism and serves as substrate for metabolites involved in plant stress responses. Thus, in the present work, expression of genes coding for the enzymes of arginine metabolism were studied in nematode-induced syncytia compared to non-infected control roots of Arabidopsis thaliana. Further, amiRNA lines were constructed and T-DNA lines were isolated to test their effects on nematode development. While the silencing of genes involved in arginine synthesis increased nematode development, most T-DNA lines did not show any significant difference from the wild type. Amino acid analyses of syncytia showed that they accumulate high arginine levels. In addition, manipulating arginine cycling had a global effect on the local amino acid composition in syncytia as well as on the systemic amino acid levels in roots and shoots.