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Arabidopsis contains 317 genes for defensin-like (DEFL) peptides. DEFLs have been grouped into different families based mainly on cysteine motifs. The DEFL0770 group contains seven genes, of which four are strongly expressed in roots. We found that the expression of these genes is downregulated in syncytia induced by the beet cyst nematode <i>Heterodera schachtii</i> as revealed by RNAseq analysis. We have studied one gene of this group, <i>At3g59930</i>, in detail. A promoter::GUS line revealed that the gene is only expressed in roots but not in other plant organs. Infection of the GUS line with larvae of <i>H. schachtii</i> showed a strong downregulation of GUS expression in infection sites as early as 1 dpi, confirming the RNAseq data. The At3g59930 peptide had only weak antimicrobial activity against <i>Botrytis cinerea</i>. Overexpression lines had no enhanced resistance against this fungus but were more resistant to <i>H. schachtii</i> infection. Our data indicate that <i>At3g59930</i> is involved in resistance to nematodes which is probably not due to direct nematicidal activity.