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Naturally Induced Secretions of the Potato Cyst Nematode Co-stimulate the Proliferation of Both Tobacco Leaf Protoplasts and Human Peripheral Blood Mononuclear Cells

¹The Graduate School for Experimental Plant Sciences, Laboratory for Nematology, Wageningen University and Research Center, Binnenhaven 10, 6709 PD, Wageningen, The Netherlands; ²The Graduate School for Experimental Plant Sciences, Laboratory for Monoclonal Antibodies, Wageningen University and Research Center, Binnenhaven 10, 6709 PD, Wageningen, The Netherlands; ³Department of Immunology, University Hospital for Children and Youth “Het Wilhelmina Kinderziekenhuis”, P.O. Box 18009, 3501 CA, Utrecht, The Netherlands

Naturally induced secretions from infective juveniles of the potato cyst nematode Globodera rostochiensis co-stimulate the proliferation of tobacco leaf protoplasts in the presence of the synthetic phytohormones α-naphtha-leneacetic acid (NAA) and 6-benzylaminopurine (BAP). With the use of a protoplast-based bioassay, a low-molecular-weight peptide(s) (<3 kDa) was shown to be responsible for the observed effect. This mitogenic oligopeptide(s) is functionally dissimilar to auxin and cytokinin and, in addition, it does not change the sensitivity of the protoplasts toward these phytohormones. In combination with the mitogen phytohemagglutinin (PHA), cyst nematode secretions also co-stimulated mitogenesis in human peripheral blood mononuclear cells (PBMC). The stimulation of plant cells isolated from nontarget tissue—these nematodes normally invade the roots of potato plants—suggests the activation of a general signal transduction mechanism(s) by an oligopeptide(s) secreted by the nematode. Whether a similar oligopeptide-induced mechanism underlies human PBMC activation remains to be investigated. Reactivation of the cell cycle is a crucial event in feeding cell formation by cyst nematodes. The secretion of a mitogenic low-molecular-weight peptide(s) by infective juveniles of the potato cyst nematode could contribute to the redifferentiation of plant cells into such a feeding cell.