Naturally induced secretions of the potato cyst nematode co-stimulate the proliferation of both tobacco leaf protoplasts and human peripheral blood mononuclear cells

Naturally induced secretions from infective juveniles of the potato cyst ne matode Globodera rostochiensis costimulate the proliferation of tobacco lea f protoplasts in the presence of the synthetic phytohormones a-naphthalenea cetic acid (NAA) and 6-benzylaminopurine (BAP). With the use of a protoplas t-based bioassay, a low-molecular-weight peptide(s) (<3 kDa) was shown to b e responsible for the observed effect. This mitogenic oligopeptide(s) is fu nctionally dissimilar to auxin and cytokinin and, in addition, it does not change the sensitivity of the protoplasts toward these phytohormones. In co mbination with the mitogen phytohemagglutinin (PHA), cyst nematode secretio ns also co-stimulated mitogenesis in human peripheral blood mononuclear cel ls (PBMC). The stimulation of plant cells isolated from nontarget tissue-th ese nematodes normality invade the roots of potato plants-suggests the acti vation 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 nemato des. The secretion of a mitogenic low-molecular-weight peptide(s) by infect ive juveniles of the potato cyst nematode could contribute to the rediffere ntiation of plant cells into such a feeding cell.