LIPO-OLIGOSACCHARIDES OF RHIZOBIUM INDUCE INFECTION-RELATED EARLY NODULIN GENE-EXPRESSION IN PEA ROOT HAIRS

This paper shows that lipo-oligosaccharides (Nod factors) synthesized by Rhizobium bacteria elicit the induction of infection-related early nodulin genes (PsENOD5 and PsENOD12) in pea root hairs. R. legominosar um bv. viciae secretes a mixture of Nod factors containing a C18 fatty acid chain with 4 (C18:4) or 1 double bond (C18:1). Purified Nod fact ors harbouring either a C18:4 or a C18:1 acyl moiety induce the expres sion of the pea early nodulin genes, PsENOD5 and PsENOD12, but the kin etics of induction are different. The expression of both early nodulin genes is induced in a transient manner by the purified Nod factors wh ile a mixture of the Nod factors extends the period during which these genes are expressed. In spite of the host-specific nature of the infe ction process, heterologous Nod factors of R. meliloti also induce the expression of PsENOD5 and PsENOD12 genes, though with a marked delay compared with the homologous compounds.