EARLY NODULIN GENE-EXPRESSION DURING NOD FACTOR-INDUCED PROCESSES IN VICIA-SATIVA

Rhizobium leguminosarum bv. viciae-secreted Nod factors are able to in duce root hair deformation, the formation of nodule primordia and the expression of early nodulin genes in Vicia sativa (vetch). To obtain m ore insight into the mode of action of Nod factors the expression of e arly nodulin genes was followed during Nod factor-induced root hair de formation and nodule primordium formation. The results of these studie s suggested that the expression of VsENOD5 and VsENOD12 is not require d for root hair deformation. In the Nod factor-induced primordia both VsENOD12 and VsENOD40 are expressed in a spatially controlled manner s imilar to that found in Rhizobium-induced nodule primordia. In contras t, VsENOD5 expression has never been observed in Nod factor-induced pr imordia, showing that the induction of VsENOD5 and VsENOD12 expression are not coupled. VsENOD5 expression is induced in the root epidermis by Nod factors and in Rhizobium-induced nodule primordia only in cells infected by the bacteria, suggesting that the Nod factor does not rea ch the inner cortical cells.