Characterization of soybean (hydroxy) proline-rich early nodulins

Abstract

Legume root nodule formation can be divided into three major stages denoted as "pre-infection", "infection and nodule formation" and "nodule function". During the formation of the root nodule the nodulin genes are differentially expressed and dependent on the time point of the induction of expression they are divided into early and late nodulin genes. The onset of expression of this latter group of genes coincides with the start of nitrogen fixation. The leghemoglobin genes are the best characterized genes resorting in this group. Early nodulin genes are expressed markedly before the nitrogen fixation process starts and hence are likely to be involved in nodule formation and infection. In order to understand these processes our research program is focussed on early nodulin genes. Previously we described the isolation and characterization of a soybean early nodulin cDNA clone, pGmENOD2, coding for N-75, a prolinerich protein, involved in root nodule morphogenesis. Here we report the analysis of two other soybean cDNA clones representing early nodulin genes. Both encode proline-rich proteins as well.