CHARACTERIZATION AND GENE-EXPRESSION OF NODULIN NPV30 FROM COMMON BEAN

We previously reported that transcripts for a 30-kD nodulin (Npv30) ar e very abundant in the nodule. In this paper we describe the isolation and characterization of Npv30 cDNA and genomic clones. Npv30 has the following characteristic features: (a) a putative signal sequence at t he deduced amino-terminal region, (b) a proline-rich stretch at the ca rboxy terminus, and (c) a characteristic domain of four cysteines that resemble metal-binding sites. In Phaseolus vulgaris L., Npv30 is enco ded by a small gene family that shares discrete sequence homologies wi th another small gene family in soybean. An antibody against a beta-ga lactosidase-Npv30 fusion protein detected two proteins of 28 and 30 kD . Although Npv30 transcripts are very abundant, they encode proteins t hat are hardly detected in nodule fractions, suggesting that these pro teins have a short half-life and/or the mRNAs are strongly regulated a t the translational level. Npv30 transcripts were detected in the infe cted cells of the nodule by in situ hybridization experiments.