Characterization and expression analysis of the yellow lupin (Lupinus luteus L.) gene coding for nodule specific proline-rich protein

The LlPRP2 gene coding for a proline-rich protein shows a high level of sim ilarity to, as well as significant differences from the family of ENOD2 nod ule-specific genes. Several sequence motifs with putative regulatory functi on were identified in the 5' and 3' noncoding regions of the LIPRP2 gene. N orthern blot analysis revealed that the expression of the LIPRP2 gene begin s 9 days after inoculation of yellow lupin roots with Bradyrhixobium sp. (L upinus); the expression is restricted to symbiotic nodules and is not detec ted in other tissues or organs. Detailed hybridization analysis showed that , when expression is activated, the LIPRP2 transcript is modified so as to produce at least three bands and a continuous distribution of decay interme diates. The modification of the LIPRP2 transcript probably involves degrada tion from the 5'- and/or 3'-ends of the RNA molecules. Southern blot analys is indicates that only one gene is present in the yellow lupin genome. The presence of genes homologous to the LIPRP2 gene was confirmed for three cul tivars of yellow lupin and for Lupinus angustifolius. However, LIPRP2 homol ogues were not detected in Lupinus albus cv. Bac, indicating that this plan t may lack the ENOD2 sequence.