Nodulin-24 is a soybean nodulin that is expressed specifically in root nodules. It was shown to have a cleavable signal sequence and localized to a symbiosome membrane. For understanding the targeting process of nodulin-24 to the symbiosome, two different sizes of nodulin-24 cDNAs were fused to β-glucuronidase (GUS) gene and the fused constructs were introduced into tobacco plant. The presence of the fusions in transgenic plants was confirmed by polymerase chin reaction (PCR). Histochemical staining of mature tobacco leaves with X-glucuronide did not show the expression of the nodulin-24/GUS fusions. However, their expression was found in apical meristems and roots of the transgenic tobacco plants. Northern analysis of mature leaves showed the presence of transcripts for the fusions. These results indicate that the fusions were expressed, and the products may be targeted to vacuole and degraded in mature leaves, but that they were not degraded in the maturing tissues.