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Precursors for radish storage proteins were identified by immunoprecipitation of cell-free protein-synthesis products. The 12s globulin polypeptides (21 000-33000 M,) are made from four larger precursors (47 500-60000 M,) and the 1.7 S albumin polypeptides (7000-12000 M,) are synthesized as eight products of M , about 20000. From a cDNA library, several clones have been identified, using heterologous cDNA probes for rapeseed cruciferin and napin, and two of them (pAE10 and pBA3) used to hybrid-select the corresponding mRNA. The napin cDNA clone selects all translation products immunoprecipitated by anti-napin antibodies whereas the cruciferin clone selects only one polypeptide among the four recognized by 12s antibodies. The 32s globulin and the 1.7s albumin message sizes were estimated to be 1950 and 800 nucleotides respectively. Experiments carried out with mRNA populations from different maturation stages suggest a sequential gene expression for the two major storage protein families. In addition two napin subfamilies can be distinguished by their expression pattern. In dry seed, napin mRNA is not detectable and the amount of cruciferin mRNA decreased considerably so that it no longer represents a major fraction of dry seed mRNA.The immature seed represents a stage of plant development during which reserve materials and especially proteins are synthesized and stored. It provides a particularly attractive model for the study of the expression of developmentally regulated genes.In several plants it has been reported that mRNA coding for storage proteins constitutes a major fraction of dry seed mRNA [I, 21. In order to challenge this hypothesis in radish, a plant on which we had already analysed the complexity and fate of stored mRNA during germination [3, 41, it was necessary to characterize the mRNAs for the major families of storage proteins from this plant. It belongs to the Cruciferae, a family of which, with the exception of rapeseed [5 -71, nothing is currently known on the biosynthesis of the storage proteins and on the organization of the corresponding genes. Such information is necessary to compare the regulation, the organization and evolution of these genes with those coding for similar proteins in different families.In radish seeds and other cruciferae two major fractions have been characterized [5, 81. The first one is the 12s socalled globulin or cruciferin. It is composed of a series of polypeptides ranging from 21 kDa to 33 kDa with heterogeneity in charge. The structure of this globulin, made of six units of two polypeptides linked by disulfide bonds, is closely related to that of the legumin group [9]. The second most important radish storage protein is a 1.7s basic albumin, also named napin [5, 6, 81, consisting of subunits with molecular mass in the range of 7-12 kDa associated by disulfide bridges. We have isolated poly(A)-rich RNA from immature seeds and analysed their in vitro translation products. We report here the immunodetection of precursor molecules of 12s and 1.7s proteins and the ...

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