Developmentally regulated expression of soybean proline-rich cell wall protein genes

Previously, we reported the characterization of a developmentally regulated proline-rich cell wall protein (SbPRP1) gene of soybean; the encoded protein is represented by a consensus amino acid repeat structure of Pro-Pro-Val-Tyr-Lys [Hong, J.C., Nagao, R.T., and Key, J.L. (1987). J. Biol. Chem. 262, 8367-8376]. Two other closely related members of this family of proline-rich protein (PRP) genes (SbPRP2 and SbPRP3), which differ from the extensin family of cell wall proteins, have been characterized (J.C. Hong, R.T. Nagao, and J.L. Key, unpublished results). Here we report studies on the regulation of expression of this gene family during soybean development by analyzing various plant organs, including leaves, stems, and roots of etiolated seedlings and light-grown plants, as well as young and mature pods, seed coats, and cotyledons. These organs were tested at different stages of development (young and fully mature tissue). Although a high level of sequence homology is observed at the nucleotide and amino acid sequence level among these three PRP genes/proteins, there are marked differences in the patterns of expression of each gene in different plant organs and organ regions. SbPRP1 is highly expressed and is the predominant form of PRP transcript in the mature hypocotyl, root, and immature seed coat. SbPRP2 is the major form of PRP in the apical hypocotyl and young suspension culture cells. SbPRP3 is the major form of PRP gene expressed in aerial parts; it is highly expressed in leaves, although no expression is detected in the roots.(ABSTRACT TRUNCATED AT 250 WORDS)