Localization of peroxidase mRNAs in soybean seeds by in situ hybridization

The soybean Ep gene encodes an anionic peroxidase enzyme that accumulates i n large amounts in seed coat tissues. We have isolated a second peroxidase gene, Prx2, that is also highly expressed in developing seed coat tissues. Sequence analysis of Prx2 cDNA indicates that this transcript encodes a cat ionic peroxidase isozyme that is far removed from Ep in peroxidase phylogen y. To determine the expression patterns for these two peroxidases in develo ping seeds, the abundance and localization of the Ep and Prx2 transcripts w ere compared by in situ hybridization. Results show the expression of Ep be gins in a small number of cells flanking the vascular bundle in the seed co at, spreads to encircle the seed, and then migrates to the hourglass cells as they develop. Expression of Prx2 occurs throughout development in all ce ll layers of the seed coat, and is also evident in the pericarp and embryo. Nonetheless, the Ep-encoded enzyme accounts for virtually all of the perox idase activity detected in mature seed coats. The Prx2 enzyme is either ins oluble in a catalytically inactive form, or is subject to degradation durin g seed maturation.