Characteristics of soybean 1-Cys peroxiredoxin and its behavior in seedlings under flooding stress

By previous proteomic analysis, the amount of proteins exhibiting similarity to 1-Cys peroxiredoxin (Prx), a thiol-dependent peroxidase, was shown to be higher in seedlings of soybean [Glycine max (L.) Merr.] suffering from flooding stress than in normally grown seedlings. In this study, we characterized soybean 1-Cys Prx to elucidate the relationship of the protein to flooding stress. In the soybean genome, two genes corresponding to 1-Cys Prx (designated as GmPer1a, GmPer1b) exist. GmPer1a encodes a polypeptide containing the putative catalytic site, and a recombinant GmPer1a protein exhibited peroxidase activity. On the other hand, the GmPer1b contains a stop codon inside the deduced polypeptide-coding region, indicating that GmPer1b might be a pseudogene. The GmPer1a was expressed in developing seeds and transiently in germinating seeds of soybean. It was no longer expressed in 2-day-old seedlings, and was not induced by flooding treatment. The GmPer1 protein was synthesized in developing seeds, and was degraded during germination and growth. In addition, two forms of GmPer1 protein existed in both submerged and normally grown seedlings, and the amount of both forms was higher in the submerged seedlings. These suggest that both normal and post-translationally modified forms of GmPer1 might remain in seedlings suffering from flooding stress as a result of growth retardation.