A distinct subfamily of papain-like cystein proteinases regulated by senescence and stresses in Glycine max

GMCP3 encodes a cystein proteinase of Glycine max belonging to the papain-like family (C1A in MEROPS database) that was previously found to be involved in the mobilization of protein reserves during seed germination. Here, we report that GMCP3 is induced by senescence and diverse stresses in non-seed tissues, thus indicating a more general function in plants. Cladistic analysis of papain-like proteins of plants indicated that GMCP3, along with related proteases of other species, belongs to a distinct new group within the C1A family, which can also be distinguished by the four-exon structure of the gene. We also describe the genomic organization of GMCP3 revealing the presence of two closely related copies that are transcriptionally regulated in a similar way, although only one appears to be functional.