Abstract
Vacuolar processing enzyme (VPE) is involved in the pathogen-, the toxin-induced cell death and the cell death during seed coat formation. Arabidopsis has four VPE homologues, and two VPEs play the role in vegetative organs. Both the mRNA level and activity of the vegetative VPE were increased in the leaves during senescence. The VPE activity was suppressed in extract from ethylene-insensitive plant and salicylic acid-deficient plant. This result indicates that two phytohormones are involeved in the VPE activity during senescence. Leaf senescence delayed slightly in the Arabidopsis VPE-null mutant, which lacks all four VPE genes. Some proteinases that localize in the vacuoles accumulated in the leaves of the VPE-null mutant compared with wild-type leaves. Our results suggest that vegetative VPE regulates the activation of some functional proteins in the vacuoles during leaf senescence.
