Abstract
Vacuolar processing enzyme (VPE) is responsible for the maturation of vacuolar proteins. Arabidopsis δVPE was specifically and transiently expressed in two cell layers of the seed coat (ii2 and ii3) at an early stage of seed development. At this stage, cell death occurs in ii2 and ii3 cell layers. In a δVPE-deficient mutant, cell death of the two layers of the seed coat was delayed. Immunocytochemical analysis localized δVPE to electron-dense structures inside and outside the walls of seed coat cells that undergo cell death. We investigated the protein compornents of the structures. Interestingly, δVPE exhibits caspase-1-like activity, which has been detected in various types of plant cell death. Our results suggest that, at the early stage of seed development, δVPE is involved in cell death of limited cell layers, the purpose of which is to form a seed coat.
S. Nakaune et al., The Plant Cell, 2005, vol.17, 876-887
