Vacuolar processing enzymes in the plant life cycle

Abstract

Summary Vacuolar processing enzyme (VPE) is a cysteine‐type endopeptidase that has a substrate‐specificity for asparagine or aspartic acid residues and cleaves peptide bonds at their carboxyl‐terminal side. Various vacuolar proteins are synthesized as larger proprotein precursors, and VPE is an important initiator of maturation and activation of these proteins. It mediates programmed cell death (PCD) by provoking vacuolar rupture and initiating the proteolytic cascade leading to PCD. Vacuolar processing enzyme also possesses a peptide ligation activity, which is responsible for producing cyclic peptides in several plant species. These unique functions of VPE support developmental and environmental responses in plants. The number of VPE homologues is higher in angiosperm species, indicating that there has been differentiation and specialization of VPE function over the course of evolution. Angiosperm VPEs are separated into two major types: the γ‐type VPEs, which are expressed mainly in vegetative organs, and the β‐type VPEs, whose expression occurs mainly in storage organs; in eudicots, the δ‐type VPEs are further separated within γ‐type VPEs. This review also considers the importance of processing and peptide ligation by VPE in vacuolar protein maturation.

Structural and functional studies of Arabidopsis thaliana legumain beta reveal isoform specific mechanisms of activation and substrate recognition

“…In contrast to mammals, where only one functional legumain isoform is expressed, Arabidopsis thaliana contains four genes coding for legumains (α, β, γ, and δ-VPE) and other plants, even up to eight functional variants ( 4 ). Plant legumains are expressed primarily in seeds and vegetative organs, consistent with their phylogenetic grouping into two angiosperm clades, the seed type (β-VPE) and nonseed or vegetative type VPEs (α-, γ- and δ-VPE) ( 5 – 8 ). Vegetative legumains are found in lytic vacuoles and have been suggested to play critical roles in plant programmed cell death and may functionally substitute for the caspases, which are absent in plants ( 9 ).…”

MhNRAMP1 From Malus hupehensis Exacerbates Cell Death by Accelerating Cd Uptake in Tobacco and Apple Calli

“…The excessive accumulation of reactive oxygen species (ROS) caused by Cd exacerbates DNA damage and increases cell membrane permeability and the loss of transmembrane potential (Li et al, 2003;Michelle et al, 2014;Li et al, 2017;Huybrechts et al, 2019;Wang et al, 2019b). Vacuolar rupture is a unique and important factor causing cell death in higher plants, which is mediated by vacuolar processing enzyme (VPE) (Yamada et al, 2020). VPE causes vacuolar rupture and initiates the proteolytic cascade leading to cell death and also possesses peptide ligation activity for producing cyclic peptides, which support developmental and environmental responses in plants (Jiang et al, 2019;Yamada et al, 2020).…”

“…Vacuolar rupture is a unique and important factor causing cell death in higher plants, which is mediated by vacuolar processing enzyme (VPE) (Yamada et al, 2020). VPE causes vacuolar rupture and initiates the proteolytic cascade leading to cell death and also possesses peptide ligation activity for producing cyclic peptides, which support developmental and environmental responses in plants (Jiang et al, 2019;Yamada et al, 2020). VPE is therefore recognized as a moderator in response to environmental tolerances.…”

Genome-Wide Identification and Characterization of Vacuolar Processing Enzyme Gene Family and Diverse Expression Under Stress in Apple (Malus × Domestic)

“…Expression of IbVPE1 from sweet potato in Arabidopsis affected leaf development, flowering time and chlorophyll catabolism (Jiang et al, 2019). Previous study also reported VPEs were involved in the regulation of seed size in barley (Radchuk et al, 2018;Yamada et al, 2019), the breakdown of apical bud dominance in potato tubers (Teper-Bamnolker et al, 2012), the development and senescence of root nodules (Van Wyk et al, 2014;Cilliers et al, 2017), and the floral bud abortion of radish (Zhang et al, 2013).…”