Vacuolar processing enzymes, AmVPE1 and AmVPE2, as potential executors of ethylene regulated programmed cell death in the lace plant (Aponogeton madagascariensis)

Abstract

Perforation formation in Aponogeton madagascariensis (Mirb.) H.Bruggen (lace plant) is an excellent model for studying developmentally regulated programmed cell death (PCD). In this study, we isolated and identified two lace plant vacuolar processing enzymes (VPEs) and investigated their involvement in PCD and throughout leaf development. Lace plant VPE transcript levels were determined during seven different stages of leaf development. PCD and non-PCD cells from “window” stage leaves (in which perforations are forming) were separated through laser-capture microscopy and their transcript levels were also determined. VPE activity was also studied between the cell types, through a VPE activity-based probe JOPD1. Additionally, VPE transcript levels were studied in plants treated with an ethylene biosynthesis inhibitor, aminoethoxyvinylglycine (AVG). The two isolated VPEs, AmVPE1 and AmVPE2, are vegetative type VPEs. AmVPE1 had higher transcript levels during a pre-perforation developmental stage, immediately prior to visible signs of PCD. AmVPE2 transcript levels were higher later during window and late window stages. Both VPEs had higher transcript and activity levels in PCD compared with the non-PCD cells. AVG treatment inhibited PCD and associated increases in VPE transcript levels. Our results suggested that VPEs are involved in the execution of the ethylene-related PCD in the lace plant.

Transcriptional Regulation and Signaling of Developmental Programmed Cell Death in Plants

“…The transcription level of the ethylene receptor gene AmERS1a was significantly reduced in leaves undergoing PCD, indicating that ethylene plays an important role in dPCD during lace plant perforation (Rantong et al, 2015). Two VPE genes (AmVPE1 and AmVPE2) were identified with high expression levels in the preperforation developmental stage and late window stage of lace plants, respectively (Rantong and Gunawardena, 2018). However, the detailed transcriptional regulation mechanism is still unclear.…”

Plant Vacuolar Processing Enzymes

“…Two VPEs have been found to be involved in the execution of ethylene-related PCD in leaf pattern development in the lace plant ( Aponogeton madagascariensis (Mirb.) (Rantong and Gunawardena, 2018).…”

Determining the effect of calcium on cell death rate and perforation formation during leaf development in the novel model system, the lace plant (Aponogeton madagascariensis)

“…The sequence of intracellular remodelling of lace plant leaves undergoing PCD has also been meticulously described and shown to be highly predictable (Lord et al ., ; Wertman et al ., ; Rantong & Gunawardena, ). The time course from initial pigmentation changes to plasma membrane (PM) collapse consistently takes approximately 48 h (Wertman et al ., ).…”

“…Similarly, the time from tonoplast rupture to PM collapse has been timed at approximately 20 min (Wertman et al ., ). The above‐mentioned studies further indicate the extensively outlined and understood sequence of lace plant PCD, emphasizing the suitability of the lace plant as a model system (Gunawardena et al ., , ; Lord et al ., ; Wertman et al ., ; Dauphinee et al ., ; Rantong & Gunawardena, ).…”