Towards Understanding the Involvement of H+-ATPase in Programmed Cell Death of Psammosilene tunicoides after Oxalic Acid Application.

Xinyu Jiang,Yuan Qin,Mohammad Aqa Mohammadi,Zongshen Zhang

doi:10.3390/molecules26226957

Abstract

Psammosilene tunicoides is a unique perennial medicinal plant species native to the Southwestern regions of China. Its wild population is rare and endangered due to over-excessive collection and extended growth (4–5 years). This research shows that H+-ATPase activity was a key factor for oxalate-inducing programmed cell death (PCD) of P. tunicoides suspension cells. Oxalic acid (OA) is an effective abiotic elicitor that enhances a plant cell’s resistance to environmental stress. However, the role of OA in this process remains to be mechanistically unveiled. The present study evaluated the role of OA-induced cell death using an inverted fluorescence microscope after staining with Evans blue, FDA, PI, and Rd123. OA-stimulated changes in K+ and Ca2+ trans-membrane flows using a patch-clamp method, together with OA modulation of H+-ATPase activity, were further examined. OA treatment increased cell death rate in a dosage-and duration-dependent manner. OA significantly decreased the mitochondria activity and damaged its electron transport chain. The OA treatment also decreased intracellular pH, while the FC increased the pH value. Simultaneously, NH4Cl caused intracellular acidification. The OA treatment independently resulted in 90% and the FC led to 25% cell death rates. Consistently, the combined treatments caused a 31% cell death rate. Furthermore, treatment with EGTA caused a similar change in intracellular pH value to the La3+ and OA application. Combined results suggest that OA-caused cell death could be attributed to intracellular acidification and the involvement of OA in the influx of extracellular Ca2+, thereby leading to membrane depolarization. Here we explore the resistance mechanism of P. tunicoides cells against various stresses endowed by OA treatment.

Highlights

Oxalic acid (OA) is a simple dicarboxylic acid that widely exists in biological systems and plays functional role in plants
The regulation and execution processes of programmed cell death (PCD), the processes induced by abiotic factors, remain unknown
The processes and biochemical and molecular pathways of plant PCD induced by abiotic stress are very important for understanding the tolerance/resistance of plants to abiotic stress, enabling plant tolerance to be increased in the future by manipulating the inhibition of PCD

Summary

Introduction

Oxalic acid (OA) is a simple dicarboxylic acid that widely exists in biological systems and plays functional role in plants. The secretion of OA was essential to affect pathogenicity in plants by S. sclerotiorum fungal pathogen infection [11]. OA appears to function during plant-microbe interaction by triggering the pathways responsible for programmed cell death (PCD) in plants and may act as a signalling molecule [15]. The transduction of signals leading to the death of Arabidopsis cells in response to OA treatment was associated with the activity of the anion channel [16]. This death displayed characteristic hallmarks of PCD, such as cell shrinkage, de novo protein synthesis, cleavage of nuclear DNA, activation of anion channel-dependent, and gene expression [16]

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