The relationship between vacuolation and initiation of PCD in rice (Oryza sativa) aleurone cells

Yan Zheng,Jing Liu,Huiping Chen,Heting Zhang,Xiaojiang Deng

doi:10.1038/srep41245

Abstract

Vacuole fusion is a necessary process for the establishment of a large central vacuole, which is the central location of various hydrolytic enzymes and other factors involved in death at the beginning of plant programmed cell death (PCD). In our report, the fusion of vacuoles has been presented in two ways: i) small vacuoles coalesce to form larger vacuoles through membrane fusion, and ii) larger vacuoles combine with small vacuoles when small vacuoles embed into larger vacuoles. Regardless of how fusion occurs, a large central vacuole is formed in rice (Oryza sativa) aleurone cells. Along with the development of vacuolation, the rupture of the large central vacuole leads to the loss of the intact plasma membrane and the degradation of the nucleus, resulting in cell death. Stabilizing or disrupting the structure of actin filaments (AFs) inhibits or promotes the fusion of vacuoles, which delays or induces PCD. In addition, the inhibitors of the vacuolar processing enzyme (VPE) and cathepsin B (CathB) block the occurrence of the large central vacuole and delay the progression of PCD in rice aleurone layers. Overall, our findings provide further evidence for the rupture of the large central vacuole triggering the PCD in aleruone layers.

Highlights

Vacuolar collapse results in the loss of plasma membrane integrity and eventually leads to cell death[19,20]
When the rupture and collapse of the vacuole occurred, the permeability of the plasma membrane increased, after which the protoplast began to shrink, and FM4-64 red fluorescence observed within the cell showed that cell death had been triggered
The results showed that only a large central vacuole appeared in the cells of the rice aleurone layers treated with distilled water by using the fluorescence reagent Acridine orange (AO) and LCSM (Fig. 6A), whereas the protoplast of aleurone cells treated with cytochalasin B (CB) had disappeared (Fig. 6A)

Summary

Introduction

Vacuolar collapse results in the loss of plasma membrane integrity and eventually leads to cell death[19,20]. The proteases VPE and CathB with caspase-like activities exerted effects leading to the tonoplast rupture of plant PCD. A tubular vacuole was formed during tobacco BY-GV 7 mitosis, whereas the AF depolymerizing agents bistheonellide A (BA) or CB led to the disappearance of the tubular vacuole This indicated that AFs are involved in maintaining the state of tubular vacuoles in tobacco cell mitosis[42]. Sequential observations in aleurone cells revealed that the rupture of the large central vacuole resulted in the disruption of the plasma membrane, followed by the disintegration of the nucleus and PCD. It is hypothesized that the VPE accelerates PCD due to the induction of vacuole coalescence and the rupture of vacuoles These results contribute knowledge to fields such as biology and plant morphological anatomy, as well as provide the theoretical basis for increasing the quality of rice seed germination

Methods

Results

Conclusion