Programmed Cell Death and Aerenchyma Formation in Water-Logged Sunflower Stems and Its Promotion by Ethylene and ROS.

Xi-Lu Ni,Wen-Zhe Liu,Chang-Xiao Li,Meng-Yuan Gui,Ling-Ling Tan,Qiang Zhu

doi:10.3389/fpls.2018.01928

Abstract

Previous studies have shown that waterlogging/ hypoxic conditions induce aerenchyma formation to facilitate gas exchange. Ethylene (ET) and reactive oxygen species (ROS), as regulatory signals, might also be involved in these adaptive responses. However, the interrelationships between these signals have seldom been reported. Herein, we showed that programmed cell death (PCD) was involved in aerenchyma formation in the stem of Helianthus annuus. Lysigenous aerenchyma formation in the stem was induced through waterlogging (WA), ethylene and ROS. Pre-treatment with the NADPH oxidase inhibitor diphenyleneiodonium (DPI) partially suppressed aerenchyma formation in the seedlings after treatment with WA, ET and 3-amino-1, 2, 4-triazole (AT, catalase inhibitor). In addition, pre-treatment with the ethylene perception inhibitor 1-methylcyclopropene (1-MCP) partially suppressed aerenchyma formation induced through WA and ET in the seedlings, but barely inhibited aerenchyma formation induced through ROS. These results revealed that ethylene-mediated ROS signaling plays a role in aerenchyma formation, and there is a causal and interdependent relationship during WA, ET and ROS in PCD, which regulates signal networks in the stem of H. annuus.

Highlights

Aerenchyma formation is a major physiological and morphological adaptation of plants to waterlogging or flooding conditions (Jiang et al, 2010)
The characteristics of programmed cell death (PCD) during aerenchyma formation in maize roots was examined, and plasma membrane invagination, small vesicle formation, DNA cleavage, chromatin condensation, organelle retention in the cytoplasm, and cell wall degradation were observed during lysigenous aerenchyma formation under hypoxic conditions (Gunawardena et al, 2001a,b)
An additional 12 h of WA resulted in conspicuously deformed cells, and the cell wall was obviously distorted (Figure 1E), representing the early phase of aerenchyma formation

Summary

Introduction

Aerenchyma formation is a major physiological and morphological adaptation of plants to waterlogging or flooding conditions (Jiang et al, 2010). No published study has yet characterized aerenchyma formation in stem/root of H. annuus associated with PCD, and nor the roles of ET and ROS during aerenchyma formation under conditions of waterlogging. The parenchymal cells in the cortex of H. annuus stems were round under normal growth conditions, without treatment (control; Figure 1A).

Results

Conclusion