Programmed Degradation of Pericarp Cells in Wheat Grains Depends on Autophagy.

Yong-Bo Li,Qing-Qi Fan,Mei Yan,Xin-Xia Sui,Feng Zhi Guo,De-Zhou Cui,Chen Huang,Xiu-Sheng Chu

doi:10.3389/fgene.2021.784545

Abstract

Wheat is one of the most important food crops in the world, with development of the grains directly determining yield and quality. Understanding grain development and the underlying regulatory mechanisms is therefore essential in improving the yield and quality of wheat. In this study, the developmental characteristics of the pericarp was examined in developing wheat grains of the new variety Jimai 70. As a result, pericarp thickness was found to be thinnest in grains at the top of the spike, followed by those in the middle and thickest at the bottom. Moreover, this difference corresponded to the number of cell layers in the pericarp, which decreased as a result of programmed cell death (PCD). A number of autophagy-related genes (ATGs) are involved in the process of PCD in the pericarp, and in this study, an increase in ATG8-PE expression was observed followed by the appearance of autophagy structures. Meanwhile, following interference of the key autophagy gene ATG8, PCD was inhibited and the thickness of the pericarp increased, resulting in small premature grains. These findings suggest that autophagy and PCD coexist in the pericarp during early development of wheat grains, with both processes increasing from the bottom to the top of the spike. Moreover, PCD was also found to rely on ATG8-mediated autophagy. The results of this study therefore provide a theoretical basis for in-depth studies of the regulatory mechanisms of wheat grain development.

Highlights

Wheat, one of the most important cereal crops worldwide, is characterized by its process of grain development
Following interference of the key autophagy gene ATG8, programmed cell death (PCD) was inhibited and the thickness of the pericarp increased, resulting in small premature grains. These findings suggest that autophagy and PCD coexist in the pericarp during early development of wheat grains, with both processes increasing from the bottom to the top of the spike
8A,B) and the number of cell layers (Figures 8E,F), with an obvious delay in the process of PCD (Figure 8G). These findings indicate that PCD in the pericarp cells of developing wheat grains is dependent on ATG8-mediated autophagy

Summary

Introduction

One of the most important cereal crops worldwide, is characterized by its process of grain development. The wheat grain is a type of caryopsis, whereby the pericarp and episperm develop from the integument and are tightly integrated (Zhou et al, 2009). Development of the pericarp is closely related to grain yield and overall wheat quality. Developing from the ovary wall, it can be divided into the exocarp, mesocarp and endocarp (Xiong et al, 2013). The pericarp covers the seed tegument, and endosperm and embryo tissues of the grain (Brinton et al, 2017) and controls the water transport into the endosperm cavity (Wang and Fisher, 1994), the synthesis of organic compounds (Fujita and Taira, 1998; Foxon et al, 1990), and the temporal storage of starch (Yu et al, 2015)

Methods

Results

Conclusion