Organ and Tissue-Specific Localisation of Selected Cell Wall Epitopes in the Zygotic Embryo of Brachypodium distachyon.

Alexander Betekhtin,Joanna Lusinska,Anna Milewska-Hendel,Ewa Kurczynska,Robert Hasterok,Lukasz Chajec

doi:10.3390/ijms19030725

Alexander Betekhtin, Joanna Lusinska + Show 4 more

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https://doi.org/10.3390/ijms19030725

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Abstract

The plant cell wall shows a great diversity regarding its chemical composition, which may vary significantly even during different developmental stages. In this study, we analysed the distribution of several cell wall epitopes in embryos of Brachypodium distachyon (Brachypodium). We also described the variations in the nucleus shape and the number of nucleoli that occurred in some embryo cells. The use of transmission electron microscopy, and histological and immunolocalisation techniques permitted the distribution of selected arabinogalactan proteins, extensins, pectins, and hemicelluloses on the embryo surface, internal cell compartments, and in the context of the cell wall ultrastructure to be demonstrated. We revealed that the majority of arabinogalactan proteins and extensins were distributed on the cell surface and that pectins were the main component of the seed coat and other parts, such as the mesocotyl cell walls and the radicula. Hemicelluloses were localised in the cell wall and outside of the radicula protodermis, respectively. The specific arrangement of those components may indicate their significance during embryo development and seed germination, thus suggesting the importance of their protective functions. Despite the differences in the cell wall composition, we found that some of the antibodies can be used as markers to identify specific cells and the parts of the developing Brachypodium embryo.

Highlights

The cell wall is a protective layer that is located around the cell membrane, which is found in plant, fungi, bacteria, and archaea cells
In this work we traced the distribution of various cell wall epitopes in the Brachypodium zygotic embryo in mature stages of development
We have demonstrated that: 1. Among analysed arabinogalactan proteins (AGP) epitopes JIM13, JIM8, and LM2 were localised in cell walls of the embryo surface tissues, as well as some of them in the seed coat; and MAC207 and JIM16 were detected in cytoplasmic compartments

Summary

Introduction

The cell wall is a protective layer that is located around the cell membrane, which is found in plant, fungi, bacteria, and archaea cells. The plant cell wall is a dynamic and highly specialised network that is formed by a heterogeneous mixture of cellulose, hemicelluloses, pectins and, to some extent, proteins and phenolic compounds. As/after the cell completes its growth, additional layers of cellulose fibres are deposited on the inner surface of the primary cell wall, which produces a secondary cell wall. The cell wall composition in vascular plants is approximately 30% cellulose, 30% hemicellulose, and 35% pectins, and 1–5% structural proteins, on a dry weight basis [2,3]. The secondary cell walls are generally more cellulose-rich [4,5,6,7]

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