Forgotten Actors: Glycoside Hydrolases During Elongation Growth of Maize Primary Root.

Alsu Nazipova,Natalia Petrova,Oleg Gorshkov,Anna Kulminskaya,Elena Eneyskaya,Liudmila Kozlova,Tatyana Gorshkova

doi:10.3389/fpls.2021.802424

Abstract

Plant cell enlargement is coupled to dynamic changes in cell wall composition and properties. Such rearrangements are provided, besides the differential synthesis of individual cell wall components, by enzymes that modify polysaccharides in muro. To reveal enzymes that may contribute to these modifications and relate them to stages of elongation growth in grasses, we carried out a transcriptomic study of five zones of the primary maize root. In the initiation of elongation, significant changes occur with xyloglucan: once synthesized in the meristem, it can be linked to other polysaccharides through the action of hetero-specific xyloglucan endotransglycosidases, whose expression boosts at this stage. Later, genes for xyloglucan hydrolases are upregulated. Two different sets of enzymes capable of modifying glucuronoarabinoxylans, mainly bifunctional α-arabinofuranosidases/β-xylosidases and β-xylanases, are expressed in the maize root to treat the xylans of primary and secondary cell walls, respectively. The first set is highly pronounced in the stage of active elongation, while the second is at elongation termination. Genes encoding several glycoside hydrolases that are able to degrade mixed-linkage glucan are downregulated specifically at the active elongation. It indicates the significance of mixed-linkage glucans for the cell elongation process. The possibility that many glycoside hydrolases act as transglycosylases in muro is discussed.

Highlights

Elongation or expansion growth of plant cells generally occurs between their division and specialization
Xyloglucan Enzymes involved in the synthesis of XyGs are actively expressed in the root cap and meristem zone of maize primary root, and the intensity of their transcription is largely reduced in the active and late elongation zones (Figure 9; Kozlova et al, 2020)
Transcriptomics and proteomics data on maize primary root suggest that active XyG biosynthesis is followed by intensive rearrangement mediated by XETs in stages of early and active elongation (Figure 9)

Summary

Introduction

Elongation or expansion growth of plant cells generally occurs between their division and specialization. During this process, they irreversibly elongate or expand many times compared to the meristematic initial (Cosgrove, 2005). Primary cell walls are mainly composed of polysaccharides and are classified into two types in angiosperms (Carpita, 1996). The dicots and non-commelinid monocots possess type I cell walls in contrast to type II cell walls of commelinid monocots including Poales. Cellulose is common for both types; xyloglucans (XyGs) and pectins are the basic matrix polysaccharides for cell walls of type I, and glucuronoarabinoxylans (GAXs) and mixed-linkage glucans (MLGs) are the main hemicelluloses in cell walls of type II (Carpita, 1996)

Methods

Results

Conclusion