Root Border Cells and Mucilage Secretions of Soybean, Glycine Max (Merr) L.: Characterization and Role in Interactions with the Oomycete Phytophthora Parasitica

Abstract

Root border cells (BCs) and their associated secretions form a protective structure termed the root extracellular trap (RET) that plays a major role in root interactions with soil borne microorganisms. In this study, we investigated the release and morphology of BCs of Glycine max using light and cryo-scanning electron microscopy (SEM). We also examined the occurrence of cell-wall glycomolecules in BCs and secreted mucilage using immunofluorescence microscopy in conjunction with anti-glycan antibodies. Our data show that root tips released three populations of BCs defined as spherical, intermediate and elongated cells. The mechanism of shedding seemed to be cell morphotype-specific. The data also show that mucilage contained pectin, cellulose, extracellular DNA, histones and two hemicellulosic polysaccharides, xyloglucan and heteromannan. The latter has never been reported previously in any plant root secretions. Both hemicellulosic polysaccharides formed a dense fibrillary network embedding BCs and holding them together within the mucilage. Finally, we investigated the effect of the RET on the interactions of root with the pathogenic oomycete Phytophthora parasitica early during infection. Our findings reveal that the RET prevented zoospores from colonizing root tips by blocking their entry into root tissues and inducing their lysis.

Arabinogalactan Proteins in Plant Roots – An Update on Possible Functions

“…Root exudates, but not extracted AGPs, then strongly stimulated their germination (Cannesan et al, 2012). Root-associated, capderived cells (BC and BLC) thus act as a blind target, trapping the pathogen (extracellular root trap) and preventing its contact with the root proper (Hawes et al, 2000;Ropitaux et al, 2020).…”

The effect of crop species on DNase-producing bacteria in two soils

“…For instance, Greaves and Webley (1965) observed that the total number of nuclease-producing microorganisms were higher on the root surface and in the rhizosphere soil of pasture grasses than in non-rhizosphere soil. The plethora of compounds secreted through the root cap mucilage including genetic material (Wen et al 2009;Knox et al 2020;Ropitaux et al 2020;Chambard et al 2021) provide a source of nutrients and energy that may result in differential growth of microbial communities (Berg and Smalla 2009;Haichar et al 2014). Plant DNA enters the soil environment mainly through root exudates, root cap sloughing, pollen dispersal and degradation of plant materials (Levy-Booth et al 2007;Monticolo et al 2020).…”

Effects of Exogenous Phthalic Acid on Seed Germination, Root Physiological Characteristics, and Mineral Element Absorption of Watermelon

“…Root border cells (RBCs), also known as abscission root cap cells, are a special group of cells isolated from around the root cap and gathered at the root tip. The existence of RBCs can enhance the ability of plants to resist adversity and enhance the growth of plant roots by increasing the thickness of the adhesive layer [30,31]. RBC production rate is closely related to pectin methylesterase (PME), which can promote pectin decomposition through pectin demethylation, promote the expression of other pectin genes, and eventually, induce the release of RBCs from the root cap [32,33], and also affect the hardness of root cytoderm and regulate the development process of root [34].…”