Xyloglucan and cellulose form molecular cross-bridges connecting root border cells in pea (Pisum sativum)

Abstract

Pea (Pisum sativum) root cap releases a large number of living border cells that secrete abundant mucilage into the extracellular medium. Mucilage contains a complex mixture of polysaccharides, proteins and secondary metabolites important for its structure and function in defense. Unlike xyloglucan and cellulose, pectin and arabinogalactan proteins have been investigated in pea root and shown to be major components of border cell walls and mucilage. In this study, we investigated the occurrence of xyloglucan and cellulose in pea border cells and mucilage using cytochemical staining, immunocytochemistry and laser scanning confocal microscopy. Our data show that i) unlike cellulose, xyloglucan is highly present in the released mucilage as a dense fibrillary network enclosing border cells and ii) that xyloglucan and cellulose form molecular cross-bridges that tether cells and maintain them attached together. These findings suggest that secreted xyloglucan is essential for mucilage strengthening and border cell attachment and functioning.

Root extracellular traps versus neutrophil extracellular traps in host defence, a case of functional convergence?

“…An extensin class 1 protein was also found in the pea root secretome -as revealed by proteomic analysis (Wen et al, 2007) -and xyloglucan was observed to form a web-like fibrous structure, coating root border cells and holding them together ( Fig. 1; see also Ropitaux et al, 2019). Interestingly, defensins, histones and exDNAs are also part of the NETs that are released by human and other animal neutrophils upon activation.…”

“…An extensin class 1 protein was also found in the pea root secretome – as revealed by proteomic analysis (Wen et al , ) – and xyloglucan was observed to form a web‐like fibrous structure, coating root border cells and holding them together (Fig. ; see also Ropitaux et al , ).…”

“…Extensin macromolecules could possibly interact through isodityrosine bonds – catalysed by peroxidases present in the RET secretions – thus forming a sort of physical barrier or scaffold template that reinforces the whole network (Castilleux et al , ). The scaffold could include other molecules such as xyloglucan and exDNA on which antimicrobial compounds could assemble in a rapid‐response system to pathogen infection (Wen et al , ; Ropitaux et al , ).…”

“…other molecules such as xyloglucan and exDNA on which antimicrobial compounds could assemble in a rapid-response system to pathogen infection (Wen et al, 2017;Ropitaux et al, 2019).…”

Homogenization of Rhizosphere Bacterial Communities by Pea (Pisum sativum L.) Cultivated under Different Conservation Agricultural Practices in the Eastern Himalayas

“…2 ). The built-up of homogeneous bacterial communities in most of the rhizosphere samples can be attributed to the selection pressure of the pea roots, which continually release a large number of border cells and mucilage (Ropitaux et al, 2019), and pose a strong rhizosphere effect on the bacteria. Impact of crop plant on the diversity of rhizosphere microbes has also been observed for different crops including barley, cotton, maize and wheat (Yurgel et al, 2018; Babin et al, 2019; Kerdraon et al, 2019).…”