Immuno and Affinity Cytochemical Analysis of Cell Wall Composition in the Moss Physcomitrella patens

Abstract

In contrast to homeohydric vascular plants, mosses employ a poikilohydric strategy for surviving in the dry aerial environment. A detailed understanding of the structure, composition, and development of moss cell walls can contribute to our understanding of not only the evolution of overall cell wall complexity, but also the differences that have evolved in response to selection for different survival strategies. The model moss species Physcomitrella patens has a predominantly haploid lifecycle consisting of protonemal filaments that regenerate from protoplasts and enlarge by tip growth, and leafy gametophores composed of cells that enlarge by diffuse growth and differentiate into several different types. Advantages for genetic studies include methods for efficient targeted gene modification and extensive genomic resources. Immuno and affinity cytochemical labeling were used to examine the distribution of polysaccharides and proteins in regenerated protoplasts, protonemal filaments, rhizoids, and sectioned gametophores of P. patens. The cell wall composition of regenerated protoplasts was also characterized by flow cytometry. Crystalline cellulose was abundant in the cell walls of regenerating protoplasts and protonemal cells that developed on media of high osmolarity, whereas homogalactuonan was detected in the walls of protonemal cells that developed on low osmolarity media and not in regenerating protoplasts. Mannan was the major hemicellulose detected in all tissues tested. Arabinogalactan proteins were detected in different cell types by different probes, consistent with structural heterogneity. The results reveal developmental and cell type specific differences in cell wall composition and provide a basis for analyzing cell wall phenotypes in knockout mutants.

Evolution of Cell Wall Polymers in Tip-Growing Land Plant Gametophytes: Composition, Distribution, Functional Aspects and Their Remodeling

“…In mosses, cellulose is present in the cell wall of all species that have been investigated, including P. patens protonemal cells (Kremer et al, 2004; Moller et al, 2007; Nothnagel and Nothnagel, 2007; Goss et al, 2012; Roberts et al, 2012). In contrast, P. patens rhizoids were very weakly labeled with CBM3a (Berry et al, 2016). Cellulose probed with CBM28 (Supplemental Table 1) was not detected in the protonemal cells or rhizoids (Berry et al, 2016).…”

Interplay between Ions, the Cytoskeleton, and Cell Wall Properties during Tip Growth

“…Tip-growing cells have polymers found in most plant cells, such as cellulose, hemicellulose, and pectins. However, immunochemical data show that the amounts and distribution of these polymers differ from typical plant cells, with cellulose being sparse, while pectin is considerably enriched at the tip in pollen tubes, root hairs, and protonemata (Bosch and Hepler, 2005;Berry et al, 2016). For pollen tubes, mounting evidence increasingly supports the view that pectins, either as deposited directly or following enzymatic modification, play a major role in controlling the rigidity of the wall (Caffall and Mohnen, 2009).…”

Moss Pathogenesis-Related-10 Protein Enhances Resistance to Pythium irregulare in Physcomitrella patens and Arabidopsis thaliana

“…The bright white spots identified in solophenyl flavine stained cell walls of untreated PpPR-10 overexpressing moss lines are indicative of cell wall changes, which could contribute to the reinforcement of the cell wall. Interestingly, Berry et al (2016) have shown that xyloglucan is only present in undivided P. patens protoplasts with thicker cell walls. In addition, alterations in xyloglucan structure result in increased resistance against necrotrophic fungi in flowering plants ( Delgado-Cerezo et al, 2012 ).…”