Molecular insights into the complex mechanics of plant epidermal cell walls (2025)

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“…Actually, in the primary cell walls of plants, the lateral interactions between cellulose microfibrils were found to be determinant to mechanical properties as revealed by coarse-grained molecular dynamics simulation. 125 Since the structure of cellulose is known to differ in algae and higher plants, the structural function of cellulose in the organization of algal cell walls requires further assessment by comparing the cellulose-deficient strain with cellulose-rich species.…”

confidence: 99%

et al. 2021

Microalgae are photosyntheticorganisms widely distributed in natureand serve as a sustainable source of bioproducts. Their carbohydratecomponents are also promising candidates for bioenergy productionand bioremediation, but the structural characterization of these heterogeneouspolymers in cells remains a formidable problem. Here we present awidely applicable protocol for identifying and quantifying the glycancontent using magic-angle-spinning (MAS) solid-state NMR (ssNMR) spectroscopy,with validation from glycosyl linkage and composition analysis deducedfrom mass-spectrometry (MS). Two-dimensional 13C–13C correlation ssNMR spectra of a uniformly 13C-labeledgreen microalga Parachlorella beijerinckii revealthat starch is the most abundant polysaccharide in a naturally cellulose-deficientstrain, and this polymer adopts a well-organized and highly rigidstructure in the cell. Some xyloses are present in both the mobileand rigid domains of the cell wall, with their chemical shifts partiallyaligned with the flat-ribbon 2-fold xylan identified in plants. Surprisingly,most other carbohydrates are largely mobile, regardless of their distributionin glycolipids or cell walls. These structural insights correlatewith the high digestibility of this cellulose-deficient strain, andthe in-cell ssNMR methods will facilitate the investigations of othereconomically important algae species.

Plant height is one of the most important agronomic traits of rapeseeds. In this study, we characterized a dwarf Brassica napus mutant, named ndf-2, obtained from fast neutrons and DES mutagenesis. Based on BSA-Seq and genetic properties, we identified causal mutations with a time-saving approach. The ndf-2 mutation was identified on chromosome A03 and can result in an amino acid substitution in the conserved degron motif (GWPPV to EWPPV) of the Auxin/indole-3-acetic acid protein 7 (BnaA03.IAA7) encoded by the causative gene. Aux/IAA protein is one of the core components of the auxin signaling pathway, which regulates many growth and development processes. However, the molecular mechanism of auxin signal regulating plant height is still not well understood. In the following work, we identified that BnaARF6 and BnaARF8 as interactors of BnaA03.IAA7 and BnaEXPA5 as a target of BnaARF6 and BnaARF8. The three genes BnaA03.IAA7, BnaARF6/8 and BnaEXPA5 were highly expressed in stem, suggesting that these genes were involved in stem development. The overexpression of BnaEXPA5 results in larger rosettes leaves and longer inflorescence stems in Arabidopsis thaliana. Our results indicate that BnaA03.IAA7- and BnaARF6/8-dependent auxin signal control stem elongation and plant height by regulating the transcription of BnaEXPA5 gene, which is one of the targets of this signal.

This article comments on: Di Marzo M, Ebeling Viana V, Banfi C, Cassina V, Corti R, Herrera-Ubaldo H, Babolin N, Guazzotti A, Kiegle E, Gregis V, de Folter S, Sampedro J, Mantegazza F, Colombo L, Ezquer I. 2022. Cell wall modifications by α-XYLOSIDASE1 are required for the control of seed and fruit size. Journal of Experimental Botany 73, 1499–1515.