Chemical and Molecular Characterization of Wound-Induced Suberization in Poplar (Populus alba × P. tremula) Stem Bark

Tracking ectopic lignification in flax stems following scarification

When flax (Linum usitatissimum L.) stems are scarified, major changes occur in the organization of cell walls within the tissues that border the wound. We sought to characterize the plant's response using a variety of approaches, with a particular focus on lignin deposition within the peripheral fiber cell walls of the stem. Raman spectroscopy and imaging first showed that changes occurred in the polysaccharide matrix of the parenchyma and fiber cell walls. These changes were accompanied by rapid deposition of lignin which initially diffuses centripetally and then, once the vascular cambium was reached, propagates in a periclinal manner until 150 μm from the edges of the wounded zone. Lignin biosynthesis appears to be the result of a de novo activity, as demonstrated by the concomitant accumulation of transcripts corresponding to lignin biosynthesis genes. In addition, using bioorthogonal chemistry approaches, we showed that wounding had enhanced the capacity of fiber cell walls to incorporate modified lignin precursors, in parallel with an increase in transcripts corresponding to peroxidases in the cortical tissues. This incorporation potential was identical for the 3 different types of reporters tested. Our findings demonstrated that mechanical stress can trigger lignification, in a polarized manner within the bast fibers, providing insights into the plasticity of cell wall composition and the potential for modulating fiber properties in flax.

Imaging plant cell walls using fluorescent stains: The beauty is in the details

Plants continuously face various environmental stressors throughout their lifetime. To be able to grow and adapt in different environments, they developed specialized tissues that allowed them to maintain a protected yet interconnected body. These tissues undergo specific primary and secondary cell wall modifications that are essential to ensure normal plant growth, adaptation and successful land colonization. The composition of cell walls can vary among different plant species, organs and tissues. The ability to remodel their cell walls is fundamental for plants to be able to cope with multiple biotic and abiotic stressors. A better understanding of the changes taking place in plant cell walls may help identify and develop new strategies as well as tools to enhance plants' survival under environmental stresses or prevent pathogen attack. Since the invention of microscopy, numerous imaging techniques have been developed to determine the composition and dynamics of plant cell walls during normal growth and in response to environmental stimuli. In this review, we discuss the main advances in imaging plant cell walls, with a particular focus on fluorescent stains for different cell wall components and their compatibility with tissue clearing techniques. Lay Description: Plants are continuously subjected to various environmental stresses during their lifespan. They evolved specialized tissues that thrive in different environments, enabling them to maintain a protected yet interconnected body. Such tissues undergo distinct primary and secondary cell wall alterations essential to normal plant growth, their adaptability and successful land colonization. Cell wall composition may differ among various plant species, organs and even tissues. To deal with various biotic and abiotic stresses, plants must have the capacity to remodel their cell walls. Gaining insight into changes that take place in plant cell walls will help identify and create novel tools and strategies to improve plants' ability to withstand environmental challenges. Multiple imaging techniques have been developed since the introduction of microscopy to analyse the composition and dynamics of plant cell walls during growth and in response to environmental changes. Advancements in plant tissue cleaning procedures and their compatibility with cell wall stains have significantly enhanced our ability to perform high-resolution cell wall imaging. At the same time, several factors influence the effectiveness of cleaning and staining plant specimens, as well as the time necessary for the process, including the specimen's size, thickness, tissue complexity and the presence of autofluorescence. In this review, we will discuss the major advances in imaging plant cell walls, with a particular emphasis on fluorescent stains for diverse cell wall components and their compatibility with tissue clearing techniques. We hope that this review will assist readers in selecting the most appropriate stain or combination of stains to highlight specific cell wall components of interest.