Atypical lignification in eastern leatherwood (Dirca palustris)

Abstract

Summary Lignin is a complex phenolic biopolymer found mainly in the secondary cell walls of vascular plants, where it contributes to mechanical strength, water conduction, and plant defence. We studied the lignin of eastern leatherwood (Dirca palustris) because this slow‐growing woody shrub is known for its flexible stems. Various analytical techniques and microscopy methods were employed to examine the composition and distribution of lignin and structural polysaccharides in leatherwood xylem in comparison with trembling aspen (Populus tremuloides) and white spruce (Picea glauca). We found that leatherwood has low overall levels of lignin, a high syringyl lignin content, and a unique distribution of lignin. Most remarkably, the cell corners and middle lamellae remain unlignified in mature xylem. These findings help explain the flexibility of leatherwood and also call into question the classical model of lignification, which purports that lignin polymerization begins in the cell corners and middle lamellae. This atypical lignification regime vividly illustrates the diversity in plant secondary cell wall formation that abounds in nature and casts leatherwood as a new model for the study of lignin biogenesis.

Autofluorescence in Plants

“…Autofluorescence has applications in measuring the physiological status of crops or experimental plots based on measurements of chlorophyll fluorescence, and in imaging studies with applications in plant biochemistry, physiology, pathology, wood science, and plant biotechnology. Combining autofluorescence, including both intensity and lifetime imaging and spectroscopy, with other spectroscopic techniques such as Raman microspectroscopy and Fourier transform infra-red microspectroscopy (FTIR microscopy) may allow more accurate characterization of tissue fluorescence in plants at the cellular level in future studies [13,58]. Applications for using autofluorescence in techniques such as FRAP and FCS, which are used to track the diffusion of molecules in cells, may be forthcoming in the near future.…”

“…When investigating autofluorescence in plant tissues, it is important to recognize there may be several types of autofluorescent molecules present at the same location and thus the source of autofluorescence should be interpreted in conjunction with histochemical staining and other forms of analysis [13]. For microscopy applications, autofluorescence should be examined on fresh tissue as some autofluorescent compounds (chlorophyll, flavonoids) can easily become redistributed or be completely removed from tissue when exposed to solvent-based fixatives such as formalin aceto-alcohol (FAA) or mounting media such as glycerol-instead, aqueous buffers can be used as mounting media [14,15].…”

“…Fluorescence emission of common autofluorescent compounds found in plants[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15].…”

Phenoloxidases in Plants—How Structural Diversity Enables Functional Specificity

“…This assumption, based on the low substrate specificity of these different phenoloxidases when oxidising small phenolics in vitro, is effectively supported by the multitude of "non-canonical" constituents incorporated in lignin such as flavonoids (Lan et al, 2015) and hydroxystilbenes (del Río et al, 2017). However, these observations rarely differentiate between the cell walls of different cell types, as well as between their different cell wall layers, which exhibit drastically distinct monomeric composition, amount and structure of lignin (Terashima and Fukushima, 1988;Terashima et al, 2012;Blaschek et al, 2020a,b;Mottiar et al, 2020;Yamamoto et al, 2020). As cell wall lignification is a cell-cell cooperative process (Pesquet et al, 2013;Smith et al, 2013) mediated by the release of mobile lignin monomers in the apoplast, lignin formation in the specific cell wall layers of each cell type will require a directing force to control their distinct amount and composition, such as using different combinations of phenoloxidases.…”

Advances in Understanding Microbial Deterioration of Buried and Waterlogged Archaeological Woods: A Review

“…Lignin, the other major component of wood cell walls, is incorporated subsequent to the establishment of the cellulosic-hemicellulosic infrastructure, initially beginning in the middle lamella and progressing towards the inner cell wall. However, reports of atypical lignification suggest that lignification may not always initiate in the middle lamella [36]. Although biochemical aspects of the synthesis of lignin monomers and their transformation into lignin polymer have been extensively investigated, opinions differ as to whether or not the initial deposition of lignin monomers in the cell wall is regulated.…”