Cell Walls and the Developmental Anatomy of the Brachypodium distachyon Stem Internode

Abstract

While many aspects of plant cell wall polymer structure are known, their spatial and temporal distribution within the stem are not well understood. Here, we studied vascular system and fiber development, which has implication for both biofuel feedstock conversion efficiency and crop yield. The subject of this study, Brachypodium distachyon, has emerged as a grass model for food and energy crop research. Here, we conducted our investigation using B. distachyon by applying various histological approaches and Fourier transform infrared spectroscopy to the stem internode from three key developmental stages. While vascular bundle size and number did not change over time, the size of the interfascicular region increased dramatically, as did cell wall thickness. We also describe internal stem internode anatomy and demonstrate that lignin deposition continues after crystalline cellulose and xylan accumulation ceases. The vascular bundle anatomy of B. distachyon appears to be highly similar to domesticated grasses. While the arrangement of bundles within the stem is highly variable across grasses, B. distachyon appears to be a suitable model for the rind of large C4 grass crops. A better understanding of growth and various anatomical and cell wall features of B. distachyon will further our understanding of plant biomass accumulation processes.

Mechanical stimulation in Brachypodium distachyon: Implications for fitness, productivity, and cell wall properties

“…The size and cell number of VBs in Brachypodium are likely defined at or before the point of elongation, as their number and size do not significantly change during development and growth (Matos et al, ); thus, any treatment‐induced changes in VB area suggest that these changes are mediated close to the apical meristem by a yet to be explored signal transduction cascade. The accession‐specific differences identified here suggest that Brachypodium would be a useful experimental system to explore the underlying genetic control.…”

“…Anatomical and morphological measurements on cross sections of the second internode were carried out according to Matos, Whitney, Harrington, and Hazen () with minor modifications. Relative cross‐sectional areas were determined for the following features: epidermis, cortex, interfascicular region, pith, and vascular bundles (VBs; inner, outer, and total; these were also counted).…”

SECONDARY WALL ASSOCIATED MYB1 is a positive regulator of secondary cell wall thickening in Brachypodium distachyon and is not found in the Brassicaceae

“…SWAM1 transcript abundance in stems was approximately six‐ and three‐fold greater relative to leaf and root, respectively (Figure A). Grass stems are substantially enriched for secondary cell walls (Matos et al ., ) and account for the largest fraction of above‐ground plant biomass. However, not all cell types in the stem undergo secondary wall development.…”

“…Hand‐cut stem cross‐sections were stained with phloroglucinol−HCl and observed under an Eclipse E200MV R microscope (Nikon) and imaged using a PixeLINK 3 MP camera. Images captured at ×4 magnification were used for area measurements by freehand tracing of a perimeter in ImageJ as previously described (Matos et al ., ). First internodes of the tallest stem of mutant and vector control plants were excised when the inflorescence was first visible from the flag leaf and fixed in 2% glutaraldehyde in 50 m m phosphate buffer (33 m m Na 2 HPO 4 , 1.8 m m NaH 2 PO 4 and 140 m m NaCl, pH 7.2) at room temperature for 2 h. Next, samples were post‐fixed in phosphate buffered OsO 4 under the same conditions.…”

Seta Structure In Members Of The Coleochaetales (streptophyta)

“…To confirm that the calcofluor wasn't labeling other beta glucans, a carbohydratebinding module (CBM3a, Plant Probes) specific for crystalline cellulose was used (McCartney et al, 2004). The protocol used was adapted from Matos et al (2013). The organisms were grown on coverslips, then fixed on the coverslip in 4% formaldehyde in phosphate buffer (PB) solution for 30 minutes.…”