Tyloses and Phenolic Deposits in Xylem Vessels Impede Water Transport in Low-Lignin Transgenic Poplars: A Study by Cryo-Fluorescence Microscopy
Open Access
- 16 July 2010
- journal article
- research article
- Published by Oxford University Press (OUP) in Plant Physiology
- Vol. 154 (2), 887-898
- https://doi.org/10.1104/pp.110.156224
Abstract
Of 14 transgenic poplar genotypes (Populus tremula × Populus alba) with antisense 4-coumarate:coenzyme A ligase that were grown in the field for 2 years, five that had substantial lignin reductions also had greatly reduced xylem-specific conductivity compared with that of control trees and those transgenic events with small reductions in lignin. For the two events with the lowest xylem lignin contents (greater than 40% reduction), we used light microscopy methods and acid fuchsin dye ascent studies to clarify what caused their reduced transport efficiency. A novel protocol involving dye stabilization and cryo-fluorescence microscopy enabled us to visualize the dye at the cellular level and to identify water-conducting pathways in the xylem. Cryo-fixed branch segments were planed in the frozen state on a sliding cryo-microtome and observed with an epifluorescence microscope equipped with a cryo-stage. We could then distinguish clearly between phenolic-occluded vessels, conductive (stain-filled) vessels, and nonconductive (water- or gas-filled) vessels. Low-lignin trees contained areas of nonconductive, brown xylem with patches of collapsed cells and patches of noncollapsed cells filled with phenolics. In contrast, phenolics and nonconductive vessels were rarely observed in normal colored wood of the low-lignin events. The results of cryo-fluorescence light microscopy were supported by observations with a confocal microscope after freeze drying of cryo-planed samples. Moreover, after extraction of the phenolics, confocal microscopy revealed that many of the vessels in the nonconductive xylem were blocked with tyloses. We conclude that reduced transport efficiency of the transgenic low-lignin xylem was largely caused by blockages from tyloses and phenolic deposits within vessels rather than by xylem collapse.Keywords
This publication has 102 references indexed in Scilit:
- Suppression of 4-Coumarate-CoA Ligase in the Coniferous GymnospermPinus radiataPlant Physiology, 2008
- Perturbed Lignification Impacts Tree Growth in Hybrid Poplar—A Function of Sink Strength, Vascular Integrity, and Photosynthetic AssimilationPlant Physiology, 2008
- Stiffness gradients in vascular bundles of the palmWashingtonia robustaProceedings Of The Royal Society B-Biological Sciences, 2008
- Lignin engineeringCurrent Opinion in Plant Biology, 2008
- RNAi-mediated suppression of p -coumaroyl-CoA 3′-hydroxylase in hybrid poplar impacts lignin deposition and soluble secondary metabolismProceedings of the National Academy of Sciences of the United States of America, 2008
- Lignin modification improves fermentable sugar yields for biofuel productionNature Biotechnology, 2007
- Flavonoid Accumulation in Arabidopsis Repressed in Lignin Synthesis Affects Auxin Transport and Plant GrowthPlant Cell, 2007
- O -4-Linked coniferyl and sinapyl aldehydes in lignifying cell walls are the main targets of the Wiesner (phloroglucinol-HCl) reactionProtoplasma, 2002
- Co‐ordination of vapour and liquid phase water transport properties in plantsPlant, Cell & Environment, 2002
- Trends in wood density and structure are linked to prevention of xylem implosion by negative pressureOecologia, 2001