Submitted to: Plant Physiology Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 8/2/1997
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: Differentiating tracheary elements (TEs) in suspension cultures of Zinnia elegans mesophyll cells have been useful for biochemical and molecular analyses of lignification. To begin to exploit the system as a cell biological model, we chemically characterized the lignin, determined the polysaccharide composition of the fully lignified secondary walls, investigated the timing of lignification relative to TE autolysis, and explored the role of the culture medium in supporting lignin polymerization. The acetyl bromide test showed that secondary walls purified at 76 h culture (about 20 h after secondary wall initiation) contained about 22% lignin. Pyrolysis GC-MS showed that the lignin was rich in guiacyl units, correlating with brown TEs in the Maule test. Neutral sugar analysis suggests that the secondary wall that becomes fully lignified (as determined by resistance to polysaccharide-degrading enzymes) )is cellulose and arabinoxylan-rich. Analysis of timing of differentiation showed that the polysaccharide and protein components of the patterned secondary wall were laid down within about 7 h, then autolysis occurred. Faint phloroglucinol staining (consistent with polymerized lignin) on the patterned secondary wall was not present until about 9 h after cell death. Differentiating cultures changed to new medium at 57-69 h of culture (1-32% TEs), had fewer TEs positively stained with phloroglucinol at 92 h. This research was partially supported by the Howard Hughes Medical Institute/Undergraduate Biological Sciences Education Program and the NSF Research Experience for Undergraduates Program (for BK).