Dept. of Biochemistry
Oregon Graduate Center
The purpose of this study was to investigate the regulation of polyphenol biosynthesis in plant cell walls using Populus trichocarpa as a model woody angiosperm. When 2, 4-dichlorophenoxyacetic acid (2, 4-D) was present in the culture medium, cells grew most rapidly and did not form tracheids. An estimated 15% of the cell wall material was composed of polyphenol. If the tissues were placed on media containing Î±-naphthaleneacetic acid (NAA) or NAA plus a cytokinin, growth rate was slower, polyphenol content increased, and tracheids formed. Cells transferred from NAA plus BAP to medium containing 2, 4-D gradually produced less polyphenol and lost the ability to differentiate into tracheids. After tissues were returned to media containing NAA plus BAP, these hormone effects were reversed. Polyphenol content was directly proportional to the cytokinin concentration in the medium, while the effect of cytokinin on tracheid formation was biphasic. The polyphenol in cultured tissues resembled wood lignin in several ways. 1. Histological staining with classical lignin reagents suggested that tracheids and some parenchyma-like cells contained lignin. 2. Alkaline copper hydrolysis and permanganate oxidation of purified methylated cell walls yielded the same methoxylated benzoic acid products as wood. 3. A small amount of C6-C3 product was recovered after thioacidolysis of walls from tracheid-forming tissues, suggesting that some polyphenol was derived from phenylpropanoid units. PAL activity correlated with level of tracheid development in cultured tissues. Anionic peroxidases were present in all tissues, but, with syringaldazine as substrate, peroxidase activity in ionic and medium fractions was greater in tissues that produced tracheids. Several cloned P. trichocarpa cell lines were isolated which contained higher or lower than average polyphenol levels that remained stable. When highly habituated clones were cultured with cytokinin, they grew slowly and their oxidized walls yielded less Ï-hydroxybenzoic acid and more syringic acid. Less habituated clones grew faster with added cytokinin and yielded more Ï-hydroxybenzoic acid. Shoots could be regenerated from several clones. Plants from a stable low polyphenol cell line were grown in the greenhouse. Analysis of wood in a 2-year old stem from this plant indicated that it contained lower lignin than the parental tree.
Hoffman, Sister Angela, "Hormonal regulation of cell development and polyphenol biosynthesis in cultured Populus trichocarpa cells" (1989). Scholar Archive. 115.