Metabolism of cell wall polysaccharides in cell suspension cultures of Populus alba in relation to cell growth |
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Authors: | Koichi Kakegawa Yusuke Edashige Tadashi Ishii |
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Institution: | Forestry and Forest Products Research Institute, P.O. Box 16, Tsukuba Norin Kenkyu Danchi-nai, Ibaraki 305-8687, Japan |
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Abstract: | Changes in the composition of cell walls and extracellular polysaccharides (ECP) were studied during the growth of suspension-cultured Populus alba cells. Three growth phases, namely the cell division phase, cell elongation phase and stationary phase, were distinguished. The active deposition of polysaccharides in cell wall fractions (50 m M Na2CO3-, 1 M KOH-, 4 M KOH-soluble and 4 M KOH-insoluble) was observed during the elongation phase. A 50 m M Na2CO3-soluble pectic fraction mainly composed of 1,4-linked galactan and arabinan except acidic sugars. The 1,4-linked galactan decreased markedly during elongation. In 1 and 4 M KOH-soluble hemicellulosic fractions, non-cellulosic 1,4-glucan and xyloglucan were observed as major components, respectively. These polysaccharides also decreased during elongation. A large amount of polysaccharides was secreted into the medium as ECP. Neutral sugars were detected predominantly by sugar composition analysis. Acidic sugars, such as galacturonic acid, were less than 12% of total. In this study, active metabolism of pectic polysaccharides in addition to hemicellulosic polysaccharides, especially neutral side chains of pectin, during cell growth, was clarified. |
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