The effects of amino acid medium (AA medium) on the dissociation of rice callus tissues were examined in suspension-cultured cells, because a finely dispersed cell suspension had been obtained previously from rice callus tissues in this medium. The level of extracellular polysaccharides formed in cultured AA medium was much higher than that of those formed in cultured B5 medium. The polysaccharides were mainly composed of higher levels of arabinose, xylose, and galactose, suggesting the solubilization of arabinoxylan and (arabino)galactan. Nevertheless, wall polysaccharides in cells cultured in AA medium contained the same levels of arabinosyl-, xylosel-, and galactosyl-linkages as those in B5 medium. Based on amino acid analysis, rice cells in AA medium incorporated the amino acids in 3 days and formed ornithine and urea during the early stages of cultivation, and secreted urea into the culture medium. Transfer of rice tissue cultured in AA medium to B5 medium composed of inorganic nitrogen source caused most of the tissue aggregates to become larger than 1000 μm. However, after transfer to B5 medium containing 1 mM arginine, they were apparently maintained as a more-finely dispersed cell suspension at a size below 1000μm. These findings suggest that arginine is metabolized in rice cells to form urea, which is then secreted and may solubilize the arabinoxylan and (arabino)galactan between cells. The test of binding capacity confirmed that arabinoxylan was bound to both insoluble xyloglucan and cellulose, and that urea dissociated arabinoxylan from the complex.
ASJC Scopus subject areas
- Analytical Chemistry
- Applied Microbiology and Biotechnology
- Molecular Biology
- Organic Chemistry