Differential changes in cell wall matrix polysaccharides and glycoside-hydrolyzing enzymes in developing wheat seedlings differing in drought tolerance

The growth kinetics and variations in cell wall matrix polysaccharides and glycoside hydrolases during seedling development of the drought-tolerant wheat cultivar (cv. Hong Mang Mai) were compared with the drought-sensitive cultivar (cv. Shirasagikomugi). After 15 d of culture in water at 22 °C under constant irradiance of 98 μmol m^-2 s^-1, the length of the coleoptile and leaf sheath of Hong Mang Mai seedlings was 1.7 times longer than those of Shirasagikomugi seedlings. In the cell walls isolated from coleoptiles and leaf sheaths of the seedling of the two cultivars, the contents of arabinose, xylose, and glucose changed during development. The cell walls were fractionated progressively with 50 mM CDTA, 50 mM Na₂CO₃, 1 M KOH and 4 M KOH, and sugar composition was determined. The amount of CDTA-soluble fraction from the Hong Mang Mai cell walls was 2.4-fold higher than that from the Shirasagikomugi cell walls at 6 d of culture, and a considerable decrease was observed during development. The ratio of arabinose to xylose in 1 M KOH-soluble fraction from the two cultivars decreased. The amount of 4 M KOH-soluble fraction from the Shirasagikomugi cell walls was affected much more than those of the Hong Mang Mai cell walls. Many glycoside hydrolase activities were detected in the protein fractions from coleoptiles and leaf sheaths of the two cultivars, and the activities of licheninase, 1,3-1,4-β-glucanase, and 1,3-β-glucanase in the LiCl-soluble protein fraction increased drastically during development of the Shirasagikomugi seedlings. These findings suggest that the metabolism of the cell wall matrix polysaccharides of the drought-tolerant wheat cultivar is far different from that of the drought-sensitive wheat cultivar during seedling development.