USDA, ARS, Plant Sciences Institute, Plant Molecular Biology Lab, 10300 Baltimore Ave, 20705-2350, Beltsville, MD, USA.
Theor Appl Genet. 1996 Feb;92(2):255-62. doi: 10.1007/BF00223382.
Mutant rice cells (Oryza sativa L.) grown in liquid suspension cultures exported greater quantities of protein and β-glucanases than controls. These mutants were isolated from anther calli resistant to 1 mM lysine plus threonine (LT), regenerated and reestablished as cell suspension cultures from seeds. Cellular protein levels are genetically conditioned, and the levels of extracellular proteins and enzyme activities are inversely related to that of the cellular portions. The rechallenge of cells with 1 mM LT inhibited the expression of both β-1,3-glucanases and β-1,4-glucosidases but had no significant effect upon the levels of chitinase activity. Mutant cells were more sensitive than controls to stress caused by exogenous LT. In general, under exogenous LT stress the mutant/control ratio for extracellular glucanases increased as the assay conditions were changed from a basic to an acidic pH. The specific activity of βglucanases was highest in media and lowest in cells. Both the mutant and control cells exported β-glucanases into the suspension medium, but the level of activity in media was greater in that in which the mutant was suspended. The export was probably modulated by the internal protein levels which were highest in mutant cells without LT. Seedlings from mutants with enhanced lysine also had enhanced acidic β-glucanase activity.
在液体悬浮培养中生长的突变水稻细胞（Oryza sativa L.）比对照细胞分泌更多的蛋白质和β-葡聚糖酶。这些突变体是从对 1mM 赖氨酸加苏氨酸（LT）有抗性的花药愈伤组织中分离出来的，经过再生并从种子中重新建立为细胞悬浮培养物。细胞蛋白水平受遗传条件的控制，细胞外蛋白和酶活性的水平与细胞部分的水平呈反比。用 1mM LT 再次挑战细胞会抑制β-1,3-葡聚糖酶和β-1,4-葡萄糖苷酶的表达，但对几丁质酶活性没有显著影响。突变细胞比对照细胞对来自外源 LT 的应激更敏感。一般来说，在外部 LT 应激下，随着测定条件从碱性变为酸性，细胞外葡聚糖酶的突变体/对照比值增加。β-葡聚糖酶的比活性在培养基中最高，在细胞中最低。突变体和对照细胞都将β-葡聚糖酶分泌到悬浮培养基中，但在突变体悬浮的培养基中，活性水平更高。这种分泌可能是由内部蛋白水平调节的，在没有 LT 的突变体细胞中，蛋白水平最高。赖氨酸增强的突变体的幼苗也具有增强的酸性β-葡聚糖酶活性。
