Woffenden BJ, Freeman TB, Beers EP
Department of Horticulture, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, USA.
Plant Physiol. 1998 Oct;118(2):419-30. doi: 10.1104/pp.118.2.419.
To determine whether proteasome activity is required for tracheary element (TE) differentiation, the proteasome inhibitors clasto-lactacystin beta-lactone and carbobenzoxy-leucinyl-leucinyl-leucinal (LLL) were used in a zinnia (Zinnia elegans) mesophyll cell culture system. The addition of proteasome inhibitors at the time of culture initiation prevented differentiation otherwise detectable at 96 h. Inhibition of the proteasome at 48 h, after cellular commitment to differentiation, did not alter the final percentage of TEs compared with controls. However, proteasome inhibition at 48 h delayed the differentiation process by approximately 24 h, as indicated by examination of both morphological markers and the expression of putative autolytic proteases. These results indicate that proteasome function is required both for induction of TE differentiation and for progression of the TE program in committed cells. Treatment at 48 h with LLL but not clasto-lactacystin beta-lactone resulted in partial uncoupling of autolysis from differentiation. Results from gel analysis of protease activity suggested that the observed incomplete autolysis was due to the ability of LLL to inhibit TE cysteine proteases.
为了确定蛋白酶体活性对于管状分子（TE）分化是否必需，在百日草（Zinnia elegans）叶肉细胞培养系统中使用了蛋白酶体抑制剂clasto-乳胞素β-内酯和苄氧羰基-亮氨酰-亮氨酰-亮氨酸（LLL）。在培养开始时添加蛋白酶体抑制剂可防止原本在96小时可检测到的分化。在细胞开始分化后的48小时抑制蛋白酶体，与对照相比，并未改变TE的最终百分比。然而，如通过形态学标记和假定的自溶蛋白酶的表达检查所示，在48小时抑制蛋白酶体使分化过程延迟了约24小时。这些结果表明，蛋白酶体功能对于诱导TE分化以及在已分化细胞中TE程序的进展都是必需的。在48小时用LLL而非clasto-乳胞素β-内酯处理导致自溶与分化部分解偶联。蛋白酶活性的凝胶分析结果表明，观察到的不完全自溶是由于LLL抑制TE半胱氨酸蛋白酶的能力。
