Environmental Biotechnology National Core Research Center and PMBBRC, Graduate School of Gyeongsang National University, Jinju, Korea.
Plant Cell Rep. 2009 Nov;28(11):1623-32. doi: 10.1007/s00299-009-0762-7. Epub 2009 Aug 19.
Phytocystatins are cysteine proteinase inhibitors in plants that are implicated in the endogenous regulation of protein turnover and defense mechanisms against insects and pathogens. A cDNA encoding a phytocystatin called AtCYS6 (Arabidopsis thaliana phytocystatin6) has been isolated. We show that AtCYS6 is highly expressed in dry seeds and seedlings and that it also accumulates in flowers. The persistence of AtCYS6 protein expression in seedlings was promoted by abscisic acid (ABA), a seed germination and post-germination inhibitory phytohormone. This finding was made in transgenic plants bearing an AtCYS6 promoter-beta-glucuronidase (GUS) reporter construct, where we found that expression from the AtCYS6 promoter persisted after ABA treatment but was reduced under control conditions and by gibberellin(4+7) (GA(4+7)) treatment during the germination and post-germinative periods. In addition, constitutive over-expression of AtCYS6 retarded germination and seedling growth, whereas these were enhanced in an AtCYS6 knock-out mutant (cys6-2). Additionally, cysteine proteinase activities stored in seeds were inhibited by AtCYS6 in transgenic Arabidopsis. From these data, we propose that AtCYS6 expression is enhanced by the germination inhibitory phytohormone ABA and that it participates in the control of germination rate and seedling growth by inhibiting the activity of stored cysteine proteinases.
植物胱氨酸蛋白酶抑制剂是植物中的一种半胱氨酸蛋白酶抑制剂，它参与蛋白质周转的内源性调节和对昆虫和病原体的防御机制。已经分离出一种称为 AtCYS6（拟南芥胱氨酸蛋白酶抑制剂 6）的植物胱氨酸蛋白酶抑制剂的 cDNA。我们表明，AtCYS6 在干燥种子和幼苗中高度表达，并且它也在花朵中积累。在含有 AtCYS6 启动子-β-葡萄糖醛酸酶（GUS）报告基因构建体的转基因植物中，发现脱落酸（ABA，一种抑制种子萌发和萌发后植物激素）促进了 AtCYS6 蛋白表达的持续存在。在 ABA 处理后，但在对照条件下和在萌发和萌发后期间用赤霉素（4+7）（GA（4+7））处理时，我们发现 AtCYS6 启动子的表达减少。此外，AtCYS6 的组成型过表达延迟了萌发和幼苗生长，而在 AtCYS6 敲除突变体（cys6-2）中则增强了这些。此外，种子中储存的半胱氨酸蛋白酶活性被 AtCYS6 在转基因拟南芥中抑制。根据这些数据，我们提出 AtCYS6 的表达被抑制萌发的植物激素 ABA 增强，并且它通过抑制储存的半胱氨酸蛋白酶的活性参与控制萌发率和幼苗生长。
