The Arabidopsis xylem peptidase XCP1 is a tracheary element vacuolar protein that may be a papain ortholog
The Arabidopsis xylem peptidase XCP1 is a tracheary element vacuolar protein that may be a papain ortholog
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DOI：
10.1104/pp.010514
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发表时间：
2002-01-01
期刊：
影响因子：
7.4
通讯作者：
Beers, EP
中科院分区：
文献类型：
--
作者：
Funk, V;Kositsup, B;Beers, EP
XCP1是拟南芥木质部特异性木瓜蛋白酶样半胱氨酸肽酶。为了确定XCP1是否参与气管元件的自溶，我们利用XCP1启动子- β -葡萄糖醛酸酶融合和免疫荧光共聚焦显微镜研究了XCP1的启动子活性和定位。检测到XCP1的气管元件表达模式。共聚焦显微镜和生化亚细胞分离结果表明，XCP1定位于液泡中。XCP1的异位表达导致部分品系植株大小减小，叶片早期衰老，表现为叶片叶绿素的早期丧失。免疫印迹和肽酶活性凝胶分析显示，植株大小减小与XCP1水平升高相关。与所有其他报道的木瓜蛋白酶样酶相比，XCP1原结构域与从木瓜乳汁管中分离的木瓜蛋白酶和其他木瓜蛋白酶样酶的原结构域具有异常高的相似性（大于80%）。讨论了XCP1和木瓜蛋白酶在细胞因程序性自杀或损伤而死亡后作为自溶过程催化剂的共同功能。
XCP1 is a xylem-specific papain-like cysteine peptidase in Arabidopsis. To determine whether XCP1 could be involved in tracheary element autolysis, promoter activity and localization of XCP1 were investigated using XCP1 promoter-beta-glucuronidase fusions and immunofluorescence confocal microscopy. A tracheary element expression pattern was detected for XCP1. Results from confocal microscopy and biochemical subcellular fractionation indicated that XCP1 was localized in the vacuole. Ectopic expression of XCP1 resulted in a reduction in plant size in some lines and early leaf senescence, as indicated by early loss of leaf chlorophyll. Reduced plant size was correlated with higher levels of XCP1, as shown by immunoblot and peptidase activity gel analyses. The XCP1 prodomain exhibits exceptionally high similarity (greater than 80%) to the prodomains of papain and other papain-like enzymes isolated from papaya (Carica papaya) laticifers when compared with all other reported papain-like enzymes. The potential for XCP1 and papain to perform common functions as catalysts of autolytic processing following cell death due to programmed suicide or to wounding is discussed.