Molecular mechanism of vacuolar processing system in differentiation of plant cell

液泡功能的动态转换是高等植物细胞分化和细胞死亡事件的灵活性的原因。本研究的目的是阐明液泡加工酶（VPE）在细胞程序性死亡和细胞分化过程中的分子机制。(1)我们产生了拟南芥敲除突变体，其具有两种营养型VPE（αVPE和γVPE）和一种种子型VPE（βVPE）的每个基因的缺陷。然后将它们杂交以获得双重和三重突变体。通过对突变体的分析，我们发现正常加工的贮藏蛋白不再被检测到，表明VPE是种子贮藏蛋白加工的关键酶。(2)我们发现了一种来源于ER的特征性结构--ER体。ER体在幼苗表皮细胞中发育，含有胁迫诱导蛋白酶的前体蛋白，如VPE ...更多信息 .相比之下，莲座叶没有ER体。我们发现，创伤胁迫诱导莲座叶中许多ER体的形成。ER体的生物学功能可能与高等植物的防御系统有关。(3)在动物中控制细胞死亡的过程是由半胱氨酸蛋白酶（半胱氨酸蛋白酶）很好地组织的。在植物中，许多研究表明，半胱天冬酶样活性在垂死细胞中被诱导。为了鉴定植物中半胱天冬酶的功能同源物，我们研究了烟草花叶病毒（TMV）感染的烟草植物中的过敏性细胞死亡。VPE特异性抑制剂和caspase-1特异性抑制剂都能抑制TMV诱导的过敏性细胞死亡，由于VPE对caspase-1特异性底物具有caspase活性，因此将负责caspase-1样活性的蛋白酶鉴定为VPE。从VPE活性在TMV诱导的烟草过敏反应早期的出现来看，VPE可能参与了TMV诱导的过敏细胞死亡的早期过程。少

Dynamic transformation of vacuolar function is responsible for flexibility of differentiation and cell death events in higher plant cells. The aim of this study is to elucidate the molecular mechanism of vacuolar processing enzyme (VPE), which is known to be responsible for maturation and activation of vacuolar proteins, in the process of programmed cell death and cell differentiation.(1) We generated the Arabidopsis knockout mutants that had a defect of each gene for the two vegetative type VPEs, αVPE and γVPE, and one seed type VPE, βVPE. Then they were crossed to obtain double and triple mutants. From the analysis of the triple mutant, we found that normally processed storage proteins were no more detected, indicating that VPEs are a key enzyme in processing of seed storage proteins.(2) We found that a characteristic structure derived from ER, ER body. ER bodies develop in the epidermal cells of young seeding and contain the precursor proteins of stress-inducible protease such a VPE … More . In contrast, rosette leaves had no ER bodies. We found that wound stress induced the formation of many ER bodies in rosette leaves. It is possible that the biological function of ER bodies is related to defense systems in higher plants.(3) The process of controlled cell death in animals is well organized by caspases that are cysteine proteinases. In plants, many studies have shown that caspase-like activities are induced in dying cells. To identify a functional homolog of caspase in plants, we investigated hypersensitive cell death in tobacco mosaic virus (TMV)-infected tobacco plants. A VPE-specific inhibitor abolished the TMV-induced hypersensitive cell death, as did a caspase-1-specific inhibitor.Because VPE had caspase activity toward a caspase-1-specific substrate, the proteinase responsible for the caspase-1-like activity was identified as VPE. From the appearance of VPE activity at the early stage-of the TMV-induced hypersensitive response in tobacco leaves, it was suggested that VPE regulates the early process of the TMV-induced hypersensitive cell death. Less