Characterization of nuclease activities and DNA fragmentation induced upon hypersensitive response cell death and mechanical stress
Characterization of nuclease activities and DNA fragmentation induced upon hypersensitive response cell death and mechanical stress
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DOI：
10.1023/a:1005868402827
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发表时间：
1997-05-01
影响因子：
5.1
通讯作者：
Lam, E
中科院分区：
文献类型：
--
作者：
Mittler, R;Lam, E
程序性细胞死亡（PCD）在多细胞生物对某些入侵病原体的反应过程中被激活。这一过程的关键方面之一是核 DNA 的降解，这被认为有助于死细胞中 DNA 的回收。感染烟草花叶病毒（TMV）的烟草植物（基因型NN）的PCD伴随着核酸酶活性的诱导以及核DNA被切割成约50kb的片段。我们研究了烟草中 TMV 和细菌诱导的 PCD 过程中核酸酶活性的增加与核 DNA 断裂之间的相关性。我们发现核酸酶活性的增加并不总是与核 DNA 片段化相关。因此，除了诱导 PCD 的病原体外，机械损伤和 1 M 蔗糖或不诱导 PCD 的细菌浸润叶子也会导致核酸酶活性增加。对总叶提取物、核提取物和细胞间液（即质外体）中核酸酶活性的分析表明，在烟草的 PCD 过程中至少诱导了四种不同的核酸酶活性；其中至少三种似乎被分泌到细胞间液中。尽管后者也是对不导致 DNA 片段化的处理作出反应而诱导的，但它们可能在 PCD 的后期（当质膜的完整性受到损害时）在植物 DNA 的回收中发挥作用。这一建议得到了 DNA 降解发生在烟草 TMV 诱导 PCD 后期的发现的支持。此外，细胞间液中诱导核酸酶活性的发现提出了它们可能通过降解入侵病原体的 DNA 发挥保护功能的可能性。
Programmed cell death (PCD) is activated during the response of multicellular organisms to some invading pathogens. One of the key aspects of this process is the degradation of nuclear DNA which is thought to facilitate the recycling of DNA from dead cells. The PCD of tobacco plants (genotype NN) infected with tobacco mosaic virus (TMV) is accompanied by the induction of nuclease activities and the cleavage of nuclear DNA to fragments of about 50 kb. We examined the correlation between the increase in nuclease activities and the fragmentation of nuclear DNA during TMV- and bacteria-induced PCD in tobacco. We found that the increase in nuclease activities did not always correlate with fragmentation of nuclear DNA. Thus, in addition to pathogens that induce PCD, mechanical injury and infiltration of leaves with 1 M sucrose or bacteria that did not induce PCD also resulted in an increase in nuclease activities. Analysis of nuclease activities in total leaf extracts, nuclear extracts, and intercellular fluid !i.e., apoplast) revealed that at least four different nuclease activities are induced during PCD in tobacco; of these at least three appear to be secreted into the intercellular fluid. Although the latter were also induced in response to treatments that did not result in DNA fragmentation, they may function in the recycling of plant DNA during late stages of PCD when the integrity of the plasma membrane is compromised. This suggestion is supported by the finding that DNA degradation occurred late during TMV-induced PCD in tobacco. In addition, the finding of induced nuclease activities in the intercellular fluid raises the possibility that they may serve a protective function by degrading the DNA of invading pathogens.