Vacuolar processing enzyme is essential for mycotoxin-induced cell death in Arabidopsis thaliana
Vacuolar processing enzyme is essential for mycotoxin-induced cell death in Arabidopsis thaliana
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DOI：
10.1074/jbc.m504476200
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发表时间：
2005-09-23
影响因子：
4.8
通讯作者：
Hara-Nishimura, I
中科院分区：
文献类型：
--
作者：
Kuroyanagi, M;Yamada, K;Hara-Nishimura, I
一些相容的病原体分泌毒素以诱导宿主细胞死亡并促进其生长。毒素诱导的细胞死亡是感染的一种病原体策略。为了阐明毒素诱导细胞死亡的原因，我们研究了一种真菌毒素(伏马菌素B1(FB1))诱导的拟南芥细胞死亡。FB1诱导的细胞死亡伴随着空泡膜的破裂和损伤的形成。Fb1诱导的细胞死亡的特征在缺乏基因组全部四个VPE基因的拟南芥VPE缺失突变体中被完全取消。有趣的是，caspase-1的抑制剂和VPE抑制剂一样，可以抑制FB1诱导的损伤形成。虽然野生型叶片具有caspase-1和VPE活性，但突变体在FB1处理的叶片中没有检测到caspase-1和VPE活性，这两种活性都被caspase-1抑制剂抑制。在四种VPE同系物中，伽玛VPE是FB1诱导拟南芥叶片细胞死亡的最主要的VPE同系物。重组γ-VPE识别的VPE底物的K-m=30.3µM，识别的caspase-1底物的K-m=44.2µM，与哺乳动物caspase-1的测定值相当。γ-VPE前体被自催化转化为具有caspase-1活性的成熟形式。这些体内和体外的分析表明，γVPE是一种具有caspase-1活性的蛋白酶。我们发现，具有caspase-1活性的VPE是毒素诱导细胞死亡的关键分子。我们的发现表明，毒素诱导的细胞死亡的敏感反应是由VPE介导的空泡机制引起的，类似于超敏细胞死亡的抗性反应。
Some compatible pathogens secrete toxins to induce host cell death and promote their growth. The toxin-induced cell death is a pathogen strategy for infection. To clarify the executioner of the toxin-induced cell death, we examined a fungal toxin (fumonisin B1 (FB1))-induced cell death of Arabidopsis plants. FB1-induced cell death was accompanied with disruption of vacuolar membrane followed by lesion formation. The features of FB1-induced cell death were completely abolished in the Arabidopsis vacuolar processing enzyme (VPE)-null mutant, which lacks all four VPE genes of the genome. Interestingly, an inhibitor of caspase-1 abolished FB1-induced lesion formation, as did a VPE inhibitor. The VPE-null mutant had no detectable activities of caspase-1 or VPE in the FB1-treated leaves, although wild-type leaves had the caspase-1 and VPE activities, both of which were inhibited by a caspase-1 inhibitor. gamma VPE is the most essential among the four VPE homologues for FB1-induced cell death in Arabidopsis leaves. Recombinant gamma VPE recognized a VPE substrate with K-m = 30.3 mu M and a caspase-1 substrate with K-m = 44.2 mu M, which is comparable with the values for mammalian caspase-1. The gamma VPE precursor was self-catalytically converted into the mature form exhibiting caspase-1 activity. These in vivo and in vitro analyses demonstrate that gamma VPE is the proteinase that exhibits a caspase-1 activity. We show that VPE exhibiting a caspase-1 activity is a key molecule in toxin-induced cell death. Our findings suggest that a susceptible response of toxin-induced cell death is caused by the VPE-mediated vacuolar mechanism similar to a resistance response of hypersensitive cell death.