The compound 5-chloro-3-methyl-4-nitro-1H-pyrazole (CMNP) is a pyrazole-derivative that induces abscission selectively in mature citrus (Citrus sinensis) fruit when applied to the canopy and has herbicidal activity on plants when applied to roots. Despite the favourable efficacy of this compound, the mode of action remains unknown. To gain information about the mode of action of CMNP, the effect of application to mature citrus fruit and Arabidopsis thaliana roots was explored. Peel contact was essential for mature fruit abscission in citrus, whereas root drenching was essential for symptom development and plant decline in Arabidopsis. CMNP was identified as an uncoupler in isolated soybean (Glycine max) mitochondria and pea (Pisum sativum) chloroplasts and an inhibitor of alcohol dehydrogenase in citrus peel, but not an inhibitor of protoporphyrinogen IX oxidase. CMNP treatment reduced ATP content in citrus peel and Arabidopsis leaves. Phospholipase A2 (PLA2) and lipoxygenase (LOX) activities, and lipid hydroperoxide (LPO) levels increased in flavedo of citrus fruit peel and leaves of Arabidopsis plants treated with CMNP. An inhibitor of PLA2 activity, aristolochic acid (AT), reduced CMNP-induced increases in PLA2 and LOX activities and LPO levels in citrus flavedo and Arabidopsis leaves and greatly reduced abscission in citrus and delayed symptoms of plant decline in Arabidopsis. However, AT treatment failed to halt the reduction in ATP content. Reduction in ATP content preceded the increase in PLA2 and LOX activities, LPO content and the biological response. The results indicate a link between lipid signalling, abscission in citrus and herbicidal damage in Arabidopsis.

中文翻译：

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柑橘脱落和拟南芥植物对 5-chloro-3-methyl-4-nitro-1H-pyrazole 的反应由脂质信号传导介导

化合物 5-chloro-3-methyl-4-nitro-1H-pyrazole (CMNP) 是一种吡唑衍生物，可在成熟柑橘 (Citrus sinensis) 果实中选择性诱导脱落，当施用于树冠时，对植物具有除草活性到根。尽管该化合物具有良好的功效，但其作用方式仍然未知。为了获得有关 CMNP 作用方式的信息，探索了应用到成熟柑橘类水果和拟南芥根部的效果。果皮接触对于柑橘成熟果实的脱落是必不可少的，而根部浸湿对于拟南芥的症状发展和植物衰退是必不可少的。CMNP 被鉴定为分离的大豆 (Glycine max) 线粒体和豌豆 (Pisum sativum) 叶绿体中的解偶联剂和柑橘皮中乙醇脱氢酶的抑制剂，但不是原卟啉原 IX 氧化酶的抑制剂。CMNP 处理降低了柑橘皮和拟南芥叶片中的 ATP 含量。用 CMNP 处理的柑橘类果皮和拟南芥叶片的 flavedo 磷脂酶 A2 (PLA2) 和脂氧合酶 (LOX) 活性以及脂质过氧化氢 (LPO) 水平增加。PLA2 活性抑制剂马兜铃酸 (AT) 降低了 CMNP 诱导的 PLA2 和 LOX 活性增加，以及柑橘和拟南芥叶片中的 LPO 水平，并大大减少了柑橘的脱落并延迟了拟南芥植物衰退的症状。然而，AT 治疗未能阻止 ATP 含量的减少。ATP 含量的减少先于 PLA2 和 LOX 活性、LPO 含量和生物反应的增加。结果表明脂质信号传导之间存在联系，