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Abstract：
The neem tree (Azadirachta indica A.Juss.) contains a range of biologically active compounds-mainly triterpenoids produced in single secretory cells, which are distributed among all plant parts. Neem secretions are toxic to animal cells, triggering autolytic mechanisms that culminate in cell disruption. However, little is known about the self-toxicity of these secretions to the cells that produce them. We carried out an anatomical, histochemical, and ultrastructural investigation of neem\'s single secretory cells in the shoot apex and in young leaves. We evaluated the morphological changes as possible evidences of stress reactions to their own secretions. The subcellular apparatus involved in synthesis and compartmentation was consistent with hydrophilic and lipophilic secretions. Polymorphic plastids devoid of thylakoids and abundant smooth endoplasmic reticulum in the later stages of differentiation are comparable with previous reports on neem cotyledons with regard to terpenoid synthesis. However, secretions were compartmentalized within autophagic vacuoles and periplasmic spaces instead of in terpenoid vesicles. Cellular swelling, increased vesiculation, dilatation of endoplasmic reticulum cisternae, mitochondrial hypertrophy in the cristolysis process, autolytic vacuoles, and vacuolar degeneration culminating in protoplast autolysis are all consistent with early indications of autotoxicity. The signaling stress reaction mechanism was expressed as cytoplasmic deposits of calcium salt and by the expression of a 70-kDa heat-shock protein. The morphological and histochemical changes in the secreting cells are comparable with those described in animal cells exposed to neem oil. Our data provide evidence of cell damage and signaling reactions linked to these cells\' own secretions before autolysis.
摘要：
印尼树（AzadirachtaindicaA.Juss。）包含一系列生物活性化合物-主要是在单个分泌细胞中产生的三萜类化合物，分布在所有植物部分。印鉴分泌物对动物细胞有毒,触发自溶机制，最终导致细胞破坏。然而,对这些分泌物对产生它们的细胞的自身毒性知之甚少。我们进行了解剖，组织化学,并对茎尖和幼叶中的印em的单个分泌细胞进行了超微结构研究。我们评估了形态变化，作为对自身分泌物应激反应的可能证据。参与合成和分隔的亚细胞装置与亲水性和亲脂性分泌物一致。在分化的后期阶段，缺乏类囊体和丰富的平滑内质网的多态质体与先前关于萜类合成的印度子叶的报道相当。然而,分泌物被分隔在自噬液泡和周质空间内，而不是萜类囊泡中。细胞肿胀,增加的囊泡，内质网池扩张，裂隙过程中的线粒体肥大，自溶液泡,和最终导致原生质体自溶的液泡变性都与自毒作用的早期迹象一致。信号应激反应机制表达为钙盐的细胞质沉积物和70kDa热休克蛋白的表达。分泌细胞的形态和组织化学变化与暴露于印em油的动物细胞中描述的变化相当。我们的数据提供了自溶前与这些细胞自身分泌物相关的细胞损伤和信号传导反应的证据。
