Leaf senescence involves lipid droplet degradation that produces toxic fatty acids, but little is known about how the toxic metabolites are isolated from the rest of the cellular components. Our ultramicroscopic characterization of cytosolic lipid droplet degradation in central vacuole-absent cells and central vacuole-containing cells of senescent watermelon leaves demonstrated two degradation pathways: the small vacuole-associated pathway and the central vacuole-associated pathway. This provided an insight into the subcellular mechanisms for the isolation of the fatty acids derived from lipid droplets. The central vacuole-containing cells, including mesophyll cells and vascular parenchyma cells, adopted the central vacuole-associated pathway, indicated by the presence of lipid droplets in the central vacuole, which is believed to play a crucial role in scavenging toxic metabolites. The central vacuole-absent intermediary cells, where senescence caused the occurrence of numerous small vacuoles, adopted the small vacuole-associated pathway, evidenced by the occurrence of lipid droplets in the small vacuoles. The assembly of organelles, including lipid droplets, small vacuoles, mitochondria, and peroxisome-like organelles, occurred in the central vacuole-absent intermediary cell in response to leaf senescence. This article is protected by copyright. All rights reserved.

中文翻译：

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衰老叶片胞质脂滴降解机制的新见解

叶片衰老涉及产生有毒脂肪酸的脂滴降解，但对如何从其余细胞成分中分离有毒代谢物知之甚少。我们对衰老西瓜叶的中央液泡缺失细胞和含有中央液泡的细胞中细胞溶质脂滴降解的超显微表征证明了两种降解途径：小液泡相关途径和中央液泡相关途径。这提供了对分离来自脂滴的脂肪酸的亚细胞机制的深入了解。含有中心液泡的细胞，包括叶肉细胞和血管薄壁细胞，采用中心液泡相关途径，表现为中心液泡中存在脂滴，这被认为在清除有毒代谢物方面起着至关重要的作用。中心液泡缺失的中间细胞，其中衰老导致许多小液泡的发生，采用小液泡相关途径，小液泡中脂滴的出现证明了这一点。细胞器的组装，包括脂滴、小液泡、线粒体和过氧化物酶体样细胞器，发生在没有中央液泡的中间细胞中，以响应叶片衰老。本文受版权保护。版权所有。细胞器的组装，包括脂滴、小液泡、线粒体和过氧化物酶体样细胞器，发生在没有中央液泡的中间细胞中，以响应叶片衰老。本文受版权保护。版权所有。细胞器的组装，包括脂滴、小液泡、线粒体和过氧化物酶体样细胞器，发生在没有中央液泡的中间细胞中，以响应叶片衰老。本文受版权保护。版权所有。