Plants must cope with a variety of stressors during their life cycle, and the adaptive responses to these environmental cues involve all cellular organelles. Among them, comparatively little is known about the contribution of cytosolic lipid droplets (LDs) and their core set of neutral lipids and associated surface proteins to the rewiring of cellular processes in response to stress. Here, we analyzed the changes that occur in the lipidome and proteome of Arabidopsis (Arabidopsis thaliana) leaves after pathogen infection with Botrytis cinerea or Pseudomonas syringae, or after heat stress. Analyses were carried out in wild-type plants and the oil-rich double mutant trigalactosyldiacylglycerol1-1 sugar dependent 1-4 (tgd1-1 sdp1-4) that allowed for an allied study of the LD proteome in stressed leaves. Using liquid chromatography-tandem mass spectrometry-based methods, we showed that a hyperaccumulation of the primary LD core lipid triacylglycerol is a general response to stress and that acyl chain and sterol composition are remodeled during cellular adaptation. Likewise, comparative analysis of the LD protein composition in stress-treated leaves highlighted the plasticity of the LD proteome as part of the general stress response. We further identified at least two additional LD-associated proteins, whose localization to LDs in leaves was confirmed by confocal microscopy of fluorescent protein fusions. Taken together, these results highlight LDs as dynamic contributors to the cellular adaptation processes that underlie how plants respond to environmental stress.

中文翻译：

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拟南芥叶脂质组和蛋白质组响应病原体感染和热应激的可塑性


植物在其生命周期中必须应对各种压力源，而对这些环境线索的适应性反应涉及所有细胞器。其中，关于胞质脂滴（LD）及其核心中性脂质组和相关表面蛋白对响应应激的细胞过程重新布线的贡献知之甚少。在这里，我们分析了拟南芥（Arabidopsis thaliana）病原体感染灰霉病或丁香假单胞菌后或热应激后叶片脂质组和蛋白质组发生的变化。在野生型植物和富含油的双突变体 trigalactosyldiacylglycerol1-1 Sugar dependent 1-4 (tgd1-1 sdp1-4) 中进行了分析，从而可以对受胁迫叶子中的 LD 蛋白质组进行联合研究。使用基于液相色谱-串联质谱的方法，我们表明初级LD核心脂质三酰甘油的超积累是对应激的普遍反应，并且酰基链和甾醇组成在细胞适应过程中被重塑。同样，对胁迫处理叶片中 LD 蛋白质组成的比较分析强调了 LD 蛋白质组作为一般胁迫反应的一部分的可塑性。我们进一步鉴定了至少两种额外的 LD 相关蛋白，通过荧光蛋白融合的共聚焦显微镜证实了它们在叶子中 LD 的定位。总而言之，这些结果强调了 LD 作为细胞适应过程的动态贡献者，而细胞适应过程是植物如何应对环境压力的基础。