Proteomic analysis of isolated cyanoglobules.

Cyanoglobules are lipid droplets of cyanobacteria that share compositional and functional features with plastoglobules of plant chloroplasts. However, their roles in stress physiology remain poorly defined, particularly in filamentous cyanobacteria. Here, we characterize cyanoglobule dynamics and composition during nitrogen starvation in a non-diazotrophic derivative of Anabaena sp. PCC 7120. This experimental context enables analysis of sustained nitrogen deprivation in vegetative cells without the transient and heterogeneous effects of heterocyst differentiation and nitrogenase activity, while recognizing that the strain does not represent wild-type physiology. Nitrogen starvation induced striking morphological remodeling, including increased cyanoglobule size and abundance. Proteomic analysis revealed a cyanoglobule proteome enriched in homologs of the plant plastoglobule proteome as well as other redox regulators and isoprenoid metabolism enzymes, pointing to roles in pigment turnover and stress adaptation. Lipidome profiling revealed high levels of plastoquinone derivatives and other prenyl-lipid species. Collectively, our findings establish cyanoglobules as dynamic and stress-responsive compartments associated with redox and lipid remodeling during nutrient limitation. By leveraging a non-diazotrophic and comparative analysis, we show that key features of cyanoglobule formation and composition are observed independently of heterocyst differentiation and parallel those described in other cyanobacterial species and plant plastoglobules.蓝球脂（cyanoglobules）是蓝细菌的脂滴，与植物叶绿体的质体球（plastoglobules）在组成与功能特征上具有相似性。然而，其在胁迫生理中的功能仍有待深入阐明，尤其是在丝状蓝细菌中。本研究以鱼腥藻属（Anabaena sp.）PCC 7120的一株非固氮衍生菌株为材料，解析了氮饥饿条件下蓝球脂的动态变化与组成特征。该实验体系可在排除异形胞分化与固氮酶活性所带来的瞬时异质性影响的前提下，分析营养细胞的持续氮匮乏状态，但需注意该菌株并非野生型生理状态。氮饥饿诱导了显著的形态重塑，表现为蓝球脂的体积与丰度均显著提升。蛋白质组分析显示，蓝球脂的蛋白质组中富集了植物质体球蛋白质组的同源蛋白，以及其他氧化还原调控因子与类异戊二烯代谢酶，提示其在色素周转与胁迫适应中发挥功能。脂质组分析则检测到高水平的质体醌衍生物与其他异戊二烯脂质类物质。综上，本研究证实蓝球脂是一类动态响应胁迫的亚细胞区室，在营养限制条件下参与氧化还原与脂质重塑过程。通过采用非固氮菌株体系与对比分析方法，本研究发现蓝球脂形成与组成的关键特征并不依赖于异形胞分化，且与其他蓝细菌物种及植物质体球的相关特征高度一致。