Examination of Endogenous Peptides in <i>Medicago truncatula</i> Using Mass Spectrometry Imaging

Plant science is an important, rapidly developing area of study. Within plant science, one area of study that has grown tremendously with recent technological advances, such as mass spectrometry, is the field of plant-omics; however, plant peptidomics is relatively underdeveloped in comparison with proteomics and metabolomics. Endogenous plant peptides can act as signaling molecules and have been shown to affect cell division, development, nodulation, reproduction, symbiotic associations, and defense reactions. There is a growing need to uncover the role of endogenous peptides on a molecular level. Mass spectrometric imaging (MSI) is a valuable tool for biological analyses as it allows for the detection of thousands of analytes in a single experiment and also displays spatial information for the detected analytes. Despite the prediction of a large number of plant peptides, their detection and imaging with spatial localization and chemical specificity is currently lacking. Here we analyzed the endogenous peptides and proteins in Medicago truncatula using matrix-assisted laser desorption/ionization (MALDI)–MSI. Hundreds of endogenous peptides and protein fragments were imaged, with interesting peptide spatial distribution changes observed between plants in different developmental stages.植物科学（Plant science）是一门重要且发展迅猛的研究领域。在植物科学范畴内，随着质谱法（mass spectrometry）等近代技术的进步，植物组学（plant-omics）领域实现了长足发展；但相较于蛋白质组学（proteomics）与代谢组学（metabolomics），植物肽组学（plant peptidomics）的发展仍相对滞后。内源性植物肽（endogenous plant peptides）可作为信号分子（signaling molecules）发挥作用，现有研究表明其能够调控细胞分裂、生长发育、结瘤过程、生殖活动、共生关联以及防御反应。当前学界对在分子层面揭示内源性植物肽功能的需求日益迫切。 质谱成像（MSI）是一种极具价值的生物学分析工具，可在单次实验中同时检测数千种分析物（analytes），同时还能呈现检测到的分析物的空间分布信息。尽管学界已预测出大量植物肽，但目前仍缺乏具备空间定位与化学特异性的植物肽检测及成像手段。本研究通过基质辅助激光解吸电离-质谱成像（MALDI–MSI），对蒺藜苜蓿（Medicago truncatula）中的内源性肽与蛋白质进行了分析。研究中成功成像了数百种内源性肽及蛋白质片段，并观察到不同发育阶段的植株间存在值得关注的肽空间分布变化。