Wang Jiang, Kambhampati Shrikaar, Allen Doug K, Chen Li-Qing
Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL, United States.
Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL, United States.
Front Plant Sci. 2022 May 18;13:836665. doi: 10.3389/fpls.2022.836665. eCollection 2022.
Pollen germination is an essential process for pollen tube growth, pollination, and therefore seed production in flowering plants, and it requires energy either from remobilization of stored carbon sources, such as lipids and starches, or from secreted exudates from the stigma. Transcriptome analysis from pollen germination previously showed that 14 GO terms, including metabolism and energy, were overrepresented in . However, little is understood about global changes in carbohydrate and energy-related metabolites during the transition from mature pollen grain to hydrated pollen, a prerequisite to pollen germination, in most plants, including . In this study, we investigated differential metabolic pathway enrichment among mature, hydrated, and germinated pollen using an untargeted metabolomic approach. Integration of publicly available transcriptome data with metabolomic data generated as a part of this study revealed starch and sucrose metabolism increased significantly during pollen hydration and germination. We analyzed in detail alterations in central metabolism, focusing on soluble carbohydrates, non-esterified fatty acids, glycerophospholipids, and glycerolipids. We found that several metabolites, including palmitic acid, oleic acid, linolenic acid, quercetin, luteolin/kaempferol, and γ-aminobutyric acid (GABA), were elevated in hydrated pollen, suggesting a potential role in activating pollen tube emergence. The metabolite levels of mature, hydrated, and germinated pollen, presented in this work provide insights on the molecular basis of pollen germination.
花粉萌发是开花植物中花粉管生长、授粉以及种子生产的必要过程，它需要能量，这些能量要么来自储存碳源（如脂质和淀粉）的再利用，要么来自柱头分泌的渗出物。先前对花粉萌发的转录组分析表明，包括代谢和能量在内的14个基因本体（GO）术语在[具体内容缺失]中过度富集。然而，在大多数植物（包括[具体植物缺失]）中，从成熟花粉粒到水合花粉（花粉萌发的前提条件）转变过程中，碳水化合物和能量相关代谢物的整体变化却知之甚少。在本研究中，我们使用非靶向代谢组学方法研究了成熟、水合和萌发花粉之间差异代谢途径的富集情况。将公开可用的转录组数据与本研究生成的代谢组数据相结合，结果表明淀粉和蔗糖代谢在花粉水合和萌发过程中显著增加。我们详细分析了中心代谢的变化，重点关注可溶性碳水化合物、非酯化脂肪酸、甘油磷脂和甘油脂。我们发现，包括棕榈酸、油酸、亚麻酸、槲皮素、木犀草素/山奈酚和γ-氨基丁酸（GABA）在内的几种代谢物在水合花粉中升高，这表明它们在激活花粉管萌发方面可能发挥作用。本研究中呈现的成熟、水合和萌发花粉的代谢物水平，为花粉萌发的分子基础提供了见解。
