Lahlali Rachid, Karunakaran Chithra, Wang Lipu, Willick Ian, Schmidt Marina, Liu Xia, Borondics Ferenc, Forseille Lily, Fobert Pierre R, Tanino Karen, Peng Gary, Hallin Emil
Canadian Light Source Inc., 44 Innovation Boulevard, Saskatoon, SK, S7N 2V3, Canada.
National Research Council Canada, 110 Gymnasium Place, Saskatoon, SK, S7N 0W9, Canada.
BMC Plant Biol. 2015 Jan 28;15:24. doi: 10.1186/s12870-014-0357-5.
Fusarium head blight (FHB), a scab principally caused by Fusarium graminearum Schw., is a serious disease of wheat. The purpose of this study is to evaluate the potential of combining synchrotron based phase contrast X-ray imaging (PCI) with Fourier Transform mid infrared (FTIR) spectroscopy to understand the mechanisms of resistance to FHB by resistant wheat cultivars. Our hypothesis is that structural and biochemical differences between resistant and susceptible cultivars play a significant role in developing resistance to FHB.
Synchrotron based PCI images and FTIR absorption spectra (4000-800 cm(-1)) of the floret and rachis from Fusarium-damaged and undamaged spikes of the resistant cultivar 'Sumai3', tolerant cultivar 'FL62R1', and susceptible cultivar 'Muchmore' were collected and analyzed. The PCI images show significant differences between infected and non-infected florets and rachises of different wheat cultivars. However, no pronounced difference between non-inoculated resistant and susceptible cultivar in terms of floret structures could be determined due to the complexity of the internal structures. The FTIR spectra showed significant variability between infected and non-infected floret and rachis of the wheat cultivars. The changes in absorption wavenumbers following pathogenic infection were mostly in the spectral range from 1800-800 cm(-1). The Principal Component Analysis (PCA) was also used to determine the significant chemical changes inside floret and rachis when exposed to the FHB disease stress to understand the plant response mechanism. In the floret and rachis samples, PCA of FTIR spectra revealed differences in cell wall related polysaccharides. In the florets, absorption peaks for Amide I, cellulose, hemicellulose and pectin were affected by the pathogenic fungus. In the rachis of the wheat cultivars, PCA underlines significant changes in pectin, cellulose, and hemicellulose characteristic absorption spectra. Amide II and lignin absorption peaks, persistent in the rachis of Sumai3, together with increased peak shift at 1245 cm(-1) after infection with FHB may be a marker for stress response in which the cell wall compounds related to pathways for lignification are increased.
Synchrotron based PCI combined with FTIR spectroscopy show promising results related to FHB in wheat. The combined technique is a powerful new tool for internal visualisation and biomolecular monitoring before and during plant-microbe interactions to understand both the differences between cultivars and their different responses to disease stress.
小麦赤霉病（FHB），一种主要由禾谷镰刀菌（Fusarium graminearum Schw.）引起的赤霉病，是小麦的一种严重病害。本研究的目的是评估基于同步加速器的相衬X射线成像（PCI）与傅里叶变换中红外（FTIR）光谱相结合的潜力，以了解抗性小麦品种对FHB的抗性机制。我们的假设是，抗性和感病品种之间的结构和生化差异在对FHB的抗性形成中起重要作用。
收集并分析了抗性品种‘苏麦3号’、耐病品种‘FL62R1’和感病品种‘Muchmore’受镰刀菌侵染和未侵染穗的小花和穗轴的基于同步加速器的PCI图像以及FTIR吸收光谱（4000 - 800 cm⁻¹）。PCI图像显示不同小麦品种受侵染和未受侵染的小花及穗轴之间存在显著差异。然而，由于内部结构复杂，未接种的抗性和感病品种在小花结构方面未发现明显差异。FTIR光谱显示小麦品种受侵染和未受侵染的小花及穗轴之间存在显著差异。病原菌侵染后吸收波数的变化大多在1800 - 800 cm⁻¹光谱范围内。主成分分析（PCA）也用于确定小花和穗轴在受到FHB病害胁迫时内部的显著化学变化，以了解植物的反应机制。在小花和穗轴样品中，FTIR光谱的PCA揭示了细胞壁相关多糖的差异。在小花中，酰胺I、纤维素、半纤维素和果胶的吸收峰受病原菌影响。在小麦品种的穗轴中，PCA突出了果胶、纤维素和半纤维素特征吸收光谱的显著变化。苏麦3号穗轴中持续存在的酰胺II和木质素吸收峰，以及FHB侵染后1245 cm⁻¹处峰位移增加，可能是应激反应的一个标志，其中与木质化途径相关的细胞壁化合物增加。
基于同步加速器的PCI与FTIR光谱相结合在小麦FHB研究方面显示出有前景的结果。该联合技术是一种强大的新工具，可用于在植物 - 微生物相互作用之前和期间进行内部可视化和生物分子监测，以了解品种之间的差异及其对病害胁迫的不同反应。
