Department of Horticulture and Landscape Architecture, Colorado State University, Fort Collins, CO 80523, USA.
Proteomics and Metabolomics Facility, Colorado State University, Fort Collins, CO 80523, USA.
Int J Mol Sci. 2018 Jan 23;19(2):249. doi: 10.3390/ijms19020249.
Wheat ( L.) is an important food crop, and biotic and abiotic stresses significantly impact grain yield. Wheat leaf and stem surface waxes are associated with traits of biological importance, including stress resistance. Past studies have characterized the composition of wheat cuticular waxes, however protocols can be relatively low-throughput and narrow in the range of metabolites detected. Here, gas chromatography-mass spectrometry (GC-MS) metabolomics methods were utilized to provide a comprehensive characterization of the chemical composition of cuticular waxes in wheat leaves and stems. Further, waxes from four wheat cultivars were assayed to evaluate the potential for GC-MS metabolomics to describe wax composition attributed to differences in wheat genotype. A total of 263 putative compounds were detected and included 58 wax compounds that can be classified (e.g., alkanes and fatty acids). Many of the detected wax metabolites have known associations to important biological functions. Principal component analysis and ANOVA were used to evaluate metabolite distribution, which was attributed to both tissue type (leaf, stem) and cultivar differences. Leaves contained more primary alcohols than stems such as 6-methylheptacosan-1-ol and octacosan-1-ol. The metabolite data were validated using scanning electron microscopy of epicuticular wax crystals which detected wax tubules and platelets. Conan was the only cultivar to display alcohol-associated platelet-shaped crystals on its abaxial leaf surface. Taken together, application of GC-MS metabolomics enabled the characterization of cuticular wax content in wheat tissues and provided relative quantitative comparisons among sample types, thus contributing to the understanding of wax composition associated with important phenotypic traits in a major crop.
小麦（L.）是一种重要的粮食作物，生物和非生物胁迫显著影响粮食产量。小麦叶片和茎表面蜡质与生物重要性状有关，包括抗逆性。过去的研究已经描述了小麦表皮蜡质的组成，但是这些方案的代谢物检测范围相对较窄，通量也较低。在这里，我们利用气相色谱-质谱（GC-MS）代谢组学方法对小麦叶片和茎表皮蜡质的化学成分进行了全面的描述。此外，我们还对四个小麦品种的蜡质进行了分析，以评估 GC-MS 代谢组学在描述因小麦基因型差异而导致的蜡质组成方面的潜力。共检测到 263 种可能的化合物，包括 58 种可分类的蜡质化合物（如烷烃和脂肪酸）。许多检测到的蜡质代谢物与重要的生物学功能有关。主成分分析和方差分析用于评估代谢物的分布，这归因于组织类型（叶、茎）和品种差异。叶片中比茎中含有更多的一级醇，如 6-甲基十七烷-1-醇和辛烷-1-醇。利用表皮蜡质晶体的扫描电子显微镜对代谢物数据进行了验证，检测到了蜡质小管和血小板。在其下表皮叶片表面，柯南是唯一显示与醇有关的血小板状晶体的品种。总之，GC-MS 代谢组学的应用使我们能够对小麦组织中的表皮蜡质含量进行特征描述，并对不同样品类型进行相对定量比较，从而有助于理解与主要作物重要表型性状相关的蜡质组成。
