Metabolomic Analysis of Wheat Grains after Tilletia laevis Kühn Infection by Using Ultrahigh-Performance Liquid Chromatography-Q-Exactive Mass Spectrometry

Abstract

Tilletia laevis causes common bunt disease in wheat, with severe losses of production yield and seed quality. Metabolomics studies provide detailed information about the biochemical changes at the cell and tissue level of the plants. Ultrahigh-performance liquid chromatography-Q-exactive mass spectrometry (UPLC-QE-MS) was used to examine the changes in wheat grains after T. laevis infection. PCA analysis suggested that T. laevis-infected and non-infected samples were scattered separately during the interaction. In total, 224 organic acids and their derivatives, 170 organoheterocyclic compounds, 128 lipids and lipid-like molecules, 85 organic nitrogen compounds, 64 benzenoids, 31 phenylpropanoids and polyketides, 21 nucleosides, nucleotides, their analogues, and 10 alkaloids and derivatives were altered in hyphal-infected grains. According to The Kyoto Encyclopedia of Genes and genomes analysis, the protein digestion and absorption, biosynthesis of amino acids, arginine and proline metabolism, vitamin digestion and absorption, and glycine, serine, and threonine metabolism pathways were activated in wheat crops after T. laevis infection.

Keywords: Tilletia laevis; differential metabolites; extensively targeted metabolomics; metabolic pathway; suspension.

Figure 1

LC–MS chromatograms of the wheat grains’ metabolites (X-axis = time and Y-axis = response. (A) Relative abundance of positive ions at different time intervals. (B) Relative abundance of negative ions at different time intervals.

Figure 2

PCA and OPLS-DA of T. laevis-infected and control grains. (A) PCA of grains during different fungal hyphal growth. (B) Orthogonal partial least squares discrimination analysis (OPLS-DA) (Q = 0.938). CK stands for control, QC stands for quality control, T1 stands for suspension of teliospores, T2 stands for promycelia, T3 stands for primary basidiospores, T4 stands for H-bodies, and T5 stands for secondary basidiospores.

Figure 3

Hierarchical clustering heatmap visualizing the changes in the contents of potential metabolites in grains after different hyphal development stages in Tilletia laevis infection. (A) CK vs. T1 group. (B) CK vs. T2 group. (C) CK vs. T3 group. (D) CK vs. T4 group. (E) CK vs. T5 group. CK stands for control, QC stands for quality control, T1 stands for suspension of teliospores, T2 stands for promycelia, T3 stands for primary basidiospores, T4 stands for H-bodies, and T5 stands for secondary basidiospores.

Figure 4

Different metabolites in the grains after different hyphal development stages of Tilletia laevis infection. (A) Volcano plots of different metabolites in the suspension of teliospores (T1) and the control (CK) group. (B) Volcano plots of different metabolites in the promycelia (T2) and control (CK) group. (C) Volcano plots of different metabolites in the primary basidiospores (T3) and control (CK) group. (D) Volcano plots of different metabolites in the H-bodies (T4) and control (CK) group. (E) Volcano plots of different metabolites in the secondary basidiospores (T5) and control (CK) group.

Figure 5

KEGG enrichment analysis scatter plot representing the pathways of DEGs in response to different fungal developmental stages of T. laevis infection. The blue, white, and red colors indicate low, medium, and high expression patterns of genes, respectively. (A) CK vs. T1 group. (B) CK vs. T2 group. (C) CK vs. T3 group. (D) CK vs. T4 group. (E) CK vs. T5 group. CK stands for control, QC stands for quality control, T1 stands for the suspension of teliospores, T2 stands for promycelia, T3 stands for primary basidiospores, T4 stands for H-bodies, and T5 stands for secondary basidiospores.