Effects of MeJA on Arabidopsis metabolome under endogenous JA deficiency

Abstract

Jasmonates (JAs) play important roles in plant growth, development and defense. Comprehensive metabolomics profiling of plants under JA treatment provides insights into the interaction and regulation network of plant hormones. Here we applied high resolution mass spectrometry based metabolomics approach on Arabidopsis wild type and JA synthesis deficiency mutant opr3. The effects of exogenous MeJA treatment on the metabolites of opr3 were investigated. More than 10000 ion signals were detected and more than 2000 signals showed significant variation in different genotypes and treatment groups. Multivariate statistic analyses (PCA and PLS-DA) were performed and a differential compound library containing 174 metabolites with high resolution precursor ion-product ions pairs was obtained. Classification and pathway analysis of 109 identified compounds in this library showed that glucosinolates and tryptophan metabolism, amino acids and small peptides metabolism, lipid metabolism, especially fatty acyls metabolism, were impacted by endogenous JA deficiency and exogenous MeJA treatment. These results were further verified by quantitative reverse transcription PCR (RT-qPCR) analysis of 21 related genes involved in the metabolism of glucosinolates, tryptophan and α-linolenic acid pathways. The results would greatly enhance our understanding of the biological functions of JA.

Figure 1. Statistical analysis of normalized dataset.

(a) Score Plot, (b) Loading Plot of Principal component analysis (PCA) and (c) Hierarchical cluster analysis (HCA) using all of the 12016 ion signals. (d) S-plot of orthogonal partial least squares discriminant analysis (OPLS-DA) of wild type and opr3 leaf extracts. Compounds with a p value less than 0.05 and fold change higher than 2 are highlighted in red.

Figure 2. Heat map analysis of the identified compound revealed 5 clusters according to their variation trends.

The sequence numbers were corresponding to Supplementary Table S2.

Figure 3. Result of pathway analysis.

The p values were calculated from the enrichment analysis while the pathway impact values were calculated from pathway topology analysis.

Figure 4. Glucosinolates and tryptophan metabolism affected by OPR3 deficiency and MeJA treatment.

(a) Methionine derived glucosinolates metabolism, (b) tryptophan metabolism were influenced by OPR3 deficiency and MeJA treatment. Differential metabolites detected are labeled in red, fold changes compared to opr3 were displayed in the boxes.

Figure 5. alpha-linolenic acid metabolism was influenced by OPR3 deficiency and MeJA treatment.

Differential metabolites detected are labeled in red, fold changes compared to opr3 were displayed in the boxes.

Figure 6. Gene expression analysis by RT-qPCR.

21 genes were selected based on their functions in specific metabolic pathways (glucosinolates, tryptophan and α-linolenic acid). Data represent mean ± SD from three biological and three technical replicates. Superscript letter indicates the result of ANOVA test (p < 0.05).