Metabolomics Analysis Reveals Metabolites and Metabolic Pathways Involved in the Growth and Quality of Water Dropwort [ Oenanthe javanica (Blume) DC.] under Nutrient Solution Culture

Abstract

Water dropwort (Oenanthe javanica (Blume) DC.) is an important vegetable crop. Nutrient liquid culture has become an important cultivation method in the production of water dropwort. However, the effects of different nutrient solution cultivation methods on the growth and quality of water dropwort remains unclear. In this study, to screen the most suitable nutrient solution formula for the cultivation of water dropwort, the effects of different nutrient solution formulas (Hoagland, Cooper, Dutch greenhouse, Garden-style, Yamasaki and SCAU) on plant physiological and quality characteristics are investigated. The plant height, root length, water content (%), distribution rate of dry matter (%), chlorophyll, VC, flavonoid, total phenolic, DPPH and dietary fiber of water dropwort under different nutrient solutions were determined. According to the analytic hierarchy process (AHP) of the growth index and quality index of water dropwort under different nutrient solutions, the Yamazaki nutrient solution was considered to be the most suitable nutrient solution formula for water dropwort. To further confirm the differences of water dropwort under nutrient solution culture and soil culture, the broadly targeted metabolomics were performed. A total of 485 metabolites were detected in water dropwort under optimal nutrient solution and soil cultivation. Metabolomics analysis showed that flavonoids were the most abundant differential accumulated metabolites, and most flavonoids were up-regulated. A qRT-PCR assay indicated that the structural genes of the flavonoid biosynthesis pathway (PAL, C4H, CHS, CHI, F3H, DFR, UFGT) were significantly higher under the Yamasaki nutrient solution treatment. The current study provided a theoretical basis and technical guidance for the nutrient solution cultivation of water dropwort. Meanwhile, this study provides new insights into the study of flavonoids in water dropwort.

Keywords: Oenanthe javanica (Blume) DC.; gene expression; metabolites; nutrient solution culture.

Figure 1

Synthesis appraisal level structural model.

Figure 2

Volcanic map of differential metabolites of water dropwort under soil culture (CK) and Yamasaki nutrient solution (NK). Note: each point on the volcanic map represents a metabolite, and the abscissa represents the logarithm of the quantitative difference multiple of a metabolite in the two samples. The y−coordinate represents the VIP value. Red represents the metabolites with upregulated differential expression, green represents the metabolites with down−regulated differential expression and gray represents the detected metabolites with no significant differences.

Figure 3

Differential metabolite clustering heat map of water dropwort under soil culture (CK) and Yamasaki nutrient solution (NK).

Figure 4

Differential metabolites bar chart of water dropwort under soil culture (CK) and Yamasaki nutrient solution (NK). Red represents up−regulated differentially expressed metabolites and green represents down−regulated differentially expressed metabolites.

Figure 5

KEGG classification of differential metabolites of water dropwort under soil culture (CK) and Yamasaki nutrient solution (NK). Pink represents pathways related to metabolism, purple represents pathways related to genetic information processing, and green represents pathways related to environmental information processing.

Figure 6

KEGG pathway enrichment of differential metabolites of water dropwort under soil culture (CK) and Yamasaki nutrient solution (NK). The abscissa indicates the rich factor corresponding to each path, the ordinate is the path name, the color of the point is the p−value, and the redness level indicates that the enrichment is more significant. The size of the dots represents the number of differential metabolites enriched.

Figure 7

The total flavonoid content of water dropwort under soil culture (CK) and Yamasaki nutrient solution (NK). Different letters indicate a significant difference in the total flavonoid content of water dropwort between different treatments, at the 5% level. Error bars show the standard deviation (SD) of three biological replicates.

Figure 8

The expression levels of the gene involved in the flavonoid metabolism pathway. (a) Schematic diagram of the flavonoid synthesis pathway. (b) qRT-PCR analyzed the relative expression of flavonoid pathway structural genes. Different letters indicate a significant difference in the relative expression of the flavonoid pathway structural genes of water dropwort between different treatments, at the 5% level. Error bars show the standard deviation (SD) of three biological replicates.