Allelopathic Molecular Mechanisms of the Two Main Allelochemicals in Sweet Potato

Abstract

Sweet potato (Ipomoea batatas L.) is one of the most important global food crops. This crop exhibits excellent allelopathic potential against various weeds, but its allelopathic mechanism at the molecular level is unclear. Therefore, metabolomic and transcriptomic analyses were performed to explore the allelopathic effects, metabolic pathway, and associated genes for two major compounds with allelopathic activity, palmitic acid and linoleic acid. The sweet potato variety Ningshu 25 was employed in the current study. The results showed that palmitic acid and linoleic acid had strong allelopathic effects on seed germination, plant growth, antioxidant enzyme activity, and chlorophyll content of two weeds Digitaria sanguinalis and Bidens pilosa. The content of the two targeted metabolites was affected by different environmental conditions and was significantly increased under low temperature (15 °C). Five metabolic pathways involved in the two targeted metabolites of fatty acids were found: fatty acid biosynthesis, fatty acid elongation, fatty acid degradation, biosynthesis of cutin, suberine, and wax, and the linoleic acid metabolism pathway. The synthesis of palmitic acid is significantly enriched in the biosynthesis pathways of fatty acids, cutin, suberine, and wax, and the synthesis of linoleic acid is significantly enriched in the linoleic acid metabolism pathway. Under different environmental conditions, there were three key genes expressed-g4988, g11881, and g19673-located in the biosynthesis pathways of cutin, suberine, and wax; four key genes expressed-g31191, g60956, g49811, and g59542-located in the biosynthesis pathway of fatty acids; and six key expressed genes-g26575, g24787, g23517, g57649, g58562, and g4314-located in biosynthesis pathway of linoleic acid, respectively. Our study advances understanding of the molecular mechanisms behind allelopathic traits in sweet potato and provides a set of candidate genes for use in improving allelopathic potential in sweet potato germplasm resources.

Keywords: allelopathic effects; linoleic acid; metabolomics; palmitic acid; sweet potato; transcriptomics.

Figure 1

Cluster heat map (A) and bar chart (B) of differential metabolites clustering in Ningshu 25 under different environmental conditions.

Figure 2

Differential gene analysis ((A) = heatmap of DEGs, (B) = bar chart of the number of upregulated and downregulated genes and (C) = venn diagram of DEGs) of Ningshu 25 under different environmental conditions.

Figure 3

KEGG enrichment pathway analysis of metabolites and differential genes in Ningshu 25 under different environmental conditions.

Figure 4

Biosynthetic pathways of cutin, suberine, and wax in Ningshu 25 under different environmental conditions ((A) = under 25% shading, (B) = under 15 °C and (C) = under 25 °C).

Figure 5

Biosynthesis pathway of fatty acid biosynthesis pathways in Ningshu 25 under different environmental conditions ((A) = under 25% shading, (B) = under 15 °C and (C) = under 25 °C).

Figure 6

Biosynthesis pathways of linoleic acid in Ningshu 25 under different environmental conditions ((A) = under 25% shading, (B) = under 15 °C and (C) = under 25 °C).