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. 2020 Jun 9;20(1):265.
doi: 10.1186/s12870-020-02465-6.

Metabolite profiling of rhizosphere soil of different allelopathic potential rice accessions

Yingzhe Li  1   2 , Lining Xu  1   2 , Puleng Letuma  1   2   3 , Wenxiong Lin  4   5   6
Affiliations

Metabolite profiling of rhizosphere soil of different allelopathic potential rice accessions

Yingzhe Li et al. BMC Plant Biol. .

Abstract

Background: Identification of the allelopathy-interrelated metabolites from the allelopathic rice rhizosphere is crucial to understand the allelopathic mechanism of rice, which in turn can promote its applications to farming. In this study, the metabolites from the rhizosphere soil of five different rice lines, including allelopathic rice accession PI312777 (PI) and non-allelopathic rice accession Lemont (Le) as well as their genetic derivatives (e.g., phenylalanine ammonia-lyase (PAL) gene overexpression transgenic lines of PI and Le, namely, PO and LO respectively, and PAL RNA interference line of PI, namely, PR) were identified and comparatively analyzed to explore the positive compounds that are involved in the process of rice allelopathy.

Results: The results showed that 21 non-polar compounds and 21 polar compounds differed in content in the rhizosphere soil of PI and Le, which include several volatile fatty acids and long-chain fatty acids. The relative contents of fatty acids also differed between PAL overexpressing or RNA interference (RNAi)-silenced line and their wild-type respectively. Acetic acid content also differed among groups, i.e., it is higher in the high allelopathic potential rice. Further analysis showed that different metabolites from the ADS8 resin-extracted phase were more abundant than that those from the ADS21 resin-extracted phase, suggesting that the allelochemicals in root exudates of allelopathic rice are mainly non-polar substances. KEGG annotation of these differential metabolites revealed that these compounds were related to nutrient metabolism, secondary metabolite synthesis, signaling substance synthesis, and toxin degradation.

Conclusions: Rice allelochemicals deposited in the ADS8 resin-extracted phase were more abundant than those in the ADS21 resin-extracted phase. Allelochemicals in root exudates of allelopathic rice are mainly non-polar substances, and long-chain fatty acids are considered as allelopathy interrelated metabolites.

Keywords: Allelopathy; Fatty acids; Metabolomics; Resin extraction; Rhizosphere.

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Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
Expression of PAL (a) gene by quantitative RT-PCR (b) and protein expression by western blotting of rice roots. The original full-length western-blot images are shown in the Additional file 1: Figure S1
Fig. 2
Fig. 2
Analysis of differential metabolites between PI and Le samples absorbed by ADS-8 resin from rhizosphere soil. a The relative content of the metabolites between PI and Le displayed in the heat map, and the differential substances are arranged according to the VIP values from small to large. Each row represents a compound: of which the value of each compound represents the relative content directly normalized on the scale of the graph. Bluish color represents low content while reddish color represents high content. b The possible metabolic pathway distribution of single metabolic substance between PI and Le. c The left side represents the number of single differential substance in the same pathway where PI is lower than Le, and the right side is the opposite
Fig. 3
Fig. 3
Analysis of differential metabolites between PI and Le samples absorbed by ADS-21 resin from rhizosphere soil. a The relative content of the metabolites between PI and Le is shown in the heat map, and the differential substances are arranged according to the VIP values from small to large. Each row represents a compound. The value of each compound represents the relative content directly normalized on the scale of the graph. Blue represents low content while red represents high content. b The possible metabolic pathway distribution of single metabolic substance between PI and Le. c The left side represents the number of single differentia substance in the same pathway where PI is lower than Le, and the right side is the opposite
Fig. 4
Fig. 4
Analysis of differential metabolites between PI and PR samples absorbed by ADS-8 resin from rhizosphere soil. a The relative content of the metabolites between PI and PR is presented in the heat map, and the differential substances are arranged according to the VIP values from small to large. Each row represents a compound. The value of each compound represents the relative content directly normalized on the scale of the graph. Blue represents low content while red represents high content; b The possible metabolic pathway distribution of single metabolic substance between PI and PR. c The left side represents the number of single differential substance in the same pathway where PI is lower than PR, and the right side is the opposite
Fig. 5
Fig. 5
Analysis of differential metabolites between PI and PR samples absorbed by ADS-21 resin from rhizosphere soil. a The relative content of the metabolites between PI and PR is shown in the heat map, and the differential substances are arranged according to the VIP values from small to large. Each row represents a compound. The value of each compound represents the relative content directly normalized on the scale of the graph. Blue represents low content while red represents high content. b The possible metabolic pathway distribution of single metabolic substance between PI and PR. c The left side represents the number of single differentia substance in the same pathway where PI is lower than PR, and the right side is the opposite
Fig. 6
Fig. 6
Analysis of differential metabolites between PI and PO samples absorbed by ADS-8 resin from rhizosphere soil. a The relative content of the metabolites between PI and PO is shown in the heat map, and the differential substances are arranged according to the VIP values from small to large. Each row represents a compound. The value of each compound represents the relative content directly normalized on the scale of the graph. Bluish color represents low content while reddish color represents high content. b The possible metabolic pathway distribution of single metabolic substance between PI and PO. c The left side represents the number of single differentia substance in the same pathway where PI is lower than PO, and the right side is the opposite
Fig. 7
Fig. 7
Analysis of differential metabolites between PI and PO samples absorbed by ADS-21 resin from rhizosphere soil. a The relative content of the metabolites between PI and PO is shown in the heat map, and the differential substances are arranged according to the VIP values from small to large. Each row represents a compound. The value of each compound represents the relative content directly normalized on the scale of the graph. Blue represents low content while red indicates high content. b The possible metabolic pathway distribution of single metabolic substance between PI and PO. c The left side represents the number of single differentia substance in the same pathway where PI is lower than PO, and the right side is the opposite
Fig. 8
Fig. 8
Analysis of differential metabolites between Le and LO samples absorbed by ADS-8 resin from rhizosphere soil. a The relative content of the metabolites between Le and LO is shown in the heat map, and the differential substances are arranged according to the VIP values from small to large. Each row represents a compound. The value of each compound represents the relative content directly normalized on the scale of the graph. Blue represents low content while red represents high content. b The possible metabolic pathway distribution of single metabolic substance between Le and LO. c The left side represents the number of single differentia substance in the same pathway where Le is lower than LO, and the right side is the opposite
Fig. 9
Fig. 9
Analysis of differential metabolites between Le and LO samples absorbed by ADS-21 resin from rhizosphere soil. a The relative content of the metabolites between Le and LO is shown in the heat map, and the differential substances are arranged according to the VIP values from small to large. Each row represents a compound. The value of each compound represents the relative content directly normalized on the scale of the graph. Blue represents low content while red indicates high content. b The possible metabolic pathway distribution of single metabolic substance between Le and LO. c The left side represents the number of single differentia substance in the same pathway where Le is lower than LO, and the right side is the opposite
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