Multi-Omics Analysis of the Effects of Soil Amendment on Rapeseed (Brassica napus L.) Photosynthesis under Drip Irrigation with Brackish Water

Abstract

Drip irrigation with brackish water increases the risk of soil salinization while alleviating water shortage in arid areas. In order to alleviate soil salinity stress on crops, polymer soil amendments are increasingly used. But the regulation mechanism of a polymer soil amendment composed of polyacrylamide polyvinyl alcohol, and manganese sulfate (PPM) on rapeseed photosynthesis under drip irrigation with different types of brackish water is still unclear. In this field study, PPM was applied to study the responses of the rapeseed (Brassica napus L.) phenotype, photosynthetic physiology, transcriptomics, and metabolomics at the peak flowering stage under drip irrigation with water containing 6 g·L^-1 NaCl (S) and Na₂CO₃ (A). The results showed that the inhibitory effect of the A treatment on rapeseed photosynthesis was greater than that of the S treatment, which was reflected in the higher Na⁺ content (73.30%) and lower photosynthetic-fluorescence parameters (6.30-61.54%) and antioxidant enzyme activity (53.13-77.10%) of the A-treated plants. The application of PPM increased the biomass (63.03-75.91%), photosynthetic parameters (10.55-34.06%), chlorophyll fluorescence parameters (33.83-62.52%), leaf pigment content (10.30-187.73%), and antioxidant enzyme activity (28.37-198.57%) under S and A treatments. However, the difference is that under the S treatment, PPM regulated the sulfur metabolism, carbon fixation and carbon metabolism pathways in rapeseed leaves. And it also regulated the photosynthesis-, oxidative phosphorylation-, and TCA cycle-related metabolic pathways in rapeseed leaves under A treatment. This study will provide new insights for the application of polymer materials to tackle the salinity stress on crops caused by drip irrigation with brackish water, and solve the difficulty in brackish water utilization.

Keywords: abiotic stresses; brackish water; energy metabolism; metabolic pathways; multi-omics.

Figure 1

Effects of soil amendment (PPM) on the morphology (a), and yield of Brassica napus under different treatments (b). Fresh weight, and leaf K⁺ and Na⁺ content of Brassica napus under drip irrigation with water containing 6 g·L⁻¹ NaCl and 6 g·L⁻¹ Na₂CO₃ (c). Different lowercase letters indicate significant difference between groups at p < 0.05.

Figure 2

Effects of application of PPM on photosynthetic parameters, pigment content, fluorescence parameters, and antioxidant enzyme activities (a) of Brassica napus under drip irrigation with waters containing 6 g·L⁻¹ NaCl and 6 g·L⁻¹ Na₂CO₃ and RDA analysis of the parameters. Different lowercase letters indicate significant difference between groups at p < 0.05 (b).

Figure 3

PCA analysis, Venn diagram, up- and down- regulation statistics (a), and KEGG annotation of DEGs (differentially expressed genes) and DAMs (differentially accumulated metabolites) in different groups. *, p < 0.05 (b).

Figure 4

The expression of differentially expressed genes (DEGs) related to photosynthesis in different groups, metabolic pathway analysis, photosynthetic mechanism and energy metabolic pathway analysis (a), and RDA analysis of various parameters between groups (b). The four boxes in the metabolic pathway represent the ratios of SPPM vs. SCK, APPM vs. ACK, ACK vs. SCK and APPM vs. SPPM metabolite contents, respectively.

Figure 4

The expression of differentially expressed genes (DEGs) related to photosynthesis in different groups, metabolic pathway analysis, photosynthetic mechanism and energy metabolic pathway analysis (a), and RDA analysis of various parameters between groups (b). The four boxes in the metabolic pathway represent the ratios of SPPM vs. SCK, APPM vs. ACK, ACK vs. SCK and APPM vs. SPPM metabolite contents, respectively.

Figure 5

Relationship networks of the yield/ion content (red), photosynthetic parameters (yellow), transcription factors (blue), and DAMs (green) of B. napus under different treatments. (a) SCK treatment; (b) ACK treatment; (c) SPPM treatment; and (d)APPM treatment. The red lines indicate positive correlation, and the blue lines indicate negative correlation. Node size is positively correlated with the number of connections.

Figure 5

Relationship networks of the yield/ion content (red), photosynthetic parameters (yellow), transcription factors (blue), and DAMs (green) of B. napus under different treatments. (a) SCK treatment; (b) ACK treatment; (c) SPPM treatment; and (d)APPM treatment. The red lines indicate positive correlation, and the blue lines indicate negative correlation. Node size is positively correlated with the number of connections.

Figure 6

Regulatory mechanism of the effect of soil amendment on rapeseed (Brassica napus L.) photosynthesis under drip irrigation with brackish water.