Metabolomic and transcriptomic analysis of Lycium chinese and L. ruthenicum under salinity stress

Abstract

Background: High soil salinity often adversely affects plant physiology and agricultural productivity of almost all crops worldwide, such as the crude drug known as wolfberry. However, the mechanism of this action in wolfberry is not fully understood yet.

Results: Here in this study, we studied different mechanisms potentially in Chinese wolfberry (Lycium chinese, LC) and black wolfberry (L. ruthenicum, LR) under salinity stress, by analyzing their transcriptome, metabolome, and hormone changes. The hormone detection analysis revealed that the ABA content was significantly lower in LR than LC under normal condition, and increased sharply under salinity stress in LR but not in LC. The transcriptome analysis showed that the salinity-responsive genes in wolfberry were mainly enriched in MAPK signaling, amino sugar and nucleotide sugar metabolism, carbon metabolism, and plant hormone signal transduction pathways in LC, while mainly related to carbon metabolism and protein processing in endoplasmic reticulum in LR. Metabolome results indicated that LR harbored higher flavone and flavonoid contents than LC under normal condition. However, the flavone and flavonoid contents were hardly changed in LR, but increased substantially in LC when exposed to salinity stress.

Conclusions: Our results adds ABA and flavone to mechanism understanding of salinity tolerance in wolfberry. In addition, flavone plays a positive role in resistance to salinity stress in wolfberry.

Keywords: Abscisic acid; Flavone; Flavonoid; Lycium. Chinese; Lycium. Ruthenicum; Salinity stress; Wolfberry.

Fig. 1

Phenotype analysis of Lycium chinese and L. ruthenicum under salinity stress. a The twig cuttings of L. chinese and L. ruthenicum were planted in the MS medium containing 0 mM (CK), 150 mM, 200 mM, 250 mM or 300 mM of NaCl. Pictures were taken after three weeks of cultivation. b Seed germination rate of L. chinese and L. ruthenicum under control and 150 mM NaCl concentrations was calculated from day 3 to day 24. c The ratio of germination rate 150 mM NaCl/ CK was calculated at day 24 after seeds were sown. * P < 0.05, ** P < 0.01. N = 3. Bars = means ± SEM

Fig. 2

Hormonal variation of Lycium chinese and L. ruthenicum in response to salinity stress. Quantification of ABA (Abscisic acid), JA (Jasmonic acid), and SA (Salicylic acid) contents of L. chinese and L. ruthenicum leaves at indicated time points after NaCl treatment. ABA content in a, JA content in b, and SA content in c. Data represent the means ± SEM of three replicates. Asterisks indicate a significant difference from mock (non-stressed treatment at the same time point (N = 3, Student’s t-test: * P < 0.05, ** P < 0.01)

Fig. 3

Transcriptome data of Lycium chinese and L. ruthenicum leaves in response to salinity stress. a Number of differentially expressed genes (DEGs) in L. chinese and L. ruthenicum under salinity stress. b PCA (Principal component analysis) clustering based on the plants’ transcriptome data. c Venn diagrams of DEGs between normal and salinity stress conditions in L. chinese and L. ruthenicum

Fig. 4

Statistics of KEGG enrichment analysis of DEGs (different expressed genes) in Lycium chinese (LC) and L. ruthenicum (LR) under salinity stress. a Group LC-mock vs. LC-NaCl. b Group LR-mock vs. LR-NaCl

Fig. 5

K-means transcriptomic analysis of significant DEGs in Lycium chinese and L. ruthenicum under control and salinity stress conditions. The DEGs are divided into 10 groups, which are classified into six types. The top 10 KEGG pathways in each group are listed on the corresponding right panel

Fig. 6

Metabolome analysis of Lycium chinese and L. ruthenicum in response to salinity stress. a Number of differential expressed metabolites in L. chinese and L. ruthenicum under salinity stress. b PCA (Principal component analysis) clustering based on metabolome data. c Venn diagrams of the different expressed metabolites between control and salinity stress conditions in L. chinese and L. ruthenicum

Fig. 7

KEGG pathway enrichment of differential expressed metabolites in Lycium chinese (LC) and L. ruthenicum (LR) under normal and salinity stress conditions. a Group LC-mock vs. LC-NaCl. b Group LR-mock vs. LR-NaCl. c Group LC-mock vs. LR-mock. d Group LC-NaCl vs. LR-NaCl

Fig. 8

Heatmap of the top 20 significantly differential expressed metabolites in Lycium chinese (LC) and L. ruthenicum (LR) under control and salinity stress conditions. a Group LC-mock vs. LC-NaCl. b Group LR-mock vs. LR-NaCl. c Group LC-mock vs. LR-mock. d Group LC-NaCl vs. LR-NaCl

Fig. 9

KEGG pathway enrichment (histogram of P-values) analysis of Lycium chinese (LC) and L. ruthenicum (LR) under normal and salinity stress conditions. a Group LC-mock vs. LC-NaCl. b Group LR-mock vs. LR-NaCl. The abscissa represents metabolic pathways, the ordinate represents enriched P-values, expressed as –log(P-value); the red and green columns respectively represents the differential expressed genes and metabolites

Fig. 10

Adaptive changes in flavonoid metabolism in Lycium chinese and L. ruthenicum under salinity stress. a The flavonoid biosynthesis pathway. b Heatmap of DEGs (differentially expressed genes) involved in the flavonoid metabolic pathway. c Heatmap of differential expressed metabolites in the flavonoid metabolic pathway

Fig. 11

Alterations to flavone and flavonol metabolism in Lycium chinese and L. ruthenicum under salinity stress. a The flavone and flavonol biosynthesis pathway. b Heatmap of DEGs (differentially expressed genes) involved in the flavone and flavonol metabolic pathway. c Heatmap of differential expressed metabolites in the flavone and flavonol metabolic pathway