Transcriptome and metabolome analyses reveal the regulation of peel coloration in green, red Chinese prickly ash (Zanthoxylum L.)

Transcriptomics integrated with metabolomics to characterize key pigment compounds and genes related to anthocyanin biosynthesis in Zanthoxylum bungeanum peel

Zanthoxylum bungeanum is an important condiment with high economic value and its peel color is one of the main quality indexes. However, the key pigment compounds and related genes are still unclear affecting the quality control of the plants. In this study, the contents of four types of pigments were measured in Z. bungeanum and flavonoids were identified as the most important pigments. Based on the targeted flavonoid metabolomics of Z. bungeanum peels, 14 key pigment compounds were screened out from 152 flavonoids, among which cyanidin-3-O-rutinoside and cyanidin-3-O-glucoside were the most critical compounds for peel color. They were further verified to be present in nine varieties of Z. bungeanum by HPLC fingerprints. The 14 compounds were all associated with flavonoid and anthocyanin biosynthesis pathways and the 39 differentially expressed genes related to these pathways were annotated and screened based on transcriptomics. The genes ZbDFR, ZbANS, and ZbUFGT were identified as three key genes for anthocyanin synthesis in Z. bungeanum peels. Further qRT-PCR results confirmed the reliability of transcriptomics and the accuracy of gene screening. Subsequent protein induced expression demonstrated that ZbANS and ZbUFGT were expressed after 12 h induced by IPTG while ZbDFR was expressed after 15 h. Further transient and stable transformation analysis confirmed that both anthocyanin content and the expression of ZbDFR were significantly increased in overexpression Z. bungeanum leaves and Nicotiana benthamiana. The functional effect of stable transformation of ZbDFR was more significant than that of transient transformation with a 7.67-fold/1.49-fold difference in total anthocyanin content and a 42.37-fold/12.32-fold difference in the expression of ZbDFR. This study provides new insights into the chemical composition and the molecular mechanisms of Z. bungeanum peel color and lays an effective foundation for the color quality control, multi-purpose utilization of Z. bungeanum and the creation of new germplasm.

The establishment of comprehensive quality evaluation model for flavor characteristics of green Sichuan pepper (Zanthoxylum armatum DC.) in Southwest China

In this study, the quality indexes and sensory evaluation of Zanthoxylum armatum DC. from the main production areas in Southwest China were analyzed. Further, correlation analysis (CRA), principal component analysis (PCA) and cluster analysis (CA) were used to comprehensively evaluate the quality characteristics of Z. armatum. The results showed that the sensory indexes and physicochemical indexes of Z. armatum were significantly correlated. Five principal component factors were extracted from 12 indexes by PCA, and a comprehensive evaluation model of quality was established with Y = 0.2943Y₁ + 0.2387Y₂ + 0.1896Y₃ + 0.1679Y₄ + 0.1094Y₅. On this basis, 21 producing areas were grouped into 4 groups and 3 groups by Q-type CA, respectively. R-type CA showed that the content of hydroxyl-sanshools, linalool content and b* value were the quality characteristic indexes of Z. armatum in Southwest China. This work provided an important theory and practice reference for Z. armatum quality evaluation and in-depth product development.

Multi-environment evaluations across ecological regions reveal climate and soil effects on amides contents in Chinese prickly ash peels (Zanthoxylum bungeanum Maxim.)

BACKGROUND

Environmental factors difference is the key factor for the difference in the production, transformation and accumulation of effective components in plants. UPLC-MS/MS and multivariate statistical methods were applied to describe the region difference of amides compounds in Chinese prickly ash peels from different regions and their correlation with climatic factors and soil factors.

RESULTS

Amides compounds contents were significantly higher in high altitude areas, with obvious altitude change trend. Two ecotypes were classified based on the amides compounds contents, one was the high altitude-cool type from Qinghai, Gansu, Sichuan and western Shaanxi province, and the other one was low altitude-warm type from eastern Shaanxi, Shanxi, Henan, Hebei and Shandong province. Amides compounds content were negatively correlated with annual mean temperature, max temperature of warmest month, mean temperature of wettest quarter and mean temperature of warmest quarter (P < 0.01). Except for hydroxy-γ-sanshool and ZP-amide A, the residual amides contents were significantly positively correlated with organic carbon, available nitrogen, phosphorus and potassium in soil and negatively correlated with soil bulk density. Low temperature, low precipitation and high organic carbon in soil were conducive to amides accumulation.

CONCLUSIONS

This study aided in site specific exploration of high amides contents yielding samples, enriched the environment factors effects on amides compounds, and provided scientific foundation for the improvement of Chinese prickly ash peels quality and the location of high-quality production areas.

Evaluating the Impacts of Climate Factors and Flavonoids Content on Chinese Prickly Ash Peel Color Based on HPLC-MS and Structural Equation Model

Climate affects Chinese prickly ash peel color directly through temperature and illumination and indirectly influences it through its effect on flavonoid compounds. In this study, a comprehensive evaluation strategy based on high performance liquid chromatography-mass spectrometry (HPLC-MS) technology and a structural equation model was applied to evaluate the effects of climate factors and flavonoids on Chinese prickly ash peel color. There were obvious geographical variations of peel color and flavonoid compounds with an obvious east–west distribution trend which were divided into high-altitude type and low-altitude type. Through path analysis, the wind speed, temperature and annual sunshine duration were found to be the key environmental factors affecting the flavonoids content and peel color, and their direct effects were higher than their indirect effect. Based on HPLC-MS technology and a structural equation model, correlation models of climatic factors and flavonoids with peel color were established, and the factors that had greater weight on pericarp color were obtained. Our results provide experimental evidence that climate factors affect the peel color by affecting flavonoid biosynthesis and accumulation, reveal the geographical variation of peel color and flavonoid component contents in Chinese prickly ash peel, establish a quantization color method for rapid evaluation of peel quality, expand on the influence of climatic factors on flavonoids content and peel coloration and promote agricultural practice in areas with similar climatic conditions.

Comparative metabolomics analysis of pericarp from four varieties of Zanthoxylum bungeanum Maxim

A qualitative and quantitative analysis of metabolites was performed by metabolomics comparation on the pericarps of four varieties of Zanthoxylum bungeanum Maxim. The Zanthoxylum bunganum as scion combined with three rootstock varieties of Zanthoxylum piasezkii Maxim (YJ), July Zanthoxylum bunganum Maxim (QJ), and August Zanthoxylum bunganum Maxim (BJ), at the same time Zanthoxylum bungeanum seedlings breeding were compared as control (MJ). A total of 1429 metabolites were identified in Zanthoxylum bungeanum Maxim pericarps based on chromatography and mass spectrometry dual detection platform. While the metabolites between four varieties of Z. bungeanum varied, there was identified 31, 15, 7, 79, 42, 19 down-regulated and 55, 50, 13, 75, 43, 27 up-regulated differential metabolites between MJ and BJ, MJ and QJ, MJ and YJ, QJ and BJ, YJ and BJ, YJ and QJ. Meanwhile, the differential metabolites composition was distinct among various varieties of Z. bungeanum and dominant by phenolic compounds flavonoid and phenolic acids, especially highest in varieties July Zanthoxylum bunganum Maxim. Highlight A comparative metabolomics analyzed in four varieties of Zanthoxylum bungeanum pericarp.Total 1429 metabolites were identified and mainly in flavonoid and phenolic acid.July and August Zanthoxylum bunganum Maxim has highest antioxidant capacity.The rootstock July Zanthoxylum bunganum Maxim was recommended in Loess Plateau.

Regulation mechanisms of flavonoids biosynthesis of Hancheng Dahongpao peels (Zanthoxylum bungeanum Maxim) at different development stages by integrated metabolomics and transcriptomics analysis

BACKGROUND

Flavonoids have strong free radical scavenging and antioxidant capacity. The high abundance of flavonoids in Chinese prickly ash peels have many benefits to human health. In this study, 'Hancheng Dahongpao', a main cultivar, was taken as materials to investigate the flavonoids biosynthesis mechanism of Zanthoxylum bungeanum Maxim at three key development stages by integration of metabolomics and transcriptomics analysis.

RESULTS

A total of 19 differentially accumulated metabolites were identified, the key flavonoids compounds were kaempferol, quercetin and their glycoside derivatives, and two major anthocyanins (peonidin O-hexoside and peonidin 3-O-glucoside). 5 gene networks/modules including 15 important candidate genes were identified, which was highly correlated with flavonoids. Among these genes, ZM-163828 and ZM-184209 were strongly correlated with kaempferol and quercetin, and ZM-125833 and ZM-97481 were controlled the anthocyanins biosynthesis. Moreover, it was shown that MYB-ZM1, MYB-ZM3, MYB-ZM5, MYB-ZM6 and MYB-ZM7 coordinately controlled flavonoids accumulation through regulating the structural genes.

CONCLUSIONS

Generally, this study systematically revealed the flavonoids metabolic pathways and candidate genes involved in flavonoids biosynthesis and laid a foundation for the potential targets for the breeding of new valuable Chinese prickly ash cultivars.

Transcriptome and Metabolome Dynamics Explain Aroma Differences between Green and Red Prickly Ash Fruit

Green prickly ash (Zanthoxylum armatum) and red prickly ash (Zanthoxylum bungeanum) fruit have unique flavor and aroma characteristics that affect consumers' purchasing preferences. However, differences in aroma components and relevant biosynthesis genes have not been systematically investigated in green and red prickly ash. Here, through the analysis of differentially expressed genes (DEGs), differentially abundant metabolites, and terpenoid biosynthetic pathways, we characterize the different aroma components of green and red prickly ash fruits and identify key genes in the terpenoid biosynthetic pathway. Gas chromatography-mass spectrometry (GC-MS) was used to identify 41 terpenoids from green prickly ash and 61 terpenoids from red prickly ash. Piperitone was the most abundant terpenoid in green prickly ash fruit, whereas limonene was most abundant in red prickly ash. Intergroup correlation analysis and redundancy analysis showed that HDS2, MVK2, and MVD are key genes for terpenoid synthesis in green prickly ash, whereas FDPS2 and FDPS3 play an important role in the terpenoid synthesis of red prickly ash. In summary, differences in the composition and content of terpenoids are the main factors that cause differences in the aromas of green and red prickly ash, and these differences reflect contrasting expression patterns of terpenoid synthesis genes.