Accumulation and biosynthesis of hydroxyl-α-sanshool in varieties of Zanthoxylum bungeanum Maxim. by HPLC-fingerprint and transcriptome analyses

Zanthoxylum bungeanum Maxim. (Z. bungeanum) is well known for its pharmaceutical properties and pungent taste due to its alkylamide compounds, among which hydroxyl-alpha-sanshool has the highest content. The differences in the hydroxyl-alpha-sanshool profiles among 12 varieties of Z. bungeanum collected from a common garden were evaluated by RP-HPLC (reversed-phase high-performance liquid chromatography), HPLC fingerprint and chemometric analyses. The results showed that the peel of You Huajiao (S12) exhibited the highest content (46.936 +/- 0.122 mg/g) and Fugu Huajiao (S2) exhibited the lowest content (2.235 +/- 0.077 mg/g). The twelve varieties were divided into four groups, and their scores of similarity were between 0.424 and 1. Moreover, hydroxyl-alpha-sanshool was further proven to be the key compound in Z. bungeanum. To explore the molecular mechanisms of hydroxyl-alpha-sanshool causing these differences, 6656 differentially expressed genes (DEGs) were identified from three varieties(S2, S3 Fengxian Dahongpao and S12)and showed a significant difference in hydroxyl-alpha-sanshool expression, as determined by transcriptome analysis, including 10 DEGs related to the biosynthesis of unsaturated fatty acids and 9 DEGs related to valine biosynthesis, which were probably involved in hydroxyl-alpha-sanshool biosynthesis. The results of qRT-PCR (quantitative real-time-polymerase chain reaction) analysis for 6 DEGs selected after functional annotation were equivalent to those detected by transcriptome sequencing, implying that these DEGs may be the key genes involved in hydroxyl-alpha-sanshool biosynthesis. The present comprehensive analysis provides, for the first time, insight into the directional biosynthesis of alkylamide compounds, the selection of key functional genes and quality breeding in Z. bungeanum for further study.