| Toxicodendron vernicifluum(Stokes)F.A.Barkl.(Lacquer tree)is Cenozoic tertiary ancient relic tree species,androgynous or heterologous,has multiple variant types.It has been cultivated in China for more than 2000 years.The raw lacquer produced by sumac is a water spherical emulsion,the main components are urushiol(60%-70%),laccase(<1.0%),lacquer polysaccharide(5%-7%)and moisture(20%-30%).Urushiol,which has the highest proportion of raw paint,has a great influence on the properties of the paint film.At present,the process of urushiol biosynthesis has not been studied in depth.Therefore,exploring the biosynthesis of urushiol at the molecular level has great theoretical value and practical guiding roles.In this study,we first analyzed the differences in the content of urushiol in different tissues of sumac,and then obtained the full-length transcripts of sumac by transcriptome sequencing,and predicted the genes that may be involved in regulating the biosynthesis of urushiol.This study provides molecular biology evidence for the analysis of the biosynthetic pathways of urushiol and the improvement of later varieties of sumac.The main resultss are as follows:(1)Ultra high performance liquid chromatography(UHPLC)was used to determine the content of urushiol,and to explore the differences in the biosynthesis of urushiol between different tissues of the lacquer tree.The study found that the biosynthesis of urushiol mainly occurs in the leaf tissue,the amount of saturated urushiol in the stem is low,and the least in the root,and the accumulation of urushiol per unit mass in the leaf tissue of the lacquer tree is significantly higher than that of the root and stem.(2)Based on technologies of Pac Bio third-generation sequencing and Illumina second-generation sequencing,the lacquer tree transcriptome database was constructed.High-quality sequencing data of 7.37 G,7.7 G and 9.07 G were obtained from lacquer tree root,stem,and leaf,accordingly,and a total of 16816 Universal Gene(Unigene)were obtained by alignment with the reference sequence.Differentially expressed genes(DEGs)analysis showed that there are 5966 genes were differentially expressed between the three tissues and 498 genes were expressed between each tissue.And 14 differentially expressed genes that may be involved in regulating the biosynthesis of urushiol and the biosynthesis of hexadecanoyl-Co A and 5 differentially expressed genes encoding type III polyketide synthase were screened.The statistical results showed that most genes are expressed in the lacquer tree leaves,so the urushiol accumulation is more active in the leaves.(3)In this study,a total of 48 MYB transcription factors of T.vernicifluum were screened by bioinformatics methods,1 R3-MYB,21 R2R3-MYB and 26 R1-MYB.Most of the 48 T.vernicifluum MYB transcription factors were hydrophobic proteins,random coils and alpha helices accounted for a large proportion in the secondary structure.Gene Ontology(GO)annotation showed that those R2R3-MYB proteins could be categorized into 27 function subgroups of three main categories: biological processes,cellular components and molecular function.Phylogenetic analysis showed that 48 MYB transcription factors of T.vernicifluum were divided into 8 distinct groups,and there are 3 MYB proteins may play an important regulatory role in urushiol biosynthesis.(4)Different concentrations of Methyl Jasmonate(Me JA)were used to treat the T.vernicifluum seedlings,UHPLC was used to determine the content of urushiol,and q RT-PCR was used to identify the response of related gene expression to Me JA.The results showed that Me JA can promote the accumulation of urushiol in T.vernicifluum leaves,however,when the concentration of Me JA reached 300 mmol/L,the accumulation of urushiol would be inhibited.In addition,the saturated urushiol biosynthesis has decreased after treated with Me JA in T.vernicifluum leaves,so we speculated that Me JA may inhibit the production of saturated urushiol.There are three genes encoding type III polyketide synthase may play a positive regulatory role in the urushiol metabolism pathway. |
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