[Objective]Lycium ruthenicum was a shrub with ecological,economic and medicinal values.However,its dense branch-thorns seriously hinder its promotion as an economic forest.The purpose of this study was to explore the mechanism of sucrose promoting occurrence of the thorns in L.ruthenicum,and to provide a basis for cultivating its excellent varieties without thorns.[Method]On the basis of proving the sucrose promoted occurrence of the L.ruthenicum thorns through both energy and signal pathways,RNA-Seq was used to screen and analyze the differentially expressed genes(DEGs)and chloroplast differential genes(cpDEGs)among five samples:terminal buds of thornless shoots(TleCK),terminal buds of thorny shoots(ThoCK),terminal buds of dark-treated thorny shoots(ThoDCK),thornless shoot terminal buds from thorny stems after treatment of reducing endogenous sucrose(TleDPL)and thorny shoot terminal buds from thornless stems after spraying exogenous sucrose(ThoSuc).The expression of nine DEGs was verified by RT-qPCR.[Result]The DEG number of five compared groups(ThoCK vs.TleCK,ThoCK vs.TleDPL,ThoDCK vs.TleDPL,TleCK vs.ThoSuc and TleDPL vs.ThoSuc)were 5281,4363,3125,5226 and 3278,respectively.The DEGs of the five groups were all significantly enriched in nine GO terms and four KEGG pathways(flavonoid biosynthesis,diterpenoid biosynthesis,phenylpropanoid biosynthesis,and stilbenoid,diarylheptanoid and gingerol biosynthesis).The Venn diagram showed that there were 196 common DEGs shared by the five groups,of which 33 were predicted as transcription factor genes,and most of the transcription factor genes were predicted to be NAC and WRKY families.Three common DEGs of the five groups were annotated to the plant hormone signal transduction KEGG pathway and involved in the signal transduction of auxin,jasmonic acid and salicylic acid,respectively.Two common DEGs of the three key groups(ThoCK vs.TleCK,ThoCK vs.TleDPL and TleCK vs.ThoSuc)were predicted as TCP transcription factor genes,and the three group all had cpDEGs annotated to the photosynthesis KEGG pathway.The reliability of the RNA-Seq results was verified by the RT-qPCR of the nine DEGs.[Conclusion]The sucrose may promote the occurrence of branch-thorns by affecting the signal transduction of auxin,jasmonic acid and salicylic acid.The occurrence of branch-thorns may also be related to flavonoid accumulation and lignin reduction.Furthermore,increasing exogenous and reducing endogenous sucrose did not affect the occurrence of branch-thorns by simply reversing the expression of cpDEGs.The common DEGs annotated to the WRKY,TCP and NAC transcription factor families may be the key genes regulating the occurrence of branch-thorns.A mechanistic model of sucrose affecting branch-thorns occurrence in L.ruthenicum was established in this study.
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