Physiological responses of Sedum alfredii Hance to low temperature stress and analysis of transcriptome and metabolome

【Objective】 To analyze the impact of low temperature stress on the physiological mechanisms,transcription and metabolic regulatory network of Sedum alfredii Hance,which could provide scientific reference for subsequent research on its cold resistance mechanisms and engineering applications in cadmium-contaminated farmland remediation.【Method】Standard seedlings of S.alfredii were used as experimental materials by employing the potted method.These seedlings were then subjected to low temperature treatments（10 and-2℃）for 6 h,control（22℃）was also set,after which physiological indicators,including the contents of malondialdehyde,soluble sugar and soluble protein,the relative electrical conductivity and antioxidant enzyme activity in the leaves,were measured.Then,the transcriptome and metabolome sequencing analysis were performed. 【Result】 Low temperature stress led to extremely significant increase in the contents of malondialdehyde,soluble sugar and soluble protein,as well as relative conductivity（P＜0.01,the same below）,and significantly（P＜0.05） or extremely significantly increased antioxidant enzyme activity in S.alfredii.Compared with the control,7152 differentially expressed genes（DEGs） were obtained by transcriptome sequencing under 10℃low temperature treatment,and 12972 DEGs were obtained under-2℃low temperature treatment.Metabolome sequencing obtained 226 and 228 differential accumulated metabolites（DAMs） respectively.Under low temperature stress,transcriptome sequencing analysis results showed that the pathway of flavonoid biosynthesis,MAPK signaling,phenylpropanoid biosynthesis,as well as starch and sucrose metabolism in S.alfredii were obviously impacted.Metabolomics analysis showed that the biosynthesis of flavonoids and flavonols,metabolism of glycerophospholipids,interconversion of pentose and glucuronic acid,and monoterpene biosynthesis played key regulatory roles under low temperature stress.There was overlap between transcriptome and metabolome enrichment pathways.Correlation analysis showed that the interconversion of pentose and glucuronic acid,biosynthesis of flavonoids,and metabolism of monoterpene synthesis were enhanced.The results of real-time fluorescence quantitative PCR validated the reliability of the transcriptome data,and most DEGs in the pathways of pentose and glucuronide interconversion,flavonoid biosynthesis and monoterpenoid biosynthesis were significantly up-regulated. 【Conclusion】 Under low temperature stress,the physiological indicators of S.alfredii undergo great changes,with multiple transcriptional and metabolic pathways collectively responding to low temperature stress,interconversion of pentose and glucuronic acid,increased biosynthesis of flavonoids,and enhanced monoterpenoid synthesis metabolism.These pathways play crucial regulatory roles in enabling S.alfredii to resist low temperature stress.