联合代谢组学和转录组学分析澳洲坚果幼苗对酸胁迫的响应机制OA

[Objective]The paper aimed to explore the molecular mechanism of Macadamia integrifolia seedlings in response to acid stress,screen differentially accumulated metabolites(DAMs)and differentially expressed genes(DEGs)related to the flavonoid biosynthesis path-way,and provide theoretical basis for the breeding of acid-tolerant varieties.[Method]Using the seedling of M.integrifolia variety H2 as the research material,three acid stress treatments(pH 3,pH 4,pH 5)were set up under hydroponic conditions,with pH 6 serving as the control(CK).After 150 days of treatment,physiological and biochemical indicators of the seedling roots and leaves were measured,and extensive targeted metabolomics analysis and transcriptome sequencing were conducted on the roots.[Result]Compared with the pH 6 group(con-trol),acid stress increased the activities of CAT,APX and the contents of MDA,Pro and SS in leaves of M.integrifolia seedlings,and showed an overall upward trend with the aggravation of acid stress.However,acid stress reduced the activities of CAT,POD,APX and the contents of MDA and Pro in roots,and showed a decreasing trend with the aggravation of acid stress.There was extremely significant difference between pH 3 group and pH 6 group(P＜0.01,the same as below).Ultra performance liquid chromatography tandem mass spectrometry(UPLC-MS/MS)analysis showed that the number of DAMs in the three comparison groups of pH 3 vs pH 6,pH 4 vs pH 6,and pH 5 vs pH 6 was 890,238 and 259,respectively.In both pH 4 vs pH 6 and pH 5 vs pH 6 comparison groups,the number of up-regulated DAMs was higher than that of down-regulated ones,whereas in pH 3 vs pH 6 comparison group,the number of down-regulated DAMs was much higher than that of up-regulated ones.The enrichment analysis of KEGG pathway showed that DAMs in the comparison groups of pH 3 vs pH 6 and pH 5 vs pH 6 were significantly enriched in flavonoid biosynthesis pathway(P＜0.05).Transcriptome analysis showed that there were 60 529,19057 and 17 593 DEGs in the comparison groups of pH 3 vs pH 6,pH 4 vs pH 6 and pH 5 vs pH 6,respectively,involving plant hormone sig-nal transduction,flavonoid biosynthesis,flavonoid and flavonol biosynthesis.Through the combined analysis of transcriptomics and metabo-nomics,15 kinds of DAMs and 23 DEGs were screened.The flavanone 3-hydroxylase(F3H)related gene Cluster-143294.1 and flavonol syn-thase(FLS)related gene Cluster-131918.0 were extremely significantly positively correlated with phloretin;chalcone synthase(CHS)relat-ed gene Cluster-129867.0 was extremely significantly positively correlated with dihydromyricetin,indicating that the expression level of these genes was related to the accumulation of metabolites.[Conclusion]After acid stress,the activities of antioxidant enzymes and osmotic adjust-ment substances in leaves of M.integrifolia seedlings increased,but decreased in roots.In the flavonoid biosynthesis pathway,F3H,CHS,FLS and other enzyme related genes were up-regulated after acid stress,and promoted the accumulation of metabolites phloretin,dihydromyricetin and so on,indicating that M.integrifolia can respond to acid stress by regulating gene expression level and regulating metabolite accumulation.