蒙古黄芪响应反复干旱胁迫的代谢机制

Metabolic mechanism of Astragalus membranaceus(Fisch.)Bge.var.mongholicus(Bge.)Hsiao in response to repeated drought stress

[目的]蒙古黄芪是黄芪药材的重要基原植物,其主要种植地内蒙古、山西、甘肃等地均属于干旱、半干旱地区,不定期间歇式降雨造成了植物干旱复水循环。研究蒙古黄芪在干旱及复水过程中代谢产物的变化特征对于了解其响应自然间歇降雨的干旱胁迫机制非常关键。[方法]试验以1年生蒙古黄芪种苗为材料,进行反复干旱胁迫及复水处理后,测定盆栽土壤养分及其根长、根粗,用基于NMR的代谢组学技术分析蒙古黄芪的初生差异代谢物,并进行差异代谢物筛选及代谢通路分析;用亚硝酸钠-硝酸铝-氢氧化钠法、香草醛-冰醋酸比色法和苯酚-硫酸比色法测定反复干旱胁迫处理下蒙古黄芪根中总黄酮、总皂苷及多糖物质含量。[结果](1)蒙古黄芪在干旱胁迫时会呈现根粗减小,根长和须根密度增加的趋势。(2)干旱及复水处理下,代谢组共检测到42种代谢产物,主要是氨基酸及其衍生物、有机酸、胺类及氨类化合物和糖类等;代谢通路分析表明,植株在反复干旱胁迫过程中主要影响体内的氨基酸代谢途径,通过增加天冬氨酸、丙氨酸、谷氨酸、脯氨酸及精氨酸的含量,降低天冬酰胺、色氨酸和4-氨基丁酸的含量来增强自身抗旱性,具体表现为丙氨酸、谷氨酸、脯氨酸等代谢物增加1~3倍,色氨酸和4-氨基丁酸等代谢物下降1~2倍。(3)在第1轮干旱胁迫下蒙古黄芪总皂苷积累,而第2轮干旱胁迫后黄芪皂苷、总黄酮类、多糖3种活性物质的生成量减少,均呈下降趋势。[结论]氨基酸及其衍生物类与蒙古黄芪响应水分胁迫的机制密切相关,同时植株也会调节自身的次生代谢产物以响应环境变化。

[Objective]Astragalus membranaceus(Fisch.)Bge.var.mongholicus(Bge.)Hsiao is an important primitive plant of astragali radix,and its main planting areas are arid and semi-arid areas in Inner Mongolia,Shanxi,Gansu,and other places.Irregular intermittent rainfalls cause drought and rehydration cycle in plants.Studying the characteristics of metabolites in A.membranaceus var.mongholicus during drought and rehydration is crucial to understand the drought tolerance mechanism in response to natural intermittent rainfalls.[Methods]The seedlings of annual A.membranaceus var.mongholicus were used as materials.After repeated drought and rehydration treatment,soil nutrients and root growth in potted plants were measured.The primary metabolites of A.membranaceus var.mongholicus were analyzed using NMR based technology.Differential metabolite screening and metabolic pathway were analyzed.Total flavonoids,total saponins,and polysaccharides in the roots of A.membranaceus var.mongholicus were determined.[Results](1)A.membranaceus var.mongholicus showed a trend of decreasing in root diameter and increasing in root length and fibrous root density under drought stress.(2)Under drought and rehydration treatment,a total of 42 metabolites were detected,containing mainly amino acids and their derivatives,organic acids,amines,ammonia compounds,and sugars.Metabolic pathway analysis showed that amino acid metabolism pathways were mainly affected during repeated drought stress.Plant drought resistance was enhanced by increasing the content of aspartate,alanine,glutamate,proline,and arginine,as well as reducing the content of asparagine,tryptophan,and 4-aminobutyrate.Specifically,the increase in metabolites such as alanine,glutamate,and proline was 1-3 times,while metabolites such as tryptophan and 4-aminobutyric acid were decreased by 1-2 times.(3)Under the first round of drought stress,the accumulation of astragaloside was decreased;after the second round of drought stress,the production of three active substances,namely astragaloside,total flavonoids,and polysaccharides,showed a downward trend.[Conclusion]Amino acids and their derivatives are closely related in response to drought stress in A.membranaceus var.mongholicus.Plant regulates its secondary metabolites in response to environmental changes.