盐胁迫下外源2,4-表油菜素内酯对颠茄氮代谢及TAs代谢的影响

Effects of exogenous 2,4-Epibrassinolide on nitrogen metabolism and TAs metabolism of Atropa belladonna L.under NaCl stress

以颠茄(Atropa belladonna L.)幼苗为材料,采用盆栽试验,使用外源2,4-表油菜素内酯(2,4-Epibrassinolide, EBR)处理幼苗,研究在100 mmol L^(-1)NaCl胁迫下不同浓度(0.05、0.1、0.2、0.4mgL^(-1))外源EBR在不同处理时间(5、10、15、20d)内对颠茄氮代谢、次生代谢产物含量以及托品烷类生物碱(tropane alkaloids, TAs)合成途径中前体物质含量、关键酶基因表达量的影响,旨在明确外源EBR调控颠茄耐盐性的生理机制。盐胁迫下颠茄氮代谢受到抑制,而施加外源EBR能够有效增强颠茄的氮代谢能力,硝态氮含量显著升高,铵态氮含量降低,游离氨基酸、可溶性蛋白含量以及氮代谢关键酶活性均有不同程度的上升。盐胁迫不利于生物碱的合成和积累,显著降低了TAs途径中前体物质的合成和关键酶基因的表达。外施0.1 mg L^(-1) EBR能够有效提高鸟氨酸、精氨酸、多胺含量以及腐胺合成关键酶活性,并通过上调TAs途径中关键酶基因TR I、H6H的表达量来提高莨菪碱和东莨菪碱的含量。表明适宜浓度的外源EBR能够有效缓解盐胁迫对颠茄生理代谢的破坏,通过提高氮代谢能力、促进TAs的产生和积累,提高颠茄幼苗的耐盐性。

To explore the physiological mechanism of exogenous 2,4-Epibrassinolide(EBR)regulating NaCl tolerance of A.belladonna,potted A.belladonna seedlings was used as the experimental materials,and exogenous EBR was applied to A.belladonna seedlings with the different concentrations(0.05,0.1,0.2,and 0.4 mg L^(–1))of exogenous EBR and different treatment times(5,10,15,and 20 days)on the nitrogen metabolism,the contents of the secondary metabolites and precursor substances in the synthesis pathway of TAs,and the relative expression levels of key enzyme genes.NaCl stress caused inhibitory effect on nitrogen metabolism in A.belladonna,however the content of nitrate nitrogen increased significantly,the content of ammonium nitrogen decreased,the content of free amino acids,soluble protein,and the activity of key enzymes of nitrogen metabolism increased to some extent under exogenous EBR treatment,which indicating the exogenous EBR could effectively enhance the nitrogen metabolism capacity.NaCl stress was not conducive to the synthesis and accumulation of alkaloids.The synthesis of precursor substances and the relative expression levels of key enzyme genes in TAs pathway significantly were reduced under NaCl stress.The contents of ornithine,arginine,polyamine,and the activities of key enzymes in putrescine synthesis were increased with the exogenous EBR of 0.1 mg L^(–1).Moreover,exogenous EBR could effectively enhance the contents of hyoscyamine and scopolamine by increasing the relative expression levels of key enzyme genes TR I and H6H in TAs pathway.In conclusion,the appropriate concentration of exogenous EBR could effectively relieve the damage of NaCl stress to the physiological metabolism in A.belladonna,and the exogenous EBR could improve NaCl tolerance of belladonna seedlings by increasing nitrogen metabolism and promoting the production and accumulation of TAs.