硫苷介导的白菜抵御甜菜夜蛾幼虫取食胁迫的分子机制

Molecular mechanism of glucosinolate-mediated Brassica campestris ssp.chinensis against feeding stress of Spodoptera exigua larvae

【目的】探究甜菜夜蛾Spodoptera exigua幼虫取食对白菜Brassica campestris ssp.chinensis硫代葡萄糖苷质量摩尔浓度及组分的影响,初步明确硫苷介导的白菜抵御甜菜夜蛾幼虫取食胁迫的分子机制。【方法】使用高效液相色谱法检测甜菜夜蛾幼虫取食对白菜硫苷质量摩尔浓度和组分的影响,实时荧光定量聚合酶链式反应(RT-qPCR)分析硫苷代谢关键基因表达模式的变化,谷胱甘肽硫转移酶试剂盒检测取食白菜后甜菜夜蛾幼虫体内谷胱甘肽硫转移酶活性的变化。【结果】白菜中8种硫苷组分在甜菜夜蛾幼虫取食后显著增加(P<0.05),其中吲哚族的4-羟基吲哚-3-甲基硫苷(4OH)、1-甲氧基-3-吲哚基甲基硫苷(NEO)、3-吲哚基甲基(GBC)和脂肪族的4-戊烯基硫苷(GBN)对甜菜夜蛾幼虫取食反应最为强烈;RT-qPCR结果显示:甜菜夜蛾幼虫取食后,白菜脂肪族硫苷合成相关基因BcBCAT4、BcMAM1的显著上调可能与脂肪族硫苷的增加有关(P<0.05),而BcSOT16的上调与4OH、NEO、GBC呈正相关;取食后,甜菜夜蛾幼虫体内谷胱甘肽硫转移酶活性显著增强(P<0.05),并呈现与总硫苷和吲哚族硫苷质量摩尔浓度变化规律的一致性。【结论】甜菜夜蛾幼虫的取食能诱导白菜硫苷的合成,而硫苷质量摩尔浓度的升高会诱导幼虫体内谷胱甘肽硫转移酶活性的增强。甜菜夜蛾幼虫取食胁迫下,白菜BcSOT16、BcBCAT4、BcMAM1等硫苷合成关键基因被激活,4OH、NEO、GBC和GBN显著增加,从而更好地抵御甜菜夜蛾幼虫取食胁迫。

[Objective]With an investigation of the effects of Spodoptera exigua larvae feeding on the content and components of glucosinolates(GSLs)in Brassica campestris ssp.chinensis,this study is aimed to figure out the initial molecular mechanism of GSL-mediated resistance to the feeding stress of S.exigua larvae in B.campestris ssp.chinensis.[Method]The effect of larvae feeding on the content and components of GSLs in B.campestris ssp.chinensis‘Meiduheiyoutong’was determined with the application of high performance liquid chromatography before an analysis was conducted of the expression patterns of key genes related to GSLs metabolism using real-time fluorescence quantitative polymerase chain reaction(RT-qPCR),after which the activity of glutathione S-transferase(GSTs)in larvae after eating B.campestris ssp.chinensis was detected by GSTs kit.[Result](1)Of the eight GSLs that enjoyed a significant increase in B.campestris ssp.chinensis after S.exigua larvae’s feeding,4-hydroxy-glucobrassicin(4OH),1-methoxy-glucobrassici(NEO),glucobrassicin(GBC)and glucobrassicanapin(GBN)were the four important GSLs responsive to the feeding;(2)The significant up-regulation of aliphatic GSL synthesis-related genes BcBCAT4 and BcMAM1 in B.campestris ssp.chinensis might be related to the increase of aliphatic GSLs,and the up-regulation of BcSOT16 was positively correlated with 4OH,NEO and GBC after feeding by S.exigua larvae;(3)After feeding,the activity of GSTs in the larvae of S.exigua was significantly enhanced(P<0.05),and showed a consistency with the changes of the total GSLs and indole GSLs.[Conclusion]Feeding by S.exigua larvae can induce the synthesis of GSLs in B.campestris ssp.chinensis,and the increase of GSLs can induce the enhancement of GSTs activity in larvae.Under the feeding stress of S.exigua larvae,the activation of key GSLs synthesis genes such as BcSOT16,BcBCAT4 and BcMAM1in B.campestris ssp.chinensis may promote the increase of 4OH,NEO,GBC and GBN which will help better resist S.exigua larvae feeding stress.