大白菜和结球甘蓝硫苷及MAM基因表达分析

The Correlation Analysis of Glucosinolates Content and the MAM Gene Expression in Brassica rapa ssp.pekinensis and B.oleracea var.capitata

硫苷及其降解产物是十字花科蔬菜重要的次生代谢产物,具有防癌抗癌作用。硫苷合成基因(MAMs,methylthioalkylmalate synthases)负责硫苷侧链的延伸,MAM1催化生成短链脂肪族硫苷而MAM3催化生成长链脂肪族硫苷,因此MAM基因影响了硫苷成分的多样性。本研究利用大白菜和结球甘蓝自交系,从苗期到莲座期取样测定硫苷含量及MAM的相对表达量,分析有益硫苷在两者之间的积累差异以及MAM基因的表达调控作用。结果显示,从苗期到莲座期结球甘蓝的硫苷含量平均值均高于大白菜,大白菜中侧链长度为5C和4C脂肪族硫苷:4-戊烯基硫苷(GBN,glucobrassicanapin)和3-丁烯基硫苷(NAP,gluconapin)含量较高,而结球甘蓝中3C和4C脂肪族硫苷:3-甲基硫氧丙基硫苷(IBE,glucoiberin)、2-丙烯基硫苷(SIN,sinigrin)和4-甲磺酰基丁基硫苷(GRA,glucoraphanin)含量较高,有益硫苷SIN和GRA在结球甘蓝中的含量显著高于大白菜。在大白菜和结球甘蓝中分别发现7个MAM拷贝基因,同源基因比较发现MAM1和MAM3的相对表达量在两者之间存在显著差异。大白菜中BraMAM1.1和BraMAM1.2的表达量显著低于结球甘蓝同源基因BoMAM1.1和BoMAM1.2的表达量,而BraMAM3.2和BraMAM3.3的表达量显著高于结球甘蓝同源基因BoMAM3.1的表达量;并且结球甘蓝中3C脂肪族硫苷含量与BoMAM1.1的表达量呈显著正相关,大白菜中5C脂肪族硫苷含量与BraMAM3.2的表达量呈显著正相关。由此推测可能是BraMAM1.1的低表达而BraMAM3.2的高表达,导致了大白菜中3C脂肪族硫苷SIN积累极少而5C脂肪族硫苷GBN积累较多。

Glucosinolates and their degradation products are important secondary metabolite of cruciferous vegetables with the anti-cancer function.The Methylthioalkylmalate synthases encoded by various MAM genes are involved in glucosinolate side-chain elongation.MAM1 catalyzes the aliphatic glucosinolate synthesis with short-chain,while MAM3 catalyzes that with long-chain.In this study,the glucosinolate content and the expression of MAM genes were analyzed in Chinese cabbage and cabbage inbred lines during seedling and rosette stages,in order to associate MAM gene expression with the accumulation of beneficial glucosinolates.The results showed that the average glucosinolate content in cabbage was higher than that of Chinese cabbage from seedling to rosette stage.The content of 5C and 4C aliphatic glucosinolates(GBN and NAP)were predominant in Chinese cabbage,whereas the main glucosinolates in cabbage were 3C and 4C aliphatic glucosinolates(IBE,SIN and GRA).The anti-cancer components SIN and GRA were significantly higher in cabbage than those of Chinese cabbage.The genome annotations of Chinese cabbage and cabbage revealed seven MAM paralogous genes respectively.By analyzing the expression levels of MAMs,a significant difference in the relative expression level of MAM1 and MAM3 between Chinese cabbage and cabbage was detected.The expression level of BraMAM1.1 and BraMAM1.2 in Chinese cabbage was significantly lower than that of BoMAM1.1 and BoMAM1.2 in cabbage,while the expression level of BraMAM3.2 and BraMAM3.3 was significantly higher than that of BoMAM3.1.Moreover,the content of 3C aliphatic glucosinolates in cabbage was positively correlated with the expression of BoMAM1.1,and the content of 5C aliphatic glucosinolates in Chinese cabbage was positively correlated with the expression of BraMAM3.2.Collectively we speculated that the low expression of BraMAM1.1 and the high expression of BraMAM3.2 may respond to the low accumulation of 3C aliphatic glucosinolates(SIN)and the high accumulation of 5C aliphatic glucosinolates(GBN)in Chinese cabbage.