拟南芥PMSR2对脂肪族芥子油苷侧链的修饰作用

芥子油苷是一类由氨基酸合成的次生代谢产物,脂肪族芥子油苷主要来源于甲硫氨酸,因侧链长度和结构的不同而拥有多样化的生物活性。根据拟南芥不同组织中芥子油苷组分和含量的特点及生物信息学分析,我们推断脂肪族芥子油苷的侧链修饰反应中可能存在由甲基亚磺酰基芥子油苷向甲硫基芥子油苷转化的还原反应,候选基因为甲硫氨酸硫还原酶2(Peptide Methionine Sulfoxide Reductase 2,PMSR2)。为了验证这一假设,我们构建了过量表达PMSR2基因的转基因拟南芥,对其芥子油苷组分及含量进行了测定,并与野生型和PMSR2基因缺失的突变体进行了对比分析,结果表明,PMSR2基因的过量表达并未使芥子油苷含量与组分发生明显变化,但PMSR2基因缺失的突变体与野生型相比,MS GSL/MT GSL的值显著提高,证明PMSR2参与了脂肪族芥子油苷侧链的修饰反应,可以将MS GSL中的硫还原生成MT GSL。该酶的鉴定进一步完善了对芥子油苷合成途径及其侧链修饰的认识,为深入研究脂肪族芥子油苷的生理功能奠定了理论基础。

Side-hain Modification of Aliphatic Glucosenolates by Peptide Methionin S Reductase PMSR2 in Arabidopsis

Glucosinolates are amino acid-erived secondary metabolites. Aliphatic glucosinolates are derived from methionine and have diverse biological activity dependent on chemical modification of the side chain. According to the glucosinolates profile in different tissues of Arabidopsis (Arabidopsis thaliana) combined with bioinformatics analysis, we predicted that there is possible reduction reaction from methylsulfinylalkyl glucosinolates to methythioalkyl glucosinolates in aliphatic glucosinolates side chain modification and peptide methionine sulfoxide reductase 2(PMSR2) might be the candidate gene. To verify this assumption, transgenic plants overexpressing PMSR2 were established. Glucosinolates profile was determined and compared in PMSR2 overexpression line, wild type and pmsr2 mutant. Overexpression of PMSR2 did not alter glucosinolates profile but pmsr2 mutant showed higher MS GSL/MT GSL. The results indicated that PMSR2 is involved in side-hain modification of aliphatic glucosinolates and catalyze the conversion from methylsulfinylalkyl to methythioalkyl glucosinolates by S-educing. The identification of PMSR2 as a reductase in glucosinolates side-hain modification is helpful to better understand the biosynthesis and function of aliphatic glucosinolates.