Molecular Basis of the Evolution of Methylthioalkylmalate Synthase and the Diversity of Methionine-Derived Glucosinolates
Molecular Basis of the Evolution of Methylthioalkylmalate Synthase and the Diversity of Methionine-Derived Glucosinolates
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DOI：
10.1105/tpc.19.00046
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发表时间：
2019-07-01
期刊：
影响因子：
11.6
通讯作者：
Bisht, Naveen C.
中科院分区：
文献类型：
--
作者：
Kumar, Roshan;Lee, Soon Goo;Bisht, Naveen C.
全球栽培的十字花科植物含有多种脂肪族硫代葡萄糖苷，它们对植物防御和动物营养具有重要意义。蛋氨酸衍生的脂肪族硫代硫代葡萄糖苷侧链延长的关键步骤是由甲硫基烷基苹果酸合成酶催化，该酶可能是从亮氨酸生物合成的异丙基苹果酸合成酶进化而来的。然而，对甘蓝型油菜中甲硫基烷基苹果酸合成酶的进化及其天然产物多样性的产生的分子基础知之甚少。在这里，我们发现甘蓝型油菜基因组编码多种甲硫基烷基苹果酸合成酶，它们在表达谱和2-氧代底物偏好上存在差异，这解释了不同甘蓝型油菜材料中脂肪硫代葡萄糖苷的多样性。通过对芥菜甲基硫代烷基苹果酸合成酶的2.1埃分辨率X射线晶体结构的分析，确定了控制不同2-氧代底物专一性的关键活性部位残基和脂肪硫代葡萄糖苷侧链长度的决定因素。总体而言，这些结果为全球栽培的十字花科植物硫代葡萄糖苷图谱的多样化提供了进化和生化基础，可用于正在进行的育种战略，以操纵有益于动物健康和植物保护的硫代葡萄糖苷化合物。
The globally cultivated Brassica species possess diverse aliphatic glucosinolates, which are important for plant defense and animal nutrition. The committed step in the side chain elongation of methionine-derived aliphatic glucosinolates is catalyzed by methylthioalkylmalate synthase, which likely evolved from the isopropylmalate synthases of leucine biosynthesis. However, the molecular basis for the evolution of methylthioalkylmalate synthase and its generation of natural product diversity in Brassica is poorly understood. Here, we show that Brassica genomes encode multiple methylthioalkylmalate synthases that have differences in expression profiles and 2-oxo substrate preferences, which account for the diversity of aliphatic glucosinolates across Brassica accessions. Analysis of the 2.1 angstrom resolution x-ray crystal structure of Brassica juncea methylthioalkylmalate synthase identified key active site residues responsible for controlling the specificity for different 2-oxo substrates and the determinants of side chain length in aliphatic glucosinolates. Overall, these results provide the evolutionary and biochemical foundation for the diversification of glucosinolate profiles across globally cultivated Brassica species, which could be used with ongoing breeding strategies toward the manipulation of beneficial glucosinolate compounds for animal health and plant protection.