• Root parasitic plants such as Striga, Orobanche, and Phelipanche spp. cause serious damage to crop production world-wide. Deletion of the Low Germination Stimulant 1 (LGS1) gene gives a Striga-resistance trait in sorghum (Sorghum bicolor). The LGS1 gene encodes a sulfotransferase-like protein, but its function has not been elucidated.
• Since the profile of strigolactones (SLs) that induce seed germination in root parasitic plants is altered in the lgs1 mutant, LGS1 is thought to be an SL biosynthetic enzyme. In order to clarify the enzymatic function of LGS1, we looked for candidate SL substrates that accumulate in the lgs1 mutants and performed in vivo and in vitro metabolism experiments.
• We found the SL precursor 18-hydroxycarlactonoic acid (18-OH-CLA) is a substrate for LGS1. CYP711A cytochrome P450 enzymes (SbMAX1 proteins) in sorghum produce 18-OH-CLA. When LGS1 and SbMAX1 coding sequences were co-expressed in Nicotiana benthamiana with the upstream SL biosynthesis genes from sorghum, the canonical SLs 5-deoxystrigol and 4-deoxyorobanchol were produced.
• This finding showed that LGS1 in sorghum uses a sulfo group to catalyze leaving of a hydroxyl group and cyclization of 18-OH-CLA. A similar SL biosynthetic pathway has not been found in other plant species.

中文翻译：

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细胞色素P450和磺基转移酶催化高粱中独脚金内酯的生物合成

• 根寄生植物，例如独脚金、Orobanche和Phelipanche spp。对世界范围内的作物生产造成严重破坏。低发芽刺激素 1 ( LGS1 ) 基因的缺失使高粱 (Sorghum bicolor) 具有独脚金抗性性状。LGS1基因编码一种磺基转移酶样蛋白，但其功能尚未阐明。
• 由于在根寄生植物中诱导种子萌发的独脚金内酯 (SLs) 的分布在lgs1突变体中发生了改变，因此认为 LGS1 是一种 SL 生物合成酶。为了阐明 LGS1 的酶促功能，我们寻找在lgs1突变体中积累的候选 SL 底物，并进行了体内和体外代谢实验。
• 我们发现 SL 前体 18-羟基碳酸内酯 (18-OH-CLA) 是 LGS1 的底物。高粱中的 CYP711A 细胞色素 P450 酶（SbMAX1 蛋白）产生 18-OH-CLA。当LGS1和SbMAX1编码序列在本氏烟草中与来自高粱的上游 SL 生物合成基因共表达时，产生了典型的 SLs 5-deoxystrigol 和 4-deoxyorobanchol。
• 这一发现表明，高粱中的 LGS1 使用磺基催化羟基的离去和 18-OH-CLA 的环化。在其他植物物种中尚未发现类似的 SL 生物合成途径。