Identification of new binding targets is essential for the development of herbicides and phytotoxin-tolerant crops. Caprylic acid (CAP) is a safe and non-selective bio-herbicide in uncultivated areas. However, the herbicidal action of CAP remains unclear. Herein, metabolomic and proteomic profiling indicated that a serine hydroxymethyl transferase in Conyza canadensis (CcSHMT1) is a promising candidate binding targeted for CAP. The protein abundance and activity of CcSHMT1 were decreased in a time- and dosage-dependent manners after CAP treatment. CAP competes with phenyl-serine at the binding sites, decreasing the enzymatic activity of CcSHMT1. Overexpression of CcSHMT1, AtSHMT1 and OsSHMT1 in Arabidopsis or rice endowed plants with high tolerance to CAP treatment, whereas the knockout of osshmt1 led to death of plants under normal atmospheric conditions. Furthermore, T194A, T194A/ M195V and D209N Osshmt1 mutant plants derived from base editing exhibited tolerance to CAP. CAP bound to CcSHMT1 with high affinity, and Ala191 in the key domains of N-terminus was identified to be critical for the binding site of CAP. Collectively, our findings demonstrate that CcSHMT1 is a binding target for herbicidal activity of CAP. This study marks a key step in the druggability of SHMT inhibitors and represents an attractive target for phytotoxin-tolerant crops.

中文翻译：

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丝氨酸羟甲基转移酶是辛酸的结合靶标：发现除草剂和生产耐辛酸作物的新分子靶标

鉴定新的结合靶点对于开发除草剂和耐植物毒素作物至关重要。辛酸（CAP）是一种在未开垦地区安全且非选择性的生物除草剂。然而，CAP 的除草作用仍不清楚。在此，代谢组学和蛋白质组学分析表明Conyza canadensis中的丝氨酸羟甲基转移酶( Cc SHMT1) 是 CAP 靶向结合的有希望的候选者。CAP处理后， Cc SHMT1的蛋白质丰度和活性以时间和剂量依赖性方式降低。CAP 与苯基丝氨酸竞争结合位点，降低Cc SHMT1的酶活性。在拟南芥或水稻中过度表达CcSHMT1、AtSHMT1和OsSHMT1赋予植物对 CAP 处理的高耐受性，而osshmt1的敲除会导致植物在正常大气条件下死亡。此外，源自碱基编辑的T194A、T194A/M195V和D209N Osshmt1突变植物表现出对CAP的耐受性。CAP 以高亲和力与Cc SHMT1结合，N 端关键结构域的 Ala191 被认为对于 CAP 的结合位点至关重要。总的来说，我们的研究结果表明Cc SHMT1 是 CAP 除草活性的结合靶标。这项研究标志着 SHMT 抑制剂成药性的关键一步，并且代表了耐植物毒素作物的一个有吸引力的目标。