Arabidopsis cationic amino acid transporter (CAT) is a high affinity transporter for a systemic herbicide L-Phosphinothricin

L-phosphinothricin (PPT) is a broad-spectrum herbicide, however its transportation mechanisms remain unidentified. Here we present cationic amino acid transporters (CAT) as the high affinity transporter of PPT, explaining the different sensitivities of flowering and non-flowering plants. Comparative analysis between Arabidopsis thaliana and Marchantia polymorpha revealed non-target site mechanisms for PPT resistance in the latter. LC-MS analysis showed minimal PPT uptake by M. polymorpha, while transcriptomic analysis identified four candidate transporters for PPT uptake. Overexpression of AtCAT1 and AtCAT5 in M. polymorpha increased PPT susceptibility and uptake. Protein molecular dynamics simulation revealed the modes of PPT transportation, allowing for mutagenesis strategies to reduce PPT susceptibility. This study reports the first high affinity PPT transporter, AtCAT, and highlights the natural diversity of PPT susceptibility due to transportation. Overall design: To identify transcriptional response to GS-inhibiting herbicides, RNAseq analysis was perform on Arabidopsis seedlings and Marchantia gemmalings treated with glutamine, phosphinothricin, or methionine sulfoxime for 48h. Untreated plants were used as controls. n=3

L-草铵膦（L-phosphinothricin, PPT）是一种广谱除草剂，但其转运机制至今尚未明确。本研究鉴定出阳离子氨基酸转运蛋白（cationic amino acid transporters, CAT）为PPT的高亲和力转运蛋白，由此解释了显花植物与非显花植物对PPT敏感性的差异。通过对拟南芥（Arabidopsis thaliana）和地钱（Marchantia polymorpha）的比较分析，我们在地钱中发现了介导PPT抗性的非靶标位点机制。液相色谱-质谱联用（LC-MS）分析显示，地钱对PPT的摄取量极低；而转录组分析筛选出4个参与PPT摄取的候选转运蛋白。将AtCAT1和AtCAT5在地钱中过表达后，植株对PPT的敏感性及PPT摄取量均显著提升。蛋白质分子动力学模拟揭示了PPT的转运模式，为开发降低PPT敏感性的诱变策略提供了理论支撑。本研究首次报道了首个高亲和力PPT转运蛋白AtCAT，并阐明了由转运机制差异导致的PPT敏感性自然多样性。总体实验设计：为解析植物对谷氨酰胺合成酶抑制类除草剂的转录响应，我们对经谷氨酰胺、草铵膦或甲硫氨酸磺肟（methionine sulfoxime）处理48小时的拟南芥幼苗及地钱芽孢幼苗进行了转录组测序（RNA-seq）分析，以未处理植株作为对照，每组设置3个生物学重复（n=3）。