Meyer Lasse, Crocoll Christoph, Halkier Barbara Ann, Mirza Osman Asghar, Xu Deyang
Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Frederiksberg, Denmark.
Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
Front Plant Sci. 2023 Jul 17;14:1219783. doi: 10.3389/fpls.2023.1219783. eCollection 2023.
Glucosinolates are key defense compounds of plants in Brassicales order, and their accumulation in seeds is essential for the protection of the next generation. Recently, members of the Usually Multiple Amino acids Move In and Out Transporter (UMAMIT) family were shown to be essential for facilitating transport of seed-bound glucosinolates from site of synthesis within the reproductive organ to seeds. Here, we set out to identify amino acid residues responsible for glucosinolate transport activity of the main seed glucosinolate exporter UMAMIT29 in . Based on a predicted model of UMAMIT29, we propose that the substrate transporting cavity consists of 51 residues, of which four are highly conserved residues across all the analyzed homologs of UMAMIT29. A comparison of the putative substrate binding site of homologs within the brassicaceous-specific, glucosinolate-transporting clade with the non-brassicaceous-specific, non-glucosinolate-transporting UMAMIT32 clade identified 11 differentially conserved sites. When each of the 11 residues of UMAMIT29 was individually mutated into the corresponding residue in UMAMIT32, five mutant variants (UMAMIT29#V27F, UMAMIT29#M86V, UMAMIT29#L109V, UMAMIT29#Q263S, and UMAMIT29#T267Y) reduced glucosinolate transport activity over 75% compared to wild-type UMAMIT29. This suggests that these residues are key for UMAMIT29-mediated glucosinolate transport activity and thus potential targets for blocking the transport of glucosinolates to the seeds.
硫代葡萄糖苷是十字花目植物的关键防御化合物，它们在种子中的积累对于保护下一代至关重要。最近，通常多个氨基酸进出转运体（UMAMIT）家族的成员被证明对于促进种子结合的硫代葡萄糖苷从生殖器官内的合成部位运输到种子至关重要。在这里，我们着手鉴定负责主要种子硫代葡萄糖苷输出蛋白UMAMIT29在[此处原文缺失相关信息]中硫代葡萄糖苷运输活性的氨基酸残基。基于UMAMIT29的预测模型，我们提出底物运输腔由51个残基组成，其中四个是UMAMIT29所有分析同源物中高度保守的残基。将十字花科特异性、硫代葡萄糖苷运输分支内的同源物假定底物结合位点与非十字花科特异性、非硫代葡萄糖苷运输的UMAMIT32分支进行比较，确定了11个差异保守位点。当UMAMIT29的11个残基中的每一个分别突变为UMAMIT32中的相应残基时，与野生型UMAMIT29相比，五个突变变体（UMAMIT29#V27F、UMAMIT29#M86V、UMAMIT29#L109V、UMAMIT29#Q263S和UMAMIT29#T267Y）使硫代葡萄糖苷运输活性降低了75%以上。这表明这些残基是UMAMIT29介导的硫代葡萄糖苷运输活性的关键，因此是阻断硫代葡萄糖苷向种子运输的潜在靶点。
