PDF(Pubmed)
Abstract：
Monoterpenoid indole alkaloid (MIA) biosynthesis in Catharanthus roseus is a paragon of the spatiotemporal complexity achievable by plant specialized metabolism. Spanning a range of tissues, four cell types, and five cellular organelles, MIA metabolism is intricately regulated and organized. This high degree of metabolic differentiation requires inter-cellular and organellar transport, which remains understudied. Here, we have characterized a vacuolar importer of secologanin belonging to the multidrug and toxic compound extrusion (MATE) family, named CrMATE1. Phylogenetic analyses of MATEs suggested a role in alkaloid transport for CrMATE1, and in planta silencing in two varieties of C. roseus resulted in a shift in the secoiridoid and MIA profiles. Subcellular localization of CrMATE1 confirmed tonoplast localization. Biochemical characterization was conducted using the Xenopus laevis oocyte expression system to determine substrate range, directionality, and rate. We can confirm that CrMATE1 is a vacuolar importer of secologanin, translocating 1 mM of substrate within 25 min. The transporter displayed strict directionality and specificity for secologanin and did not accept other secoiridoid substrates. The unique substrate-specific activity of CrMATE1 showcases the utility of transporters as gatekeepers of pathway flux, mediating the balance between a defense arsenal and cellular homeostasis.
摘要：
长春花中的单萜吲哚生物碱（MIA）生物合成是植物专门代谢可实现的时空复杂性的典范。跨越一系列的组织，四种细胞类型，和五个细胞器，MIA代谢是复杂调节和组织的。这种高度的代谢分化需要细胞间和细胞器间的运输，仍未得到充分研究。这里,我们已经表征了属于多药物和有毒化合物挤出（MATE）家族的液泡导入体，命名为CrMATE1。MATEs的系统发育分析表明，CrMATE1在生物碱运输中起作用，并且在两个变种的C.roseus的植物沉默中，导致了secoippoid和MIA谱的变化。CrMATE1的亚细胞定位证实了液泡膜定位。生化鉴定是使用非洲爪狼卵母细胞表达系统进行的，以确定底物范围，方向性,和率。我们可以确认CrMATE1是一种空泡导入蛋白，在25分钟内转运1mM的底物。该转运蛋白对secologanin显示出严格的方向性和特异性，并且不接受其他secoippoidoid底物。CrMATE1独特的底物特异性活性展示了转运蛋白作为途径通量的守门人的效用，调节防御武器库和细胞稳态之间的平衡。
