Auxin controls a myriad of plant developmental processes and plant response to environmental conditions. Precise trafficking of auxin transporters is essential for auxin homeostasis in plants. Here, we report characterization of Arabidopsis CTL1, which controls seedling growth and apical hook development by regulating intracellular trafficking of PIN-type auxin transporters. The CTL1 gene encodes a choline transporter-like protein with an expression pattern highly correlated with auxin distribution and is enriched in shoot and root apical meristems, lateral root primordia, the vascular system, and the concave side of the apical hook. The choline transporter-like 1 (CTL1) protein is localized to the trans-Golgi network (TGN), prevacuolar compartment (PVC), and plasma membrane (PM). Disruption of CTL1 gene expression alters the trafficking of 2 auxin efflux transporters—Arabidopsis PM-located auxin efflux transporter PIN-formed 1 (PIN1) and Arabidopsis PM-located auxin efflux transporter PIN-formed 3 (PIN3)—to the PM, thereby affecting auxin distribution and plant growth and development. We further found that phospholipids, sphingolipids, and other membrane lipids were significantly altered in the ctl1 mutant, linking CTL1 function to lipid homeostasis. We propose that CTL1 regulates protein sorting from the TGN to the PM through its function in lipid homeostasis.

生长素控制着众多的植物发育过程和植物对环境条件的响应。生长素转运蛋白的精确运输对于植物中植物生长素的稳态至关重要。在这里，我们报告拟南芥CTL1的表征，该拟南芥CTL1通过调节PIN型生长素转运蛋白的细胞内运输来控制幼苗的生长和根尖的发育。该CTL1该基因编码一种胆碱转运蛋白样蛋白，其表达模式与生长素的分布高度相关，并富含芽和根尖分生组织，侧根原基，血管系统和根尖钩的凹面。胆碱转运蛋白样1（CTL1）蛋白位于反高尔基网络（TGN），真空前室（PVC）和质膜（PM）。CTL1基因表达的破坏改变了2种植物生长素外排转运蛋白的运输—拟南芥PM定位的植物生长素外排转运蛋白PIN形成的1（PIN1）和拟南芥位于PM的植物生长素外排转运蛋白通过PIN形成3（PIN3），从而影响植物生长素的分布以及植物的生长发育。我们进一步发现，磷脂，鞘脂和其他膜脂质在ctl1突变体中发生了显着变化，从而将CTL1功能与脂质体内平衡相关联。我们提出，CTL1通过其在脂质稳态中的作用来调节从TGN到PM的蛋白质分选。