Dharmasiri S, Swarup R, Mockaitis K, Dharmasiri N, Singh S K, Kowalchyk M, Marchant A, Mills S, Sandberg G, Bennett M J, Estelle M
Department of Biology, Indiana University, Bloomington, IN 47405, USA.
Science. 2006 May 26;312(5777):1218-20. doi: 10.1126/science.1122847. Epub 2006 May 11.
The AUX1 and PIN auxin influx and efflux facilitators are key regulators of root growth and development. For root gravitropism to occur, AUX1 and PIN2 must transport auxin via the lateral root cap to elongating epidermal cells. Genetic studies suggest that AXR4 functions in the same pathway as AUX1. Here we show that AXR4 is a previously unidentified accessory protein of the endoplasmic reticulum (ER) that regulates localization of AUX1 but not of PIN proteins. Loss of AXR4 resulted in abnormal accumulation of AUX1 in the ER of epidermal cells, indicating that the axr4 agravitropic phenotype is caused by defective AUX1 trafficking in the root epidermis.
AUX1和PIN生长素内流和外流促进因子是根生长和发育的关键调节因子。为了发生根向地性，AUX1和PIN2必须通过侧根冠将生长素转运到伸长的表皮细胞。遗传学研究表明，AXR4与AUX1在同一途径中发挥作用。我们在此表明，AXR4是一种先前未被鉴定的内质网（ER）辅助蛋白，它调节AUX1的定位，但不调节PIN蛋白的定位。AXR4的缺失导致表皮细胞内质网中AUX1异常积累，表明axr4无向地性表型是由根表皮中AUX1运输缺陷引起的。
