Noh Bosl, Bandyopadhyay Anindita, Peer Wendy Ann, Spalding Edgar P, Murphy Angus S
Department of Botany, University of Wisconsin, 430 Lincoln Drive, Madison, Wisconsin 53706, USA.
Nature. 2003 Jun 26;423(6943):999-1002. doi: 10.1038/nature01716.
Many aspects of plant growth and development are dependent on the flow of the hormone auxin down the plant from the growing shoot tip where it is synthesized. The direction of auxin transport in stems is believed to result from the basal localization within cells of the PIN1 membrane protein, which controls the efflux of the auxin anion. Mutations in two genes homologous to those encoding the P-glycoprotein ABC transporters that are especially abundant in multidrug-resistant tumour cells in animals were recently shown to block polar auxin transport in the hypocotyls of Arabidopsis seedlings. Here we show that the mdr mutants display faster and greater gravitropism and enhanced phototropism instead of the impaired curvature development expected in mutants lacking polar auxin transport. We find that these phenotypes result from a disruption of the normal accumulation of PIN1 protein along the basal end of hypocotyl cells associated with basipetal auxin flow. Lateral auxin conductance becomes relatively larger as a result, enhancing the growth differentials responsible for tropic responses.
植物生长和发育的许多方面都依赖于激素生长素从其合成的生长茎尖向下在植物体内的流动。茎中生长素运输的方向被认为是由PIN1膜蛋白在细胞内的基部定位导致的，该蛋白控制生长素阴离子的外流。最近发现，与编码P-糖蛋白ABC转运体的基因同源的两个基因发生突变，这些转运体在动物的多药耐药肿瘤细胞中特别丰富，会阻断拟南芥幼苗下胚轴中的极性生长素运输。在这里，我们表明，mdr突变体表现出更快、更强的向重力性和增强的向光性，而不是缺乏极性生长素运输的突变体预期的弯曲发育受损。我们发现，这些表型是由于PIN1蛋白沿下胚轴细胞基部末端与向基性生长素流动相关的正常积累受到破坏所致。结果，侧向生长素传导变得相对更大，增强了负责向性反应的生长差异。
