Zhao Heming, Ma Tengfei, Wang Xin, Deng Yingtian, Ma Haoli, Zhang Rongsheng, Zhao Jie
State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan, 430072, China.
Plant Cell Environ. 2015 Nov;38(11):2208-22. doi: 10.1111/pce.12467. Epub 2015 Jan 7.
Polar auxin transport, mediated by influx and efflux transporters, controls many aspects of plant growth and development. The auxin influx carriers in Arabidopsis have been shown to control lateral root development and gravitropism, but little is known about these proteins in rice. This paper reports on the functional characterization of OsAUX1. Three OsAUX1 T-DNA insertion mutants and RNAi knockdown transgenic plants reduced lateral root initiation compared with wild-type (WT) plants. OsAUX1 overexpression plants exhibited increased lateral root initiation and OsAUX1 was highly expressed in lateral roots and lateral root primordia. Similarly, the auxin reporter, DR5-GUS, was expressed at lower levels in osaux1 than in the WT plants, which indicated that the auxin levels in the mutant roots had decreased. Exogenous 1-naphthylacetic acid (NAA) treatment rescued the defective phenotype in osaux1-1 plants, whereas indole-3-acetic acid (IAA) and 2,4-D could not, which suggested that OsAUX1 was a putative auxin influx carrier. The transcript levels of several auxin signalling genes and cell cycle genes significantly declined in osaux1, hinting that the regulatory role of OsAUX1 may be mediated by auxin signalling and cell cycle genes. Overall, our results indicated that OsAUX1 was involved in polar auxin transport and functioned to control auxin-mediated lateral root initiation in rice.
由流入和流出转运蛋白介导的极性生长素运输控制着植物生长和发育的许多方面。拟南芥中的生长素流入载体已被证明控制侧根发育和向地性，但关于水稻中的这些蛋白质知之甚少。本文报道了OsAUX1的功能特性。与野生型（WT）植物相比，三个OsAUX1 T-DNA插入突变体和RNA干扰敲除转基因植物减少了侧根起始。OsAUX1过表达植物表现出增加的侧根起始，并且OsAUX1在侧根和侧根原基中高度表达。同样，生长素报告基因DR5-GUS在osaux1中的表达水平低于野生型植物，这表明突变体根中的生长素水平降低。外源1-萘乙酸（NAA）处理挽救了osaux1-1植物中的缺陷表型，而吲哚-3-乙酸（IAA）和2,4-二氯苯氧乙酸（2,4-D）则不能，这表明OsAUX1是一种假定的生长素流入载体。几个生长素信号基因和细胞周期基因的转录水平在osaux1中显著下降，这暗示OsAUX1的调节作用可能由生长素信号和细胞周期基因介导。总体而言，我们的结果表明OsAUX1参与极性生长素运输，并在控制水稻中生长素介导的侧根起始中发挥作用。
