Bustos-Sanmamed Pilar, Mao Guohong, Deng Ying, Elouet Morgane, Khan Ghazanfar Abbas, Bazin J R Mie, Turner Marie, Subramanian Senthil, Yu Oliver, Crespi Martin, Lelandais-Bri Re Christine
Institut des Sciences du Végétal (ISV), Centre National de la Recherche Scientifique (CNRS), Gif sur Yvette F-91198 Gif-sur-Yvette Cedex, France.
Donald Danforth Plant Science Center, St Louis, MO 63132, USA.
Funct Plant Biol. 2013 Dec;40(12):1208-1220. doi: 10.1071/FP13123.
Auxin action is mediated by a complex signalling pathway involving transcription factors of the auxin response factor (ARF) family. In Arabidopsis, microRNA160 (miR160) negatively regulates three ARF genes (ARF10/ARF16/ARF17) and therefore controls several developmental processes, including primary and lateral root growth. Here, we analysed the role of miR160 in root development and nodulation in Medicago truncatula Gaertn. Bioinformatic analyses identified two main mtr-miR160 variants (mtr-miR160abde and mtr-miR160c) and 17 predicted ARF targets. The miR160-dependent cleavage of four predicted targets in roots was confirmed by analysis of parallel analysis of RNA ends (PARE) data and RACE-PCR experiments. Promoter-GUS analyses for mtr-miR160d and mtr-miR160c genes revealed overlapping but distinct expression profiles during root and nodule development. In addition, the early miR160 activation in roots during symbiotic interaction was not observed in mutants of the nodulation signalling or autoregulation pathways. Composite plants that overexpressed mtr-miR160a under two different promoters exhibited distinct defects in root growth and nodulation: the p35S:miR160a construct led to reduced root length associated to a severe disorganisation of the RAM, whereas pCsVMV:miR160a roots showed gravitropism defects and lower nodule numbers. Our results suggest that a regulatory loop involving miR160/ARFs governs root and nodule organogenesis in M. truncatula.
生长素的作用是由一个复杂的信号通路介导的，该通路涉及生长素响应因子（ARF）家族的转录因子。在拟南芥中，微小RNA160（miR160）负调控三个ARF基因（ARF10/ARF16/ARF17），因此控制包括主根和侧根生长在内的多个发育过程。在此，我们分析了miR160在蒺藜苜蓿根发育和结瘤中的作用。生物信息学分析鉴定出两个主要的蒺藜苜蓿miR160变体（mtr-miR160abde和mtr-miR160c）以及17个预测的ARF靶标。通过对RNA末端平行分析（PARE）数据和RACE-PCR实验的分析，证实了根中四个预测靶标的miR160依赖性切割。对mtr-miR160d和mtr-miR160c基因的启动子-GUS分析揭示了在根和根瘤发育过程中重叠但不同的表达模式。此外，在结瘤信号或自调控途径的突变体中未观察到共生相互作用期间根中miR160的早期激活。在两种不同启动子下过表达mtr-miR160a的复合植株在根生长和结瘤方面表现出明显缺陷：p35S:miR160a构建体导致根长度减少，与根顶端分生组织的严重紊乱有关，而pCsVMV:miR160a根表现出向地性缺陷和较低的根瘤数。我们的结果表明，一个涉及miR160/ARFs的调控环控制着蒺藜苜蓿的根和根瘤器官发生。
