Li Guangjie, Song Haiyan, Li Baohai, Kronzucker Herbert J, Shi Weiming
State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China (G.L., H.S., B.L., W.S.); andDepartment of Biological Sciences, University of Toronto, Toronto, Ontario, Canada M1C 1A4 (H.J.K.).
State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China (G.L., H.S., B.L., W.S.); andDepartment of Biological Sciences, University of Toronto, Toronto, Ontario, Canada M1C 1A4 (H.J.K.)
Plant Physiol. 2015 Dec;169(4):2608-23. doi: 10.1104/pp.15.00904. Epub 2015 Oct 14.
A stunted root system is a significant symptom of iron (Fe) toxicity, yet little is known about the effects of excess Fe on lateral root (LR) development. In this work, we show that excess Fe has different effects on LR development in different portions of the Arabidopsis (Arabidopsis thaliana) root system and that inhibitory effects on the LR initiation are only seen in roots newly formed during excess Fe exposure. We show that root tip contact with Fe is both necessary and sufficient for LR inhibition and that the auxin, but not abscisic acid, pathway is engaged centrally in the initial stages of excess Fe exposure. Furthermore, Fe stress significantly reduced PIN-FORMED2 (PIN2)-green fluorescent protein (GFP) expression in root tips, and pin2-1 mutants exhibited significantly fewer LR initiation events under excess Fe than the wild type. Exogenous application of both Fe and glutathione together increased PIN2-GFP expression and the number of LR initiation events compared with Fe treatment alone. The ethylene inhibitor aminoethoxyvinyl-glycine intensified Fe-dependent inhibition of LR formation in the wild type, and this inhibition was significantly reduced in the ethylene overproduction mutant ethylene overproducer1-1. We show that Auxin Resistant1 (AUX1) is a critical component in the mediation of endogenous ethylene effects on LR formation under excess Fe stress. Our findings demonstrate the relationship between excess Fe-dependent PIN2 expression and LR formation and the potential role of AUX1 in ethylene-mediated LR tolerance and suggest that AUX1 and PIN2 protect LR formation in Arabidopsis during the early stages of Fe stress.
根系发育不良是铁（Fe）毒性的一个显著症状，但关于过量铁对侧根（LR）发育的影响却知之甚少。在这项研究中，我们发现过量铁对拟南芥根系不同部位的侧根发育有不同影响，且对侧根起始的抑制作用仅在过量铁暴露期间新形成的根中出现。我们表明根尖与铁的接触对于侧根抑制既是必要的也是充分的，并且生长素途径而非脱落酸途径在过量铁暴露的初始阶段起核心作用。此外，铁胁迫显著降低了根尖中PIN-FORMED2（PIN2）-绿色荧光蛋白（GFP）的表达，并且在过量铁条件下，pin2-1突变体的侧根起始事件明显少于野生型。与单独铁处理相比，同时外源施加铁和谷胱甘肽可增加PIN2-GFP的表达以及侧根起始事件的数量。乙烯抑制剂氨基乙氧基乙烯甘氨酸增强了野生型中铁依赖的侧根形成抑制作用，而在乙烯过量产生突变体ethylene overproducer1-1中这种抑制作用显著降低。我们表明生长素抗性1（AUX1）是过量铁胁迫下内源性乙烯对侧根形成影响的介导过程中的关键成分。我们的研究结果证明了过量铁依赖的PIN2表达与侧根形成之间的关系以及AUX1在乙烯介导的侧根耐受性中的潜在作用，并表明AUX1和PIN2在铁胁迫早期保护拟南芥的侧根形成。
