The natural auxin indole-3-acetic acid (IAA) is a key regulator of many aspects of plant growth and development. Synthetic auxin herbicides mimic the effects of IAA by inducing strong auxinic signaling responses in plants. Synthetic auxins are crucial herbicides in agriculture, made more important by the recent introduction of transgenic synthetic auxin resistant soybean and cotton. Currently, 41 weed species have evolved resistance to synthetic auxin herbicides and, in all but one case, the molecular basis of these resistance mechanisms is unknown. To determine the mechanism of 2,4-D resistance in a Sisymbrium orientale (Indian hedge mustard) weed population, we performed a transcriptome analysis of 2,4-D-resistant (R) and -susceptible (S) genotypes that revealed an in-frame 27-nucleotide deletion removing 9 amino acids in the degron tail (DT) of the auxin co-receptor Aux/IAA2 (SoIAA2). The deletion allele co-segregated with 2,4-D resistance in recombinant inbred lines. Further, this deletion was also detected in several 2,4-D resistant field populations of this species. Arabidopsis transgenic lines expressing the SoIAA2 mutant allele were resistant to 2,4-D and dicamba. The IAA2-DT deletion reduced binding to TIR1 in vitro with both natural and synthetic auxins, causing reduced association and increased dissociation rates. This novel mechanism of synthetic auxin herbicide resistance assigns a new in planta function to the DT region of this Aux/IAA co-receptor for its role in synthetic auxin binding kinetics and reveals a potential biotechnological approach to produce synthetic auxin resistant crops using gene editing.

中文翻译：

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生长素共受体IAA2的德格隆尾中的框内缺失突变赋予了对侧柏中除草剂2,4-D的抗性

天然的生长素吲哚-3-乙酸（IAA）是植物生长和发育的许多方面的关键调节剂。合成的植物生长素除草剂通过诱导植物中强烈的植物生长素信号传导响应来模拟IAA的作用。合成植物生长素是农业中至关重要的除草剂，最近引入转基因合成植物生长素抗性大豆和棉花变得更加重要。目前，有41种杂草物种已对合成生长素除草剂产生了抗药性，除一种情况外，除其他外，尚不清楚这些抗药性机理的分子基础。为了确定东方Sisymbrium Orientale（印度树篱芥末）杂草种群中2,4-D抗性的机制，我们对2进行了转录组分析 4-D抗性（R）和易感性（S）基因型，揭示了框内27个核苷酸的缺失，去除了生长素共受体Aux / IAA2（SoIAA2）的degron尾部（DT）中的9个氨基酸。缺失等位基因与重组自交系中的2，4-D抗性共分离。此外，在该物种的几个2，4-D抗性田间种群中也检测到了这种缺失。表达SoIAA2突变体等位基因的拟南芥转基因株系对2,4-D和麦草畏具有抗性。IAA2-DT缺失会降低天然和合成生长素在体外与TIR1的结合，从而导致缔合减少和解离速率增加。