Montgomery Jacob S, Soni Neeta, Marques Hill Sofia, Morran Sarah, Patterson Eric L, Edwards Seth A, Ratnayake Sandaruwan, Hung Yu-Hung, Pandesha Pratheek H, Slotkin R Keith, Napier Richard, Dayan Franck, Gaines Todd
Department of Agricultural Biology, Colorado State University, Fort Collins, Colorado, USA.
Department of Plant, Soil, and Microbial Sciences, Michigan State University, East Lansing, Michigan, USA.
Plant J. 2025 Jul;123(2):e70339. doi: 10.1111/tpj.70339.
A dicamba-resistant population of kochia (Bassia scoparia) identified in Colorado, USA in 2012 was used to generate a synthetic mapping population that segregated for dicamba resistance. Linkage mapping associating dicamba injury with genotype derived from restriction-site-associated DNA sequencing identified a single locus in the kochia genome associated with resistance on chromosome 4. A mutant version of Auxin/Indole-3-Acetic Acid 16 (AUX/IAA16; a gene previously implicated in dicamba resistance in kochia) was found near the middle of this locus in resistant plants. Long-read sequencing of dicamba-resistant plants identified a recently inserted long-terminal repeat (LTR) retrotransposon TRIM element near the beginning of the second exon of AUX/IAA16, leading to disruption of normal splicing and a mutated degron domain. Stable transgenic lines of Arabidopsis thaliana ectopically expressing the mutant and wild-type alleles of AUX/IAA16 were developed. Arabidopsis thaliana plants expressing the mutant AUX/IAA16 allele grew shorter roots on control media. However, transgenic root growth was less inhibited on media containing either dicamba (5 μM) or IAA (0.5 μM) when compared with non-transgenic plants or those expressing the wild-type allele of AUX/IAA16. In vitro assays indicate reduced binding affinity and more rapid dissociation of the mutant AUX/IAA16 with TIR1 in the presence of several auxins, and protein modeling suggests the substitution of the glycine residue in the degron domain of AUX/IAA16 is especially important for resistance. A fitness cost associated with the mutant allele of AUX/IAA16 has implications for resistance evolution and management of kochia populations with this resistance mechanism.
2012年在美国科罗拉多州发现的一个对麦草畏具有抗性的地肤（Bassia scoparia）种群被用于构建一个用于分离麦草畏抗性的合成作图群体。通过将麦草畏损伤与来自限制性位点相关DNA测序的基因型进行连锁作图，在地肤基因组中确定了一个与4号染色体上的抗性相关的单一位点。在抗性植株中，该位点中部附近发现了生长素/吲哚 - 3 - 乙酸16（AUX/IAA16，一个先前与地肤麦草畏抗性有关的基因）的突变版本。对麦草畏抗性植株进行长读长测序，在AUX/IAA16第二个外显子起始处附近发现了一个最近插入的长末端重复（LTR）逆转座子TRIM元件，导致正常剪接中断和一个突变的降解结构域。构建了稳定表达AUX/IAA16突变体和野生型等位基因的拟南芥转基因株系。在对照培养基上，表达突变型AUX/IAA16等位基因的拟南芥植株根系生长较短。然而，与非转基因植株或表达AUX/IAA16野生型等位基因的植株相比，在含有麦草畏（5 μM）或吲哚 - 3 - 乙酸（IAA，0.5 μM）的培养基上，转基因根系生长受到的抑制较小。体外试验表明，在几种生长素存在的情况下，突变型AUX/IAA16与运输抑制剂响应蛋白1（TIR1）的结合亲和力降低且解离更快，蛋白质建模表明AUX/IAA16降解结构域中甘氨酸残基的取代对抗性尤为重要。与AUX/IAA16突变等位基因相关的适合度代价对抗性进化以及具有这种抗性机制的地肤种群的管理具有重要意义。
