Data from: Herbicide resistance-endowing ACCase gene mutations in hexaploid wild oat (Avena fatua): Insights into resistance evolution in a hexaploid species

Many herbicide-resistant weed species are polyploids, but far too little about the evolution of resistance mutations in polyploids is understood. Hexaploid wild oat (Avena fatua) is a global crop weed and many populations have evolved herbicide resistance. We studied plastidic acetyl-coenzyme A carboxylase (ACCase)-inhibiting herbicide resistance in hexaploid wild oat and revealed that resistant individuals can express one, two or three different plastidic ACCase gene resistance mutations (Ile-1781-Leu, Asp-2078-Gly and Cys-2088-Arg). Using ACCase resistance mutations as molecular markers, combined with genetic, molecular and biochemical approaches, we found in individual resistant wild-oat plants that (1) up to three unlinked ACCase gene loci assort independently following Mendelian laws for disomic inheritance, (2) all three of these homoeologous ACCase genes were transcribed, with each able to carry its own mutation and (3) in a hexaploid background, each individual ACCase resistance mutation confers relatively low-level herbicide resistance, in contrast to high-level resistance conferred by the same mutations in unrelated diploid weed species of the Poaceae (grass) family. Low resistance conferred by individual ACCase resistance mutations is likely due to a dilution effect by susceptible ACCase expressed by homoeologs in hexaploid wild oat and/or differential expression of homoeologous ACCase gene copies. Thus, polyploidy in hexaploid wild oat may slow resistance evolution. Evidence of coexisting non-target-site resistance mechanisms among wild-oat populations was also revealed. In all, these results demonstrate that herbicide resistance and its evolution can be more complex in hexaploid wild oat than in unrelated diploid grass weeds. Our data provide a starting point for the daunting task of understanding resistance evolution in polyploids.

已有诸多抗除草剂杂草物种为多倍体，但学界对多倍体中抗药性突变的演化机制仍知之甚少。六倍体野燕麦（Avena fatua）是全球性农田杂草，多数种群已演化出除草剂抗药性。我们以六倍体野燕麦为研究对象，探讨其对质体乙酰辅酶A羧化酶（plastidic acetyl-coenzyme A carboxylase, ACCase）抑制剂类除草剂的抗药性，发现抗药性个体可表达1种、2种或3种不同的质体ACCase基因抗药性突变（Ile-1781-Leu、Asp-2078-Gly及Cys-2088-Arg）。我们以ACCase抗药性突变作为分子标记，结合遗传学、分子生物学与生物化学手段，对抗药性野燕麦单株进行分析后发现：① 最多存在3个不连锁的ACCase基因座，其遗传遵循二体遗传的孟德尔独立分配定律；② 这3个部分同源ACCase基因均发生转录，且各自可携带独立的突变；③ 在六倍体遗传背景下，单个ACCase抗药性突变仅赋予相对低水平的除草剂抗药性，而在禾本科（Poaceae，草本）无关二倍体杂草物种中，相同突变可赋予高水平抗药性。单个ACCase抗药性突变所赋予的低抗药性，可能源于六倍体野燕麦中部分同源基因所表达的易感型ACCase产生的稀释效应，以及/或部分同源ACCase基因拷贝的差异表达。因此，六倍体野燕麦的多倍体特性可能延缓抗药性的演化。此外，本研究还发现野燕麦种群中存在非靶标抗药性机制共存的证据。综上，本研究结果表明，六倍体野燕麦的除草剂抗药性及其演化过程，相较于无关二倍体草本杂草更为复杂。本研究的数据为解析多倍体抗药性演化这一艰巨任务提供了研究起点。