Institut National de la Recherche Agronomique, UMR1347 Agroécologie, Dijon, France.
Ann Bot. 2013 Apr;111(4):681-91. doi: 10.1093/aob/mct018. Epub 2013 Feb 7.
Selective pressures exerted by agriculture on populations of arable weeds foster the evolution of adaptive traits. Germination and emergence dynamics and herbicide resistance are key adaptive traits. Herbicide resistance alleles can have pleiotropic effects on a weed's life cycle. This study investigated the pleiotropic effects of three acetyl-coenzyme A carboxylase (ACCase) alleles endowing herbicide resistance on the seed-to-plant part of the life cycle of the grass weed Alopecurus myosuroides.
In each of two series of experiments, A. myosuroides populations with homogenized genetic backgrounds and segregating for Leu1781, Asn2041 or Gly2078 ACCase mutations which arose independently were used to compare germination dynamics, survival in the soil and seedling pre-emergence growth among seeds containing wild-type, heterozygous and homozygous mutant ACCase embryos.
Asn2041 ACCase caused no significant effects. Gly2078 ACCase major effects were a co-dominant acceleration in seed germination (1·25- and 1·10-fold decrease in the time to reach 50 % germination (T50) for homozygous and heterozygous mutant embryos, respectively). Segregation distortion against homozygous mutant embryos or a co-dominant increase in fatal germination was observed in one series of experiments. Leu1781 ACCase major effects were a co-dominant delay in seed germination (1·41- and 1·22-fold increase in T50 for homozygous and heterozygous mutant embryos, respectively) associated with a substantial co-dominant decrease in fatal germination.
Under current agricultural systems, plants carrying Leu1781 or Gly2078 ACCase have a fitness advantage conferred by herbicide resistance that is enhanced or counterbalanced, respectively, by direct pleiotropic effects on the plant phenology. Pleiotropic effects associated with mutations endowing herbicide resistance undoubtedly play a significant role in the evolutionary dynamics of herbicide resistance in weed populations. Mutant ACCase alleles should also prove useful to investigate the role played by seed storage lipids in the control of seed dormancy and germination.
农业对耕地杂草种群施加的选择压力促进了适应性特征的进化。萌发和出苗动态以及除草剂抗性是关键的适应性特征。除草剂抗性等位基因可能对杂草的生命周期产生多效性影响。本研究调查了赋予除草剂抗性的三种乙酰辅酶 A 羧化酶 (ACCase) 等位基因对禾本科杂草节节麦种子到植株部分生命周期的多效性影响。
在两项系列实验中，使用遗传背景均匀且分离出亮氨酸 1781、天冬氨酸 2041 或甘氨酸 2078 ACCase 突变的节节麦种群，这些突变是独立出现的，用于比较含有野生型、杂合和纯合突变 ACCase 胚胎的种子的萌发动态、在土壤中的存活率和幼苗出苗前生长。
天冬氨酸 2041 ACCase 没有产生显著影响。甘氨酸 2078 ACCase 主要影响是共显性加速种子萌发（纯合和杂合突变胚胎达到 50%萌发的时间 (T50) 分别减少 1.25 倍和 1.10 倍）。在一项实验系列中观察到针对纯合突变胚胎的分离失真或致命萌发的共显性增加。亮氨酸 1781 ACCase 主要影响是共显性延迟种子萌发（纯合和杂合突变胚胎的 T50 分别增加 1.41 倍和 1.22 倍），同时致命萌发也大幅共显性降低。
在当前的农业系统下，携带亮氨酸 1781 或甘氨酸 2078 ACCase 的植物具有由除草剂抗性赋予的适应优势，这种优势分别通过对植物物候的直接多效性影响而增强或平衡。赋予除草剂抗性的突变相关的多效性影响无疑在杂草种群中除草剂抗性的进化动态中发挥了重要作用。突变 ACCase 等位基因也应该有助于研究种子储存脂质在控制种子休眠和萌发中的作用。
