Dillon Andrew, Varanasi Vijay K, Danilova Tatiana V, Koo Dal-Hoe, Nakka Sridevi, Peterson Dallas E, Tranel Patrick J, Friebe Bernd, Gill Bikram S, Jugulam Mithila
Department of Agronomy, Wheat Genetics Resource Center, Kansas State University, Manhattan, Kansas 66506 (A.D., V.K.V., S.N., D.E.P., M.J.).
Department of Plant Pathology, Kansas State University, Manhattan, Kansas 66506 (T.V.D., D.-H.K., B.F., B.S.G.); and.
Plant Physiol. 2017 Feb;173(2):1226-1234. doi: 10.1104/pp.16.01427. Epub 2016 Dec 12.
Recent and rapid evolution of resistance to glyphosate, the most widely used herbicides, in several weed species, including common waterhemp (Amaranthus tuberculatus), poses a serious threat to sustained crop production. We report that glyphosate resistance in A tuberculatus was due to amplification of the 5-enolpyruvylshikimate-3-P synthase (EPSPS) gene, which encodes the molecular target of glyphosate. There was a positive correlation between EPSPS gene copies and its transcript expression. We analyzed the distribution of EPSPS copies in the genome of A tuberculatus using fluorescence in situ hybridization on mitotic metaphase chromosomes and interphase nuclei. Fluorescence in situ hybridization analysis mapped the EPSPS gene to pericentromeric regions of two homologous chromosomes in glyphosate sensitive A tuberculatus In glyphosate-resistant plants, a cluster of EPSPS genes on the pericentromeric region on one pair of homologous chromosomes was detected. Intriguingly, two highly glyphosate-resistant plants harbored an additional chromosome with several EPSPS copies besides the native chromosome pair with EPSPS copies. These results suggest that the initial event of EPSPS gene duplication may have occurred because of unequal recombination mediated by repetitive DNA. Subsequently, gene amplification may have resulted via several other mechanisms, such as chromosomal rearrangements, deletion/insertion, transposon-mediated dispersion, or possibly by interspecific hybridization. This report illustrates the physical mapping of amplified EPSPS copies in A tuberculatus.
包括普通豚草（Amaranthus tuberculatus）在内的几种杂草对最广泛使用的除草剂草甘膦的抗性最近迅速演变，这对持续的作物生产构成了严重威胁。我们报告称，豚草对草甘膦的抗性是由于5-烯醇丙酮酸莽草酸-3-磷酸合酶（EPSPS）基因的扩增，该基因编码草甘膦的分子靶标。EPSPS基因拷贝数与其转录本表达之间存在正相关。我们使用有丝分裂中期染色体和间期核的荧光原位杂交技术分析了豚草基因组中EPSPS拷贝的分布。荧光原位杂交分析将EPSPS基因定位到草甘膦敏感豚草两条同源染色体的着丝粒周围区域。在抗草甘膦的植物中，在一对同源染色体着丝粒周围区域检测到一组EPSPS基因。有趣的是，两株对草甘膦高度抗性的植物除了带有EPSPS拷贝的天然染色体对外，还拥有一条带有多个EPSPS拷贝的额外染色体。这些结果表明，EPSPS基因复制的初始事件可能是由于重复DNA介导的不等交换所致。随后，基因扩增可能通过其他几种机制发生，例如染色体重排、缺失/插入、转座子介导的扩散，或者可能是通过种间杂交。本报告阐述了豚草中扩增的EPSPS拷贝的物理定位。
