产生对草甘膦不敏感的EPSPS蛋白是抗草甘膦作物开发的最主要的策略。孟山都公司利用农杆菌cp4菌株中的cp4 epsps基因开发的转基因玉米NK603和转基因大豆40-3-2，依据的就是这个原理。最近，孟山都公司在草甘膦抗性杂草中发现了新的对草甘膦不敏感的EPSPS蛋白，为抗草甘膦作物培育开辟了新的路径。
孟山都的研发人员在抗草甘膦的牛筋草中找到了EPSPS蛋白的变异体，102位点的T变为I或106位点的P变为S或两个位点都变化（TIPS）。将AtEPSPS-TIPA转入模式植物拟南芥中验证其功能，结果显示，转基因植株的抗性水平受AtEPSPS-TIPA的拷贝数影响，在不同发育时期下，多拷贝转基因植株草甘膦抗性水平最高可达到40.6倍。该结果不仅发现了比CP4 EPSPS抗性更强的EPSPS变异体，而且其位点的变化可通过基因编辑实现，这些都为新型抗草甘膦作物开发提供了新策略。
Pest Manag Sci. 2017 Jul 5.
Evaluation of glyphosate-resistance in Arabidopsis thaliana expressing an altered target site EPSPS.
Author
Sammons RD, You J, Qi Y……Ostrander E, Wang D, Heck G.
Monsanto Co, 700 Chesterfield Parkway, St. Louis, MO, 63017.
Abstract
BACKGROUND:
Glyphosate-resistant goosegrass has recently evolved and is homozygous for the double mutant of EPSPS (T102 I, P106 S or TIPS). These same mutations combined with EPSPS over-expression, have been used to create transgenic glyphosate-resistant crops. Arabidopsis thaliana (Wt EPSPS Ki ≈ 0.5 μM) was engineered to express a variant AtEPSPS-T102 I, P106 A (TIPA Ki = 150 μM) to determine the resistance magnitude for a more potent variant EPSPS that might evolve in weeds.
RESULTS:
Transgenic A. thaliana plants, homozygous for one, two or four copies of AtEPSPS-TIPA, had resistance (IC50 values, R/S) as measured by seed production ranging from 4.2-16-fold. Plants treated in reproductive stage were male sterile with a range of R/S from 10.1-40.6-fold. A significant hormesis(~63% gain in fresh weight) was observed for all genotypes when treated at the initiation of reproductive stage with 0.013 kg ha-1. AtEPSPS-TIPA enzyme activity was proportional to copy number and correlated with resistance magnitude.
CONCLUSIONS:
A. thaliana, as a model weed expressing one copy of AtEPSPS-TIPA (300-fold more resistant), had only 4.2-fold resistance to glyphosate for seed production. Resistance behaved as a single dominant allele. Vegetative tissue resistance was 4.7-fold greater than reproductive tissue resistance and was linear with gene copy number.
