Synonymous mutation gene design to overexpress ACCase in creeping bentgrass to obtain resistance to ACCase-inhibiting herbicides.
Overexpression of a native gene can cause expression of both introduced and native genes to be silenced by posttranscriptional gene silencing (PTGS) mechanisms. PTGS mechanisms rely on sequence identity between the transgene and native genes; therefore, designing genes with mutations that do not cause amino acid changes, known as synonymous mutations, may avoid PTGS. For proof of concept, the sequence of acetyl-coA carboxylase (ACCase) from creeping bentgrass (Agrostis stolonifera L.) was altered with synonymous mutations. A native bentgrass ACCase was cloned and used as a template for the modified gene. Wild-type (WT) and modified genes were further modified with a non-synonymous mutation, coding for an isoleucine to leucine substitution at position 1781, known to confer resistance to ACCase-inhibiting herbicides. Five-hundred calli of creeping bentgrass 'Penn A-4' were inoculated with Agrobacterium containing either the WT or modified genes, with or without the herbicide-resistance mutation. Six herbicide-resistant-transgenic events containing the modified gene with the 1781 mutation were obtained. Transcription of the modified ACCase was confirmed in transgenic plants, showing that gene-silencing mechanisms were avoided. Transgenic plants were confirmed to be resistant to the ACCase-inhibiting herbicide, sethoxydim, providing evidence that the modified gene was functional. The result is a novel herbicide-resistance trait and shows that overexpression of a native enzyme with a gene designed with synonymous mutations is possible.
Department of Crop and Soil Sciences, Institute of Plant Breeding Genetics and Genomics, University of Georgia, 111 Riverbend Rd., Athens, GA, 30602, USA. dougheckart@gmail.com.
Douglas L
DL
Heckart
Department of Crop and Soil Sciences, Institute of Plant Breeding Genetics and Genomics, University of Georgia, 115 Coastal Way, Tifton, GA, 31793, USA.
Brian M
BM
Schwartz
Department of Crop and Soil Sciences, Institute of Plant Breeding Genetics and Genomics, University of Georgia, Griffin Campus, 1109 Experiment St., Griffin, GA, 30223, USA.
Paul L
PL
Raymer
Department of Crop and Soil Sciences, Institute of Plant Breeding Genetics and Genomics, University of Georgia, 111 Riverbend Rd., Athens, GA, 30602, USA.
Wayne A
WA
Parrott
D000103:Acetyl-CoA Carboxylase / Q000235:genetics* / Q000378:metabolism; D031703:Agrostis / Q000187:drug effects* / Q000235:genetics*; D003512:Cyclohexanones / Q000494:pharmacology; D053209:Herbicide Resistance / Q000235:genetics*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000187:drug effects / Q000235:genetics; D000069456:Silent Mutation
D003512:Cyclohexanones; D010940:Plant Proteins; C049437:sethoxydim; D000103:Acetyl-CoA Carboxylase
Acetyl coenzyme A carboxylase (ACCase); Aryloxyphenoxypropionate (APP); Cyclohexandione (CHD); Herbicide-resistance; Posttranscriptional gene silencing; Sethoxydim resistant; Synonymous mutation; Synthetic gene design