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1.
PLoS One ; 13(8): e0202921, 2018.
Article in English | MEDLINE | ID: mdl-30138445

ABSTRACT

Hybrid crops produce higher yields than their inbred parents due to heterosis. For high purity of hybrid seeds, it is critical to eliminate self-pollination. Manual or mechanical removal of male parts (such as detasseling in maize) is labor-intensive, fuel and time-consuming, and can cause physical damage to female plants, resulting in significant seed yield reductions. Many male-sterility systems either require a maintainer for male-sterile line propagation or are often affected by environmental factors. Roundup® Hybridization System (RHS) utilizes glyphosate to induce male sterility, which effectively eliminates the need for maintainer lines and removal of male parts for commercial hybrid seed production. The first-generation RHS (RHS1) is based on low expression of a glyphosate-insensitive 5-enolpyruvylshikimate-3-phosphate synthase (CP4 EPSPS) in pollen. This report presents the second-generation RHS (RHS2) technology built on RNA interference (RNAi) combined with CP4 EPSPS. It utilizes maize endogenous male tissue-specific small interfering RNAs (mts-siRNAs) to trigger cleavage of the CP4 EPSPS mRNA specifically in tassels, resulting in glyphosate-sensitive male cells due to lack of the CP4 EPSPS protein. Male sterility is then induced by glyphosate application at the stages critical for pollen development, and the male-sterile plants are used as the female parent to produce hybrid seed. The endogenous mts-siRNAs are conserved across maize germplasms, and the inducible male sterility was replicated in representative germplasms through introgression of a CP4 EPSPS transgene containing the mts-siRNA target sequence. This technology combines the relative simplicity and convenience of a systemic herbicide spray methodology with targeted protein expression to create an inducible male sterility system for industrial production of row crop hybrid seeds in an environmentally-independent manner.


Subject(s)
Crops, Agricultural/genetics , Hybridization, Genetic , Zea mays/genetics , Crops, Agricultural/physiology , Genetic Engineering/methods , Glycine/analogs & derivatives , Glycine/metabolism , Pollen/metabolism , RNA Interference , Seeds/genetics , Seeds/physiology , Zea mays/physiology , Glyphosate
2.
Pest Manag Sci ; 70(2): 212-8, 2014 Feb.
Article in English | MEDLINE | ID: mdl-23460547

ABSTRACT

BACKGROUND: Hybrid corn varieties exhibit benefits associated with heterosis and account for most of the corn acreage in the USA. Hybrid seed corn is produced by crossing a female parent which is male-sterile and therefore incapable of self-pollination with a male parent as the pollen donor. The majority of hybrid seed corn is produced by mechanical detasseling which involves physically removing the tassel, a process that is laborious and costly. RESULTS: Glyphosate-resistant corn was developed via expression of a glyphosate insensitive 5-enolpyruvyl-shikimate 3-phosphate synthase enzyme (CP4-EPSPS). Experimentation with molecular expression elements resulted in selective reduction of CP4-EPSPS expression in male reproductive tissues. The resulting plant demonstrated sterile tassel following glyphosate application with little to no injury to the rest of the plant. Using (14)C-glyphosate as a marker, we also examined the translocation of glyphosate to the tassel via spray application in a track sprayer to simulate field application. The results allowed optimization of spray parameters such as dose, spray timing and target to maximize tassel delivery of glyphosate for efficient sterilization. CONCLUSION: The Roundup hybridization system (RHS) is a novel process for hybrid seed production based on glyphosate-mediated male sterility. RHS replaces mechanical detasseling with glyphosate spray and greatly simplifies the process of hybrid seed corn production.


Subject(s)
Genetic Engineering/methods , Glycine/analogs & derivatives , Hybridization, Genetic/drug effects , Plant Infertility/drug effects , Seeds/drug effects , Zea mays/genetics , Zea mays/physiology , 3-Phosphoshikimate 1-Carboxyvinyltransferase/genetics , 3-Phosphoshikimate 1-Carboxyvinyltransferase/metabolism , Dose-Response Relationship, Drug , Gene Expression Regulation, Plant/drug effects , Gene Expression Regulation, Plant/genetics , Glycine/pharmacology , Herbicides/pharmacology , Plant Infertility/genetics , Plants, Genetically Modified , Protein Transport/drug effects , Seeds/genetics , Seeds/physiology , Time Factors , Zea mays/drug effects , Glyphosate
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