Identification of genetic elements associated with EPSPs gene amplification

Area of Science:

• Plant genetics
• Molecular biology
• Herbicide resistance

Background:

• Weed populations exhibit high genetic plasticity and rapid adaptation to environmental pressures.
• Glyphosate is a critical herbicide, and resistance in weeds like Palmer amaranth poses a significant agricultural challenge.
• The 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene amplification confers glyphosate resistance in Amaranthus palmeri, but the mechanism is unknown.

Purpose of the Study:

• To investigate the molecular mechanism behind EPSPS gene amplification in glyphosate-resistant Amaranthus palmeri.
• To identify genetic elements or repetitive sequences associated with gene amplification.

Main Methods:

• Sequencing of the EPSPS gene and flanking genomic regions in susceptible and resistant Amaranthus palmeri.
• Analysis of introns and sequence polymorphisms within amplified EPSPS copies.
• Identification of mobile genetic elements and repetitive sequences near EPSPS loci.

Main Results:

• EPSPS gene amplification in resistant biotypes involves at least 30 kb of DNA, including introns, indicating a DNA-mediated process.
• Two EPSPS loci were identified in susceptible plants; only one locus was amplified in resistant plants.
• Sequences homologous to miniature inverted-repeat transposable elements (MITEs) and a putative Activator (Ac) transposase were found adjacent to amplified EPSPS genes in resistant individuals.

Conclusions:

• EPSPS gene amplification in Amaranthus palmeri is a recent event, likely mediated by DNA-based mechanisms.
• The presence of MITEs and transposase-related sequences suggests a potential role for transposable elements or unequal recombination in the amplification process.
• Further research is required to elucidate the precise mechanism controlling this DNA-mediated gene amplification.