Herbicide resistant weeds: A call to integrate conventional agricultural practices, molecular biology knowledge and new technologies.

Herbicide resistant (HR) weeds are of major concern in modern agriculture. This situation is exacerbated by the massive adoption of herbicide-based technologies along with the overuse of a few active ingredients to control weeds over vast areas year after year. Also, many other anthropological, biological, and environmental factors have defined a higher rate of herbicide resistance evolution in numerous weed species around the world.

A novel triple amino acid substitution in the EPSPS found in a high-level glyphosate-resistant Amaranthus hybridus population from Argentina.

Background: The evolution of herbicide-resistant weeds is one of the most important concerns of global agriculture. Amaranthus hybridus L. is a competitive weed for summer crops in South America.

The complex allosteric and redox regulation of the fumarate hydratase and malate dehydratase reactions of Arabidopsis thaliana Fumarase 1 and 2 gives clues for understanding the massive accumulation of fumarate.

Arabidopsis thaliana possesses two fumarase genes (FUM), AtFUM1 (At2g47510) encoding for the mitochondrial Krebs cycle-associated enzyme and AtFUM2 (At5g50950) for the cytosolic isoform required for fumarate massive accumulation. Here, the comprehensive biochemical studies of AtFUM1 and AtFUM2 shows that they are active enzymes with similar kinetic parameters but differential regulation. For both enzymes, fumarate hydratase (FH) activity is favored over the malate dehydratase (MD) activity; however, MD is the most regulated activity with several allosteric activators.

Allosteric substrate inhibition of Arabidopsis NAD-dependent malic enzyme 1 is released by fumarate.

Plant mitochondria can use L-malate and fumarate, which accumulate in large levels, as respiratory substrates. In part, this property is due to the presence of NAD-dependent malic enzymes (NAD-ME) with particular biochemical characteristics. Arabidopsis NAD-ME1 exhibits a non-hyperbolic behavior for the substrate L-malate, and its activity is strongly stimulated by fumarate.