Cloning of genes encoding for C-P lyase fromPseudomonas isolates PG2982 and GLC11: Identification of a cryptic allele on the chromosome ofP. aeruginosa

Agnes Rimando, a Pioneer in the Fate of Glyphosate and Its Primary Metabolite in Plants

Glyphosate is the most used herbicide on the planet because of its excellent efficacy on almost all weed species and due to the large-scale adoption of transgenic, glyphosate-resistant (GR) crops. Agnes Rimando became an expert in glyphosate analysis almost 20 years ago to support research on GR crop safety and on mechanisms of evolved glyphosate resistance by weeds. Her work was the first to show that the amount of glyphosate and its primary metabolite aminomethylphosphonic acid (AMPA) that accumulates in GR soybean seed from plants treated with approved glyphosate doses can approach their legal limits. However, she later found that only trace amounts of these compounds accumulate in the seed of GR maize treated with recommended glyphosate doses. She showed that GR canola, the only transgenic crop with a transgene encoding an enzyme for degradation of glyphosate, metabolizes glyphosate to AMPA very rapidly. Her work was instrumental in providing support for the view that "yellow flash" symptoms sometimes observed in field-grown GR soybeans are due to accumulation of enough AMPA to cause mild phytotoxicity. She did the chemical analyses in the only paper to survey the capacity of an array of plant species to metabolize glyphosate to AMPA. She found a wide range in this capacity, with grasses with little or no metabolism of glyphosate to AMPA and with legumes readily metabolizing glyphosate. Lastly, she found no evidence of enhanced degradation of glyphosate to be a mechanism of evolved resistance to glyphosate by two weed species but that it might be involved in natural tolerance to glyphosate of some weeds.

Carbon-Phosphorus Lyase-the State of the Art

Organophosphonates are molecules that contain a very chemically stable carbon-phosphorus (C-P) bond. Microorganisms can utilize phosphonates as potential source of crucial elements for their growth, as developed several pathways to metabolize these compounds. One among these pathways is catalyzed by C-P lyase complex, which has a broad substrate specifity; therefore, it has a wide application in degradation of herbicides deposited in the environment, such as glyphosate. This multi-enzyme system accurately recognized in Escherichia coli and genetic studies have demonstrated that it is encoded by phn operon containing 14 genes (phnC-phnP). The phn operon is a member of the Pho regulon induced by phosphate starvation. Ability to degradation of phosphonates is also found in other microorganisms, especially soil and marine bacteria, that have homologous genes to those in E. coli. Despite the existence of differences in structure and composition of phn gene cluster, each of these strains contains phnGHIJKLM genes necessary in the C-P bond cleavage mechanism. The review provides a detailed description and summary of achievements on the C-P lyase enzymatic pathway over the last 50 years.