Natural products containing phosphorus-carbon bonds have found widespread use in medicine and agriculture1. One such compound, phosphinothricin tripeptide (PTT), contains the unusual amino acid phosphinothricin (PT) attached to two alanine residues (Fig. 1). Synthetic PT (glufosinate) is a component of two top-selling herbicides (Basta® and Liberty®), and is widely used with resistant transgenic crops including corn, cotton and canola. Recent genetic and biochemical studies showed that during PTT biosynthesis 2-hydroxyethylphosphonate (HEP) is converted to hydroxymethylphosphonate (HMP) (Fig. 1)2. Reported here are the in vitro reconstitution of this unprecedented C(sp3)-C(sp3) bond cleavage reaction and X-ray crystal structures of the enzyme. The protein is a mononuclear non-heme iron(II)-dependent dioxygenase that converts HEP to HMP and formate. In contrast to most other members of this family, the oxidative consumption of HEP does not require additional cofactors or the input of exogenous electrons. The current study expands the scope of reactions catalyzed by the 2-His-1-carboxylate mononuclear non-heme iron family of enzymes.

Hydroxyethylphosphonate dioxygenase (HEPD) catalyzes the O2-dependent cleavage of the carbon−carbon bond of 2-hydroxyethylphosphonate (2-HEP) to afford hydroxymethylphosphonate (HMP) and formate without input of electrons or use of any organic cofactors. Two mechanisms have been proposed to account for this reaction. One involves initial hydroxylation of substrate to an acetal intermediate and its subsequent attack onto an Fe(IV)-oxo species. The second mechanism features initial hydroperoxylation of substrate followed by a Criegee rearrangement. To distinguish between the two mechanisms, substrate analogues were synthesized and presented to the enzyme. Hydroxymethylphosphonate was converted into phosphate and formate, and 1-hydroxyethylphosphonate was converted to acetylphosphate, which is an inhibitor of the enzyme. These results provide strong support for a Criegee rearrangement with a phosphorus-based migrating group and require that the O−O bond of molecular oxygen is not cleaved prior to substrate activation. (2R)-Hydroxypropylphosphonate partitioned between conversion to 2-oxopropylphosphonate and hydroxymethylphosphonate, with the latter in turn converted to phosphate and formate. Collectively, these results support a mechanism that proceeds by hydroperoxylation followed by a Criegee rearrangement.

Stereochemical investigations have shown that the conversion of 2-hydroxyethylphosphonate to hydroxymethylphosphonate by the enzyme HEPD involves removal of the pro-S hydrogen at C2 and, surprisingly, the loss of stereochemical information at C1. As a result, the mechanisms previously proposed for HEPD must be re-evaluated.

Third time's the charm! The structure of the phosphonate antibiotic A53868, first isolated in 1983 from Streptomyces luridus, has proven quite elusive. Originally reported as 1 and later revised to 2, the actual structure of the compound is the unusual dehydro aminophosphonic acid 3.

Transgene stacking in trait development process through genetic engineering is becoming complex with increased number of desired traits and multiple modes of action for each trait. We demonstrate here a novel gene stacking strategy by combining bidirectional promoter (BDP) and bicistronic approaches to drive coordinated expression of multi-genes in corn. A unidirectional promoter, Ubiquitin-1 (ZMUbi1), from Zea mays was first converted into a synthetic BDP, such that a single promoter can direct the expression of two genes from each end of the promoter. The BDP system was then combined with a bicistronic organization of genes at both ends of the promoter by using a Thosea asigna virus 2A auto-cleaving domain. With this gene stacking configuration, we have successfully obtained expression in transgenic corn of four transgenes; three transgenes conferring insect (cry34Ab1 and cry35Ab1) and herbicide (aad1) resistance, and a phiyfp reporter gene using a single ZMUbi1 bidirectional promoter. Gene expression analyses of transgenic corn plants confirmed better coordinated expression of the four genes compared to constructs driving each gene by independent unidirectional ZmUbi1 promoter. To our knowledge, this is the first report that demonstrates application of a single promoter for co-regulation of multiple genes in a crop plant. This stacking technology would be useful for engineering metabolic pathways both for basic and applied research.

Im dritten Anlauf: Die Struktur des antibiotischen Phosphonats A53868, das erstmals 1983 aus Streptomyces luridus isoliert wurde, konnte lange nicht aufgeklärt werden. Zunächst wurde 1 postuliert, später dann 2, und nun zeigte sich, dass es sich bei der Verbindung um die ungewöhnliche Dehydroaminophosphonsäure 3 handelt.

Antibiotics U 1200Reassignment of the Structure of the Antibiotic A53868 Reveals an Unusual Amino Dehydrophosphonic Acid. -The structure of the antibiotic A53868 is revised as (I) and confirmed by synthesis. -(WHITTECK, J. T.; NI, W.; GRIFFIN, B. M.; ELIOT, A. C.; THOMAS, P. M.; KELLEHER, N. L.; METCALF, W. W.; VAN DER DONK*, W. A.; Angew. Chem., Int. Ed. 46 (2007) 47, 9089-9092; Dep. Chem., Univ. Ill., Urbana, IL 61801, USA; Eng.) -Mischke 14-222

Pink-pigmented facultative methylotrophs (PPFMs) in the genera Methylobacterium and Methylorubrum are highly abundant members of the plant microbiome that have indicated benefits through application to food crops. Several inherent characteristics make PPFMs difficult to successfully ferment and to process into stable forms for production and distribution into agricultural channels. This paper focuses on some of the ways in which NewLeaf Symbiotics has utilized a deep expertise in PPFMs to successfully manufacture and apply them. It details some ways in which formulations can enable the successful application of PPFMs by adding functional materials such as surfactants and film-forming polymers. This paper discusses a case study of using in-furrow and seed treatment application methods in the corn market.