Protoporphyrinogen oxidase (Protox) catalyses the oxidation of protoporphyrinogen IX to protoporphyrin IX during the synthesis of tetrapyrrole molecules. Protox is encoded by the hemY gene in eukaryotes and by the hemG gene in many γ-proteobacteria, including Escherichia coli. It has been suggested that other bacteria possess a yet unidentified type of Protox. To identify a unique bacterial gene encoding Protox, we first introduced the Arabidopsis hemY gene into the genome of the cyanobacterium, Synechocystis sp. PCC6803. We subsequently mutagenized the cells by transposon tagging and screened the tagged lines for mutants that were sensitive to acifluorfen, which is a specific inhibitor of the hemY-type Protox. Several cell lines containing the tagged slr1790 locus exhibited acifluorfen sensitivity. The slr1790 gene encodes a putative membrane-spanning protein that is distantly related to the M subunit of NADH dehydrogenase complex I. We attempted to disrupt this gene in the wild-type background of Synechocystis, but we were only able to obtain heteroplasmic disruptants. These cells accumulated a substantial amount of protoporphyrin IX, suggesting that the slr1790 gene is essential for growth and Protox activity of cells. We found that most cyanobacteria and many other bacteria possess slr1790 homologs. We overexpressed an slr1790 homolog of Rhodobacter sphaeroides in Escherichia coli and found that this recombinant protein possesses Protox activity in vitro. These results collectively demonstrate that slr1790 encodes a unique Protox enzyme and we propose naming the slr1790 gene “hemJ.

No abstract

No abstract

Postemergence applications of BAS 9052 OH, {2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one}, at 0.25 and 0.5 kg ai/ha were made to 27 temperate and 28 tropical species ofGramineae. Annual bluegrass (Poa annuaL. ♯3POAAN) and rattail fescue (Festuca myurosL. ♯ VLPMY) were resistant to these rates of BAS 9052 OH. Five species of fescue and three species of bluegrass received postemergence applications of BAS 9052 OH at rates of 0.1 to 6.4 kg ai/ha. The germination of seeds and the subsequent growth of the seedlings of these species as influenced by various concentrations of BAS 9052 OH were also studied. Meadow fescue (Festuca pratensisHuds. ♯ FESPR), tall fescue (Festuca arundinaceaSchreb. ♯ FESAR), Kentucky bluegrass (Poa pratensisL. ♯ POAPR), and rough-stalked meadowgrass (Poa trivialisL. ♯ POATR) were most susceptible; annual bluegrass was somewhat less resistant; hard fescue (Festuca longifoliaThuill) was resistant; red fescue (Festuca rubraL. ♯ FESRU) and rattail fescue were very resistant.

The herbicidal action of sethoxydim {2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one} on corn (Zea maysL. ‘Goldencrossbantam’) was investigated in preemergence and postemergence experiments and hydroponic culture. Soil-applied sethoxydim did not inhibit corn germination. Leaves failed to emerge through the coleoptile with a high herbicide rate (1.6 kg ai/ha), but chlorotic leaves emerged at a lower rate (0.8 kg ai/ha). Growth of corn seedlings treated with a foliar application of 0.2 kg ai/ha was inhibited within 1 day after treatment, but at a lower application rate (0.05 kg ai/ha) growth continued with chlorotic zones on newly expanding leaves. Over the concentration range 3 × 10-5to 1 × 10-6M, sethoxydim inhibited the growth of primary roots of corn in hydroponic culture within 24 h. Cytological investigation showed that sethoxydim inhibited cell division but did not interfere with mitosis.