SummaryTranscription factors regulate multiple aspects of plant growth and development. Here we report the identification and functional analysis of a plant-specific, novel transcription factor in Arabidopsis. We isolated a dominant, gain-of-function mutant that displays reduced lengths in all aerial organs including hypocotyl, rosette leaf, cauline leaf, inflorescence stem, floral organs and silique. Molecular cloning revealed that these phenotypes are caused by elevated expression of the Arabidopsis thaliana Ovate Family Protein 1 (AtOFP1). This mutant was designated as Atofp1-1D. We show that the altered morphology of Atofp1-1D mutant is caused by reduced cell length resulting from reduced cell elongation, and demonstrate that a mutant harboring a transposon insertion that disrupts the OVATE domain of AtOFP1 is indistinguishable from wild-type plants. Plants overexpressing other closely related AtOFP genes phenocopy plants overexpressing AtOFP1, implying a possible overlapping function among members of the AtOFP gene family. We found that AtOFP1 localizes in the nucleus, and that AtOFP1 functions as an active transcriptional repressor. Chromatin immunoprecipitation results indicated that AtGA20ox1, a gene encoding the key enzyme in GA biosynthesis, is a target gene regulated by AtOFP1. Consistent with this, exogenous gibberellic acid can partially restore defects in cell elongation in plants overexpressing AtOFP1, suggesting that such a reduced cell elongation is caused, in part, by the deficiency in gibberellin biosynthesis. Taken together, our results indicate that AtOFP1 is an active transcriptional repressor that has a role in regulating cell elongation in plants.

Mutants of Escherichia coli K-12 deficient in pyruvate oxidase were isolated from an aceEF (pyruvate dehydrogenase-deficient) strain by selection for a complete absence of growth on medium lacking acetate. Extracts of two of the mutants were shown to contain normal levels of pyruvate oxidase antigen, although the enzymatic activities of the extracts were reduced or absent. The poxB locus was mapped by using closely linked transposon insertions to min 18.7 of the E. coli linkage map between the cmlA and aroA loci, a location far removed from that of the regulatory gene, poxA.

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Ammonia nitrogen is one of the important pollutants in urban rainfall. Though iron ions and aluminum ions as a filler for plant retention system have a good effect on the removal of ammonia nitrogen, their adsorption characteristics was rarely studied. This paper uses different media (sand, iron powder, aluminum powder) with different pH values and ionic strengths in the Bioretention system to study the adsorption mechanism of ammonia nitrogen in an artificial rainwater. The result shows that Langmuir isothermal adsorption model is more in line with the ammonia nitrogen adsorption process, and the sand has the best adsorption capacity among three samples. Effect of pH values on adsorption kinetics is also studied.

Bioretentions can remarkably improve the rainwater quality. Though iron and aluminum as fillers in bioretentions can remove nitrate nitrogen, its adsorption mechanism is not clear yet and was rarely studied. This paper takes sand, iron powder and aluminum powder as the research objects to study the adsorption characteristics of nitrate nitrogen in the bioretention with different pH values and different ionic strength. The results show that aluminum powder has the highest the adsorption capacity. Langmuir adsorption isotherm equation and the quasi-secondary kinetic model are adopted to analyze the experimental data.