Characterization and plant expression of glyphosate-tolerant enolpyruvylshikimate phosphate synthase

Abstract BACKGROUND: Glyphosate tolerance is a dominant trait in modern biotech crops. RESULTS: A gene encoding a glyphosate-tolerant EPSP synthase (aroA 1398 ) from bacterial strain ATX1398 was cloned and characterized. The protein is initiated at a GTG translational start codon to produce a protein that provides robust glyphosate resistance in Escherichia coli (Mig) Cast & Chalm. The aroA 1398 protein was expressed and purified from E. coli, and key kinetic values were determined (K i = 161 µM; K m (PEP) = 11.3 µM; k cat = 28.3 s −1 ). The full-length enzyme is 800-fold more resistant to glyphosate than the maize EPSP synthase while retaining high affinity for the substrate phosphoenol pyruvate. To evaluate further the potential of aroA 1398 , transgenic maize events expressing the aroA 1398 protein were generated. T 0 plants were screened for tolerance to glyphosate sprays at 1.3× commercial spray rates, and T 1 plants were selected that completely resisted glyphosate sprays at 1×, 2× and 4× recommended spray rates in field trials. CONCLUSION: These data suggest that aroA 1398 is a suitable candidate for conferring glyphosate tolerance in transgenic crop plants

Improved Histograms for Selectivity Estimation of Range Predicates

Many commercial database systems maintain histograms to summarize the contents of relations and permit efficient estimation of query result sizes and access plan costs. Although several types of histograms have been proposed in the past, there has never been a systematic study of all histogram aspects, the available choices for each aspect, and the impact of such choices on histogram effectiveness. In this paper, we provide a taxonomy of histograms that captures all previously proposed histogram types and indicates many new possibilities. We introduce novel choices for several of the taxonomy dimensions, and derive new histogram types by combining choices in effective ways. We also show how sampling techniques can be used to reduce the cost of histogram construction. Finally, we present results from an empirical study of the proposed histogram types used in selectivity estimation of range predicates and identify the histogram types that have the best overall performance. 1 Introduction..

XTABLES: Bridging

This paper describes the design and implementation of the XTABLES middleware system, which we believe achieves this goal. In particular, XTABLES provides a general framework to create XML views of relational data, query XML views, and store and query XML documents using a relational database system. Some of the novel features of the XTABLES architecture are that it (1) provides users with a single XML query language for creating and querying XML views of relational data, (2) executes queries efficiently by pushing most computation down to the relational database engine, (3) allows users to query seamlessly over relational data and meta-data, and (4) allows users to write queries that span XML documents and XML views of relational dat