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Wang, Lijuan [1], Reiter, Wolf-Dieter [2].

Cloning and Characterization of D-Arabinose 5-Phosphate Isomerase in Arabidopsis.

The pectic polysaccharide rhamnogalacturonan II (RG-II) is required for plant growth, cell adhesion, reproductive tissue development and fertilization. RG-II has an α-1,4-linked homogalacturonan backbone, which is substituted with four structurally different oligosaccharide side chains designated A, B, C, and D. The C side chain contains 3-deoxy-D-manno-octulosonate (KDO) that is very rare in plants. A study in bacteria showed that arabinose 5-phosphate isomerase (API) is the first enzyme in the biosynthesis of bacterial KDO, which catalyzes the interconversion of D-ribulose 5-phospate (Ru5P) and D-arabinose 5-phosphate (A5P). An Arabidopsis thaliana ortholog (AtAPI) was cloned and expressed in E .coli. We found that the recombinant protein is stable for at least one month when stored at -80°C. The pH optimum of the enzyme is 7.4 and the temperature optimum is 40°C. The enzyme is specific for Ru5P and A5P. Kinetic studies are ongoing. To determine the effect of downregulating API activity in Arabidopsis, we introduced this gene into two different RNA interference (RNAi) constructs downstream of the CaMV 35S promoter and a dexamethasone-inducible promoter, respectively. Only a few slow-growing T1 transformants were found with the constitutive construct whereas transformants with the inducible construct were quite normal. Analysis of these transformants will help us to better understand the role of KDO for the structure and function of RG-II.


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1 - University of Connecticut, Molecular and Cell Biology, Torrey Life Sciences, Room 403, 75 North Eagleville Road, Unit 3125, Storrs, CT, 06269, United states
2 - University of Connecticut, Molecular and Cell Biology

Keywords:
KDO
arabinose 5-phosphate isomerase.

Presentation Type: Plant Biology Abstract
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P17032
Abstract ID:1556


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