Ananieva, Elitsa , Erickson, Les , Ely, Amanda , Robinson, Jamille , Burnette, Ryan , Gillaspy, Glenda E. .
The Function of Myo-Inositol Polyphosphate 5-Phosphatase Genes in Plants.
In eukaryotes, various inositol phosphates function in signaling pathways as second messengers. One such second messenger, Ins(1,4,5)P3, signals to increase cellular calcium concentration which leads to downstream physiological responses. In plants, the regulation of Ins(1,4,5)P3 levels has been shown to be crucial for responses to ABA, salt, cold and gravity. Myo-inositol polyphosphate 5-phosphatases (EC 18.104.22.168; 5PTases) regulate the level of Ins(1,4,5)P3, and other inositol-containing molecules, by hydrolyzing the 5-phosphate from the inositol ring. In the model plant Arabidopsis thaliana, there are 15 genes that encode enzymes called At5PTases. All eukaryotes contain 5PTase enzymes, however plants are unique in that some 5PTase genes encode for 5PTase enzymes containing WD40 repeat sequences at their N-termini. To determine the function of plant 5PTase enzymes during signaling, we have identified mutants for several of the At5PTases. At5ptase1 and At5ptase2 seedlings undergo greater hypocotyl elongation when grown in the dark, and this increase in growth is accompanied by an increase in Ins(1,4,5)P3 levels. In addition, At5ptase1 and At5ptase2 seeds are hypersensitive to ABA in seed germination experiments, supporting the idea that second messenger Ins(1,4,5)P3 is important in ABA signaling. In contrast, a mutant in a WD40 repeat-containing 5PTase (At5PTase13), is insensitive to ABA and glucose in a seed germination assay. Consistent with the decreased sensitivity to ABA, the endogenous Ins(1,4,5)P3 level is reduced in At5ptase13 mutants upon exposure to a 6% glucose stress. To determine if the WD40 region of At5PTase13 is part of a protein complex, we used the yeast two hybrid assay and identified the Arabidopsis SNF1-like kinase (SnRK1.1) as an interacting protein. These data suggest that 5PTases function in different ways to impact plant signaling.
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1 - Virginia Tech, Biochemistry
2 - Salisbury University, Biology
3 - V, Biochemistry, 542 Latham Hall, Blacksburg, VA, 24061, USA
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM