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Abstract Detail

Cell biology

Sullivan, Victoria [1], Lyzenga, Wendy [2], Liu, Hongxia [3], Stone, Sophia [4].

The kinase activity of CIPK26 influences is own stability and the stability of KEG, an E3 ligase.

The ubiquitin proteasome system (UPS) controls a multitude of cellular processes through the selective degradation of proteins. The E3 ubiquitin ligases of the UPS enable the pathway to achieve specificity through identifying targets for ubiquitination and mediating the attachment of ubiquitin molecules onto the target proteins. During growth and development, E3 ligases in plants maintain normal developmental processes mediating hormone signaling, responses to biotic and abiotic stimuli. Keep on Going (KEG), a multidomain RING-type E3 ligase, has critical functions throughout plant development. KEG is crucial in Arabidopsis seedling establishment and growth; KEG knockout lines undergo growth arrest following germination. It has been previously demonstrated that KEG acts as a negative regulator of abscisic acid (ABA) signaling through the proteasomal-dependent degradation of the ABA-responsive transcription factors Abscisic Acid Insensitive 5 (ABI5), ABF1 and ABF3, members of the bZIP subfamily of transcription factors. Previous work has also implicated KEG in targeting Calcineurin B-like Interacting Protein Kinase 26 (CIPK26), a positive regulator of the ABA signaling network, for degradation. However, KEG is also capable of self-regulation through self-ubiquitination in the presence of ABA. With this work we demonstrate that CIPK26 is capable of phosphorylating KEG in vitro, and present evidence suggesting a role for the kinase activity of CIPK26 in promoting the degradation of KEG. We aim to specifically demonstrate that the presence of constitutively active CIPK26 promotes KEG degradation, as compared to a kinase dead version of CIPK26, which does not. Previous research has shown that CIPK26 is degraded by the 26S proteasome, here we show that the kinase activity of CIPK26 affects its stability; constitutively active CIPK26 is more stable than wild type and kinase dead versions. We propose a model where, in the presence of ABA, an activated CIPK26 is stable because it phosphorylates KEG to promote KEG degradation.

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1 - Dalhousie University , Biology , 5078 Life Science Centre, Department of Biology, , Dalhousie University, 1355 Oxford St., Halifax, NS, B3H 4J1, Canada
2 - Saskatoon Research Center Plant Molecular, Plant Molecular, Agriculture and Agri-Food Canada, Saskatoon Research Center, Saskatoon, SK, Canada
3 - Dalhousie University , Department of Physiology and Biophysics, Sir Charles Tupper Medical Building, 6299 South St, Halifax, NS, B3H 4R2, Cana
4 - Dalhousie University , Biology, 5132 Life Science Centre, Department of Biology,, Dalhousie University, 1355 Oxford St., Halifax, NS, B3H 4J1, Canada

none specified

Presentation Type: Poster:Posters for Topics
Session: P
Location: Hall D/The Shaw Conference Centre
Date: Monday, July 27th, 2015
Time: 5:30 PM
Number: PCL009
Abstract ID:1078
Candidate for Awards:CSPB President's Award for Best Student Presentation

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