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Molecular and cellular characterisation of AXR4 function: A key regulator of root auxin and nitrate responses

Reference	BB/C514958/1
Principal Investigator / Supervisor	Professor Malcolm Bennett
Co-Investigators / Co-Supervisors	Dr Ian Derek Kerr, Dr Ranjan Swarup
Institution	University of Nottingham
Department	Sch of Biosciences
Funding type	Research
Value (£)	254,973
Status	Completed
Type	Research Grant
Start date	01/03/2005
End date	29/02/2008
Duration	36 months

Abstract

The principle aim of the study will be to determine the molecular and cellular mechanism(s) that enable AXR4 to regulate both auxin and nitrate responses in roots. Our study is greatly facilitated by the AXR4 gene having recently been identified by Mark Estelle's laboratory in the US, prompting a close collaboration to characterise AXR4 function in Arabidopsis. The AXR4 sequence is predicted to encode a Type II membrane protein with a short N terminal sequence, a single transmembrane (TM) spanning domain and a large C terminal domain with a predicted a/b fold, which shares sequence similarity with acyl transferase enzymes. Insight into AXR4 comes from AUX1 localisation studies which reveal axr4 blocks the root auxin response by disrupting the trafficking of the putative auxin permease AUX1. We will perform a molecular and cellular characterisation of AUX1 function by:- Investigating how axr4 disrupts trafficking of the auxin permease AUX1 by adopting a series of molecular cell biology based approaches designed to identify the compartment(s) in which AUX1 export is arrested and that AXR4 is normally localised. Investigate whether axr4 also blocks the lateral root nitrate response by disrupting trafficking of selected nitrate transporters, or represents a novel component of (or required by) the nitrate response pathway. Probe AXR4 function using (A) FRET and cross linking approaches to assess whether AXR4 functions as an export receptor that is required to interact with AUX1 during vesicular trafficking and (B) employ proteomics to test whether AUX1 trafficking requires post-translational modification by AXR4. Reconstitute a functional auxin influx carrier in a heterologous system by co-expressing AUX1 and AXR4. Synthesise the results from our molecular, cellular and whole plant studies to create a model for the regulation of the auxin and nitrate responses in roots by AXR4.

Summary

unavailable

Committee	Closed Committee - Plant & Microbial Sciences (PMS)
Research Topics	X – not assigned to a current Research Topic
Research Priority	X – Research Priority information not available
Research Initiative	X - not in an Initiative
Funding Scheme	X – not Funded via a specific Funding Scheme

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