School of Biological Sciences
University of Sydney
The Macleay Building A12
Sydney, NSW 2006
Ph: +612 90367590
PhD in Science (2008)
Dept. Medical & Molecular Biosciences
University of Technology, Sydney
Research conducted at CSIRO Molecular & Health Technologies
Thesis: Molecular cloning and characterisation of a new insect ecdysone receptor from the green vegetable bug, Nezara viridula.
Bachelor in Biological and Biomedical Sciences (1998) with First Class Honors (1999) and University Medal.
Honours research conducted at CSIRO Molecular & Health Technologies
Thesis: Expression, purification and properties of the ligand binding domain of the nuclear receptor protein, Ultraspiracle.
Being intrigued by the phase change of solitarious grasshoppers to gregarious, swarming locusts, I joined Greg Sword’s group, in close collaboration with that of Steve Simpson, to investigate the molecular biology underlying these reversible and inheritable behavioral states.
As part of my PhD project, which I completed at CSRIO Molecular and Health Technologies, I cloned the first heteropteran ecdysone receptor from the agricultural pest, Nezara viridula. The ecdysone receptor is a heterodimeric nuclear receptor, which binds the steroid hormone, 20-hydroxyecdysone and is central to the growth and reproduction of most known arthropods.
I constructed a N. viridula cDNA library which I screened with radioactively labeled probes I had synthesised. This allowed me to identify and clone the two subunits of the ecdysone receptor, EcR and USP. I found two splice variants of the ligand binding region of EcR. To test the functional significance of these variants, I co-expressed the ligand binding region of both EcR variants with USP using recombinant baculoviruses and then affinity purified each recombinant heterodimer. My research was the first to characterise the binding of a pentamomorphan ecdysone receptor to its proposed natural ligand, makisterone A, as opposed to 20-hydroxyecdysone.
My current research is aimed towards identifying genes which are differentially expressed between the solitary and gregarious phases of the Australian Plague Locust, Chortoicetes terminifera. This project is not only of Australian economical significance but also examines an ideal candidate for differential gene expression studies of locust behavioural phase change. This is because C. terminifera displays behavioural differences in between the solitary and gregarious phases but no striking difference in appearance as can be seen in related species, Locusta migratoria and Schistocerca gregaria.
In my attempt to achieve maximal transcriptome coverage, I will be using two techniques to look for differentially expressed genes, namely cDNA subtractive hybridisation and cDNA-AFLP. Both methods require no prior sequence information. cDNA-AFLP in particular offers a sensitive and robust method by which even different levels of gene expression can be investigated. I am also considering a proteomic approach using a combination of 2D electrophoresis and MALDI-TOF.
I have begun preliminary epigenetic studies in search of a genetic basis by which the behavioural state of the mother is inherited by her offspring. I am working with PhD student Katie Robinson in seeking answers to this very exciting question!
Graham LD, Johnson WM, Tohidi-Esfahani D, Pawlak-Skrzecz A, Bliese M, Lovrecz
GO, Lu L, Howell L, Hannan GN & Hill RJ (in press), 'Ecdysone receptors of pest
insects – molecular cloning, characterisation, and a ligand binding domain-based
fluorescence polarisation screen', in G. Smagghe (ed.), Ecdysone, Structures and
Functions, Springer pp. 445-472.
Hannan GN, Graham LD, Pawlak A, Noyce L, Tohidi-Esfahani D, Pollard M, Howell L,
Lovrecz G, Lu L, Carmichael J, Pilling P, Johnson WM, Bliese M, Lawrence MC, Hill
RJ (2006); Ecdysone receptor function and structure. Journal of Insect Science 7:13.
Hannan GN, Graham LD, Pawlak A, Noyce L, Eaton R, Tohidi-Esfahani D, Lovrecz G,
Peck G, Lu L, Lou C, Hill RJ (2002); Cloning and comparative characterisation of ecdysone receptors from five insect species spanning three orders. Journal of Insect Science, 2:16.
Tohidi-Esfahani, D., Hannan, G.N., Graham, L.D. & Hill , R.J. 2007, Nezara viridula Ecdysone Receptor, no US 2007/673456A, U.S.A.
Hill , R.J., Hannan, G.N., Graham, L.D. & Tohidi-Esfahani, D. 2007, Nezara viridula Ecdysone Receptor, no AU2007200540A, Australia