Honours supervisors and projects

Professor David Smyth

Molecular genetics of flower development in Arabidopsis

Phone: 9905 3861
E-mail: david.smyth@sci.monash.edu.au

Genes controlling development can be identified by the disruptions they cause when in mutant form.  By using this approach in the model plant Arabidopsis thaliana we are now gaining a fuller understanding of how all plants grow and differentiate.  The recent completion of sequencing of the Arabidopsis genome has provided us with the full catalog of 25,489 genes present in this species.

In the following projects, several different transcription factor genes are being studied to find out exactly how they generate the floral organs of the mature plant.  The concepts, methods and interpretations used here are applied universally in molecular genetics, and so the projects offer a rigorous entry to research in this general field, be it green (plant) or red (animal) in flavour.  Many techniques of molecular genetics are used, including cloning, sequencing, transformation and localisation of gene expression using reporter genes and RT PCR.

Projects will be available in two areas:

1. One project area will involve the PETAL LOSS perianth development gene [see Brewer P.B. et al. (2004) PETAL LOSS, a trihelix transcription factor gene, regulates perianth architecture in the Arabidopsis flower. Development 131, 4035-4045].  This gene controls sepal separation, likely by inhibiting growth between them.  Petal development is also supported because the number is reduced in petal loss mutants.  It encodes a trihelix transcription factor and is one of a family of 28 genes in Arabidopsis.

As an example of projects in this area, the expression pattern of a recently duplicated relative of the PETAL LOSS gene with some overlap in function (SISTER OF PETAL LOSS) could be mapped to individual cells in developing Arabidopsis flowers using confocal microscopy of transgenic plants expressing the PETAL LOSS protein translationally fused with green fluorescent protein (GFP). Another example is a project to follow up candidate proteins that may interact with the PETAL LOSS protein (indicated using yeast two hybrid screening approaches). This would involve such techniques as co-immunoprecipitation of the two proteins, and bi-molecular fluorescence complementation (testing their interaction to see if they bring together two halves of a fluorecent protein to which they have been fused).

2. The other project area will involve the SPATULA carpel development gene. Within the female reproductive organs of the flower this gene controls the development of the placental tissues (where ovules arise), the pollen tract, and fruit development [see Heisler, M.G.B., Atkinson, A., Bylstra, Y.H., Walsh, R. and Smyth, D.R. (2001) SPATULA, a gene that controls development of carpel margin tissues in Arabidopsis, encodes a bHLH protein. Development 128, 1089-1098]. SPATULA is a transcription factor of the bHLH class that was first discovered in mammals as the cMYC oncogene.  In Arabidopsis the bHLH family has 162 members.

As an example of projects in this area, the expression pattern of the tomato gene equivalent to SPATULA could be mapped in the developing tomato carpels and fruit using Northerns, RT-PCR and/or in situ hybridization techniques.  By comparing where the orthologous gene is expressed in Arabidopsis and tomato (which have very different carpel and fruit developmental patterns), conclusions about its general function in fruit development may be drawn.

Recent Honours students working in this project area have gained employment as follows: Michael Groszmann, CSIRO Plant Industry; Aydin Kilinc and Edwin Lampugnani, PhD students, Arabidopsis development, Monash University; Ben Kolevski, Research Assistant, Drosophila development, Cancer UK, London; Yasmin Bylstra, Research Assistant, Biotechnology, Oxford University; and Georgia Stamaratis, Research Assistant, Peter MacCallum Cancer Research Institute.