Associate Professor Steve McKechnie
Centre for Environmental Stress and Adaptation Research
Climatic adaptation in Drosophila
Telephone: 9905 3863
Email: stephen.mckechnie@sci.monash.edu.au
Understanding the biological and genetic basis of climatic adaptation is the focus in our laboratory. The ability of cells and tissues to cope with the thermal stress is a major component of climatic adaptation and the molecular and cellular mechanisms involved are little understood. These mechanisms evolved early in the history of life and evidence suggests they are highly conserved across all organisms. By elucidating these processes in Drosophila we can identify new enabling genes, discover new mechanisms, and provide a valuable model for understanding these processes in all species. We are dissecting the physiological and molecular genetics of variation in thermal stress resistance that occurs in D. melanogaster. In this species opposing latitudinal clines occur along the eastern coastline of Australia in tolerance to both heat and cold. In these 2009 honours projects we aim to elucidate a new mechanism and understand the functional role of a key gene. The projects will also provide an understanding of how genetic variation in structured in this species, allowing it to expand its range and successfully occupy a wide range of climatic ecologies. The projects provide training and experience with experimental design and analysis, and with molecular-genetic, biochemical and physiological tools that are widely applicable in medical and agricultural research.
Accumulated evidence suggests that the rates of protein synthesis can be a factor that determines thermal tolerance. Further, the hsr-omega RNA gene, that we hypothesise to be involved in controlling rates of protein synthesis in Drosophila, shows interesting genotype variation and variation in expression that relates to thermal tolerance variation, both to heat tolerance AND cold tolerance variation. Furthermore, we believe that this gene is centrally involved in a least two molecular mechanisms that facilitate control of protein synthesis with concomitant affects on thermal tolerance. The objectives of one or more Honours projects in my laboratory will be to provide evidence to both support this hypothesis and to elucidate the cellular mechanisms involved. Experimental approaches will likely include an in vitro tissue assay that quantifies the rate of incorporation of labelled amino acids into newly synthesised proteins, before and after heat-shock, with comparisons between strains that vary in expression of the hsr-omega gene. The hsr-omega RNA gene will need to be genotyped and assayed for variation in expression across strains (using real-time PCR). A new qPCR assay may need to be developed for expedient genotype determination of common allelic repeat variation. These alleles vary in the number of tandem 280bp DNA repeats that occur at the 5’ end of the gene, and repeat number varies climatically along a latitudinal gradient. Also important will be the characterisation of both heat and cold tolerance variation among a set of wild-type strains, as well as between wild-type and hsr-omega mutant strains. Characterisation of strains for thermal tolerance may include pre-culture under different thermal environments. Characterising variation in expression of hsr-omega over time following different thermal stress treatments, in wild-type and hsr-omega mutant strains, will also be important. Projects can also be ‘customised’ to suit interests of particular students, including field-based projects (investigating thermal stress ecology), and genotype-stress tolerance association studies using controlled laboratory simulations of thermal stresses that are experienced in the field.
