Exploration of seasonal change of thermal tolerance and proteins in three Australian desert plants

Milner KV1, Van Sluyter SC2, French K3, Valenzuela SM1 and Leigh A1

  1. School of Life Sciences, University of Technology Sydney, NSW.
  2. Department of Biological Sciences, Macquarie University, NSW.
  3. School of Biological Sciences, University of Wollongong, NSW.

Plants in Australia’s southern semi-arid zone experience a wide range of temperatures (4.6 °C mean minimum in winter and 34.2 °C mean maximum in summer) and show plasticity in their thermal tolerance thresholds with the ability to shift photosynthetic thresholds upwards 5 °C from winter to summer. An understanding of how they are able to make these threshold adjustments is required. With a new absolute protein quantification method, we have the opportunity to identify protein changes that may explain this ability. A selection of three species from different functional groups were used to explore species differences. Acacia ligulata a widespread nitrogen-fixing shrub, Myoporum montanum a widespread shrub and Solanum oligacanthum a perennial herb or subshrub were grown in an experimental garden in semi-arid South Australia. Sampling occurred in winter, spring and summer where the assessment of thermal tolerance included a series of temperature assays for photosynthetic thermal tolerance (T50using chlorophyll fluorescence) and membrane stability (Tcrit using electrical conductivity). Protein identification and absolute quantitation used a new extraction method and QconCAT-spiked samples coupled with MS/MS and SWATH acquisition. All species were able to adjust upwardly thermal tolerance thresholds from cooler to warmer months. However, the changes seen in proteins of interest differed depending on plant species. This early exploration of temporal protein changes provides insight into acclimatisation mechanisms Australian desert plants use to cope in a difficult climate.