Format: ORAL

Sarah J. McInnes1, Ryan Tangney1,2, Mark K.J. Ooi1

1 Centre for Ecosystem Science, School of Biological Earth and Environmental Sciences, University of New South Wales, Kensington, NSW, Australia 2 Kings Park Science, Biodiversity, and Conservation Science, Department of Biodiversity, Conservation, and Attractions, Kings Park, WA, Australia

Fire is a key ecological driver and many plant species have evolved to persist in fire-prone regions. During fire, different life stages of plants, including seeds, are exposed to temperatures as high as 150C, yet are able to persist. This suggests that molecular processes within the seed provide a mechanism for survival. In this study, we sought to understand the molecular aspects of seed persistence during the extreme heat of wildfire. We focused on Acacia pycnantha, a species native to fire-prone southeastern Australia, which has heat-triggered germination cues and recruits prolifically post-fire, and therefore has a life-cycle tightly linked with fire. We explored the physiology of Acacia pycantha under heat stress through pairing molecular biology with traditional seed biology methods. To examine seed survival under extreme heat, we subjected seeds to 10-minute heat shock treatments ranging from 25C to 150C, and subsequently conducted germination trials. Seed water-content isotherms were constructed to determine seed hydration profiles post-heat stress, and mRNA extracted to create gene expression profiles. Gene expression was examined at different seed hydration levels after heating at the optimum temperature (92 C) for dormancy-break to understand the mechanisms that support persistence during the extreme heat from fires. We report on the genes, and thus mechanisms, that are expressed during extreme temperatures and the role these may have in enabling species persistence. This work is essential for ecological understanding and informing conservation efforts as fire regimes shift under a changing climate.