NSF Award
2419773
High-altitude organisms experience unique physiological challenges resulting from low atmospheric O2. However, responses can vary from mild to severe depending on how long species have been exposed to such environments. This is because the time required to acclimatize or adapt can vary from thousands to millions of years. Particularly affected by low O2 are mitochondria, the powerhouses of the cell because they play a central role in energy production via oxidative phosphorylation, where adenosine triphosphate (ATP) is generated and then used for everything ranging from ion transport to muscle contraction, nerve impulse propagation, substrate phosphorylation, and chemical synthesis. Here, two key hypotheses will be tested: (1) that in high-altitude species exposed to hypoxia longer, the rate of mitochondrial respiration has declined to match O2 supply, and that efficiency has increased to maximize the energy, ATP, produced per unit O2 consumed; and (2) that high-altitude populations will have augmented antioxidant defenses to limit reactive oxygen species, to which high-altitude populations may be especially vulnerable. This will be done using high-resolution respirometry of isolated mitochondria across waterbirds in the high Andes, and in collaboration with partners with expertise in biochemistry and physiology. Fundamental questions will be answered about the tempo by which animals evolve in extreme environments that also challenge >80 million humans living at high altitude. Broader impacts will include training of graduate and undergraduate students, development of a K-8 specimen-based science program in a rural elementary school, and enhancement of undergraduate courses in the U.S. and an internationally-recognized workshop. <br/><br/>High-altitude (HA) hypoxia creates unique physiological challenges that vary with the evolutionary time organisms have been exposed to these low O2 environments. In mountains such as the Andes, this can range from thousands to millions of years. Particularly affected by low O2 are mitochondria, because they play a central role in energy production via oxidative phosphorylation, where ATP molecules are generated at the site of O2 consumption and then used for everything ranging from ion transport to muscle contraction, nerve impulse propagation, substrate phosphorylation, and chemical synthesis. Two key hypotheses will be tested: (1) that in HA species exposed to hypoxia longer, rates of mitochondrial respiration have declined to match O2 supply, and that mitochondrial efficiency has increased to maximize the energy, ATP, produced per unit of O2 consumed; and (2) that HA populations will have augmented antioxidant defense capacities to limit production of reactive oxygen species (ROS), to which HA populations may be especially vulnerable. This will be done using high-resolution respirometry of isolated mitochondria across 14 different waterbird families. The study will answer fundamental questions about how animals have evolved to survive in hypoxia across longer and shorter evolutionary time scales.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
