A research team of Australian and US scientists that is tracing the evolutionary origin of a drug-like protein ring found in sunflowers have discovered a diverse, 18-million-year-old group of buried proteins in daisy seeds.
Researchers at The University of Western Australia, working with academics from The University of Queensland, CSIRO, La Trobe University, The University of Tennessee and The University of Texas have unearthed a new family of seed proteins that provide an explanation of how a protein could appear from scratch’ – a process called “de novo protein evolution.”
Associate Professor Joshua Mylne, an ARC Future Fellow in UWA’s School of Chemistry and Biochemistry and ARC Centre of Excellence in Plant Energy Biology, led the team of Australian and US scientists in the study “Evolutionary origins of a bioactive peptide buried within preproalbumin,” supported by the Australian Research Council, that revealed this new family of proteins. Dr. Mylne notes in a UWA release that the researchers had used new genes to find the corresponding proteins in the seeds.
“This led to the discovery of a rapidly evolving family of tiny proteins that are super-stable and related to a protein discovered first in sunflowers and demonstrated subsequently to have potential as a drug for cancer,” Dr. Mylne says. “Although this work is of interest to researchers by providing an understanding of how new proteins can evolve from scratch, it also provides a toolbox of peptides that drug designers can use to stabilize drugs.”
The study paper, published in the international journal Plant Cell, is titled “Evolutionary Origins of a Bioactive Peptide Buried within Preproalbumin” (Plant Cell 2014 tpc.114.123620; First Published on March 28, 2014) is co-authored by Alysha G. Elliott, Christina Delay, Huanl Liu, Zaiyang Phua, K. Johan Rosengren, Aurlie H. Benfield, Jose L. Panerod, Michelle L. Colgrave, Achala S. Jayasen, Kerry M. Dunse, Marilyn A. Anderson, Edward E. Schilling, Daniel Ortiz-Barrientos, David J. Craik and Joshua S. Mylne, variously of The University of Queensland, Australia; the University of Texas at Austin; eCSIRO Animal, Food, and Health Sciences at St Lucia, Australia; The University of Western Australia at Perth; La Trobe University at Melbourne, Australia; and the University of Tennessee.
Lead author Dr. Alysha Gai Elliott of the University of Queensland comments that the team discovered a new family of seed proteins that they predict would be found in as many 4,700 species of daisy. Dr’ Elliott’s Ph.D. thesis at The Institute for Molecular Bioscience, The University of Queensland is “A new class of daisy seed peptides” (2013).
The Plant Cell paper’s coauthors describe how a sunflower gene called PawS1 that makes two proteins (a seed storage protein plus a small protein that blocks digestive enzymes) actually evolved more than 18 million years ago. Over that long interval, the PawS1 genes have evolved an interesting family of protein rings that differ in sequence and structure. The coauthors note that the de novo evolution of proteins is now considered a frequented route for biological innovation, but the genetic and biochemical processes that lead to each newly created protein are often poorly documented.
The researchers say the common sunflower (Helianthus annuus) contains the unusual gene PawS1 (Preproalbumin with SFTI-1) that encodes a precursor for seed storage albumin; however, in a region usually discarded during albumin maturation, its sequence is matured into SFTI-1, a protease-inhibiting cyclic peptide with a motif homologous to unrelated inhibitors from legumes, cereals, and frogs.
To understand how PawS1 acquired this additional peptide with novel biochemical functionality, the scientists cloned PawS1 genes, revealing that this dual destiny is over 18 million years old. This new family of mostly backbone-cyclic peptides is structurally diverse, but the protease-inhibitory motif was restricted to peptides from sunflower and close relatives from its subtribe.
The co-authors describe a widely distributed, potential evolutionary intermediate PawS-Like1 (PawL1), which is matured into storage albumin, but makes no stable peptide, despite possessing residues essential for processing and cyclization from within PawS1. Using sequences the researchers cloned, they were able to retrodict the likely stepwise creation of PawS1’s additional destiny within a simple albumin precursor. They propose that relaxed selection enabled SFTI-1 to evolve its inhibitor function by converging upon a successful sequence and structure.
“Conventional wisdom is that new proteins usually arise gradually,” Dr. Mylne says. “Scientists are now beginning to realise that quite often, completely new proteins appear suddenly. Most of these studies are done with genes, but what we’ve done is work with the proteins the genes make too. What we’ve been able to do is propose the evolutionary steps that these rings had to undergo in order to be born.”
Paper co-author Jose L. Panero is Associate Professor, Section of Integrative Biology, Assistant Director of the Plant Resources Center at the University of Texas, Austin. As a plant systematist, Dr. Panero is interested in the distribution, diversity, and evolution of flowering plants, and his research focuses on the elucidation of phylogenetic relationships among Neotropical members of the sunflower family (Asteraceae) using traditional and molecular techniques. Another important activity of the Panero lab and the University of Texas Herbarium is documentation of the floristic diversity of the southwestern USA and Mexico. Ongoing research involves documenting the vascular plant flora of the states of Durango and Oaxaca, in southern and northwestern Mexico. Important benefits of these activities include the identification of economically important and endangered species, their distribution, and a better management of the natural resources of the area. Opportunities for graduate study in Dr. Panero’s lab are available for students interested in pursuing floristic and monographic projects dealing primarily with the Neotropical flora.
In Fall 2013, three new biology departments – Department of Integrative Biology, Department of Molecular Biosciences, and “Department of Neuroscience – were officially instated in the College of Natural Sciences at The University of Texas at Austin. The Department of Integrative Biology is an academic unit whose faculty have teaching and research interests in Behavior, Ecology, Evolution, Population Biology, and Systematics. The department includes 40 faculty who work on a wide diversity of organisms including animals, bacteria, and plants.
Areas of research in the section include animal behavior, behavioral ecology, biomechanics, community ecology, conservation biology, developmental genetics, empirical and theoretical population genetics, floristics, functional morphology, molecular evolution, neuroendocrinology, plant-animal interactions, phylogenetics, population ecology, quantitative genetics, systematics, and tropical ecology.
The departments were created to reflect the changing field of biology, as greater connections emerge between biology and computer science, mathematics, engineering and physics, and to promote innovation in biology research and education.
The faculty and staff associated with the three new departments were previously part of the School of Biological Sciences, which has been dissolved.
A unit called the Biology Instructional Office has been created to support undergraduate biology education, which spans the three new departments.
University of Western Australia
The University of Texas at Austin
University of Western Australia
The University of Texas at Austin