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“Towards a physical understanding of growth anisotropy in plants” - Siobhan Braybrook

Friday, November 17, 2017 at 11:15am

Plant Science Building, 404

Siobhan Braybrook
Assistant Professor of Molecular, Cell and Developmental Biology, UCLA

Biography: Siobhan obtained her undergraduate honours degree in Plant Biology from the University of Guelph (Canada) in June 2003.  Her undergraduate work with Dr. Annette Nassuth involved cold tolerance and virus detection in cultivated grape (Vitis vinifera). Her honours research thesis was conducted under the supervision of Dr. Robert Mullen and Dr. J. Derek Bewley, and concerned the sub-cellular localization of a specific enzyme required for tomato seed germination.

In December, 2008, Siobhan obtained her doctorate in Plant Biology at the University of California at Davis (USA), under the mentorship of Dr. John Harada.  Her thesis involved the identification of the transcriptional network controlled by the important embryo specific transcription factor, LEAFY COTYLEDON2.  

Siobhan’s post-doctoral tenure was in the lab of Dr. Cris Kuhlemeier, at the University of Bern (Switzerland).  She was supported as a US National Science Foundation International Research fellow (Jan 2010- Dec 2011, OISE 0853105).  She developed projects concerning (1) patterning in sunflower, (2) the mechanics of simple cell growth, and (3) the identification of mechano-molecular mechanisms involved in shape growth in plants.

In January 2013, Siobhan started as a Career Development Fellow at the Sainsbury Laboratory at Cambridge University. She has since started The Plant Mechanics Group here which studies plant growth mechanics - see more here.

In April 2013, Siobhan was elected a Trapnell Fellow in the Natural Sciences at King's College Cambridge. More information on King's College is available here.

Research Interests: The Braybrook Group at UCLA studies the generation of form in walled organisms. We follow questions of form that capture our minds and hearts and wield quantitative tools to craft new hypotheses about our world. This means we apply and develop quantitative methods, utilise the best biological system to answer our question, and constantly look both forwards and backwards to identify key concepts and tools in the field. We are dynamic, just like our systems! In all organisms, the growing of a shape is a complex process requiring specific gene products, signaling, mechanical alterations, and coordination of cell growth. Our Team addresses this fundamental process in biology using a multidisciplinary approach including: plant physiology, biochemistry, genetics, molecular biology, materials science, and physics. We focus on understanding how shapes are generated in walled organisms: plants and alage. For a plant and algal cells, the cell wall is the main structural element, controlling shape and growth of the cell and therefore tissue as a whole. Recent work in plants has correlated key aspects of organ growth and shape generation, in plants, with mechanical properties of tissues and cell walls. Our Team has two main goals: 1) to understand the mechanics of shape growth in plants and algae, and 2) to understand the cell wall as a dynamic composite material.

Abstract: The growth of shape and pattern in biological systems is a fundamental pillar of developmental biology. A major research strategy aimed at understanding these processes has been to investigate the molecular mechanisms behind their instruction. Our lab continues on this path but adds another dimension as well: how are such instructions physically manifested? In walled-celled organisms, this may be reduced to a seemingly simple goal: understanding how the cell wall and turgor pressure combine to regulate growth.

Our lab has been investigating the role of the cell wall matrix in the physical process of cell growth and examining how collections of cell behaviours result in organ level growth patterns. Our main study system is the hypocotyl, a relatively simple cylindrical organ that undergoes extreme anisotropic growth (more in length than girth) after germination in order to push the shoot apex of many plants out into the light, enabling the start of phototrophy. By combining quantitative growth measurements, at organ and cell levels, we have developed a comprehensive physical model of hypocotyl anisotropy beyond the simple cellulose-based hypothesis of Green. We have recently been exploring how the modulation of anisotropy might contribute to early seedling emergence from soils in response to carbon availability.


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Plant Biology


plant biology, sips, nysaes, CALScomm




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Tara Reed

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Siobhan Braybrook

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