Scientists at the John Innes Centre and the University of East Anglia are pioneering a powerful combination of computer modelling and experimental genetics to work out how the complex shapes of organs found in nature are produced by the interacting actions of genes. Their findings will influence our thinking about how these complex shapes have evolved.
“How do hearts, wings or flowers get their shape?” asks Professor Enrico Coen from the John Innes Centre. “Unlike man-made things like mobile phones or cars, there is no external hand or machine guiding the formation of these biological structures; they grow into particular shapes of their own accord.”
“Looking at the complex, beautiful and finely tuned shapes produced by nature, people have often wondered how they came about. We are beginning to understand the basic genetic and chemical cues that nature uses to make them.”
So, how does this happen? In a recent breakthrough, funded by the Biotechnology and Biological Sciences Research Council (BBSRC), scientists on Norwich Research Park have begun to answer this question, using the snapdragon flower as a convenient subject.
Computer model of the growth of a snapdragon flower, produced by the groups of Professor Andrew Bangham of the University of East Anglia and Professor Enrico Coen of the John Innes Centre
In the snapdragon flower, two upper petals and three lower petals form defined shapes, precisely coming together to form a tube with a hinge. When a bee lands on the lower petals the hinge opens up the flower, allowing access to nectar and pollen. The shape of petals is known to be affected by four genes, but precisely how these genes work in combination to produce the specialised flower shape, and how this shape evolved, was unknown. The same is true for many organ shapes, but the snapdragon flower provides a good system to study this problem, as it is genetically well characterised and growth can be followed at the cellular level.
By changing when and how the genes involved in growth are turned on and off, and tracking how these changes affect the development of shape over time, the researchers got pointers as to how genes control the overall shape. They then used computer modelling to show how the flower could generate itself automatically through the application of some basic growth rules.
A key finding was that genes control not only how quickly different regions of the petal grow, but also their orientations of growth. It is as if each cell has a chemical compass that allows it to get its bearings within the tissue, giving it the information needed to grow more in some directions than others. Genes also influence the cell’s equivalent of magnetic poles; key regions of tissue that chemical compasses point to. Publishing in the journal PLoS Biology, the researchers show how these principles allow very complex biological shapes to generate themselves.
“We are now trying to get a better understanding of exactly how the chemical compasses work and determining the molecular nature of the poles that coordinate their orientations,” said Professor Enrico Coen of the John Innes Centre.
The study also throws light on how different shapes may evolve. In the computational model, small changes to the genes that influence the growth rules produce a variety of different forms. The shape of the snapdragon flower, with the closely matched upper and lower petal shapes, could have arisen through similar ‘genetic tinkering’ during evolution. Evolutionary tinkering could also underlie the co-ordinated changes required for the development of many other biological structures, such as the matched upper and lower jaws of vertebrates.
References: Genetic Control of Organ Shape and Tissue Polarity, Green AA, Kennaway JR, Hanna AI, Bangham JA, Coen E (2010) PLoS Biol8(11): e1000537. doi:10.1371/journal.pbio.1000537
Quantitative Control of Organ Shape by Combinatorial Gene Activity, Cui M-L, Copsey L, Green AA, Bangham JA, Coen E (2010) PLoS Biol 8(11):e1000538. doi:10.1371/journal.pbio.1000538
Funding: This work was funded grants from the Biotechnology and Biological Sciences Research Council BB/D017742/1 to EC and BB/F005997/1
About the John Innes Centre:
The John Innes Centre, www.jic.ac.uk, is an independent, world-leading research centre in plant and microbial sciences with over 500 staff. JIC is based on Norwich Research Park and carries out high quality fundamental, strategic and applied research to understand how plants and microbes work at the molecular, cellular and genetic levels. The JIC also trains scientists and students, collaborates with many other research laboratories and communicates its science to end-users and the general public. The JIC is grant-aided by the Biotechnology and Biological Sciences Research Council, www.bbsrc.ac.uk.
BBSRC is the UK funding agency for research in the life sciences and the largest single public funder of agriculture and food-related research.
Sponsored by Government, BBSRC annually invests around £470 million in a wide range of research that makes a significant contribution to the quality of life in the UK and beyond and supports a number of important industrial stakeholders, including the agriculture, food, chemical, healthcare and pharmaceutical sectors.