Amazing stuff! Why are leaves flat and how are leaves shaped?
"... discovered which genetic mechanisms control leaves' growth into a flat structure capable of efficiently capturing sunlight. ...
"The basis of such pattern formation is polarity; that is, the ability to distinguish, in this case, between top and bottom. It is usually created by a concentration gradient of a substance, called morphogen, that is low on one side and higher on the other," ...
The team discovered that "small RNAs" play a decisive role in controlling the growing leaf. As mobile messengers, they are used for communication between the cells and help the cells to perceive their relative position to each other in the structure ... In addition, the small RNAs transmit information that coordinates which genes need to be activated or inhibited on the top and bottom side to give the leaf the right shape and function. ..."
"... "This regulatory mechanism works autonomously in the growing leaf; there is no central control in the plant," ..."
From the abstract:
"The formation of a flat and thin leaf presents a developmentally challenging problem, requiring intricate regulation of adaxial–abaxial (top–bottom) polarity. The patterning principles controlling the spatial arrangement of these domains during organ growth have remained unclear. Here we show that this regulation in Arabidopsis thaliana is achieved by an organ-autonomous Turing reaction‐diffusion system centered on mobile small RNAs. The data illustrate how Turing dynamics transiently instructed by prepatterned information is sufficient to self‐sustain properly oriented polarity in a dynamic, growing organ, presenting intriguing parallels to left–right patterning in the vertebrate embryo. Computational modelling demonstrates that this self-organizing system continuously adapts to coordinate the robust planar polarity of a flat leaf while affording flexibility to generate the tissue patterns of evolutionarily diverse organ shapes. Our findings identify a small-RNA-based Turing network as a dynamic regulator of organ polarity that accounts for leaf shape diversity at the level of the individual organ, plant or species."
Cells in plant leaves organize themselves to ensure optimal area for photosynthesis (official press release) University of Tübingen team discovers mechanism of shape formation in plants – as predicted by mathematician Alan Turing
How small RNAs craft a world of leaf shapes: This series of simulations examines a leaf section to re-veal how minor variations in gene interactions can lead to distinct spatial patterns of gene activity. These differences between the top (red) and bottom (blue) parts may determine the ultimate shape of the leaf. Left: Illustrates a typical flat leaf maintaining a stable bipolar gene activity pattern. Center: Shows a leaf with a shifted polarity, resulting in a structure akin to that seen in the specialized morphology of carnivorous plants. Right: Displays a loss of polarity, where a radial gene activity pattern contributes to the formation of tendril-like features, common in climbing plants.
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