New Forms Of Leaves Are Found For Thale Cress

Anyone who looks at their salad plate or their garden can see how different the shapes of the leaves can be. Spinach leaves, for example, have smooth edges and have a comparatively simple shape, whereas parsley leaves have deep and complex notches, apparently composed of many individual subunits. In a new study published in Cell, scientists at the Max Planck Institute for Plant Breeding Research in Cologne have determined how key genes of development influence the growth of cells to produce such differences in leaf shape. With this knowledge, the researchers were able to make the thale cress, which usually produces simple leaves, produce leaves of complexity similar to those of bitter hair, a plant related to complex leaves.

All the leaves develop from small buds, which consist of only a few cells. The buds always look the same, no matter what kind of leaf they eventually form. Not only that, but very similar leaf shapes can emerge from very different growth patterns. This made it even more difficult to identify the pathways responsible for the diversity of naturally occurring leaf shapes.

The scientists used for the first-time advanced images to compare the way in which particular regulatory genes directed cell growth in both the cress model (Arabidopsis thaliana) and in the plant related to hair bittercress (Cardamine hirsuta). Then, computer scientists combined genetic and microscopic data to help understand how genes produce form.

For a few hours after shoot formation, the leaves of both plant species grew in a similar manner. A set of genetic rules common to both species causes the slow and slow growing cells to alternate in position along the edge of the leaf and this allows the leaves to produce repeated buds. However, the two species then began to produce different forms: the hairy bittercress began to develop its individual subunits called leaflets, while thale cress only formed shallow teeth at the edge of the leaf.

These differences are caused by two regulatory genes that are only active in the bitter hair. One of these, called RCO, slows cell growth around growths, which makes them become much deeper. The other, STM, controls growth more generally, by slowing the maturation of cells and allowing them to continue directional growth for longer, resulting in large brochures. It is the combination of both effects that leads to a complex sheet with its subunits.

To test their ideas on the shape of the leaf, the researchers then activated the RCO and STM genes at the appropriate times and places in a thale cress leaf shoot. This led the outbreak to form a complex sheet instead of its usual simple sheet. "This was a rewarding experiment," says Tsiantis, "a bit like turning the tail feathers of a sparrow into those of a peacock." Our results are significant, because although there is much information about which genes influence the development of different plants or animals, it is much less clear how these genes modify the amount, direction and duration of growth to produce the final morphologies of different species. "

The preliminary findings of the Cologne researchers suggest that, in certain circumstances, complex leaves could use carbon dioxide better than simple leaves. Therefore, transforming simple leaves into complex leaves through a bit of their growth could potentially increase the yield of certain agricultural crops, "concludes Tsiantis.

By: Preeti Narula

Content: https://www.sciencedaily.com/releases/2019/05/190523143044.htm