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In autumn, it is not only the colors that catch the eye, but also the different sizes and shapes of leaves. But how are the leaf shapes of different plants so different? Scientists at the Max Planck Institute for Plant Breeding Research in Cologne have now discovered how a protein called LMI1 can control leaf growth and shape.
Francesco Vuolo and his colleagues at Max Planck's laboratory, Miltos Tsiantis, director, study the mechanisms underlying the dazzling variation of leaf shapes that can be seen in nature. Recently, they have focused their efforts on research on parts of poorly understood leaves, called stipules. These growths form at the base of the leaf during development and their size and function vary greatly among plant species. In the model plant Arabidopsis, the mature stipules remain tiny, although they constitute a substantial part of the young leaf. In other plants, such as garden pea, stipules form a large part of the leaf.
Using a combination of genetics, microscopy and mathematical models, they were able to show that LMI1 maintains the small stipules. If the protein is produced in a cell during leaf development, it simply continues to grow instead of dividing. This form of cell maturation prevents the cell from growing into other types of cells and limits the pool of cells available for subsequent tissue growth. This, in turn, reduces the size of the final organ despite the early increase in cell growth. "The leaf remains smaller despite larger cells," says Vuolo.
LMI1 also plays a decisive role in the regulation of leaf morphology in other plants. The research team discovered that LMI1 was not produced in the large stipule in the form of pea leaf, but in the upper part of the pea leaf, where organ forming forms occur. climbing in the form of thread called tendrils. "The cells of the tendrils grow bigger and divide less," said Vuolo. The production pattern of LMI1 in the pea leaf is therefore probably responsible for its characteristic shape, with thread-like tendrils at the tip of the leaf and large stipules at the base.
These important findings shed new light on the developmental origin of the stipules, suggesting that it is actually cryptic leaves maintained in a repressed state by LMI1. The British natural scientist, Charles Darwin, who had written this subject in 1865, already had relations between different parts of the plant such as stipules, leaves and tendrils. This study therefore solves the problems of ways to investigate the role of growth in the evolution of leaf shape. "One day, they could contribute to the selection of new plant varieties for agriculture with modified leaves or other organs.For example, we are currently studying the role of LMI1 protein in the growth of tomato as an important agricultural trait, "said Tsiantis. , Director at the Max Planck Institute for Plant Breeding Research.
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Original publication
Francesco Vuolo, Daniel Kierzkowski, Adam Runions, Mohsen Hajheidari, RemcoA. Mentink, Mainak Das Gupta, Zhang Zhongjuan, Daniela Vlad, Wang Yi, Ales Pecinka, Xiangchao Gan, Angela Hay, Peter Huijser, Miltos Tsiantis
The homeodomain LMI1 protein regulates organ proportions by spatial modulation of endoreduplication.
Genes and development; October 26, 2018
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