Welcome back from the fall vacation break. Did you ever wonder how a leaf becomes its leaf form? Jiyan Qi et al (2017) had this question and wrote a paper about it. We know that a leaf is constructed by different tissues/parts: because of differences in gene expression the upper side (adaxial domain) looks different from the lower side (abaxial domain). But which mechanism creates the flat leaf form with upper and lower side? The bud… ergo the start of a developing leaf… is round! Jiyan Qi et al (2017) showed that “relatively simple changes in mechanical properties can account for dynamic shape changes during asymmetric leaf development”. To make a long story short: In the developing (round) leaf the lower side has a higher auxin concentration as the upper side. Auxin is a plant hormone and can lead for example to cell wall loosening by de-methyl-esterification of pectins, a major component of the primary cell wall. The lower sider gets more elastic as the upper side. This difference in elasticity leads to the leaf asymmetry. With proceeding development, the rigid zone of the upper side moves to the middle. “From a physical perspective, the stiff cells receive stronger constraints from their neighbouring […] cells, such that they prefer to grow and divide by pressing on the soft inner cells“. The leaf stretches and gets flat. Just as side note: What I like about the paper is that they use computational models to test their hypothesis if differences in cell wall stiffness and epidermal restriction can lead to the leaf asymmetry. They model what would happen if the cell wall elasticity of the upper and lower region is changed/mixed up. Then they test the model predictions by manipulating the cell wall plasticity experimentally.
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IdeaI love to increase my general science knowledge by reading papers from different fields of science. Here I share some of them. Archiv
März 2018
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