Tissues213-page16 - location Molecular biologists today are...

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Plant Tissues - 16 Arabidopsis "fass" mutants have been used to study the role of cytoplasmic microtubules in cell division orientation. Fass mutants are squat and disorganized with a seemingly random cell orientation. Fass mutants lack the preprophase band of microtubules, so the plane of division is random. The cellulose fibrils cannot orient for expansion and the entire plant becomes compact and disordered even as they develop into tiny adults. Normal and Fass seedling Fass adult Morphogenesis and Pattern Formation Form and differentiation of cells in plants is dependent upon their position in the meristems. As organs develop from shoot and root meristems, this positional information is retained and gene activity varies in each cell depending on its
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Unformatted text preview: location. Molecular biologists today are studying the role of specific protein and mRNA gradients that serve to orient differentiating cells. A substance diffusing from a shoot apex may signal other cells information about distance from the apex needed for differentiation. Radial position can be determined by radial diffusion from outermost cells. Polarity, from the first division of the zygote, determines shoot versus root in the plant axis. Gradients can act differently in root and in shoot tissues. The roles of specific genes, including plant homeotic genes, are actively being investigated. For example, homeotic genes control the degree of leaflet development. Multiple Leaflets caused by mutant homeotic gene activity...
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