MUTATIONS AFFECTING THE RADIAL ORGANIZATION OF THE ARABIDOPSIS ROOT DISPLAY SPECIFIC DEFECTS THROUGHOUT THE EMBRYONIC AXIS

The primary root of Ararabidopsis thaliana has a remarkably uniform ce llular organisation. The fixed radial pattern of cell types in the mat ure root arises from proliferative divisions within the root meristem. The root meristem, in turn, is laid down during embryogenesis. We hav e analysed six mutations causing alterations in the radial organisatio n of the root. Embryonic phenotypes resulting from wooden leg, gollum, pinocchio, scarecrow, shortroof and fass mutations are described. Whi le mutations in the fass gene affect morphogenesis of all cells, the f ive other mutations cause alterations in specific layers, Wooden leg a nd gollum mutations interfere with the proper organisation of the vasc ular tissue. Shortroot, scarecrow and Pinocchio affect the endodermis and cortex. The layer-specific phenotypes caused by all five mutations are also apparent in the hypocotyl. All these phenotypes originate fr om defects in the radial organisation of the embryonic axis, Secondary roots, which are formed post-embryonically, also display layer-specif ic phenotypes.