FIGURE 7:

Model of eyespot assembly. EYE3 is required for biogenesis of the carotenoid-filled pigment granules, which are possibly formed from thylakoid membrane–associated plastoglobules (A). Photoreceptor molecules are guided by the D4 microtubule rootlet to the location where the eyespot is to be assembled (B) and where they aggregate and are stabilized by proteins such as MIN1 (C). Positioning of eyespot proteins “downstream” of the photoreceptor is mediated by hypothetical connecting proteins (D) that act as a link between molecules in the plasma membrane and chloroplast envelope proteins. EYE2 is positioned in the chloroplast envelope and nucleates the pigment granule arrays (E), which then self-assemble in a closely packed arrangement (F) and associate with thylakoid membranes via other protein–protein interactions (G).