Transgenic Arabidopsis plants expressing a fungal cutinase show alterations in the structure and properties of the cuticle and postgenital organ fusions

A major structural component of the cuticle of plants is cutin, Analysis of the function of cutin in vivo has been limited because no mutants with spe cific defects in cutin have been characterized. Therefore, transgenic Arabi dopsis plants were generated that express and secrete a cutinase from Fusar ium solani f sp pisi. Arabidopsis plants expressing the cutinase in the ext racellular space showed an altered ultrastructure of the cuticle and an enh anced permeability of the cuticle to solutes. In addition, pollen could ger minate on fully differentiated leaves of cutinase-expressing plants but not on control leaves. These differences coincided with strong postgenital org an fusions. The junctions of the fusions contained pectic polysaccharides. As fused organs grew apart from each other, organ deformations and protrusi ons of epidermal cells developed at positions with high mechanical stress. These results demonstrate that an intact cutin layer not only is important for plant-environment interactions but also prevents fusions between differ ent plant organs and is therefore necessary for normal epidermal differenti ation and organ formation.