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Leaf development

Studies of A. thaliana have provided considerable insights with regards to the genetics of leaf morphogenesis, particularly in dicotyledon-type plants. Much of the understanding has come from analyzing mutants in leaf development, some of which were identified in the 1960s, but were not analysed with genetic and molecular techniques until the mid-1990s. A. thaliana leaves are well suited to studies of leaf development because they are relatively simple and stable.

Using A. thaliana, the genetics behind leaf shape development have become more clear and have been broken down into three stages: The initiation of the leaf primordium, the establishment of dorsiventrality, and the development of a marginal meristem. Leaf primordia are initiated by the suppression of the genes and proteins of class I KNOX family (such as SHOOT APICAL MERISTEMLESS). These class I KNOX proteins directly suppress gibberellin biosynthesis in the leaf primordium. Many genetic factors were found to be involved in the suppression of these class I KNOX genes in leaf primordia (such as ASYMMETRIC LEAVES1, BLADE-ON-PETIOLE1, SAWTOOTH1, etc.). Thus, with this suppression, the levels of gibberellin increase and leaf primordium initiate growth.

The establishment of leaf dorsiventrality is important since the dorsal (adaxial) surface of the leaf is different from the ventral (abaxial) surface.