A key problem in plant developmental biology is to unravel the processes leading to the generation of these different leaf forms. To do this effectively it is essential to compare the function of leaf development pathways in species with different types of leaf architecture. The object of my research is to understand how variations in the function of leaf development pathways contribute to the evolution of the multitude of distinct leaf forms apparent in nature. As a paradigm for answering these questions I am studying the genetic components governing development of compound leaves. The challenge therefore is to explain the differences underlying the formation of these two distinct types of leaf architecture.
Leaves arise from the differentiation of cells at the shoot apical meristem.
In contrast the compound leaves of tomato plants express knox genes. This expression pattern, in combination with the increased leaf dissection obtained by overexpressing knox genes in tomato, has led to the suggestion that differential regulation of knox gene expression may be responsible for the dissected leaf morphology. However, very little is known regarding the upstream and downstream components of the KNOX developmental pathway and it still unclear how differential regulation of this pathway is responsible for generating compound leaf morphology in tomato. In order to gain further insight into the factors controlling developmental transitions from meristematic to leaf cell fates I am employing molecular genetic screens to identify Arabidopsis mutants that phenocopy or suppress the effects of KNOX misexpression on leaf development. Current results suggest that the plant growth regulator gibberellin maybe a downstream component of the homeobox pathway.