Molecular and genetic analysis of leaf polarity and compound leaf development in tomato

The upper leaf surface (adaxial) is structurally different from the lower (abaxial) surface. Ab-adaxial organization is important for formation of the leaf lamina in simple leafed species. Compound leaves have regions where lamina formation between leaflets is interrupted. Recently, several genes have been studied for their roles in establishing ab-adaxiality and compound leaf development. In nature, compound leaves are classified into two forms: pinnate and palmate. The relationship between ab-adaxiality and these compound leaf forms is largely unknown.;To understand the relationship between ab-adaxiality and different leaf forms (pinnate vs. palmate compound leaves), ab-adaxial features of leaves from various species were examined. The adaxial domain was significantly reduced in peltately palmate compound leaves, suggesting that the extent of the adaxial domain is important for final leaf morphology. AntisenseLePHAN (tomato PHAN) transgenic tomatoes produced peltately palmate compound leaves instead of pinnate compound leaves, suggesting a possible role of PHAN in regulating leaflet position in tomato. PHAN expression domain is reduced in these peltately palmate leaves.;To test if PHAN function in control of leaflet position is conserved in higher plants, PHAN orthologs from various species were cloned and their expression patterns were examined in the leaf primordia of these species. The expression patterns suggest that reduction of PHAN expression in the leaf primordia is important to make peltately palmate compound leaves and this mechanism is conserved in independently arisen compound leafed species.