The Role of YABBY Gene Family Members in Promoting Lamina Expansion

University Of California-Davis, Davis CA

Investigators

Abstract

Lateral organs of seed plants, such as leaves and floral organs, are formed from the flanks of apical meristems. Therefore, an inherent positional relationship exists between them: leaf primordia have an adaxial side adjacent to the meristem, and an abaxial one away from the meristem. Surgical and genetic studies suggest that a signal, whose source is the meristem, is required to induce adaxial identity, and in its absence, abaxial fates are acquired by default. Subsequently, the asymmetric adaxial-abaxial axis provides cues for proper lamina growth. Several key players involved in this process were identified recently, and it has been suggested that complex relationships between and within various members of these plant-specific gene families (class III HD-ZIPs, YABBYs and KANADIs) may account for a significant portion of the morphological variation in lateral organs of seed plants. The class III HD-ZIP genes promote adaxial fates and are expressed in the meristem and adaxially in lateral organs. In contrast, the KANADI and YABBY genes promote abaxial fates, and their expression is confined to the abaxial domains of developing lateral organs. Thus, the adaxial and abaxial factors are expressed in mutually exclusive domains, and interaction between these domains is required for proper leaf lamina development. Several lines of evidence suggest that YABBY gene activity may be intimately involved with the development of the lamina. The overall aim of this proposal is to better understand YABBY function addressing the role of YABBY gene family members in promoting abaxial cell fates and in promoting lamina development. The proposed experiments should clarify our understanding of YABBY function in the promotion of abaxial cell fates and the development of leaf lamina. In the long term, the ability to manipulate the size and shape of lateral organ, such as leaves, could lead to increased productivity of many crop species.