Transcription Factors Regulating Compound Leaf Development in Tomato

University Of California-Davis, Davis CA

Investigators

Abstract

0316877 Sinha Generally, the upper (adaxial) part of the leaf is anatomically and physiologically different from the bottom (abaxial) part of the leaf in higher plants. This asymmetry (ab-adaxiality) is established early in the leaf primordium and the shoot apical meristem (SAM) seems to provide positional cues for the initial establishment of this asymmetry. The KNOX1 genes play an important role in maintaining indeterminacy in the SAM and in subsequent shoot development while several genes, like PHAN, PHAV, PHAB, REV, in several species are thought to specify the adaxial and abaxial domains of lateral organs. PHAN is reported to be a negative regulator of KNOX genes and the expression domains of PHAN and KNOX genes do not overlap in apices making simple leaves. However, in tomato expression of the KNOX1 genes TKN1 and LeT6 and PHAN is detected in the center of the SAM. This proposal aims to understand the molecular basis of compound leaf development in the model organism Lycopersicon esculentum (tomato) using both forward and reverse genetics and then to see if the developmental principles discovered in tomato are applicable to various types of compound leaves of independent evolutionary origins. Preliminary data suggests that the KNOX1 genes are an important part of the developmental cascade leading to compound leaves in a variety of species. Further, the domain and amount of PHAN expression regulates leaflet placement in diverse compound leaves. The proposed research will utilize a combination of methods involving analysis of developmental mutations in KNOX1 interacting genes and promoters comparisons for orthologous KNOX1 genes and PHAN from simple and compound leafed species. In addition transgenic approaches will exchange promoter:reporter gene fusions between simple and compound leafed species, and downregulate and upregulate expression of the KNOX1 interacting proteins and proteins that regulate ab-adaxiality in leaves will used to thoroughly dissect compound leaf development in tomato. The long-term goal of this research is to eventually apply the principles learnt in tomato to understanding leaf development in an evolutionary context. Broader impacts of this activity included the training of post-doctoral fellows, graduate students and undergraduates in research methodology. Several undergraduate students have been trained in research and have co-authored papers in the past funding period and many of the undergraduate students come from minority groups. These activities will be maintained in the current funding period.