Regulation of Compound Leaf Development in Tomato

University Of California-Davis, Davis CA

Investigators

Abstract

Principal Investigator: Neelima Roy Sinha Proposal Number: IOB-0641696 Proposal Title: Regulation of Compound Leaf Development in Tomato Leaves arise at the growing tips of plants on shoot apical meristems. Leaves are responsible for most of the fixed carbon in a plant, are critical to plant productivity and human survival, and can range in complexity from simple to compound. Compound leaves can have leaflets in a pinnate or palmate arrangement. The long-term goal of this research is to determine the differences between the indeterminate shoot apical meristem and determinate cells that give rise to leaves, and between simple and compound leaves. This research will provide information on the steps that give rise to pinnate vs. palmate compound leaves and will use genetics, as well as developmental analyses. This analysis will be extended to see if the developmental principles discovered in tomato are applicable to various types of compound leaves of independent evolutionary history. The proposed research will utilize a multi-pronged approach that includes analysis of a number of genes that are important developmental regulators in other model plant species. A deeper understanding of how the expression of one family of genes, the KNOX1 genes, is regulated at the shoot apex should result from this work. New regulators of leaf development are expected to be identified during the course of this research. The specific aims of the proposed research are to: 1. Perform a clonal analysis of tomato leaf development; this will involve marking cells in young leaves and following their progeny to track how cell division gives rise to leaf shapes. 2. Identify genetic loci that regulate leaf development in tomato. Quantitative and genome scanning approaches will be utilized to identify new regulators of leaf development. 3. Analyze the regulation of KNOX1 gene expression using molecular biology and developmental biology techniques. 4. Elucidate the role of HDZIPIII, NAM/CUC, LFY, UFO and JAG genes in leaf development, which are known to regulate plant form in the model organisms Arabidopsis but their role in leaf development is not yet understood. The intellectual merits of the proposed research include providing information crucial to understanding a basic problem in plant biology - why some shoot apical meristems produce simple leaves, while others make compound leaves. Leaves function in photosynthetic light capture and variation in their shape has important physiological and ecological consequences. In many species, leaf complexity in an individual can change due to environmental conditions (heterophyllic variation) and can vary over developmental time (heteroblastic variation). In addition, this research should generate an understanding of how gene expression is regulated both in the apical meristem and in developing leaves. This research will also determine if other genes thought to regulate vegetative and reproductive development (based on model organisms like Arabidopsis) have a role in compound leaf development. In addition cutting edge techniques of whole genome analysis and quantitative approaches will help us to identify as yet unknown genes that have played a role in the formation of leaves. Broader impacts of this research activity include training of a post-doctoral fellow, a graduate student and undergraduate students. The PI's laboratory has trained students at all these levels in the past. Undergraduate students undertake independent research projects, several have co-authored papers and many of the undergraduate students come from minority groups. In addition to research training, the post-doctoral fellows and graduate students will also be trained in undergraduate mentorship.