The survival of seed plants, and thus the security of humankind's food supply, requires the development of ovules that when fertilized will develop into seeds. In flowering plants the ovules develop within the gynoecium, the female reproductive structure. In Arabidopsis thaliana the gynoecium is made up of two carpels that are fused along their edges or margins to form a tube-like structure. Ovules arise on the inner surface of the gynoecial tube from specialized meristematic regions known as the Carpel Margin Meristems (CMMs). Genetic mutations that disrupt the development of the CMM result in a reduction of seed formation. Thus proper development of the CMMs is critical for female fertility in Arabidopsis and agricultural productivity in many crop plants. The main objective of the proposed research is to generate an understanding of the molecular mechanisms of early CMM development.
Regional specification within the developing gynoecium refers to the assignment of different positional identities to different parts of the structure. Regional specification is critical for the development of the CMM. Specifically, adaxial (or inner) identity and margin identity must be properly specified to ensure CMM formation and thus ovule development. Experimental data indicates that three key regulatory genes, SEUSS, LEUNIG and AINTEGUMENTA, play a crucial role in the early development of the CMM. Dr Franks proposes a bipartite model in which 1) the SEUSS, LEUNIG and AINTEGUMENTA genes are required for the expression of the adaxial identity marker PHABULOSA within the developing gynoecium and 2) PHABULOSA expression is critical for the early development of the CMM. He proposes a variety of molecular genetic experiments to thoroughly test this model: 1) specific molecular markers will be used to follow regional specification during gynoecial development in mutant plants in which the activity of one or more of above-mentioned key regulators (SEUSS, LEUNIG and AINTEGUMENTA) is compromised; 2) the expression patterns of the SEUSS and LEUNIG gene products within the developing gynoecium will be determined; 3) the significance of adaxial identity specification during CMM development by the PHABULOSA gene will be investigated; 4) and a unique genetic modifier screen will be utilized to identify novel regulators of CMM development.
In many crop plants the development of the CMM is critical for agricultural productivity. By generating an enhanced molecular understanding of the regulation and control of CMM development, the proposed research may enable methods to engineer agricultural varieties with enhanced yield and thus meet the growing global demand for food. Additionally, the PI will enhance the societal benefits of his research program by fully integrating his scientific research efforts with his graduate and undergraduate teaching and training responsibilities. Materials and research results will be widely dispersed through publication in scientific journals and through web-based vehicles to interested scientists and all levels of educators. Furthermore, Dr. Franks will organize interested graduate students to prepare and present demonstrations at local elementary schools that will help to encourage an interest in scientific studies from this early age.
