Plants are comprised of a series of repeated lateral organ segments that develop from small clumps of morphogenic tissue called shoot meristems. The leaf is a ground state lateral organ; the developmental mechanisms generating leaves are repeated and modified during development of inflorescences and flowers. Thus, an understanding of leaf development is central to our comprehension of overall plant development. Previous molecular genetic analyses in diverse plant species have generated testable models for mechanisms of leaf initiation and growth. In addition, comparative approaches are important for better understanding how diverse leaf morphologies have evolved, and may be utilized for agronomic advantage in the future. This research will exploit recessive mutations that affect the initiation and/or expansion of leaves. Experiments will investigate the expression patterns and functions of these genes, helping to elucidate more about the development and morphological evolution of leaves. Three specific aims are proposed.
(1) The maize/Arabidopsis genes NARROW SHEATH (NS)/PRESSED FLOWER (PRS) are required for the initiation of lateral leaf domains from shoot meristems. Maize and Arabidopsis leaves are simple, whereas tomato forms compound leaves comprised of many leaflets. The NS/PRS gene will be cloned from tomato, and molecular-genetic analyses will determine the function of this gene during the development of compound tomato leaves.
(2) The developmental timing and meristematic tissue layer-specificity of PRS accumulation and function will be analyzed with fluorescently tagged proteins and specific antibodies. These experiments will investigate mechanisms of PRS non-cell autonomy, wherein PRS functions beyond those cells and tissues in which PRS is expressed.
(3) The RAGGEDSEEDLING2 gene will be identified and analyses of RGD2 expression during maize development will generate models for how RGD2 functions during the lateral growth and expansion of leaves.
These research activities will be performed in parallel with efforts to introduce middle school aged students in Georgia to plant biological research.
