 We are studying pattern formation in land plants, which represent one of the several independent evolutions of multicellular organisms. We are using Arabidopsis, a diminutive flowering plant that is a model for studying may aspects of plant biology as it is amenable to genetic and genomics approaches. We are particularly interested in the genetic control of pattern formation, focusing on the roles of three families of transcription factors. The first, Class III HD-Zip genes are required for the proper development of the shoot apical meristem, from which all above ground plant organs are derived, the top sides of leaves, and the central portion of vascular bundles, the xylem. The second, the KANADI gene family, has a complementary role in that these genes are required for the proper differentiation of the bottom parts of leaves and the peripheral portion of the vascular bundles, the phloem. Members of the first two gene familis are found in all land plant suggesting they are part of an ancient genetic system directing pattern formation along the central-peripheral axis of plants. The third gene family, the YABBY gene family, is found only in seed plants and plays an important role in the development of leaves. In the long term, the ability to manipulate the size and shape of leaves and the production of vasculature could lead to increased productivity of many crop and tree species.
Pattern formation in plants: How does a single cell develop into a multicellular embryo with specific tissue and organ patterns. |
 We are investigating gene function in a variety of model land plants as an approach to elucidating the molecular basis of morphological evolution in land plants. The origin of land plants was one of the most important events in the earth’s evolutionary history, allowing metazoans to colonize land. Land plants evolved from a freshwater charophycean green algal ancestor and that ancestor likely possessed certain developmental features that were inherited by land plants and are shared with extant charophytes. In particular, land plants share with the Charales growth by an apical cell and retention of the zygote. However, the origin and diversification of embryophytes involved dramatic evolutionary changes in life history and body plan that allowed for more complex forms. Key features associated with the evolution of the land plant body plan were the origin of a multicellular diploid sporophyte (from the retained zygote), three dimensional tissue patterning and differentiation in both haploid and diploid phases, sporophytic shoot apical meristem (SAM) with the capacity for branching, lignified vascular tissues; production of lateral organs from the SAM, and the origin of roots.
Morphological evolution in land plants: What were the genetic mechanisms that transformed a diminutive determinate sporophyte, such as that found in a moss, into an enormous indeterminate one, such as that found in the giant sequoia. |
