Molecular factors affecting plant architecture

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All aerial tissues of plants are derived from a small number of stem cells present at the apex, or shoot apical meristem. As these cells divide, they are pushed away from their origin, the central zone, into the peripherial zone, where they encounter a different molecular environment and are induced to undergo differentiation. Depending on when and where this occurs during the plant life cycle a lateral organ is elaborated, taking the form of a flower, a leaf, or a stem. We now know some of the molecular components that govern stem cell proliferation and differentiation and we know quite a lot about floral, leaf and root development. What has been conspicuously lacking is a description of stem development.  Several years ago my laboratory embarked on such a project, choosing to focus on the brevipedicellus (bp) mutant of the model plant Arabidopsis thaliana.  This mutant exhibits a number of developmental defects. It is a semi-dwarf and we have shown that the process of cell division is compromised. The mutant also exhibits two distinct types of 'bends': one at stem branch points, and the other at floral branch points. In addition, the short stem that supports the flower, the pedicel, is very short (hence the mutant moniker). The BP gene encodes a regulatory factor, and many lines of evidence suggest that it serves to promote a growth competent state, such that in its absence, growth and differentiation are compromised.My laboratory has made significant inroads towards understanding stem and pedicel development, and the proposed research is aimed at furthering our knowledge of how BP regulates (and is regulated by) other genes that control morphogenesis.  We will use a battery of genetic, molecular, biochemical and cytological tools to identify interacting partners and dissect the biochemical and signal transduction pathways that mediate BP action. These studies will solidify our understanding of how plant architecture is specified at the cellular and molecular levels, and may be used to contemplate directed changes to plants of agronomic value such as to increase their productivity. This research affords the opportunity to train a number of scientists, preparing them for careers in basic and applied research.