We are studying the control of morphogenesis in plants, using maize and Arabidopsis as model systems. Plants grow and develop new organs throughout their lives from groups of self-perpetuating cells called meristems. Meristems are situated at the growing tips of shoots and roots. We are investigating the shoot apical meristem, which is responsible for the production of new leaves and flowers.
A section through a maize shoot apex showing the expresion pattern of knotted 1 (kn1) mRNA. kn1 is expressed in the shoot apical meristem and is downregulated at the sites of leaf initiation.
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By studying mutations that perturb the functions of the shoot meristem, we hope to understand how this elusive organ functions. Specifically, we are examining mutations in maize that affect the pattern of leaf initiation and meristem size. Using these mutants, we hope to isolate the genes involved and ultimately define the molecular mechanisms that control meristem activity.
An essential gene involved in meristem function is the knotted1 (kn1) gene of maize. This gene is expressed in the shoot meristem, and it encodes one of the homeo domain proteins—a class of proteins that is also important in animal development. Mutations in kn1 affect the self-maintenance of the meristem. We recently demonstrated that the KN1 protein can pass from cell to cell through plasmodesmata, suggesting a novel mechanism by which plant cells communicate and coordinate their development. We are investigating the regulation of cell-to-cell movement (trafficking) of KN1 as a model for understanding the developmental significance of plasmodesmal trafficking of plant proteins. These studies might identify novel strategies for controlling plant pathogenic viruses, which also traffic through plasmodesmata to spread their infection.
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Selected Publications
Jackson, D., B. Veit, and S. Hake. 1994. Expression of maize KNOTTED1 related homeobox genes in the shoot apical meristem predicts patterns of morphogenesis in the vegetative shoot. Development 120: 405–413.
Lucas, W.J., S. Bouché-Pillon, D.P. Jackson, L. Nguyen, L. Baker, B. Ding, and S. Hake. 1995. Selective trafficking of KNOTTED1 homeodomain protein and its mRNA through plasmodesmata. Science 270: 1980–1983.
Jackson, D. and S. Hake. 1997. Morphogenesis on the move: cell-to-cell trafficking of plant regulatory proteins. Curr. Opin. Genet. Dev. 7: 495–500.
Jackson, D. and S. Hake. 1999. Control of phyllotaxy in maize by the ABPHYL1 gene. Development 126: 315–323.
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