Genetic Approaches to Study Polarity in Plants

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0112461QuartranoWithin all cells, asymmetries are found in relation to gradients of external signals such as light, gravity, neighboring cells, etc. These asymmetries generate an intracellular polarity, as axis with different ends, which often results in the differentiation of subsequent daughter cells. To understand the molecular mechanisms used to interpret environmental inputs that bring about changes in cell polarity requires a system that combines experimental tractability at the cellular, molecular and genetic levels. Impressive progress has been made to establish the common moss plant (e.g. Physcomitrella patens) as an excellent model to explore the molecular basis of cellular polarity, primarily because moss is the only plant system in which homologous recombination is available for functional genetic approaches, i.e., gene knockouts and gene replacements, which can be used to confirm the role of a specific gene in polar processes. The moss system is now ideally and uniquely suited to confirm hypotheses concerning the nature of the proteins involved, e.g., proteins in the secretory system and cytoskeletal proteins. Using moss as a model, our main objective is to identify and demonstrate the function of specific genes in these polar processes by a combined molecular, cellular and genetic approach. Genes involved in the realignment of the polar axes in response to gravity in apical cells of moss will be isolated and identified using a number of random genetic approaches. A more targeted approach will focus on genes already identified that are likely to play a role in polarity, e.g. those functioning in actin cytoskeleton dynamics. The particular properties of the moss system and approaches outlined in this proposal will allow us to identify genes that play important roles in one of the most fundamental processes of living organisms, i.e., how cellular asymmetries are established and maintained to direct polar development and pattern formation.