Ethylene in Seed Germination and Early Root Development

On Nature. Seed germination is a model system for the analysis of plant development. Cell elongation and differentiation processes are under the control of hormones and submitted to the influence of environmental factors. Hormones (abscisic acid, auxin, gibberellic acid, ethylene and others) interact with each other as well as with diverse components of cell metabolism. Arabidopsis is the model system for the study of developmental processes in plants and research in this species is now helped by a multiplicity of resources (massive genome sequences available, collections of mutants and lines expressing GFP, direct observation in confocal microscopy among others). The analysis of seed germination in Arabidopsis using these tools offers a unique opportunity to dissect the interaction of hormonal pathways during development and its relationship to cellular processes. Ethylene is one of the hormones whose mechanism of action has been most thoroughly investigated and may serve a pivotal role in this analysis. An important requirement is the accurate description of phenotypes for the known mutants with altered sensitivity or response to hormones. This chapter reviews our recent description of root apex curvature as a new phenotype associated with the ethylene signal-transduction pathway mutants. New Arabidopsis sequences induced during germination have been recently isolated. Their expression analysis may be a useful tool to investigate hormonal interactions during seed germination. 1