Principal investigator: José Luis Micol.
Investigators: Carla Navarro Quiles, Sergio Navarro Cartagena, Riad Nadi, Lucía Juan Vicente, Samuel Daniel Lup Haruta and Àngela Ortega Menaches.
Instituto de Bioingeniería. Universidad Miguel Hernández.

Analysis of the contribution of the DEAL and EODL genes to Arabidopsis leaf margin morphogenesis

Cytokinins play many morphogenetic roles in plants, in not few cases in crosstalk to auxin, in processes as dissimilar as ovule development and lateral root formation. For example, cytokinins are known to favor leaf complexity in the development of the compound leaves of Solanum lycopersicum (Solanaceae) and Cardamine hirsuta (Brassicaceae). No role has been assigned for cytokinins, however, in patterning the margins of simple leaves, such as those of Arabidopsis. Instead, auxin localization has been considered enough to explain simple leaf serration, which also requires the PIN-FORMED1 (PIN1) auxin efflux carrier and the CUP-SHAPED COTYLEDON2 (CUC2) transcription factor.

We already initiated a study of the desigual (deal) Arabidopsis mutants, which exhibit extra-lobed and disorganized leaf margins and hence leaf bilateral symmetry breaking with incomplete penetrance. We found a yet to be identified enhancer of deal (eodl) dominant modifier of spontaneous origin, which strongly increases the penetrance and expressivity of the phenotype of the deal mutants.

This grant application represents a natural continuation of previous projects of mine, in which my group studied other aspects of leaf development in Arabidopsis. Here, I pose the hypothesis that cytokinins play a role in simple leaf margin morphogenesis via crosstalk with auxin, as is known to occur in other plant developmental events. This hypothesis will be tested through genetic, biochemical, cell biology and bioinformatic approaches to the analysis of the action and interactions of the EODL and DEAL genes.

The hypothesis of the contribution of cytokinins to margin morphogenesis in simple leaves is supported by traits that remained unnoticed of the phenotypes of mutants and transgenic lines obtained by previous authors: these plants ha in cytokinin biosynthesis or signaling, or suffered increased cytokinin degradation, and in all cases leaf margin serrations were altered.