Genetic and molecular dissection of leaf morphogenesis in Arabidopsis thaliana
With the purpose of contributing to the dissection of the mechanisms underlying leaf ontogeny, we are following a genetic approach to the causal analysis of leaf morphogenesis, based on the isolation of Arabidopsis thaliana mutants with abnormalities in the venation pattern, marginal configuration, shape or size of their rosette leaves. By screening for such variations in ecotypes, in mutants from already existing collections and in newly isolated mutants, we have identified 139 genes whose mutations perturb the above mentioned elements of leaf architecture.
We propose in this project the genetic and molecular analysis of three of the genes identified in our laboratory: HEMIVENATA (HVE), ULTRACURVATA1 (UCU1) and INCURVATA2 (ICU2). Mutations in these genes impair leaf venation pattern formation, causing the absence of many vascular elements (hve), or determine spirally rolled downwards (ucu1) or involute (icu2) leaves, the latter two displaying deviations from the planarity that characterizes wild-type leaves, which can be regarded as perturbations in putative mechanisms coordinating the growth of the dorsal and ventral tissues of this organ. We have shown, in addition, that the phenotype of the icu2 mutant is suppressed in an agamous background, as it is known for mutations in the Polycomb group gene CURLY LEAF.
We aim to positionally clone the HVE, UCU1 and ICU2 genes, subject them to structural and phylogenetic analyses, and determine their spatial and temporal expression patterns. Double mutant combinations will be obtained, involving hve, ucu1 and icu2 alleles, as well as mutations in other genes affecting leaf architecture. The Hve, Ucu1 and Icu2 leaf phenotypes will be characterized by scanning electron and light microscopy. Expression of floral genes in the leaves of icu2 will be studied by RT-PCR.