Broad Leaves, Narrow Leaves, or No Leaves at All - Genetic Dissection of Barley Leaf Growth

Crop yield depends on plant architecture including leaf shape. Understanding the molecular basis of leaf development and growth is therefore expected to help optimise plant architecture for improved crops. Classical morphological studies suggest that the contribution of different regions of the early leaf primordium (the so-called ‘upper leaf’ and ‘lower leaf’) to the mature leaf differs substantially between monocotyledonous and dicotyledonous species. This raises the question whether and to which extent findings on the genetic control of leaf growth in the model Arabidopsis thaliana will be transferable to monocotyledonous species and calls for more studies on the leaf growth in the latter. Therefore, we have chosen to study three barley mutants with distinct leaf morphologies: a mutant broader leaves than wild type, one with narrower leaves or one with no leaf blades at all. Phenotypic characterization indicates that the differences in leaf width in the former are due to differences in cell proliferation. Using genetic mapping and targeted BAC sequencing, the three mutations were localized to small genetic intervals. The broad-leaf phenotype of the first mutant appears to be due to the loss of function of a hitherto uncharacterized transcription factor. Functional studies of this factor are under way. We will present our current progress on the genetic mapping and phenotypic characterization of the mutants, and on the functional analysis of the candidate gene.