XVI International Botanical Congess

Disease lesion mimic mutants, of which there are many in maize, are characterized by the presence of aberrant cell death of plant parts. To understand what goes awry during this phenomenon, genes for two contrasting lesion mimic mutants were cloned. In the lethal leaf spot mutant lesions, which need a cell damaging event for initiation and photosynthetically harvested light for continuous enlargement, form because the plants are unable to hydroxylate a phenolic mediator of cell death. In contrast, Les22 appears to suffer from porphyria, a cell damaging syndrome that results from partial blockage in the porphyrin (chlorophyll) pathway. How defects in both mutants result in cell damage and how this cell death is initiated intracellularly will be discussed. Guri S. Johal