CONICET | Buscador de Institutos y Recursos Humanos

Differentiation of gametes is a crucial step in the life cycle of all organisms with sexual reproduction. In the model plant Arabidopsis thaliana, the development of the female gametophyte involves three events of programmed cell death whose molecular bases are still poorly understood. In this work we present the study of the gametophytic mutant oiwa, which carries an insertion in a gene coding for a mitochondrial Mn-superoxide dismutase (Mn-SOD). While transient, localized oxidative bursts were observed associated with cell death events in WT embryo sacs -followed by a rapid restoration of the redox state-, mutant embryo sacs seem not able to reduce ROS levels after cell death, as observed by the use of specific probes at different stages of development both by confocal and DIC microscopy. To determine the specific stage of development affected in oiwa, acomprehensive phenotypic analysis was performed. Mutant embryo sacs appear to have difficulties attracting pollen tubes, as a high percentage of ovules are not fertilized. Also, in those fertilized embryo sacs, embryogenesis is arrested at a zygotic stage, suggesting a maternal effect.Our results indicate that tight regulation of ROS homeostasis is crucial for fertilization and embryogenesis and that Mn-SOD plays a critical role in its regulation during female gametophyte development.