OIWA REGULATES ROS HOMEOSTASIS DURING EMBRYO SAC DEVELOPMENT IN ARABIDOPSIS THALIANA

MARTIN, MARÍA VICTORIA; ZABALETA, EDUARDO; PAGNUSSAT, G

Vienna

Congreso; The 23rd International Conference on Arabidopsis Research (ICAR 2012).; 2012

Gregor Mendel Institute of Molecular Plant Biology (GMI), Universität Wien and Universität für Bodenkultur Wien

Differentiation of gametes is a crucial step in the life cycle of all organisms with sexual reproduction. In Arabidopsis thaliana, gametes are specified inside the embryo sac or megagametophyte, a haploid structure formed by seven cells derived from a functional megaspore. The developmental program that starts with megaspore mother cell specification and ultimately results in gametophyte fertilization involve three events of programmed cell death (PCD). Here we show that the PCD events that take place during sporogenesis and embryo sac development are associated with transient and localized oxidative bursts followed by a rapid restoration of the redox state. In the gametophytic mutant oiwa, which carries an insertion in a gene coding for a mitochondrial Mn-superoxide dismutase (Mn-SOD), 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. As a result, cell specification and fertilization is impaired. Mutant embryo sacs showed miss-specification of antipodal, egg cell and synergide cells. An important fraction of the ovules have difficulties attracting pollen tubes and in those ovules that were able to get fertilized, embryogenesis is arrested at a zygotic stage. Expression pattern studies show that OIWA is expressed from FG1 stage during gametogenesis and it is strongly expressed in antipodal cells. Our results indicate that a tight regulation of ROS homeostasis is crucial for gametophytic cell specification and fertilization, and suggest that ROS might act as cellular signals interfering with cell differentiation in oiwa embryo sacs.