Modification of the ROS landscape in the shoot apical meristem of Arabidopsis thaliana during flowering

The shoot apical meristem (SAM) ensures continuous production of aerial organs in plants and its maintenance is critical for shoot growth and development. The vegetative SAM is organized in different zones and sub-populations of meristematic cells can be distinguished: stem cells are located in the central zone (CZ) and their daughter cells are pushed away toward the peripheral zone (PZ) where faster cell division and leaf initiation occur. Several genes are differentially expressed in CZ and PZ, among which genes encoding proteins of reactive oxygen species (ROS) metabolism. It was then inferred that ROS are unevenly distributed in the SAM, the superoxide ion being more abundant in the CZ while hydrogen peroxide would accumulate in the PZ. How this “ROS landscape” interferes with the changes in gene expression that occur in the SAM at the transition to flowering is presently unknown. To address this question, transgenic plants of Arabidopsis thaliana that ectopically express different enzymes of ROS metabolism in the expression domains of genes involved in the transition to flowering are being generated. In this model plant, flowers are initiated in the PZ of the SAM while the CZ remains indeterminate; specific genes are thus expressed in these two domains. In situ hybridization allowed us to confirm the expression domains of the transgenes and phenotyping of the plants is ongoing.