Figure 2.

Regulatory dynamics driving de novo stem cell formation during meristem formation. (A) Stem cell formation in Arabidopsis thaliana rosette AMs. Neither WUS nor CLV3 are expressed in the axils of young rosette leaf primordia from which the AM will initiate (first panel). WUS expression becomes expressed in the inner part of the axil (second panel) and later activates CLV3 in an inner, overlapping domain (third panel). These stages can be defined as premeristem. Finally, WUS and CLV3 expressions resolve in two separate domains, in the inner and apical part of the rosette AM, respectively (last panel). (B) Stem cell formation in Arabidopsis thaliana cauline AMs. Neither WUS nor CLV3 are expressed in the axils of young cauline leaf primordia from which the AM will initiate (first panel). WUS expression becomes expressed in the apical part of the axil (second panel) and later activates CLV3 in an apical, overlapping domain (third panel). These stages can be defined as premeristem. Finally, WUS and CLV3 expressions resolve in two separate domains, in the inner and apical part of the cauline AM, respectively (last panel). (C) Stem cell formation in Arabidopsis thaliana embryo meristems. CLV3 expression is activated by the WOX1, 2, 3, and 5 genes at the premeristem stage, while in established and active meristems WUS activates CLV3 expression. (D) Stem cell formation in rice AMs. FON2 (the CLV3 ortholog) expression is activated by TAB1 (the WUS ortholog) at the premeristem stage, while in established and active meristems WOX4 activates FON2 expression. TAB1 or WOX4 promotes OSH1 (the STM ortholog) expression in premeristems and meristems, respectively. In (C) and (D), black arrows mean expression activation while red lines mean repression. Genes and interactions indicated in light gray are not present at the described stage.