Keeping meristems at balance – stem cell maintenance and termination in flowers with two meristem types

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The maintenance of stem cell activity in the floral meristem is required for the establishment of the basic structure of a flower. Only one type of floral meristem exists in the flowers of most plants, from which floral organs initiate successively in a simple, straightforward way generating a whorled arrangement of floral organs. Some plants produce a second, ring-like meristem whose prolonged activity allows the production of stamens even after the central floral meristem ceased in the process of carpel development. This evolutionary novelty leads to a more flexible growth mode allowing adjustment of stamen number until late in flower development.The molecular basis underlying the formation of the ring meristem is unclear, yet it is very likely that ectopic expression, alternative rewiring and patterning of the stem cell determination program is modified. The aim of this project is to obtain mechanistic insights into the development and maintenance of two neighboring meristems. Moreover, we aim to elucidate the molecular base of ring meristem origin. We want to compare two closely related Papaveraceae species, one with (Eschscholzia californica) and one without ring meristem (Pteridophyllum racemosum) regarding 1) genes regulating the stem cell activity of meristems, 2) their expression pattern and genetic functions. In addition, we 3) aim to identify the similarities and differences of the distinct meristem types and 4) want to understand the evolutionary processes leading to the origin of the ring meristem at the molecular scale. We believe that launching this project will significantly improve our understanding of essential biological issues such as “the maintenance of stem cell activity”, “the origin of novel meristem types”, “the molecular basis of flower diversification in basic structure”, and reaches into the basic ecological question addressing the molecular base for resource allocation between male and female reproductive structures.