Open and closed inflorescences: more than simple opposites.
The absence of a terminal flower in inflorescences ('open inflorescences') is currently explained by the maintenance of putative stem-cells in the central zone (CZ) of the inflorescence meristem (IM) governed by the CLAVATA-WUSCHEL regulatory loop. Disruption of this regulatory pathway, as in Arabidopsis TERMINAL FLOWER LOCUS 1 mutants, leads to terminal flower production. However, recent studies in other taxa reveal novel mechanisms of inflorescence termination; for example, the SEPALLATA-like MADS-box floral identity gene GERBERA REGULATOR OF CAPITULUM DEVELOPMENT 2 in Gerbera excludes the retention of a CZ as an ontogenetic cause for the openness of these inflorescences. Moreover, comparative histological studies show that the retention of a CZ in the IM, mostly a feature of the 'typical open families', is absent in open inflorescences of other families. Concerning these groups, new evidence suggests that spatial constraints at the IM could play a role at the time when terminal flower production (or not) is determined. This indicates that the multiple loss and re-gain of the terminal flower in angiosperms is necessarily based on more than one ontogenetic pathway.
Bull-Hereñu
Kester
K
Institut für Spezielle Botanik, Johannes Gutenberg Universität, D-55099 Mainz, Germany. bull@uni-mainz.de
Classen-Bockhoff
Regine
R
D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D056626:Inflorescence / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D063245:Plant Development; D018521:Plant Physiological Phenomena; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D010944:Plants / Q000235:genetics
D010940:Plant Proteins