A floral third whorl-specific marker gene in the dioecious species white campion is differentially expressed in mutants defective in stamen development.

The CCLS4 gene of white campion is specifically expressed in anther epidermis and endothecium from pre- to post-meiotic stages. We report on a detailed in situ analysis of the gene's expression and show that it is a marker of the floral third whorl. The gene is expressed (1) in the anther (epidermis, parietal cells and the derived endothecium) in normally developing stamens and (2) in distinct sub-domains of third-whorl epidermis in mutants exhibiting aberrant states of parietal differentiation. Our results suggest that CCLS4 may fulfil different functions during pre- and post-meiotic anther development and reveal the complex role parietal cells may play during early stamen formation.