Stigma Specification and Stigma Papillae Growth in Arabidopsis thaliana

The flower is debatably the most complex of the plant organs, composed of far more tissues than any other plant organ system, and, as such, the molecular mechanisms that govern tissue specification and development have only just begun to be explored. One tissue that has seen little research is the stigma. The stigma is the apical-most part of the gynoecium and is designed to trap pollen grains on specialized cells called stigma papillae and provide the means for them to germinate. Using a forward genetic screen, many mutants which exhibit defects in stigma development were identified. The identification of the genes with the causative mutations will uncover new genes involved in stigma development which can be linked to previously discovered genes to build a more comprehensive gene regulatory network of stigma specification. Over the course of the screen, a new mutant, lily, was identified which has open buds throughout most of flower development. This valuable genetic tool allows microscopy and chemical applications at younger stages than emasculation allows. Here, lily was used to show the importance of reactive oxygen species in stigma specification and identity maintenance. In addition to specification, the morphological differentiation of stigma papillae was investigated. Using reverse and chemical genetics, live-imaging, and morphometrics, it was found that stigma papillae grow via an anisotropic diffuse growth mechanism. Collectively, these findings constitute a substantial breaking of ground for stigma research, providing a solid foundation for future investigation.