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Abstract

Plant stem cells continuously proliferate and are able give rise to all cell types of the organism. To understand plant growth and development it is, therefore, of central importance to study the mechanisms of stem cell maintenance and differentiation. Recent findings indicate that the bZIP transcription factor PERIANTHIA (PAN) is one of the key players in regulating the fate choice between proliferation and differentiation in Arabidopsis shoots. Genetic and molecular studies indicate that PAN on the one hand affects the function of the stem cell niche in the shoot apical meristem, while on the other hand it is also necessary for the activation of the differentiation gene AGAMOUS (AG) in flowers. We have found that PAN directly binds to AG regulatory sequences and that this regulatory interaction is required for AG activation and proper termination of stem cell maintenance during flower development. In addition, PAN itself seems to be target of complex regulatory mechanisms, both at the transcriptional, as well as the posttranscriptional level, adding another layer of complexity. Taken together, PAN is embedded into a complex regulatory network and plays important roles in stem cell regulation that had previously gone unnoticed.