Specification of Floral Reproductive Organs by the C Function Regulator AGAMOUS in Arabidopsis thaliana

Our knowledge of the molecular mechanisms that underlie the specification of floral reproductive organs is vastly incomplete. To understand the basis of floral reproductive organ specification in more detail, we identified the genes that are, directly or indirectly, transcriptionally regulated by the B and C class homeotic transcription factors using chromatin immunoprecipitation combined with next-generation sequencing and genome-wide expression profiling in young Arabidopsis flowers. From these data we concluded that the B and C class selector proteins relay their developmental signal through the activation and repression of numerous signaling molecules including transcription factors, kinases and methyltransferases. We then implemented process-oriented analyses of these data and found that the B and C class proteins often cooperatively control developmental processes, while also displaying marked antagonistic as well as independent activities. One example of cooperative regulation of development is the suppression of leaf developmental programs in emerging flower buds. Using trichome initiation as an example, we showed that the B and C class proteins directly inhibit core aspects of leaf development by suppressing the expression of key regulatory genes.