Identification of novel auxin responses during Arabidopsis embryogenesis

Plants normally form one embryo per seed. Under special circumstances, such as death of the embryo, a second embryo can develop from a supportive structure called the suspensor. These suspensor cells therefore provide a reservoir of stem cells for the generation of secondary embryos. At the start of this project, the mechanisms that control the formation of secondary embryos were completely unclear. By conducting a systematic screen for cellular responses to the plant hormone auxin during embryogenesis we found that auxin prevents embryo development from suspensor cells. The detailed analysis of auxin response components allowed us to identify the auxin-dependent transcription factors that mediate auxin action in the suspensor. Furthermore, we found that the control of expression of these auxin response transcription factors contributes to early embryo pattern formation. This work identified the first molecular players in the control of suspensor-embryo transformation and provides a stepping stone for elucidating the genetic networks that control embryo identity in plants.