the distal tip of the nucellus. The auxin output was traced to megasporogenesis.
GFP was used to determine when auxin was localized
Auxin is localized (concentrated) in early development but is more dispersed during gametophyte development.
the process by which a cell decreases the quantity of a cellular component, such as RNA or protein, in response to an external variable. An increase of a cellular component is called upregulation.
Downregulated Auxin Response Factors with microRNA.
Restricted down regulation of ARF to embryo sac.
Looked at GFP expression in developing embryos.
Cells lacked identity
Determine origin of discrete auxin maxima
Looked at auxin efflux facilitators called PINs
No PIN expression in gametophyte, but there was PIN expression in nucellus until first stage
SO auxin flux may occur in nuccellus during early stages of development
Encode key enzymes in auxin biosynthesis
YUCCA expression first appears in micropylar region of nucellus outside embryo sac in first stage
Suggests auxin might be synthesized initially at the nucellus and subsequently at the micropylar pole of the embryo sac
Distorted polarization of auxin
Cell identity problems. Too many synergid cell?
Would attract 2 pollen tubes
1. Sphorophytic signals lead to auxin source specified within gametophyte at the micropylar pole that result in a gradient of auxin along the micropylar-chalazal axis
2. Gametophytic auxin might not be the primary signal but instead might be the result of a patterning caused by unknown X factor which induces YUC expression in micropylar nuclei resulting in asymetric auxin distribution.