The development of the specialized cells that make up the female reproductive unit in flowering plants, the gametophyte, requires the hormone auxin. However, auxin's function is unknown, and its movements to and within these cells are unclear. Pagnussat et al. (see the Perspective by Friedman) provide evidence that auxin is synthesized at specific positions within the female gametophyte and exerts a positional effect and that a gradient of auxin controls patterning of these specialized cells.
G. C. Pagnussat, M. Alandete-Saez, J. L. Bowman, V. Sundaresan, Auxin-dependent patterning and gamete specification in the Arabidopsis female gametophyte. Science 324, 1684–1689 (2009). [Abstract] [Full Text]