Research Article

Auxin-Dependent Patterning and Gamete Specification in the Arabidopsis Female Gametophyte

Science  26 Jun 2009:
Vol. 324, Issue 5935, pp. 1684-1689
DOI: 10.1126/science.1167324

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Flower Functionalization

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 and movement to and within these cells are unclear. Pagnussat et al. (p. 1684, published online 4 June; see the Perspective 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.

Abstract

The female reproductive unit of flowering plants, the haploid female gametophyte, is highly reduced relative to other land plants. We show that patterning of the Arabidopsis female gametophyte depends on an asymmetric distribution of the hormone auxin during its syncitial development. Furthermore, this auxin gradient is correlated with location-specific auxin biosynthesis, rather than auxin efflux that directs patterning in the diploid sporophytic tissues comprising the rest of the plant. Manipulation of auxin responses or synthesis induces switching of gametic and nongametic cell identities and specialized nonreproductive cells to exhibit attributes presumptively lost during angiosperm evolution. These findings may account for the unique egg cell specification characteristic of angiosperms and the formation of seeds with single diploid embryos while containing endosperm that can have variable numbers of parental haploid genomes.

  • * Present address: Instituto de Investigaciones Biológicas, Universidad Nacional de Mar del Plata, 7600 Mar del Plata, Argentina.

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