The female gametes of flowering plants are produced within a structure known as the gametophyte, which develops inside the carpel of the flower. The female gametophyte (FG) contains several cell types, and it has been proposed that their fate is specified, according to position, by an internal auxin gradient. Ueli Grossniklaus and co-workers () set out to model this proposed auxin gradient in silico, to understand better how it might regulate fate determination. Using physiologically plausible parameters, they found that only very shallow auxin gradients could be maintained, which were unlikely to allow robust patterning of the FG, suggesting that cell fate may not be defined by an auxin gradient. Indeed, more detailed examination of auxin patterns suggested that no such gradient exists in either Arabidopsis or maize. Instead, dynamic auxin signals could be observed in surrounding sporophytic tissues, and the authors propose that auxin may act indirectly in the sporophyte rather than directly in the FG to control FG cell fate.
