In plants, gametes and the accessory cells that support them are formed from haploid gametophytes during a tightly regulated developmental program that involves cell division, cell specification and cell differentiation. Now, on , Ueli Grossniklaus and colleagues report that WYRD (WYR), which encodes a putative plant ortholog of the inner centromere protein (INCENP, a protein that controls chromosome segregation and cytokinesis in yeasts and animals), is required for cell specification in the female gametophyte and for seed development in Arabidopsis. The wyr mutant, which was identified in a screen for mutations affecting egg cell differentiation, produces additional egg cells at the expense of accessory cells. Disruption of WYR, the researchers report, also affects mitotic divisions in the male gametophyte (pollen) and the endosperm, and has a parental effect on embryo cytokinesis, which suggests that WYR is involved in cell-cycle regulation. Finally, WYR expression is upregulated in gametic cells. Together, these results reveal a new developmental function for the conserved cell-cycle-associated INCENP protein in plant reproduction.
