An intriguing feature of early zygote development in Chlamydomonas reinhardtii is the active elimination of chloroplast DNA from the mating-type minus parent due presumably to the action of a zygote-specific nuclease. Meiotic progeny thus inherit chloroplast DNA almost exclusively from the mating-type plus parent. The plus-linked nuclear mutation mat3 prevents this selective destruction of minu...

Developmental mechanisms that yield multicellular diversity are proving to be well conserved within lineages, generating interest in their origins in unicellular ancestors. We report that molecular regulation of the haploid-diploid transition in Chlamydomonas, a unicellular green soil alga, shares common ancestry with differentiation pathways in land plants. Two homeoproteins, Gsp1 and Gsm1, co...

The Arabidopsis zygote divides asymmetrically into an embryonic apical cell and a basal cell with mostly extra-embryonic fate. This fundamental asymmetry sets the stage for further embryonic development, but the events mediating it are poorly understood. We have identified a MAPKK kinase gene, named YODA, that promotes extra-embryonic cell fates in the basal lineage. In loss-of-function mutants...

BACKGROUND Since there is considerable disagreement in grading cytoplasmic haloes, this prospective study was set up to evaluate if certain subtypes of haloes are related to further development. METHODS Out of a total of 152 patients, 713 zygotes could be checked for the formation of a halo. Where present, haloes were subdivided into concentric (symmetric) and polar (asymmetric) types. In add...