Switch (swi1) an Arabidopsis thaliana mutant affected in the female meiotic switch

In this paper, we describe a novel plant mutant affected exclusively in the female mitosis-meiosis switch. The major effect of the swi1 mutation in Arabidopsis thaliana L. is to delay megasporogenesis events by inserting additional mitotic divisions of the mega- sporocyte. As a result of this delay, megagametogenesis is also affected. The absence of cellular polarity in the megasporocytes was also observed. Ovule ontogenesis is not affected by the mutation. The swi1 mutant is particularly interesting for studying sporophyt-gametophyte interactions. The swi1 mutation, obtained from a T-DNA tagging experiment, is monogenic recessive and mapped on chromosome five, at 16 cM from the yellow inflorescence marker.