Hundreds of land plant lineages have independently evolved separate sexes in either
gametophytes (dioicy) or sporophytes (dioecy), but 43% of all dioecious angiosperms are
found in just 34 entirely dioecious clades, suggesting that their mode of sex determination
evolved a long time ago. Here, we review recent insights on the molecular mechanisms that
underlie the evolutionary change from individuals that each produce male and female
gametes to individuals specializing in the production of just one type of gamete. The …