The nature of nurture: the conserved role of tapetal-like cells in sporogenesis between mosses and angiosperms

The emergence of land plants, also known as Embryophytes, was a momentous event in the evolution of terrestrial life. The origin of a land flora led to carbon sequestration, increased oxygen concentrations, and soil formation, thereby dramatically altering the pedosphere and the atmosphere, paving the way for the co-evolution and terrestrialization of other eukaryotic lineages. This major shift in the trajectory of plant evolution was succeeded by a single common ancestor to all land plants, that if alive today would be grouped amongst the charophycean algae (Delwiche & Cooper, 2015). During the transition to a terrestrial habitat, the ancestral land plant overcame several environmental challenges, such as severe desiccation and damaging solar radiation, via evolution of adaptations directed by novel genetic pathways. Comparative studies of extant charophyte algae and Embryophytes have identified several autapomorphies of Embryophytes that have been key to life on land. Of these novel adaptations, the earliest trait to evolve in the ancestral Embryophytes based on the fossil record is sporogenesis, the development of spores coated in sporopollenin, one of the toughest biopolymers known to man. This unique land plant innovation allowed plants to package future progeny into microscopic propagules that are both desiccation and UV tolerant (Gray, 1993). In the recently published article in New Phytologist, Lopez-Obando et al. (2022; doi: 10.1111/nph.17972) delve into the sporogenesis pathway of the moss Physcomitrium patens, revealing insights into the genetic regulation behind this ancestral Embryophyte innovation.