Insights from the developmental genes of sedges and grasses

The evolution of stomatal morphology is a defining trait among plant
lineages. Grasses (Poaceae) have distinctive dumbbell-shaped stomata that
enhance water-use efficiency compared to the more common kidney-shaped
stomata. In the closely related sedges (Cyperaceae), both kidney-shaped
and dumbbell-like stomata can be found. Dumbbell-like stomata in sedges
share morphological features with grasses, suggesting potential
conservation of developmental pathways. To investigate the evolution of
dumbbell and dumbbell-like stomata, we analyzed genomic and transcriptomic
data from 29 sedge species and 5 grass species. Using their predicted
proteomes, we identified orthologues involved in stomatal development and
reconstructed their phylogenetic histories. Among the 16 gene families
analyzed, EPFL9, YODA, SCR, and SHR were expanded in grasses but not in
sedges. POLAR, SPCH, and ABI were expanded in both lineages, seven
families were conserved in both, BASL was lost in both, and, in the
SCRM/ICE family, SCRM was lost while ICE was duplicated in sedges. Gene
family expansion in grasses occurred primarily in genes involved in early
stages of stomatal development, while gene families non-duplicated or
independently expanded act in later stages. The non-duplicated or
independently expanded genes shared by sedges and grasses contribute to
development of the two lateral subsidiary cells as well as the guard
cells, suggesting shared regulatory networks underlying the stomata
morphology typical of the order Poales. Our study provides a crucial guide
to further test functional proteins underlying paracytic dumbbell-like
stomata development.