The Role of Grass Orthologues During Stomatal Development.

Gas exchange between the plant and the atmosphere takes place through stomatal pores formed by paired guard cells. Grasses develop a unique stomatal structure that consists of two dumbbell-shaped guard cells flanked by lateral subsidiary cells. These structures confer a very efficient gas exchange capacity, which may have contributed to the evolutionary success of grasses. Recent works have identified orthologues of Arabidopsis in three grass species: in , in maize, and in rice. These genes induce the recruitment of subsidiary cells, and it appears to rely upon the ability of intercellular movement, from the guard mother cell to subsidiary mother cells, of the proteins encoded by them. Unexpectedly, this function of these grass genes contrasts with that of Arabidopsis , which promotes guard mother cell identity. These orthologues also appear to control guard mother cell fate progression, with the action of being less severe than those of and The emerging picture unravels that grass genes have not only diverged, due to neo-functionalization, from Arabidopsis , but also among them.