Abstract
Compared with C3 plants, C4 plants maintain lower stomatal conductance (gs), attributed to decreased maximal stomatal conductance (gsmax), without losing photosynthetic CO2 uptake rate. Which stomatal characteristics caused the decreased gsmax and how did the characteristics change along C4 evolution as well as the molecular mechanism underlying this change remains unknown.
Stomatal patternings were examined in Flaveria genus, which contains species at different evolutionary stages from C3 to C4 photosynthesis. We further used comparative transcriptomics, transgenic experiments and semi-in-vitro analysis to identify the gene underlying the decreased gsmax in C4 species.
Results were as follows: the evolution from C3 to C4 species was accompanied by a stepwise decrease in stomatal density (SD) and dramatic decreased SD occurred between C3-C4 species and C4-like species; FSTOMAGEN gene positively controls SD and its changed expression underlies the decreased SD during C4 evolution; Furthermore, this mechanism is shared between monocotyledons and dicotyledons, indicated by the lower expression of FSTOMAGEN homologs in maize than rice.
This study suggests that lower SD is another major feature of C4 evolution, besides C4 enzymes and Kranz anatomy. FSTOMAGEN can be used to engineer lowered SD, a C4 feature required in the current effort of C4 crop engineering.
Competing Interest Statement
The authors have declared no competing interest.