Antisense reduction in NADP-ME in C4 F. bidentis alters stomatal sensitivity to [CO2]

Emmanuel L. Bernardo, Cristina Rodriguez-Sales, Johannes Kromdijk
Institute of Crop Science, College of Agriculture and Food Science, University of the Philippines Los Baños, College, Laguna 4031 Philippines

Stomata have the crucial role of balancing the uptake of CO2 for photosynthesis and water loss via transpiration by adjusting its aperture. In C4 plants, the C4 photosynthetic mechanism must balance the CO2 supplied through the stomatal pores to the C3 cycle and the photosynthetic demand for CO2 of the C4 cycle. It was hypothesized that perturbing the C4 cycle, resulting in reduced carbon flux into the bundle sheath cells, may alter stomatal regulation. To test this hypothesis, we performed gas exchange measurements on transgenic C4 F. bidentis with reduced NADP-ME activity. While responses to red light and stomatal sensitivity to blue light appeared unaffected by the decrease in NADP-ME activity, the results showed that NADP-ME antisense lines of C4 F. bidentis had unaltered gs at higher operational Ci than WT. However, when measurements were performed at common (WT) Ci, gs was higher in the mutant lines, suggesting that disruption of the C4 cycle disrupted stomatal sensitivity to [CO2].