Manipulating Guard Cell Anatomy and Physiology Using Biotechnological Approaches to Understanding Impact on Crop Performance

Stomata are pores on the leaf surrounded by specialized epidermal cells called guard cells (GCs). GCs increase or decrease in volume in response to internal and external stimuli thereby regulating stomata aperture. In most plants, the changes exhibited by GCs alter stomatal aperture and affect the flux of gases between the internal leaf environment and the atmosphere and therefore have great control on photosynthetic processes and water loss from the plant. The number and patterning of stomata on a leaf are determined by a developmental pathway involving the epidermal patterning factor (EPF) protein family. Several EPF members affect epidermal cell density, stomata density as well as cell spacing, through their role in regulating cell division and differentiation. Understanding and manipulating EPFs has the potential to increase plant productivity and increase food supply. The co-ordination of stomata activities and photosynthesis may involve GC chloroplasts, during photosynthetic electron transport chain (ETC) and Calvin cycle activities. Ferredoxin (Fd) protein plays an important role in regulating the production of ATP and photosynthetic reductants as well as activation of the Calvin cycle enzymes. Anatomical features such as stomata density, number and patterning all influence stomatal gas exchange and water use efficiency (WUE) of the plant. This study utilized transgenic plants expressing the cyanobacteria inorganic carbon transporter (ictB), which have already been shown to have high photosynthetic rates and plant growth for multiple genes cloning of EPF1, EPF2, EPFL9 and Fd. Preliminary work on gene expression, chlorophyll fluorescence, stomata density and gas-exchange analysis were carried out to assess different photosynthetic parameters. The operating efficiency of PSII was similar for all T0 and T1 generations of all EPFs and Fd plants. Stomata density analysis confirmed that EPF1 and EPF2 genes are negative regulators of stomata while EPF9 increase stomata density. EPF1 and EPF2 plants showed lower conductance and compare to EPF9. Fd was found to enhance plant’s electron transport and Calvin cycle activities.