Plant CO2 Sensors

About

It is currently unknown how plants sense the level of CO2 in the atmosphere. Previously, no CO2 sensors have been identified in plants. Knowledge of how atmospheric CO2 is perceived could be used to manipulate plant CO2 responses so that the carbon and water use efficiency during plant growth could be optimized. The water use efficiency defines how well a plant can balance the loss of water through stomata with the net CO2 uptake for photosynthesis, and hence biomass accumulation.   Description UC San Diego investigators have found a new method to manipulate the exchange of water and CO2 through guard-cell stomata by controlling newly discovered CO2 sensor genes. One can thereby modify net CO2 uptake and water use efficiency in plants by modulating expression of these genes in guard cells. These findings suggest a potentially vital role for the identified genes in the sensing/signaling of CO2 in plants. These investigators have also identified a guard cell-specific promoter that drives higher levels of expression than any other promoter in guard cells. Plant guard cells control CO2 uptake and water loss and are critically important for drought tolerance. This promoter has strength and specificity allowing effective transgene expression or silencing. Compared with other well-known guard cell promoters, this super-strong guard cell promoter is around 20 times stronger. Compared with the commonly used universal strong cauliflower mosaic virus 35S promoter, this super-strong guard cell promoter drives much higher expression of reporter genes specifically in guard cells with a minimum background expression in the surrounding cells. The plants with mutated CO2 sensor genes show a stomatal response as measured by real-time gas exchange analysis to changes in CO2 concentration. The proteins encoding the CO2 sensing genes can bind CO2.