Intracellular carbon dioxide and redox state of plastoquinone pool as regulators of ethylene biosynthesis pathway

Plants, like animals, are exposed to numerous and diverse stress factors. Their response to
environmental stimuli is mediated with a vast number of substances. Hormones may play a role of
such agents, and one of them is ethylene (ET). This simple - in terms of the chemical structure -
particle participates in the regulation of reactions to biotic stresses (derived from bacteria, fungi,
viruses, etc.) and abiotic (inanimate components of the environment). We know that ET biosynthesis
is modified by several factors, and one of them is the intracellular concentration of carbon dioxide
(CO2). In our model, we use a plant (ice plant) which besides the classic photosynthesis type C3 (CO2
fixed mainly during the day), can switch to CAM photosynthesis (CO2 fixed mainly in the dark). The
implementation of CAM, although it allows a significant water saving (stomata closed during the day),
has certain consequences. One of them is the daily oscillations of intracellular CO2 concentration and
this can affect the daily production of ET. Using the model that allows us to run experiments on plants
carrying out C3 and CAM at the same developmental stage, we intend to check how the presence of
circadian CO2 oscillations modifies the work of the most important components of the ET biosynthesis
pathway. It has recently been shown that plant reactions to abiotic stress factors are regulated by the
redox state of the plastoquinone pool (PQ), a component of the electron transport pathway in the
chloroplast. PQ and ET form a regulatory system where PQ plays a superior role, and ET - together
with components of the antioxidative system (regulation of cell redox homeostasis) are executives.
Using the described model, we intend to check, how the modification of the redox state of the PQ pool
affects the components of the ET biosynthesis pathway, and thus its daily production. In addition,
using this model, we intend to determine how the work of the PQ-ET regulatory system is affected
with the presence of different types of photosynthesis.