ABSTRACT
Ribulose-1,5-bisphosphate carboxylase/oxygenase activase, RuBisCO (RCA) is a plant nuclear gene that encodes a chloroplast protein, which plays a crucial role in photosynthesis (Pn). RCA is known to facilitate the process of releasing sugar-phosphate inhibitors at RCA catalytic sites during CO2 fixation. Most plant species exhibit two RCA isoforms, that is, shorter RCA-β and larger RCA-α. They are present either by alternative splicing from one gene or expressed from different genes. The process of RuBisCO activation by RCA isoforms has widely been studied in higher plants. The catalytic properties of RuBisCO are mostly regulated as a response to short-term variations in the environment and limit the efficiency of Pn, although these regulations may not be optimally correlated with crop yield. Many of these environmental factors are closely related to decrease RuBisCO activation, which is caused by impairment in RCA functions. With the socioeconomic development, environment has undergone a drastic change over the years bearing the negative impacts of various anthropogenic activities. Environmental (abiotic) stress [e.g., heat, hypoxia, drought, pH, salinity, heavy metal (HM) pollution, elevated ozone (O3) concentration, and ultraviolet-B irradiance] can strongly affect senescence and decrease RuBisCO activity related to downregulation of the enzyme’s activation state by either de-carbamylation or binding of inhibitory sugar phosphates in response to high temperature or drought. On the other hand, the harmful effects of HM stress (like cadmium), low temperature, O3 concentration, and ultraviolet-B (UV-B) stress on the activity of RuBisCO are linked with variations in the enzyme concentration.
