PROGRESS ON PHYSIOLOGICAL RESPONSE AND SIGNAL TRANSDUCTION MECHANISM OF CYANOBACTERIA IN IRON DEFICIENT ENVIRONMENT

Cyanobacteria are one of the oldest photosynthetic oxygen evolving organisms on Earth and play a crucial role in global primary productivity, accounting for about a quarter of the world's total carbon sequestration. Iron, an essential trace element, is vital for the growth and reproduction of cyanobacteria and an important cofactor in many key physiological reactions. As photosynthetic organisms, cyanobacteria exhibit a higher demand for iron than other non-photosynthetic organisms to support photosynthetic electron transport and chlorophyll synthesis. Although iron is abundant in the Earth's environment, its bioavailability is low, which is an important factor limiting global primary productivity. In order to solve the contradiction between their own high-speed rail demand and the lack of iron in the environment, cyanobacteria have developed a unique iron deficiency adaptation mechanism during long-term evolution to meet their growth needs under iron limited conditions. This review summarized a series of physiological responses to iron deficiency stress and the absorption mechanisms of iron elements in cyanobacteria. It also provides an overview of the signal transduction mechanism by which cyanobacteria sense environmental iron concentration, and describes the molecular mechanisms of various transcription regulators in maintaining the intracellular iron homeostasis.