عملکرد – ساختار در کانال های یون گیاهی همبستگی دارد  Structure–Function Correlates in Plant Ion Channels

In plants, membrane ion transport systems play an important role in maintaining cellular homeostasis and adaptation to environmental changes. This chapter focuses on K þ transport systems because the most knowledge on structure–function correlates of plant ion transporters is available for these proteins. Potassium (K þ ) is the most abundant cation in plant cells. It is present in concentrations that may reach up to 10% of the plant dry weight. K þ has to be absorbed by the roots from the soil, where it is present only in low concentrations, and transported into the aerial part of the plant body. In particular, in leaves, K þ is important for controlling the turgor pressure and the electrochemical membrane potential. The K þ flux across the plasma membrane is highly associated with ion homeostasis and adaptation of the plant to environmental changes. For example, guard cells forming the stomata possess several active K þ transport systems, which control swelling and shrinkage of the cells. This in turn controls CO2 absorption from the air as well as the transpiration stream needed to pump up nutrients from roots to shoots. To satisfy the various needs for K þ transport activities in plant cells, divergent types of K þ channels and K þ transporters have evolved in plants, and these were uncovered during research in the past two decades. The most knowledge was obtained on the model plant Arabidopsis thaliana. Comparison of these channels and transporters with others from different organisms increased the understanding of diverse K þ transport systems and their regulation beyond the organism barrier.