This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Potassium (K) is one of the three essential nutrients for plants. It plays a critical role in a wide range of processes, including cell growth, photosynthesis and regulation of water balance.
Plants take up K from the soil and circulate it throughout their bodies via molecules called K+ channels. The function of one such K+ channel (called AKT5) in the model plant Arabidopsis thaliana has remained a mystery, despite more than 30 years of study. Understanding the gateways for what is essentially the life force of plants is crucial for finding new ways to boost agricultural productivity.
To solve this mystery, the Uozumi laboratory at Tohoku University has identified the K+ channel activity of AKT5 in the Arabidopsis plant. This research reveals AKT5's actual function for the first time. Physiologically, AKT5 promotes leaf stalk growth, offering new insights into developing efficient high-density cropping systems.
The findings were published in Science Advances. "The leaf stalk is the edible part of many vegetables, such as celery and Swiss chard," explains Nobuyuki Uozumi. "By regulating AKT5 activity in these plants, it may be possible to tailor the size and texture of these stalks to meet consumer needs." The research group attempted to detect the K+ transport activity of AKT5 using animal cell expression systems.
Initially, no activity was detected. However, when a specific enzyme that adds phosphate groups to proteins was introduced together with AKT5, K+ transport activity was detected for the first time. AKT5 is activated when a phosphate group attaches to a specific amino acid in the protein, which is why there was no activity when K+ alone was added.
To better understand how AKT5 is activated, the researchers used cryo-electron microscopy to determine its three-dimensional structure in the pre-open and closed states. AKT5 adopts a shape very similar to other known K+ channels, yet it can transform. In fact, when a single amino acid in AKT5 was changed (aspartate at position 403 was replaced with alanine), the structure of the molecule changed dramatically, and AKT5 gained K+ transport activity even without phosphorylation.
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