A research team led by RIKEN has discovered a discovery that can be used to improve crop nutrient absorption. The transporter is related to the downward trend of plant roots due to gravity. This phenomenon is called root geotropism1. googletag.cmd.push(function(){googletag.display(‘div-gpt-ad-1449240174198-2′);});
Charles Darwin was one of the first scientists to study the gravity of plant roots. Through simple but elegant experiments, Darwin proved that the root tips of plants can sense gravity, and they can transmit signals to nearby tissues, thereby bending the roots toward gravity. We now know that the plant hormone auxin plays a key role in this gravitational response.
Plant hormones have many physiological functions and can help plants resist environmental fluctuations. In order to function properly, their distribution and activity in cells and tissues must be precisely designed. This usually involves transporters that mediate the cellular uptake or export of hormones or their precursors.
Now, RIKEN biologists have demonstrated that the previously described transporter NPF7.3 can regulate the auxin response and root gravity in the model plant Arabidopsis.
Mitsunori Seo of the RIKEN Sustainable Resources Science Center said: “We noticed that seedlings with mutations in the gene encoding NPF7.3 showed abnormal root growth.” “A closer inspection revealed a specific defect in the gravitational response, as previously reported. The function of NPF7.3 as a nitrate and potassium transporter cannot be explained. This makes us suspect that the protein may also have other previously uncharacterized functions.”
Subsequent experiments showed that NPF7.3 acts as a transporter of indole-3-butyric acid (IBA), and the IBA absorbed by specific root cells through NPF7.3 is converted into indole-3-acetic acid (IAA), which is the main internal Source auxin. This helps to establish an auxin gradient in the root tissue, which in turn guides the gravitational response.
IBA is a secondary precursor of IAA, and the role of IBA-derived IAA in gravitational motion was previously unknown. However, it seems that other plants (including crop species) also have similar regulatory mechanisms, which may lead to agricultural and horticultural applications.
Seo said: “We will be able to modify the root system structure by regulating IBA transmission.” “This will improve the absorption of water and nutrients by the root system, thereby promoting crop production.”
NPF proteins were originally identified as nitrate or peptide transporters, but it is clear that they are more adaptable than previously thought. Seo explained: “Recent studies, including this one, have shown that this transporter family can deliver a variety of compounds, including plant hormones and secondary metabolites.” “The next big question is, we want to know how the NPF protein recognizes this. Multiple substrates.”
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