Potassium is an indispensable element in plants. Hak / Kup / KT, the most important family of potassium transporters, is not only involved in the absorption and transport of potassium ions, but also in the regulation of plant growth, development and salt tolerance. However, the mechanism of Kup / Hak / KT protein family regulating auxin polar transport (PAT) by chemical osmosis remains to be studied.
The potassium transporter oshak5 has a very high affinity for potassium ions, and even after the inactivation of oshak5, even increasing the concentration of potassium ions can not restore the normal phenotype of plants. After inactivation and overexpression of oshak5 gene in rice cultivar Japan Qinghe Dongjin, xu Guohua team of Nanjing Agricultural University found that the inactivation of oshak5 reduced pat, tiller number and length of lateral root and root hair of rice, while the overexpression of oshak5 increased pat, root hair and tiller number, which were independent of potassium concentration. The researchers also found that NPA and bum, transporter inhibitors, eliminated oshak5's over expression of Pat. This is because the expression of oshak5 reduces transmembrane potential (depolarization), increases extracellular pH and increases plasma membrane ATPase activity. The results showed that oshak5 had dual regulatory effects on the change of cytochemical osmotic gradient and the regulation of ATP dependent auxin transport. These two effects may be the basis of oshak5 affecting rice structure.
In a word, the potassium transporter oshak5 plays an important role in maintaining the rice structure. Oshak5 can be an important gene to improve the yield of rice and other crops.
Plant Communications, 28 April 2020
Potassium transporter OsHAK5 alters rice architecture via ATP-dependent transmembrane auxin fluxes
Tianyuan Yang, Huimin Feng, Song Zhang…… Angus Murphy, Ling Yu*, Guohua Xu*
*: State Key Laboratory of Crop Genetics and Germplasm Enhancement, MOA Key Laboratory of Plant Nutrition and Fertilization in Lower-Middle Reaches of the Yangtze River, Nanjing Agricultural University, China
Plant HAK/KUP/KT family members function as plasma membrane (PM) H+-K+ symporters and may modulate chemiosmotically driven polar auxin transport (PAT). Here, we show that inactivation of OsHAK5, a rice K+ transporter gene, decreased rootward and shootward PAT, tiller number and length of both lateral roots and root hairs, while OsHAK5-overexpression increased PAT, root hair and tiller number irrespective of K+ supply. Inhibitors of ATP-binding-cassette type-B transporters, NPA and BUM, abolished the OsHAK5-overexpression effect on PAT. The mechanistic basis of these changes includes OsHAK5 decrease of transmembrane potential (depolarization), increase of extracellular pH, and enhancement of PM-ATPase activity. These findings highlight the dual roles of OsHAK5 in altering cellular chemiosmotic gradients (generated continuously by PM H+-ATPase) and regulating an ATP-dependent auxin transport. Both functions may underlie the prominent effect of OsHAK5 on rice architecture. This regulation is likely to be exploited in future manipulations to increase crop yield in the field.
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Xu Guohua team of Nanjing Agricultural University revealed the role of rice phosphorus transporter OsPht1; 3 in the condition of phosphorus deficiency