Departamento de Nutrición Vegetal, CEBAS-CSIC, Campus de Espinardo, Murcia, 30100, Spain.
Physiol Plant. 2014 Nov;152(3):558-70. doi: 10.1111/ppl.12205. Epub 2014 May 26.
The high-affinity K(+) transporter HAK5 is a key system for root K(+) uptake and, under very low external K(+), the only one capable of supplying K(+) to the plant. Functional HAK5-mediated K(+) uptake should be tightly regulated for plant adaptation to different environmental conditions. Thus, it has been described that the gene encoding the transporter is transcriptionally regulated, being highly induced under K(+) limitation. Here we show that environmental conditions, such as the lack of K(+), NO(3)(-) or P, that induced a hyperpolarization of the plasma membrane of root cells, induce HAK5 transcription. However, only the deprivation of K(+) produces functional HAK5-mediated K(+) uptake in the root. These results suggest on the one hand the existence of a posttranscriptional regulation of HAK5 elicited by the low K(+) signal and on the other that HAK5 may be involved in yet-unknown functions related to NO(3)(-) and P deficiencies. These results have been obtained here with Solanum lycopersicum (cv. Micro-Tom) as well as Arabidopsis thaliana plants, suggesting that the posttranscriptional regulation of high-affinity HAK transporters take place in all plant species.
高亲和力 K(+)转运体 HAK5 是根 K(+)摄取的关键系统，在极低的外部 K(+)条件下，它是唯一能够向植物供应 K(+)的系统。为了使植物适应不同的环境条件，HAK5 介导的功能性 K(+)摄取应该受到严格的调控。因此，已经描述了转运体的基因是转录调控的，在 K(+)限制下高度诱导。在这里，我们表明，环境条件，如缺乏 K(+)、NO(3)(-)或 P，会导致根细胞质膜超极化，从而诱导 HAK5 的转录。然而，只有剥夺 K(+)才能在根中产生功能性的 HAK5 介导的 K(+)摄取。这些结果一方面表明存在由低 K(+)信号引发的 HAK5 的转录后调控，另一方面表明 HAK5 可能参与与 NO(3)(-)和 P 缺乏相关的未知功能。这些结果是在番茄（Micro-Tom 品系）和拟南芥植物中获得的，表明高亲和力 HAK 转运体的转录后调控在所有植物物种中都存在。
