**Abbreviations**

*Cell Growth*

post-translational modification of K+

tonoplast and might mobilize K+

functional assumption.

to ensure stress adaptation.

**4. Conclusion**

<sup>−</sup> and K<sup>+</sup>

addressed.

stresses.

**Acknowledgements**

NO3

The HAK/KUP/KT transporters were proposed to act as K+

Thus, numerous studies in the field of K<sup>+</sup>

channels [102, 129, 130]. Potassium starvation


membrane transport and intracellular

or NO3

or NO3

from the vacuole under potassium deficiency condi-

symporters in the

<sup>−</sup> and K<sup>+</sup>

<sup>−</sup> and K<sup>+</sup>

<sup>−</sup> shortage, these

<sup>−</sup> starvation.

in

was shown to increase the abundance of HAK transcripts in a wide variety of plants, including barley, rice, *Arabidopsis thaliana*, *Solanum lycopersicum* and some others [19]. Thereby, the mRNA levels of HAK1-type genes were most remarkably increased [17, 105, 129]. The mechanisms, underlying expressional regulation of the HAK1-type genes might rely on alterations of membrane potential, as well as to reactive oxygen species (ROS) and to hormone-mediated signaling [105]. Recently, it was shown that transcription of AtHAK5 in *A. thaliana* roots can be induced by low-potassium nutritional stress via the transcription factor RAP2.11 that directly binds to the promoter region of *AtHAK5* and may be involved in the low-potassium signaling pathway [88].

tions [131]. Indeed, in *Arabidopsis thaliana*, OsHAK10 and five members of the KUP family have been found to be localized in the tonoplast [19] that supports the above

potassium distribution in plants with regard to the changes in the availability of potassium in the environment indicate that the mechanisms supporting ion homeostasis of the plant cell might be involved in plant responses to potassium deficiency

Nutrient deficiency, including moderate or severe shortages of NO3

soils, represents a serious challenge to modern agriculture, negatively affecting plant productivity and crop yields. Fortunately, plants possess an array of finely tuned mechanisms of nutritional stress adjustment and maintenance of cell ion homeostasis. Hence, the plant response to nitrate and potassium deficiency relies both on transcriptional and post-transcriptional regulation of high-affinity

abundance and activity of transporters. Importantly, this includes not only an

studies need to be extended to a broad selection of crop plants. To characterize the adaptive potential of these plants, various exposure times need to be

Currently, proteomics and metabolomics studies, aiming to improve stress

The use of these techniques in research on nutrient stresses seems to be promising. Indeed, these approaches deliver valuable information about the accumulation of important secondary metabolites in plants under different types of environmental

This work was supported by the Russian Science Foundation (project number 17-16-01042) and the EU through EFRE with the state of Saxony-Anhalt

(Agrochemical Institute Piesteritz, IB grant no. ZS/2016/04/78153).

from their storage vacuolar pools and subsequent redistribution to the metabolic cytosolic pool. In general, these data indicate that the ion homeostasis system plays an important role in plant cell responses to nutrient deficiency. Since these

increase in the activity of root ion carriers but also mobilization of NO3

responses depend on plant taxonomy and duration of K<sup>+</sup>

tolerance in crop plants, became mainstream in the study of K+

membrane transport mechanisms, impacting on the increase of

**72**


*Cell Growth*
