Nitrogen (N), potassium (K), and phosphorus (P) are essential macronutrients for plant growth and development, and their availability affects crop yield. Compared with N, the relatively low ...availability of K and P in soils limits crop production and thus threatens food security and agricultural sustainability. Improvement of plant nutrient utilization efficiency provides a potential route to overcome the effects of K and P deficiencies. Investigation of the molecular mechanisms underlying how plants sense, absorb, transport, and use K and P is an important prerequisite to improve crop nutrient utilization efficiency. In this review, we summarize current understanding of K and P transport and signaling in plants, mainly taking Arabidopsis thaliana and rice (Oryza sativa) as examples. We also discuss the mechanisms coordinating transport of N and K, as well as P and N.
Potassium (K) and phosphorus (P) are essential macronutrients for plant growth, development, and crop yield. This review summarizes the current understanding of K and P transport and signaling in plants and discusses the mechanisms coordinating N (nitrogen), K, and P.
As one of the most important mineral nutrient elements, potassium (K(+)) participates in many plant physiological processes and determines the yield and quality of crop production. In this review, we ...summarize K(+) signaling processes and K(+) transport regulation in higher plants, especially in plant responses to K(+)-deficiency stress. Plants perceive external K(+) fluctuations and generate the initial K(+) signal in root cells. This signal is transduced into the cytoplasm and encoded as Ca(2+) and reactive oxygen species signaling. K(+)-deficiency-induced signals are subsequently decoded by cytoplasmic sensors, which regulate the downstream transcriptional and posttranslational responses. Eventually, plants produce a series of adaptive events in both physiological and morphological alterations that help them survive K(+) deficiency.
•K+ channels and transporters are involved in diverse physiological processes.•Plants can sense external K+ deficiency and generate low-K+ signals in plant cells.•The transcription of many K+ ...transporter genes are induced by low-K+ stress.•Phosphorylation is crucial for the regulation of both K+ channels and transporters.•Coordination of K+/NO3− absorption and translocation is necessary for plants.
As an essential macronutrient, potassium (K+) plays crucial roles in diverse physiological processes during plant growth and development. The K+ concentration in soils is relatively low and fluctuating. Plants are able to perceive external K+ changes and generate chemical and physical signals in plant cells. The signals can be transducted across the plasma membrane and into the cytosol, and eventually regulates the downstream targets, particularly K+ channels and transporters. As a result, K+ homeostasis in plant cells is modulated, which facilitates plant adaptation to K+ deficient conditions. This minireview focuses on the latest research progress in the diverse functions of K+ channels and transporters as well as their regulatory mechanisms in plant response to low-K+ stress.
Potassium （K^＋） is one of the essential macronutrients for plant growth and development. K^＋ uptake from environment and K^＋ translocation in plants are conducted by K^＋ channels and transporters. In ...this study, we demonstrated that KT/HAK/KUP transporter KUP7 plays crucial roles in K^＋ uptake and translocation in Arabidopsis root. The kup7 mutant exhibited a sensitive phenotype on Iow-K^＋ medium, whose leaves showed chlorosis symptoms compared with wild-type plants. Loss of function of KUP7 led to a reduction of K^＋ uptake rate and K^＋ content in xylem sap under W-deficient conditions. Thus, the K^＋ content in kup7 shoot was significantly reduced under Iow-K^＋ conditions. Localization analysis revealed that KUP7 was predominantly targeted to the plasma membrane. The complementation assay in yeast suggested that KUP7 could mediate K^＋ transport. In addition, phosphorylation on S80, S719, and S721 was important for KUP7 activity. KUP7 was ubiquitously expressed in many organs/tissues, and showed a higher expression level inArabidopsis root. Together, our data demonstrated that KUP7 is crucial for K^＋ uptake inArabidopsis root and might be also involved in K^＋ transport into xylem sap, affecting K^＋ translocation from root toward shoot, especially under K^＋-Iimited conditions.
•Potassium (K) nutrition assures crop yield, quality and tolerance.•Deficiency in K has become a limitation for the development of agriculture.•Genetic improvement of crop K utilization efficiency ...(KUE) is urgently required.•Evidence has been obtained that modification of root architecture can improve K acquisition.•Manipulation of K uptake and transport within the plant is a realistic approach to improving KUE.
Potassium (K) is one of the essential macronutrients for higher plants, not only important for plant growth and development, but also crucial for crop yield and quality. The deficiency in K in large areas of arable land worldwide has become a limitation for sustainable development of agriculture, and threatens the world food security. Along with the increased limitation of K fertilizer supply, the genetic improvement of K utilization efficiency (KUE) of crop plants may become a feasible way to solve the problem. K nutrition depends on an underlying relationship with metabolic regulation which together influence crop yield, quality and responses to environmental stress. Manipulation of root architecture together with K transport and distribution within the plant offer great potential to improve KUE.
The changes in external K^＋ concentration affect plant root growth. However, the molecular mechanism for perceiving a K^＋ signal to modulate root growth remains unknown. It is hypothesized that the ...K^＋ channel AKTI is involved in low K^＋ sensing in the Arabidopsis root and subsequent regulation of root growth. Along with the decline of external K^＋ concentration, the primary root growth of wild-type plants was gradually inhibited. However, the primary root of the akt1 mutant could still grow under low K^＋（LK） conditions. Application of NAA inhibited akt1 root growth, but promoted wild-type root growth under LK conditions. By using the ProDR5：GFP and ProPIN1：PIN1-GFP lines, we found that LK treatment reduced auxin accumulation in wild-type root tips by degrading PIN1 proteins, which did not occur in the akt1 mutant. The LK-induced PIN1 degradation may be due to the inhibition of vesicle trafficking of PIN1 proteins. In conclusion, our findings indicate that AKT1 is required for an Arabidopsis response to changes in external K^＋, and subsequent regulation of K^＋-dependent root growth by modulating PINt degradation and auxin redistribution in the root.
The phytohormone abscisic acid (ABA) modulates a number of processes during plant growth and development. In this study, the molecular mechanism of Arabidopsis RAV (Related to ABI3/VP1) transcription ...factor RAV1 involving ABA signaling was investigated. RAV1‐underexpressing lines were more sensitive to ABA than wild‐type plants during seed germination and early seedling development, whereas RAV1‐overexpressing lines showed strong ABA‐insensitive phenotypes. Overexpression of RAV1 repressed ABI3, ABI4, and ABI5 expression, and RAV1 bound to the ABI3, ABI4, and ABI5 promoters in vitro and in vivo, indicating that RAV1 directly down‐regulates the expression of ABI3, ABI4, and ABI5. The interruption of ABI5 function in RAV1‐U abi5 plants abolished the ABA‐hypersensitive phenotype of RAV1‐U plants, demonstrating that ABI5 is epistatic to RAV1. RAV1 interacted with SNF1‐RELATED PROTEIN KINASE SnRK2.2, SnRK2.3 and SnRK2.6 in the nucleus. In vitro kinase assays showed that SnRK2.2, SnRK2.3 and SnRK2.6 phosphorylated RAV1. Transient expression assays revealed that SnRK2.2, SnRK2.3 and SnRK2.6 reduced the RAV1‐dependent repression of ABI5, and the ABA‐insensitive phenotype of the RAV1‐overexpressing line was impaired by overexpression of SnRK2.3 in the RAV1 OE3 plants. Together, these results demonstrated that the Arabidopsis RAV1 transcription factor plays an important role in ABA signaling by modulating the expression of ABI3, ABI4, and ABI5, and that its activity is negatively affected by SnRK2s.
Potassium (K+) is an essential macronutrient for plant growth and development. Transporters from the KT/HAK/KUP family play crucial roles in K+ homeostasis and cell growth in various plant species. ...However, their physiological roles in maize are still unknown. In this study, we cloned ZmHAK5 and ZmHAK1 and investigated their functions in maize (Zea mays L.). In situ hybridization showed that ZmHAK5 was mainly expressed in roots, especially in the epidermis, cortex, and vascular bundle. ZmHAK5 was characterized as a high‐affinity K+ transporter. Loss of function of ZmHAK5 led to defective K+ uptake in maize, under low K+ conditions, whereas ZmHAK5‐overexpressing plants showed increased K+ uptake activity and improved growth. ZmHAK1 was upregulated under low K+ stress, as revealed by RT‐qPCR. ZmHAK1 mediated K+ uptake when heterologously expressed in yeast, but its transport activity was weaker than that of ZmHAK5. Overexpression of ZmHAK1 in maize significantly affected K+ distribution in shoots, leading to chlorosis in older leaves. These findings indicate that ZmHAK5 and ZmHAK1 play distinct roles in K+ homeostasis in maize, functioning in K+ uptake and K+ distribution, respectively. Genetic manipulation of ZmHAK5 may represent a feasible way to improve K+ utilization efficiency in maize.
Transporters from the KT/HAK/KUP family play crucial roles in K+ homeostasis and cell growth in plants. Here we demonstrate that K+ transporters ZmHAK5 and ZmHAK1 play distinct roles in K+ homeostasis in maize, functioning in K+ uptake and K+ distribution, respectively.
Since phosphorus is an essential nutrient for plants, plants have evolved a number of adaptive mechanisms to respond to changes in phosphate (Pi) supply. Previously, we reported that the ...transcription factor WRKY6 modulates Pi homeostasis by downregulating PHOSPHATE1 (PHO1) expression and that WRKY6 is degraded during Pi starvation in Arabidopsis thaliana. However, the molecular mechanism underlying low-Pi-induced WRKY6 degradation was unknown. Here, we report that a ubiquitin E3 ligase, PHOSPHATE RESPONSE UBIQUITIN E3 LIGASE1 (PRU1), modulates WRKY6 protein levels in response to low-Pi stress. Apru1 mutant was more sensitive than the wild type to Pi-deficient conditions, exhibiting a reduced Pi contents in the shoot, similar to the pho1-2 mutant and WRKY6-overexpressing line. PRU1 interacted with WRKY6 in vitro and in vivo. Under low-Pi stress, the ubiquitination and subsequent degradation of WRKY6, as well as the consequential enhancement of PHO1 expression, were impaired in pru1. PRU1 complementation lines displayed no obvious differences compared with wild-type plants. Further genetic analysis showed that disruption of WRKY6 abolished the low-Pi sensitivity of pru1, indicating that WRKY6 functioned downstream of PRU1. Taken together, this study uncovers a mechanism by which PRU1 modulates Pi homeostasis, through regulating the abundance of WRKY6 in response to low-Pi stress in Arabidopsis.
Drought is a major threat to plant growth and crop productivity. Calcium-dependent protein kinases (CDPKs, CPKs) are believed to play important roles in plant responses to drought stress. Here, we ...report that Arabidopsis thaliana CPK8 functions in abscisic acid (ABA)- and Ca2+-mediated plant responses to drought stress. The cpk8 mutant was more sensitive to drought stress than wild-type plants, while the transgenic plants overexpressing CPK8 showed enhanced tolerance to drought stress compared with wild-type plants. ABA-, H2O2-, and Ca2+-induced stomatal closing were impaired in cpk8 mutants. Arabidopsis CATALASE3 (CAT3) was identified as a CPK8-interacting protein, confirmed by yeast two-hybrid, coimmunoprecipitation, and bimolecular fluorescence complementation assays. CPK8 can phosphorylate CAT3 at Ser-261 and regulate its activity. Both cpk8 and cat3 plants showed lower catalase activity and higher accumulation of H2O2 compared with wild-type plants. The cat3 mutant displayed a similar drought stress-sensitive phenotype as cpk8 mutant. Moreover, ABA and Ca2+ inhibition of inward K+ currents were diminished in guard cells of cpk8 and cat3 mutants. Together, these results demonstrated that CPK8 functions in ABA-mediated stomatal regulation in responses to drought stress through regulation of CAT3 activity.
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