The sugar transporter ZmSUGCAR1 of the nitrate transporter 1/peptide transporter family is critical for maize grain filling.

Maternal-to-filial nutrition transfer is central to grain development and yield. nitrate transporter 1/peptide transporter (NRT1-PTR)-type transporters typically transport nitrate, peptides, and ions. Here, we report the identification of a maize (Zea mays) NRT1-PTR-type transporter that transports sucrose and glucose. The activity of this sugar transporter, named Sucrose and Glucose Carrier 1 (SUGCAR1), was systematically verified by tracer-labeled sugar uptake and serial electrophysiological studies including two-electrode voltage-clamp, non-invasive microelectrode ion flux estimation assays in Xenopus laevis oocytes and patch clamping in HEK293T cells. ZmSUGCAR1 is specifically expressed in the basal endosperm transfer layer and loss-of-function mutation of ZmSUGCAR1 caused significantly decreased sucrose and glucose contents and subsequent shrinkage of maize kernels. Notably, the ZmSUGCAR1 orthologs SbSUGCAR1 (from Sorghum bicolor) and TaSUGCAR1 (from Triticum aestivum) displayed similar sugar transport activities in oocytes, supporting the functional conservation of SUGCAR1 in closely related cereal species. Thus, the discovery of ZmSUGCAR1 uncovers a type of sugar transporter essential for grain development and opens potential avenues for genetic improvement of seed-filling and yield in maize and other grain crops.

CPK28-mediated phosphorylation enhances nitrate transport activity of NRT2.1 during nitrogen deprivation.

Nitrate (NO3 -) serves as the primary inorganic nitrogen source assimilated by most terrestrial plants. The acquisition of nitrate from the soil is facilitated by NITRATE TRANSPORTERS (NRTs), with NRT2.1 being the key high-affinity nitrate transporter. The activity of NRT2.1, which has multiple potential phosphorylation sites, is intricately regulated under various physiological conditions. Here, we discovered that CALCIUM-DEPENDENT PROTEIN KINASE 28 (CPK28) positively regulates nitrate uptake under nitrogen deprivation conditions. We found CPK28 as the kinase targeted by immunoprecipitation followed by mass spectrometry and examined the in-planta phosphorylation status of NRT2.1 in cpk28 mutant plants by employing quantitative MS-based phosphoproteomics. Through a combination of in vitro phosphorylation experiment and immunoblotting using phospho-specific antibody, we successfully demonstrated that CPK28 specifically phosphorylates NRT2.1 at Ser21. Functional analysis conducted in Xenopus oocytes revealed that co-expression of CPK28 significantly enhanced high-affinity nitrate uptake of NRT2.1. Further investigation using transgenic plants showed that the phosphomimic variant NRT2.1S21E, but not the nonphosphorylatable variant NRT2.1S21A, fully restored high-affinity 15NO3 - uptake ability in both nrt2.1 and cpk28 mutant backgrounds. This study clarifies that the kinase activity of CPK28 is promoted during nitrogen deprivation conditions. These significant findings provide valuable insights into the intricate regulatory mechanisms that govern nitrate-demand adaptation.

The relationship between coronary artery calcification and bone metabolic markers in maintenance hemodialysis patients.

BACKGROUND: To study the influencing factors for coronary artery calcification (CAC) in maintenance hemodialysis (MHD) patients and the relationship between CAC and bone metabolism markers and to attempt to find a reliable marker linking vascular calcification and bone metabolism in MHD patients. METHODS: A total of 123 patients were enrolled. CAC was assessed by multislice spiral computed tomography (MSCT), and the CAC score (CACS) was evaluated using the Agaston method. Routine laboratory parameters, including triglycerides (TG), total cholesterol (TC), glucose (Glu), calcium (Ca), phosphorus (P), magnesium (Mg), etc., were measured. Serum markers of bone metabolism, such as alkaline phosphatase(ALP), calcitonin (CT), 25-hydroxy vitamin D [25-(OH)D], intact parathyroid hormone (iPTH), total type I procollagen amino-terminal peptide (tPINP), N-terminal mid-fragment of osteocalcin (N-MID OC), and ß-type I collagen crosslinked carboxyl-terminal peptide (ß-CTX), were also measured. RESULTS: Among 123 MHD patients, 37 patients (30.08%) did not have CAC, and 86 patients (69.92%) had CAC, including 41 patients (47.67%) with mild calcification and 45 patients (52.33%) with moderate to severe calcification. Age, Body Mass Index(BMI), the prevalence of hypertension and diabetes mellitus, TC, Glu, P, and Ca×P in the calcification group were higher than those in the noncalcification group, whereas Mg, iPTH, tPINP, N-MID OC, and ß-CTX were lower than those in the noncalcified group (P < 0.05). Compared with the mild calcification group (0 0.05). A logistic regression model was used to evaluate the influencing factors for CAC. The results showed that age, BMI, TC, Glu, P, and Ca×P were risk factors for CAC and its severity in MHD patients, whereas diabetes mellitus, Mg, and N-MID OC were protective factors for CAC in MHD patients. In addition, N-MID OC was a protective factor for the severity of CAC. After adjusting for the corresponding confounding factors, the results of the risk factors were consistent, and N-MID OC was still an independent protective factor for CAC and its severity. CONCLUSIONS: Elevated serum P and Ca×P were independent risk factors for CAC in MHD patients, and serum Mg may be an independent protective factor for CAC. CAC was closely related to abnormal bone metabolism and bone metabolic markers in MHD patients. Relatively low bone turnover can promote the occurrence and development of CAC. N-MID OC may be a reliable bone metabolic marker linking vascular calcification and bone metabolism in MHD patients.

Two calcium-dependent protein kinases enhance maize drought tolerance by activating anion channel ZmSLAC1 in guard cells.

Stomatal closure is an important process to prevent water loss in plants response to drought stress, which is finely modulated by ion channels together with their regulators in guard cells, especially the S-type anion channel AtSLAC1 in Arabidopsis. However, the functional characterization and regulation analyses of anion channels in gramineous crops, such as in maize guard cells are still limited. In this study, we identified an S-type anion channel ZmSLAC1 that was preferentially expressed in maize guard cells and involved in stomatal closure under drought stress. We found that two Ca2+ -dependent protein kinases ZmCPK35 and ZmCPK37 were expressed in maize guard cells and localized on the plasma membrane. Lesion of ZmCPK37 resulted in drought-sensitive phenotypes. Mutation of ZmSLAC1 and ZmCPK37 impaired ABA-activated S-type anion currents in maize guard cells, while the S-type anion currents were increased in the guard cells of ZmCPK35- and ZmCPK37-overexpression lines. Electrophysiological characterization in maize guard cells and Xenopus oocytes indicated that ZmCPK35 and ZmCPK37 could activate ZmSLAC1-mediated Cl- and NO3- currents. The maize inbred and hybrid lines overexpressing ZmCPK35 and ZmCPK37 exhibited enhanced tolerance and increased yield under drought conditions. In conclusion, our results demonstrate that ZmSLAC1 plays crucial roles in stomatal closure in maize, whose activity is regulated by ZmCPK35 and ZmCPK37. Elevation of ZmCPK35 and ZmCPK37 expression levels is a feasible way to improve maize drought tolerance as well as reduce yield loss under drought stress.

The Transcription Factor MYB59 Regulates K+/NO3 - Translocation in the Arabidopsis Response to Low K+ Stress.

Potassium and nitrogen are essential nutrients for plant growth and development. Plants can sense potassium nitrate (K+/NO3 -) levels in soils, and accordingly they adjust root-to-shoot K+/NO3 - transport to balance the distribution of these ions between roots and shoots. In this study, we show that the transcription factorMYB59 maintains this balance by regulating the transcription of the Arabidopsis (Arabidopsis thaliana) Nitrate Transporter1.5 (NRT1.5)/ Nitrate Transporter/Peptide Transporter Family7.3 (NPF7.3) in response to low K+ (LK) stress. The myb59 mutant showed a yellow-shoot sensitive phenotype when grown on LK medium. Both the transcript and protein levels of NPF7.3 were remarkably reduced in the myb59 mutant. LK stress repressed transcript levels of both MYB59 and NPF7.3 The npf7.3 and myb59 mutants, as well as the npf7.3 myb59 double mutant, showed similar LK-sensitive phenotypes. Ion content analyses indicated that root-to-shoot K+/NO3 - transport was significantly reduced in these mutants under LK conditions. Moreover, chromatin immunoprecipitation and electrophoresis mobility shift assay assays confirmed that MYB59 bound directly to the NPF7.3 promoter. Expression of NPF7.3 in root vasculature driven by the PHOSPHATE 1 promoter rescued the sensitive phenotype of both npf7.3 and myb59 mutants. Together, these data demonstrate that MYB59 responds to LK stress and directs root-to-shoot K+/NO3 - transport by regulating the expression of NPF7.3 in Arabidopsis roots.

KUP9 maintains root meristem activity by regulating K+ and auxin homeostasis in response to low K.

Potassium (K) is essential for plant growth and development. Here, we show that the KUP/HAK/KT K+ transporter KUP9 controls primary root growth in Arabidopsis thaliana. Under low-K+ conditions, kup9 mutants displayed a short-root phenotype that resulted from reduced numbers of root cells. KUP9 was highly expressed in roots and specifically expressed in quiescent center (QC) cells in root tips. The QC acts to maintain root meristem activity, and low-K+ conditions induced QC cell division in kup9 mutants, resulting in impaired root meristem activity. The short-root phenotype and enhanced QC cell division in kup9 mutants could be rescued by exogenous auxin treatment or by specifically increasing auxin levels in QC cells, suggesting that KUP9 affects auxin homeostasis in QC cells. Further studies showed that KUP9 mainly localized to the endoplasmic reticulum (ER), where it mediated K+ and auxin efflux from the ER lumen to the cytoplasm in QC cells under low-K+ conditions. These results demonstrate that KUP9 maintains Arabidopsis root meristem activity and root growth by regulating K+ and auxin homeostasis in response to low-K+ stress.

Correction: Arabidopsis WRKY6 Transcription Factor Acts as a Positive Regulator of Abscisic Acid Signaling during Seed Germination and Early Seedling Development.

[This corrects the article DOI: 10.1371/journal.pgen.1005833.].

Diagnosis, treatment and genetic analysis of a case of familial aldosteronism type II with WFS1 gene mutation.

Primary aldosteronism (PA) is a disease characterized by hypertension and hypokalemia due to the excessive aldosterone secretion from the adrenal cortex, which leads to the retention of both water and sodium, and the inhibition of the renin-angiotensin system as well. Familial hyperaldosteronism type II (FH-II) is known as an autosomal dominant hereditary disease, which is a scarce cause of PA. In this report, we cllected the clinical data of a patient with repeated hypertension and hypokalemia of uncertain diagnosis since 2014. Nevertheless, we discovered by genetic sequencing in 2021 that the CLCN2 and WFS1 gene mutation of the patient, whose mother belongs to heterozygote genotype and father belongs to wild-type genotype. Combined with a series of endocrine function tests and imaging studies, the patient was finally certified her suffering from FH-II and WFS1 gene mutation. By summarizing and analyzing the characteristics and genetic test results of this case, we recommended gene sequencing for patients with PA whose etiology is difficult to be determined clinically. This case also provides new clinical data for subsequent genetic studies of the disease.

The Ubiquitin E3 Ligase PRU1 Regulates WRKY6 Degradation to Modulate Phosphate Homeostasis in Response to Low-Pi Stress in Arabidopsis.

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. A pru1 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.

STOP1 Regulates LKS1 Transcription and Coordinates K+/NH4+ Balance in Arabidopsis Response to Low-K+ Stress.

Potassium and nitrogen are essential mineral elements for plant growth and development. The protein kinase LKS1/CIPK23 is involved in both K+ and NH4+ uptake in Arabidopsis root. The transcripts of LKS1 can be induced by low K+ (0.1 mM) and high NH4+ (30 mM); however, the molecular mechanism is still unknown. In this study, we isolated the transcription factor STOP1 that positively regulates LKS1 transcription in Arabidopsis responses to both low-K+ and high-NH4+ stresses. STOP1 proteins can directly bind to the LKS1 promoter, promoting its transcription. The stop1 mutants displayed a leaf chlorosis phenotype similar to lks1 mutant when grown on low-K+ and high-NH4+ medium. On the other hand, STOP1 overexpressing plants exhibited a similar tolerant phenotype to LKS1 overexpressing plants. The transcript level of STOP1 was only upregulated by low K+ rather than high NH4+; however, the accumulation of STOP1 protein in the nucleus was required for the upregulation of LKS1 transcripts in both low-K+ and high-NH4+ responses. Our data demonstrate that STOP1 positively regulates LKS1 transcription under low-K+ and high-NH4+ conditions; therefore, LKS1 promotes K+ uptake and inhibits NH4+ uptake. The STOP1/LKS1 pathway plays crucial roles in K+ and NH4+ homeostasis, which coordinates potassium and nitrogen balance in plants in response to external fluctuating nutrient levels.

Potassium and phosphorus transport and signaling in plants.

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.

Role of the ATP-dependent chromatin remodeling enzyme Fun30/Smarcad1 in the regulation of mRNA splicing.

The yeast ATP-dependent chromatin remodeling enzyme Fun30 has been shown to regulate heterochromatin silencing, DNA repair, transcription, and chromatin organization. Although chromatin structure has been proposed to influence splice site recognition and regulation, whether ATP-dependent chromatin remodeling enzyme plays a role in regulating splicing is not known. In this study, we find that pre-mRNA splicing efficiency is impaired and the recruitment of spliceosome is compromised in Fun30-depleted cells. In addition, Fun30 is enriched in the gene body of individual intron-containing genes. Moreover, we show that pre-mRNA splicing efficiency is dependent on the chromatin remodeling activity of Fun30. The function of Fun30 in splicing is further supported by the observation that, Smarcad1, the mammalian homolog of Fun30, regulates alternative splicing. Taken together, these results provide evidence for a novel role of Fun30 in regulating splicing.

CALCIUM-DEPENDENT PROTEIN KINASE 32-mediated phosphorylation is essential for the ammonium transport activity of AMT1;1 in Arabidopsis roots.

Protein kinase-mediated phosphorylation modulates the absorption of many nutrients in plants. CALCIUM-DEPENDENT PROTEIN KINASES (CPKs) are key players in plant signaling to translate calcium signals into diverse physiological responses. However, the regulatory role of CPKs in ammonium uptake remains largely unknown. Here, using methylammonium (MeA) toxicity screening, CPK32 was identified as a positive regulator of ammonium uptake in roots. CPK32 specifically interacted with AMMONIUM TRANSPORTER 1;1 (AMT1;1) and phosphorylated AMT1;1 at the non-conserved serine residue Ser450 in the C-terminal domain. Functional analysis in Xenopus oocytes showed that co-expression of CPK32 and AMT1;1 significantly enhanced the AMT1;1-mediated inward ammonium currents. In transgenic plants, the phosphomimic variant AMT1;1S450E, but not the non-phosphorylatable variant AMT1;1S450A, fully complemented the MeA insensitivity and restored high-affinity 15NH4+ uptake in both amt1;1 and cpk32 mutants. Moreover, in the CPK32 knockout background, AMT1;1 lost its ammonium transport activity entirely. These results indicate that CPK32 is a crucial positive regulator of ammonium uptake in roots and the ammonium transport activity of AMT1;1 is dependent on CPK32-mediated phosphorylation.

NRT1.5/NPF7.3 Functions as a Proton-Coupled H+/K+ Antiporter for K+ Loading into the Xylem in Arabidopsis.

Potassium and nitrogen are essential macronutrients for plant growth and have a positive impact on crop yield. Previous studies have indicated that the absorption and translocation of K+ and NO3- are correlated with each other in plants; however, the molecular mechanism that coordinates K+ and NO3- transport remains unknown. In this study, using a forward genetic approach, we isolated a low-K+-sensitive Arabidopsis thaliana mutant, lks2, that showed a leaf chlorosis phenotype under low-K+ conditions. LKS2 encodes the transporter NRT1.5/NPF7.3, a member of the NRT1/PTR (Nitrate Transporter 1/Peptide Transporter) family. The lks2/nrt1.5 mutants exhibit a remarkable defect in both K+ and NO3- translocation from root to shoot, especially under low-K+ conditions. This study demonstrates that LKS2 (NRT1.5) functions as a proton-coupled H+/K+ antiporter. Proton gradient can promote NRT1.5-mediated K+ release out of root parenchyma cells and facilitate K+ loading into the xylem. This study reveals that NRT1.5 plays a crucial role in K+ translocation from root to shoot and is also involved in the coordination of K+/NO3- distribution in plants.

Phosphorylation at Ser28 stabilizes the Arabidopsis nitrate transporter NRT2.1 in response to nitrate limitation.

Nitrate is one of the main inorganic nitrogen sources for plants. Nitrate absorption from soils is achieved through the combined activities of specific nitrate transporters. Nitrate transporter 2.1 (NRT2.1) is the major component of the root high-affinity nitrate transport system in Arabidopsis thaliana. Studies to date have mainly focused on transcriptional control of NRT2.1. Here, we show that NRT2.1 protein stability is also regulated in response to nitrogen nutrition availability. When seedlings were transferred to nitrate-limited conditions, the apparent half-life of NRT2.1 in roots increased from 3 to 9 h. This stabilization of NRT2.1 protein occurred rapidly, even prior to the transcriptional stimulation of NRT2.1. Furthermore, we revealed that phosphorylation at serine 28 (Ser28) of NRT2.1 is involved in regulating the stability of this protein. Substitution of Ser28 by alanine resulted in unstable NRT2.1, and this loss-of-phosphorylation mutant (NRT2.1S28A ) failed to complement the growth-restricted phenotype of the nrt2.1 mutant when a low concentration of nitrate was the sole nitrogen source. These results demonstrate that phosphorylation at Ser28 is crucial for NRT2.1 protein stabilization and accumulation in response to nitrate limitation.

Electrophysiological Identification and Activity Analyses of Plasma Membrane K+ Channels in Maize Guard Cells.

Stomatal movement, which plays an essential role in plant transpiration and photosynthesis, is controlled by ion channels that mediate K+ and anion fluxes across the plasma membrane (PM) of guard cells. These channels in dicots are accurately regulated by various physiological factors, such as pH, abscisic acid (ABA) and Ca2+; however, the data in monocots are limited. Here the whole-cell patch-clamping technique was applied to analyze the properties and regulations of PM K+ channels in maize guard cells. The results indicated that the hyperpolarization-activated inward-rectifying channels were highly K+-selective. These inward K+ (Kin) channels were sensitive to extracellular K+. Their slope factor (S) decreased when the apoplastic K+ concentration decline, causing a positive shift of the half-activation potential (V1/2). Their activities were promoted by apoplastic acidification but inhibited by apoplastic and cytosolic alkalization. Nevertheless, the outward K+ (Kout) channel activities were uniquely promoted by cytosolic alkalization. Both apoplastic and cytosolic ABA inhibited Kin channels independent of cytosolic Ca2+ ([Ca2+]cyt). And two Ca2+-dependent mechanisms with different Ca2+ affinities may mediate resting- and high-[Ca2+]cyt-induced inhibition on Kin channels, respectively. However, resting [Ca2+]cyt impaired the inhibition of Kin channels induced by apoplastic ABA, not cytosolic ABA. Furthermore, the result that high [Ca2+]cyt attenuated ABA-induced inhibition highlighted the importance of [Ca2+]cyt for Kin channel regulation. There may exist a Ca2+-dependent regulation of the Ca2+-independent ABA signaling pathways for Kin channel inhibition. These results provided an electrophysiological view of the multiple level regulations of PM K+ channel activities and kinetics in maize guard cells.

Arabidopsis WRKY6 Transcription Factor Acts as a Positive Regulator of Abscisic Acid Signaling during Seed Germination and Early Seedling Development.

The phytohormone abscisic acid (ABA) plays important roles during seed germination and early seedling development. Here, we characterized the function of the Arabidopsis WRKY6 transcription factor in ABA signaling. The transcript of WRKY6 was repressed during seed germination and early seedling development, and induced by exogenous ABA. The wrky6-1 and wrky6-2 mutants were ABA insensitive, whereas WRKY6-overexpressing lines showed ABA-hypersensitive phenotypes during seed germination and early seedling development. The expression of RAV1 was suppressed in the WRKY6-overexpressing lines and elevated in the wrky6 mutants, and the expression of ABI3, ABI4, and ABI5, which was directly down-regulated by RAV1, was enhanced in the WRKY6-overexpressing lines and repressed in the wrky6 mutants. Electrophoretic mobility shift and chromatin immunoprecipitation assays showed that WRKY6 could bind to the RAV1 promoter in vitro and in vivo. Overexpression of RAV1 in WRKY6-overexpressing lines abolished their ABA-hypersensitive phenotypes, and the rav1 wrky6-2 double mutant showed an ABA-hypersensitive phenotype, similar to rav1 mutant. Together, the results demonstrated that the Arabidopsis WRKY6 transcription factor played important roles in ABA signaling by directly down-regulating RAV1 expression.

Colorimetric tyrosinase assay based on catechol inhibition of the oxidase-mimicking activity of chitosan-stabilized platinum nanoparticles.

It is found that catechol inhibits the oxidase-mimicking activity of chitosan-protected platinum nanoparticles (Chit-PtNPs) by competing with the substrate for the active site of the Ch-PtNPs. The inhibition mechanism of catechol is different from that of ascorbic acid in that it neither reacts with O2•- nor reduces the oxidized 3,3',5,5'-tetramethylbenzidine (TMB). Tyrosinase (TYRase) catalyzes the oxidation of catechol, thus restoring the activity of oxidase-mimicking Chit-PtNPs. By combining the Chit-PtNP, catechol, and TYRase interactions with the oxidation of TMB to form a yellow diamine (maximal absorbance at 450 nm), a colorimetric analytical method was developed for TYRase determination and inhibitor screening. The assay works in the 0.5 to 2.5 U·mL-1 TYRase activity range, and the limit of detection is 0.5 U·mL-1. In our perception, this new assay represents a powerful approach for determination of TYRase activity in biological samples. Graphical abstract Schematic representation of a colorimetric method for tyrosinase (TYRase) detection and inhibitor screening. It is based on the fact that catechol can inhibit the oxidase-like activity of chitosan-stabilized platinum nanoparticles (Ch-PtNPs) by competing with the substrate for the active sites and TYRase can catalyze the oxidation of catechol.

ZmHAK5 and ZmHAK1 function in K+ uptake and distribution in maize under low K+ conditions.

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.

[Incidence of neonatal asphyxia and contributing factors for the develpment of severe asphyxia in Hubei Enshi Tujia and Miao Autonomous Prefecture: a multicenter study].

OBJECTIVE: To investigate the incidence of neonatal asphyxia and possible contributing factors for the development of severe asphyxia in Hubei Enshi Tujia and Miao Autonomous Prefecture, China. METHODS: A total of 16 hospitals in Hubei Enshi Tujia and Miao Autonomous Prefecture were selected as research centers. A retrospective analysis was performed for the clinical data of 22 294 live births in these 16 hospitals from January to December, 2016 to investigate the incidence rate of neonatal asphyxia and possible contributing factors for the development of severe asphyxia. RESULTS: Of the 22 294 neonates born alive, 733 (3.29%) were diagnosed with neonatal asphyxia, among whom 627 had mild asphyxia and 106 had severe asphyxia. The neonates with low maternal education level, maternal anemia during pregnancy, chorioamnionitis, abnormal amniotic fluid, abnormal umbilical cord, placenta previa, placental abruption, Tujia Minority, preterm birth, and low birth weight had a higher incidence of severe asphyxia (P<0.05). CONCLUSIONS: The incidence rate of neonatal asphyxia in Hubei Enshi Tujia and Miao Autonomous Prefecture is higher. Low maternal education level, maternal anemia during pregnancy, chorioamnionitis, abnormal amniotic fluid, abnormal umbilical cord, placenta previa, placental abruption, Tujia Minority, preterm birth, and low birth weight may be related to the development of severe neonatal asphyxia.