Potassium nutrition of maize:Uptake,transport,utilization,and role in stress tolerance

Potassium(K) is an essential macronutrient for plant growth and development and influences yield and quality of agricultural crops.Maize(Zea mays) is one of the most widely distributed crops worldwide.In China,although maize consumes a large amount of K fertilizer,the K uptake/utilization efficiency(KUE)of maize cultivars is relatively low.Elucidation of KUE mechanisms and development of maize cultivars with higher KUE are needed.Maize KUE is determined by K+uptake,transport,and remobilization,which depend on a variety of K+channels and transporters.We review basic information about K+channels and transporters in maize,their functions and regulation,and the roles of K+in nitrogen transport,sugar transport,and salt tolerance.We discuss challenges and prospects for maize KUE improvement.

Ipomoea batatas HKT1 transporter homolog mediates K^+ and Na^+ uptake in Saccharomyces cerevisiae

Soil salinity causes the negative effects on the growth and yield of crops. In this study, two sweet potato （Ipomoea batatas L.） cultivars, Xushu 28 （X-28） and Okinawa 100 （O-100）, were examined under 50 and 100 mmol L-1 NaCI stress. X-28 cultivar is relatively high salt tolerant than O-100 cultivar. Interestingly, real-time quantitative polymerase chain reaction （RT-qPCR） results indicated that sweet potato high-affinity K^＋ transporter 1 （IbHKT1） gene expression was highly induced by 50 and 100 mmol L-1 NaCI stress in the stems of X-28 cultivar than in those of O-100 cultivar, but only slightly induced by these stresses in the leaves and fibrous roots in both cultivars. To characterize the function of IbHKT1 transporter, we performed ion-flux analysis in tobacco transient system and yeast complementation. Tobacco transient assay showed that IbHKT1 could uptake sodium （Na^＋）. Yeast complementation assay showed that IbHKT1 could take up K^＋ in 50 mmol L^-1 K^＋ medium without the presence of NaCI. Moreover, Na^＋ uptake significantly increased in yeast overexpressing IbHKTI. These results showed that IbHKT1 transporter could have K^＋-Na^＋ symport function in yeast. Therefore, the modes of action of IbHKT1 in transgenic yeast could differ from the mode of action of the other HKT1 transporters in class I. Potentially, IbHKT1 could be used to improve the salt tolerance nature in sweet potato.

Arsenic uptake and transport of Pteris vittata L.as influenced by phosphate and inorganic arsenic species under sand culture

In order to understand the similarity or difference of inorganic As species uptake and transport related to phosphorus in Ashyperaccumulator, uptake and transport of arsenate （As（V）） and arsenite （As（Ⅲ）） were studied using Pteris vittata L. under sand culture. Higher concentrations of phosphate were found to inhibit accumulation of arsenate and arsenite in the fronds of P. vittata. The reduction in As accumulation was greater in old fronds than in young fronds, and relatively weak in root and rhizome. Moderate increases, from 0.05 to 0.3 mmol/L, in phosphate reduced uptake of As（Ⅲ） more than As（Ⅴ）, while the reverse was observed at high concentrations of phosphate （≥1.0 mmol/L）. Phosphate apparently reduced As transport and the proportion of As accumulated in fronds of P. vittata when As was supplied as As（Ⅴ）. It may in part be due to competition between phosphorus and As（Ⅴ） during transport. In contrast, phosphate had a much smaller effect on As transport when the As was supplied as As（Ⅲ）. Therefore, the results from present experiments indicates that a higher concentration of phosphate suppressed As accumulation and transport in P. vittata, especially in the fronds, when exposed to As（Ⅴ）, but the suppression of phosphate to As transport may be insignificant when P. vittata exposed to As（Ⅲ） under sand culture conditions. The finding will help to understand the interaction of P and As during their uptake process in P. vittata.

Cerebral ischemic preconditioning enhances the binding characteristics and glutamate uptake of glial glutamate transporter-1 in hippocampal CA1 subfield of rats

Glial glutamate transporter-1(GLT-1)is the predominant subtype of glutamate transporters and is responsible for the clearance of extracellular glutamate and for limiting the concentration of extracellular glutamate.Our previous studies have shown that the up-regulation of GLT-1 expression plays an important role

Effect of Fertilizer N Forms on Physiological Metabolism and Potassium Uptake of Flue-Cured Tobacco

The growth, chlorophyll composition, photosynthesis, respiration, K uptake and root K+ secretion offlue-cured tobacco as thected by different concentrations of N supplied as urea, NaNO3 and NH4NO3 werestudied under the experimental condition of sand culture. The results showed that the content of K in thefiue-cured tobacco was not merely related with root vitality and uptake but also closely related with root cellmembrane structure and K+ secretion.

Membrane-Potential Alteration During K+ Uptake of Different Salt-Tolerant Wheat Varieties

K＋ is the most abundant cation in plant cells and plays an important role in many ways.K＋ uptake of plant has respect to its salt resistant capacity.There are two categories of channel transportation for plants to uptake K＋,one is through K＋ channels and the other is through nonselective cation channels（NSCCs）.The transmembrane localization of K＋ may change membrane potential（MP）.In this paper,three wheat varieties with different salt tolerance were selected and the MP was measured by microelectrode during K＋ uptake.The results showed that the effects of K＋ uptake on MP through K＋ channels or NSCCs were distinct.K＋ influx through K＋ channels led to MP hyperpolarization,while K＋ influx through NSCCs resulted in depolarization.Diverse MP alteration of wheat varieties with different salt tolerance was mainly due to NSCCs-mediated K＋ uptake.Compared with the salt-tolerant wheat,the MP hyperpolarization during K＋ uptake of saltsensitive wheat was much more evident,probably because of the cation outflux through NSCCs during this process.

The Potassium Transporter AtKUP12 Enhances Tolerance to Salt Stress through the Maintenance of the K^(+)/Na^(+)Ratio in Arabidopsis

Potassium(K^(+))is a necessary nutrient for plant growth and crop production.The K^(+)transporter plays crucial roles in the absorption and transport of K^(+)in plants.Most K^(+)transporters in Arabidopsis have been reported,but AtKUP12,which is a member of the KT/KUP/HAK family,has not yet been the subject of relevant in-depth research.In the present study,we demonstrated that AtKUP12 plays a crucial role in K^(+)uptake in Arabidopsis under 100μM low-K^(+)and 125 mM salt stress conditions.AtKUP12 transcripts were induced by K^(+)deficiency and salt stress.We analyzed the K^(+)uptake of AtKUP12 using the K^(+)uptake-deficient yeast R5421 and Arabidopsis mutant atkup12.Transformation with AtKUP12 rescued the growth defect of mutant yeast and atkup12 mutant plants at the low-K^(+)concentration,which suggested that AtKUP12 might be involved in high-affinity K^(+)uptake in low-K^(+)environments.In comparison to the wild-type(WT)and atkup12-AtKUP12 complementation lines,atkup12 showed a dramatic reduction in potassium concentration,K^(+)/Na^(+)ratio,and root and shoot growth on 12-day-old seedlings under the salt conditions;however,there was no significant difference between the complementation and WT lines.Taken together,these results demonstrate that AtKUP12 might participate in salt tolerance in Arabidopsis through K^(+)uptake and K^(+)/Na^(+)homeostasis.

Brassinosteroids modulate nitrogen physiological response and promote nitrogen uptake in maize(Zea mays L.)

Brassinosteroids(BRs)are steroid hormones that function in plant growth and development and response to environmental stresses and nutrient supplies.However,few studies have investigated the effect of BRs in modulating the physiological response to nitrogen(N)supply in maize.In the present study,BR signalingdeficient mutant zmbri1-RNAi lines and exogenous application of 2,4-epibrassinolide(e BL)were used to study the role of BRs in the regulation of physiological response in maize seedlings supplied with N.Exogenous application of e BL increased primary root length and plant biomass,but zmbri1 plants showed shorter primary roots and less plant biomass than wild-type plants under low N(LN)and normal N(NN)conditions.LN induced the expression of the BR signaling-associated genes Zm DWF4,Zm CPD,Zm DET2,and Zm BZR1 and the production of longer primary roots than NN.Knockdown of Zm BRI1 weakened the biological effects of LN-induced primary root elongation.e BL treatment increased N accumulation in shoots and roots of maize seedlings exposed to LN or NN treatment.Correspondingly,zmbri1 plants showed lower N accumulation in shoots and roots than wild-type plants.Along with reduced N accumulation,zmbri1 plants showed lower NO3-fluxes and^(15)NO_(3)^(-)uptake.The expression of nitrate transporter(NRT)genes(Zm NPF6.4,Zm NPF6.6,Zm NRT2.1,Zm NRT2.2)was lower in zmbri1 than in wild-type roots,but e BL treatments up-regulated the transcript expression of NRT genes.Thus,BRs modulated N physiological response and regulated the transcript expression of NRT genes to promote N uptake in maize.

Free fatty acids receptors 2 and 3 control cell proliferation by regulating cellular glucose uptake

BACKGROUND Colorectal cancer(CRC)is a worldwide problem,which has been associated with changes in diet and lifestyle pattern.As a result of colonic fermentation of dietary fibres,short chain free fatty acids are generated which activate free fatty acid receptors(FFAR)2 and 3.FFAR2 and FFAR3 genes are abundantly expressed in colonic epithelium and play an important role in the metabolic homeostasis of colonic epithelial cells.Earlier studies point to the involvement of FFAR2 in colorectal carcinogenesis.AIM To understand the role of short chain FFARs in CRC.METHODS Transcriptome analysis console software was used to analyse microarray data from CRC patients and cell lines.We employed short-hairpin RNA mediated down regulation of FFAR2 and FFAR3 genes,which was validated using quantitative real time polymerase chain reaction.Assays for glucose uptake and cyclic adenosine monophosphate(cAMP)generation was done along with immunofluorescence studies to study the effects of FFAR2/FFAR3 knockdown.For measuring cell proliferation,we employed real time electrical impedancebased assay available from xCELLigence.RESULTS Microarray data analysis of CRC patient samples showed a significant down regulation of FFAR2 gene expression.This prompted us to study the FFAR2 in CRC.Since,FFAR3 shares significant structural and functional homology with FFAR2,we knocked down both these receptors in CRC cell line HCT 116.These modified cell lines exhibited higher proliferation rate and were found to have increased glucose uptake as well as increased level of glucose transporter 1.Since,FFAR2 and FFAR3 signal through G protein subunit(Gαi),knockdown of these receptors was associated with increased cAMP.Inhibition of protein kinase A(PKA)did not alter the growth and proliferation of these cells indicating a mechanism independent of cAMP/PKA pathway.CONCLUSION Our results suggest role of FFAR2/FFAR3 genes in increased proliferation of colon cancer cells via enhanced glucose uptake and exclude the role of PKA mediated cAMP signalling.Alternate pathways could be involved that would ultimately result in increased cell proliferation as a result of down regulated FFAR2/FFAR3 genes.This study paves the way to understand the mechanism of action of short chain FFARs in CRC.

Decarboxylated osteocalcin,a possible drug for type 2 diabetes,triggers glucose uptake in MG63 cells

BACKGROUND Uncarboxylated osteocalcin(GluOC)has been reported to improve glucose metabolism,prevent type 2 diabetes,and decrease the severity of obesity in mice with type 2 diabetes.GluOC can increase glucose uptake in a variety of cells.Glucose metabolism is the main source of energy for osteoblast proliferation and differentiation.We hypothesized that decarboxylated osteocalcin(dcOC),a kind of GluOC,can increase glucose uptake in MG63 cells(osteoblast-like osteosarcoma cells)and influence their proliferation and differentiation.AIM To investigate the effects of dcOC on glucose uptake in human osteoblast-like osteosarcoma cells and the possible signaling pathways involved.METHODS MG63 cells(human osteoblast-like osteosarcoma cells)were treated with dcOC(0,0.3,3,10,or 30 ng/mL)for 1 and 72 h,and glucose uptake was measured by flow cytometry.The effect of dcOC on cell proliferation was measured with a CCK-8 assay,and alkaline phosphatase(ALP)enzyme activity was measured.PI3K was inhibited with LY294002,and hypoxia-inducible factor 1 alpha(HIF-1α)was silenced with siRNA.Then,GPRC6A(G protein-coupled receptor family C group 6 subtype A),total Akt,phosphorylated Akt,HIF-1α,and glucose transporter 1(GLUT1)levels were measured by Western blot to elucidate the possible pathways by which dcOC modulates glucose uptake.RESULTS The glucose uptake of MG63 cells was significantly increased compared with that of the paired control cells after short-term(1 h)treatment with dcOC at different concentrations(0.3,3,and 10 ng/mL groups,P<0.01;30 ng/mL group,P<0.05).Glucose uptake of MG63 cells was significantly increased compared with that of the paired control cells after long-term(72 h)treatment with dcOC at different concentrations(0.3,3,and 10 ng/mL groups,P<0.01;30 ng/mL group,P<0.05).DcOC triggered Akt phosphorylation in a dose-dependent manner,and the most effective stimulatory concentration of dcOC for short-term(1 h)was 3 ng/mL(P<0.01).LY294002 abolished the dcOC-mediated(1 h)promotion of Akt phosphorylation and glucose uptake without affecting GLUT1 protein expression.Long-term dcOC stimulation triggered Akt phosphorylation and increased the protein levels of HIF-1α,GLUT1,and Runx2 in a dose-dependent manner.Inhibition of HIF-1αwith siRNA abolished the dcOC-mediated glucose uptake and substantially decreased GLUT1 protein expression.DcOC interven-tion promoted cell proliferation in a time-and dose-dependent manner as determined by the CCK-8 assay.Treatment with both 3 ng/mL and 10 ng/mL dcOC affected the ALP activity in MG63 cells after 72 h(P<0.01).CONCLUSION Short-and long-term dcOC treatment can increase glucose uptake and affect proliferation and ALP activity in MG63 cells.This effect may occur through the PI3K/Akt,HIF-1α,and GLUT1 signaling factors.

Icariin ameliorates memory deficits through regulating brain insulin signaling and glucose transporters in 3×Tg-AD mice

Icariin,a major prenylated flavonoid found in Epimedium spp.,is a bioactive constituent of Herba Epimedii and has been shown to exert neuroprotective effects in experimental models of Alzheimer’s disease.In this study,we investigated the neuroprotective mechanism of icariin in an APP/PS1/Tau triple-transgenic mouse model of Alzheimer’s disease.We performed behavioral tests,pathological examination,and western blot assay,and found that memory deficits of the model mice were obviously improved,neuronal and synaptic damage in the cerebral cortex was substantially mitigated,and amyloid-βaccumulation and tau hyperphosphorylation were considerably reduced after 5 months of intragastric administration of icariin at a dose of 60 mg/kg body weight per day.Furthermore,deficits of proteins in the insulin signaling pathway and their phosphorylation levels were significantly reversed,including the insulin receptor,insulin receptor substrate 1,phosphatidylinositol-3-kinase,protein kinase B,and glycogen synthase kinase 3β,and the levels of glucose transporter 1 and 3 were markedly increased.These findings suggest that icariin can improve learning and memory impairments in the mouse model of Alzheimer’s disease by regulating brain insulin signaling and glucose transporters,which lays the foundation for potential clinical application of icariin in the prevention and treatment of Alzheimer’s disease.

K-ATP channel openers facilitate glutamate uptake by GluTs in rat primary cultured Astrocytes

Increasing evidence, including from our laboratory, has revealed that opening of ATP sensitive potassium channels(K-ATP channels) plays the neuronal protective roles both in vivo and in vitro. Thus K-ATP channel openers(KCOs) have been proposed as potential neuroprotectants. Our previous studies demonstrated that K-ATP channels could regulate glutamate uptake activity in PC12 cells as well as in synaptosomes of rats. Since glutamate transporters(GluTs) of astrocytes play crucial roles in glutamate uptake and KATP channels are also expressed in astrocytes, the present study showed whether and how KATP channels regulated the function of GluTs in primary cultured astrocytes. The results showed that nonselective KCO pinacidil, selective mitochondrial KCO diazoxide, novel, and blood-brain barrier permeable KCO iptakalim could enhance glutamate uptake, except for the sarcolemmal KCO P1075. Moreover pinacidil, diazoxide, and iptakalim reversed the inhibition of glutamate uptake induced by 1-methyl-4-phenylpyridinium(MPP+). These potentiated effects were completely abolished by mitochondrial K-ATP blocker 5-hydroxydecanoate. Furthermore, either diazoxide or iptakalim could inhibit MPP+-induced elevation of reactive oxygen species (ROS) and phosphorylation of protein kinases C(PKC). These findings are the first to demonstrate that activation of K-ATP channel, especially mitochondrial K-ATP channel, improves the function of GluTs in astrocytes due to reducing ROS production and downregulating PKC phosphorylation. Therefore, the present study not only reveals a novel pharmacological profile of KCOs as regulators of GluTs, but also provides a new strategy for neuroprotection.

Anti-Hyperglycemic Effect of Single Administered Gardeniae Fructus in Streptozotocin-Induced Diabetic Mice by Improving Insulin Resistance and Enhancing Glucose Uptake in Skeletal Muscle

The mechanisms of Gardeniae Fructus (GF) for anti-hyperglycemic action were demonstrated in streptozotocin (STZ)-diabetic mice. Six hours after single intraperitoneal administration of GF (300 mg/kg) or H2O into 3 hour-fasted STZ-diabetic mice, glucose and insulin tolerances were assessed by intraperitoneal glucose (1.5 g/kg) tolerance test (IPGTT) and intraperitoneal insulin (0.65 U/kg) tolerance test (IPITT), respectively. Effects of GF on insulin signaling pathways in soleus muscle such as glucose uptake, expression of glucose transporter 4 (GLUT4) in the plasma membrane and phosphorylation of Akt (P-Akt) in cytosolic fraction were examined in STZ-diabetic mice. In IPGTT test, GF significantly accelerated clearance of exogenous glucose and its glucose-lowering action was greater than H2O-treated controlin STZ-diabetic mice. GF also promoted an exogenous glucose-increased insulin level in STZ-diabetic mice. In IPITT test, GF decreased glucose level to the greater extent than H2O-treated control in STZ-diabetic mice. Furthermore, GF significantly decreased high HOMA-IR in STZ-diabetic mice from 21.6 ± 2.4 to 12.4 ± 1.9 (mg/dl × μU/ml). These results implied that GF improved insulin resistance in STZ-diabetic mice. GF increased glucose uptake of soleus muscle 1.5 times greater than H2O-treated control in STZ-diabetic mice. GF enlarged insulin (10 nmol/ml)-increased glucose uptake to 1.8 time-greater. Correspondingly, GF increased expression of GLUT4 in the plasma membrane of soleus muscle to 1.4 time-greater, and P-Akt in the cytosolic fraction of soleus muscle to 1.9 time-greater than those in H2O-treated control. In conclusion, the improvement of GF on insulin resistance is associated with the repair of insulin signaling via P-Akt, GLUT4 and glucose uptake pathway in soleus muscle of STZ-diabetic mice.

异氟烷抑制星形胶质细胞葡萄糖摄取

本文探讨了异氟烷对星形胶质细胞葡萄糖摄取的影响,应用培养的大鼠星形胶质细胞,通过免疫荧光观察异氟烷对星形胶质细胞结构的影响;利用6-NBDG检测异氟烷对星形胶质细胞葡萄糖吸收影响;通过RT-PCR和免疫印迹检测葡萄糖转运体的变化。与对照组相比,异氟烷诱导GFAP向细胞膜处聚集,抑制星形胶质细胞葡萄糖摄取及GLuT1的表达。异氟烷可以通过抑制星形胶质细胞葡萄糖转运体的表达,抑制葡萄糖摄取。

异氟烷短期内可逆的抑制星形胶质细胞葡萄糖摄取

本文主要探讨了异氟烷处理后复灌对星形胶质细胞葡萄糖吸收的影响。利用培养的大鼠星形胶质细胞,2%异氟烷孵育6h,分别复灌24h、48h、72h,观察星形胶质细胞的形态;利用CCK-8试剂盒检测星形胶质细胞活性;加入荧光标记6-NBDG,观察星形胶质细胞葡萄糖吸收的变化;运用RT-PCR检测葡萄糖转运体GLuT1的变化。实验结果表明,异氟烷处理后复灌的星形胶质细胞形态无明显差别,细胞活性均不受影响;复灌24h葡萄糖摄取受抑制,48h恢复;复灌24h的GLuT1 mRNA水平降低,48h恢复;异氟烷可抑制星形胶质细胞葡萄糖转运体的表达并导致葡萄糖摄取障碍,但在短期可逆转。

钝化剂对湘中稻田土壤Cd有效性及水稻Cd积累的影响

为了揭示不同钝化剂对湘中地区不同程度Cd污染土壤Cd有效性及水稻Cd积累的影响,筛选出适合湘中地区中轻度Cd污染农田安全利用的钝化材料,采用盆栽和大田两种试验方式,分别研究了巯基化海泡石(SGP)、海泡石复合材料(ISS)、铁改性木本泥炭(IMP)和生物有机肥(OF)4种钝化材料对中度和轻度Cd污染土壤pH值、土壤有机质、土壤Cd形态、土壤有效态Cd含量以及不同时期水稻各部位Cd含量的影响。研究结果表明:1)在盆栽试验中:与CK相比,施用钝化剂的处理,在水稻分蘖期、灌浆期与成熟期,土壤有效态Cd含量分别降低1.59%~25.40%,3.57%~26.79%和15.67%~37.32%;与CK相比,水稻成熟期弱酸提取态Cd含量降低了4.29%~7.27%,可氧化态Cd含量提高了6.86%~11.00%;水稻根系、茎和稻壳中Cd含量分别降低26.45%~44.34%,35.79%~59.01%和21.24%~45.36%;2)在大田试验中:与CK相比,在水稻分蘖期与灌浆期,ISS和OF处理土壤pH值提高了约0.3个pH单位;水稻灌浆期与成熟期土壤有效态Cd含量分别降低15.11%~35.95%和27.19%~49.24%;水稻根系、茎叶和糙米中Cd含量分别降低61.29%~84.86%,41.00%~84.42%和26.47%~85.29%;水稻根—茎、茎—壳转运系数分别为0.18~0.31和0.32~1.11。研究结果表明,施用SGP、IMP和ISS处理均可显著降低中轻度Cd污染土壤的有效态Cd含量,影响水稻各部位对Cd的转运吸收,从而降低植株对土壤Cd的吸收和积累,使Cd在叶片中富集而减少在稻米中的积累。ISS处理可显著提高土壤pH值。

玉米种植密度对大豆玉米带状复合种植体系干物质养分积累与转运的影响

为探索大豆玉米带状复合种植模式下适宜的玉米种植密度,通过田间试验,研究大豆玉米带状复合种植模式(3+2)下,玉米种植密度(52500、60000和67500株·hm^(-2),分别以SM1、SM2和SM3表示)和玉米单作(MM,种植密度60000株·hm^(-2))对大豆玉米带状复合种植体系产量及玉米干物质、养分积累和转运的影响。结果表明,与单作相比,带状复合种植体系玉米产量降低5.25%~14.30%,其中SM2产量与MM差异未达显著水平,但带状复合种植体系总产值显著提高10.80%~16.71%。在复合种植模式下,与SM1和SM3相比,SM2显著提高玉米穗粒数和百粒重,延长干物质快速积累的时间,提高干物质积累最大增长速率,促进花后干物质向籽粒中转运,提高养分吸收,产量分别较SM1和SM3提高10.56%和9.67%。综上,相比较玉米单作,大豆玉米带状复合种植(3+2模式)可实现“玉米不减产或稍减产,多收一季豆”;在大豆玉米带状复合种植模式下,大丰30系列玉米的种植密度在60000株·hm^(-2)左右时可作为晋南小麦玉米一年两熟轮作区合理的密度选择,实现稳产高效。本研究可为晋南小麦玉米一年两熟轮作区推广大豆玉米带状复合种植及提高我国大豆自给率提供理论依据。

高等植物K^+吸收及转运的分子机制研究进展

K^+是植物生长必需的营养元素。K^+被植物根系吸收后,有效地向地上部转运,在跨膜转运的过程中主要由次级K^+转运蛋白和K^+通道介导。KT/HAK/KUP和HKT家族是参与植物体内K+吸收及转运的两类主要K+转运蛋白,其中HKT家族参与K^+转运的成员仅存在于单子叶植物中,它们在植物生长发育、渗透调节等过程中均发挥重要作用。Shaker家族是K^+通道中最早发现且研究最为深入的一类电压门控型通道,是植物K^+吸收的重要途径之一。本研究从结构特征、定位和组织表达、功能调控等方面对植物KT/HAK/KUP家族、HKT家族和Shaker通道进行综述,最后对未来的主要研究方向做了展望。

GLUT1、GLUT2介导的葡萄糖摄取对小鼠牙齿早期发育的影响

目的:探究葡萄糖转运蛋白(glucose transporter,GLUT)1、GLUT2介导的葡萄糖摄取对小鼠牙齿早期发育的影响。方法:收集胚胎13.5 d(embryonic day 0.5,E13.5)、E14.5、E16.5、E18.5和出生后1 d(postnatal day 1,P1)时期的下颌磨牙牙胚、上颌切牙牙胚;实时荧光定量聚合酶链反应(real time-quantitative polymerase chain reaction,RT-qPCR)和Western blot检测牙胚中Glut1、Glut2 mRNA和蛋白水平;免疫组织化学染色检测牙胚中GLUT1、GLUT2、Ki67、糖原水平。将下颌磨牙牙胚在无糖DMEM培养基、高糖且含不同浓度的根皮素(0、0.25、0.5 mmol/L)的DMEM培养基中培养9 d;并对其进行苏木精-伊红(hematoxylin-eosin,HE)染色。结果:(1)在E13.5时期,GLUT1在成釉器中高表达,细胞增殖活跃,糖原在牙板和牙囊中大量沉积;在E14.5、E18.5时期,GLUT1在成釉器中表达逐渐降低,细胞增殖减少,糖原在成釉器和牙乳头中大量沉积;在P1时期,GLUT1在中间层和内釉上皮中表达较多,细胞增殖增多,糖原在牙乳头中少量沉积。在整个牙胚发育阶段,GLUT2表达相对较少。(2)GLUT1在前成釉细胞、前成牙本质细胞中高表达,而在分化后的成釉细胞、成牙本质细胞中表达较少;GLUT2与GLUT1呈现相反的表达趋势。(3)0.5 mmol/L根皮素能够抑制E13.5时期外植体牙胚发育,0.25 mmol/L根皮素不抑制E13.5、E14.5时期外植体牙胚发育,但能够导致牙胚变小,且具有根皮素浓度依赖性。无糖培养基能够抑制E13.5、E14.5时期外植体牙胚发育。结论:GLUT1、GLUT2在牙齿早期发育中的表达受到精确的时空调控,由GLUT1、GLUT2介导的葡萄糖摄取在小鼠牙齿早期发育中发挥重要作用。

植物硅转运蛋白研究进展

硅作为一种非金属元素,不仅在植物的生长发育过程中发挥重要的功能,同时在植物抵御生物和非生物胁迫中也发挥着重要的作用。研究表明硅的吸收与转运由硅转运蛋白参与完成,根据对硅酸的转运特性主要分为硅内流转运蛋白和硅外流转运蛋白。该文对已鉴定出的硅转运蛋白的结构特点、功能、调控方式进行了总结,对植物吸收与转运硅的过程进行了系统性解析,提出了存在的问题,并对未来的研究方向进行了展望。