三种不同表面活性剂对羟基磷灰石纳米颗粒的表面修饰的比较

目的:本研究旨在通过不同方法修饰羟基磷灰石纳米颗粒并检测其稳定性及分散性。方法:首先采用水合热合成法制备羟基磷灰石纳米颗粒,然后用透射电镜(TEM)和场发射扫描电镜(SEM)对其表面形态结构进行表征。我们首次用溴化十六烷三甲基铵(CTAB),PEG2000和人血清对羟基磷灰石纳米颗粒通过共价结合或表面吸附的方式进行表面嫁接,并利用透射电镜,傅里叶红外光谱(FT-IR)和X射线衍射(XRD)对新合成的这三种纳米羟基磷灰石复合物的形貌,结构和晶粒粒径进行表征。对这三种羟基磷灰石纳米颗粒悬浮液的时间沉降曲线进行分析。在分散性上通过检测这三种羟基磷灰石复合物悬浮液在不同pH值下的Zeta电位并绘制Zeta-pH曲线。结果:我们发现CTAB修饰的羟基磷灰石纳米颗悬浮液的悬浮稳定性最佳,其次是PEG2000,最后是人血清。在pH=7.0时,CTAB修饰的羟基磷灰石纳米颗粒的zeta电位值是25.68 m V,而PEG2000修饰的Zeta电位是4.32m V,人血清修饰的Zeta电位是-13.23m V。结论:CTAB表面修饰的羟基磷灰石纳米颗粒相对于其它两种表面活性剂复合物具有更好的分散性和悬浮稳定性,与DNA/RNA结合能力更强。本课题的结果给羟基磷灰石纳米颗粒载体的应用提供了一种新的选择,有望利用亲和力更高的基因载体实现基因治疗,具有广阔的应用前景。     

APP/PS1小鼠中PEG-PLA纳米粒的表面蛋白冠组成及其脑内递送的实验研究

摘要 目的：研究阿尔茨海默病（Alzhemer''s disease,AD）模型鼠中聚乙二醇聚乳酸（poly(ethylene glycol)-poly(l-lactide),PEG-PLA）纳米粒表面蛋白冠组成及其对脑内递送特性的影响。方法：制备PEG-PLA纳米粒,测定纳米粒的zeta电位及粒径,采用透射电子显微镜观察纳米粒形态。通过双光子显微镜观察APP/PS1小鼠与野生型（Wild Type,WT）小鼠脑内PEG-PLA纳米粒分布特性。采用液相色谱-质谱联用（LC-MS）技术对PEG-PLA纳米粒分别与APP/PS1小鼠和WT小鼠血浆孵育形成的两种不同蛋白冠进行蛋白组学分析。结果：制备的PEG-PLA纳米粒粒径均一,分散性较好。静脉注射PEG-PLA后,APP/PS1小鼠脑内纳米粒量明显高于WT小鼠。蛋白质组学结果显示,APP/PS1小鼠血浆孵育组PEG-PLA纳米粒表面蛋白冠中凝聚素（Clusterin）明显高于WT小鼠血浆孵育组,该蛋白与纳米粒逃避机体清除有关。此外,纳米粒蛋白冠中血管性血友病因子（Von Willebrand factor）、玻连蛋白（Vitronectin）、肌球蛋白重链-9（Myosin-9）等参与细胞粘附作用相关蛋白在APP/PS1小鼠血浆孵育组也明显多于WT小鼠血浆孵育组。结论：PEG-PLA纳米粒在AD模型小鼠中表现出的高入脑量,可能与AD疾病影响纳米粒蛋白冠组成有关。     

蛋白冠与纳米粒子的相互作用

近年来,尽管纳米粒子在生物医学领域的研究中取得了巨大的进展,但很少能进入临床试验阶段,其中,很大程度取决于人们缺乏对纳米粒子与生理环境之间相互作用的认知,对纳米粒子进入体内后的生物学特性了解有限。在生理环境下,蛋白质会吸附于纳米粒子表面,从而形成蛋白冠,这种纳米粒子-蛋白冠复合物的形成严重影响纳米粒子的生物学特性,限制了纳米粒子的临床应用,因此,蛋白质与纳米粒子之间的相互作用应该被深入研究。目前,对纳米粒子-蛋白冠复合物的研究属于一个相对较新的研究领域。概括了蛋白冠的研究现状,对蛋白冠与纳米粒子相互作用所产生的影响进行了重点阐述,也介绍了预防和减少蛋白冠形成的方法,为纳米粒子的进一步研发提供了思路。     

PhaP介导EGFR靶向多肽修饰的肿瘤靶向PHBHHx纳米药物递送载体的构建

聚羟基脂肪酸(PHA)颗粒表面结合蛋白Pha P具有与疏水性高分子材料表面紧密结合的能力,本研究将EGFR靶向多肽(ETP)与PhaP进行融合表达,构建了ETP-PhaP融合蛋白表达的重组工程菌Escherichia coli BL21(DE3)(pPI-ETP-P)。经对工程菌株的诱导表达及ETP-PhaP融合蛋白的纯化后,通过PhaP蛋白介导能够有效地将ETP-PhaP融合蛋白修饰于3-羟基丁酸-3-羟基己酸共聚酯(PHBHHx)纳米微球表面,构建成为具有EGFR靶向作用的药物递送载体。分别检测宫颈癌细胞系SiHa(EGFR高表达)和CaSKi(EGFR低表达)对ETP-PhaP修饰的PHBHHx纳米药物载体和未经修饰的纳米药物载体的吞噬情况。结果显示,纯化的ETP-PhaP融合蛋白能够很好地吸附于PHBHHx颗粒的表面,经ETP-PhaP融合蛋白修饰的PHBHHx纳米药物载体对EGFR高表达的宫颈癌Si Ha细胞的靶向效果强于EGFR低表达的CaSKi细胞系。这一结果表明了PhaP介导的PHBHHx纳米微球表面EGFR靶向多肽修饰具有简便、高效的优势,为疏水性纳米药物载体表面功能多肽修饰提供了一种新策略。     

壳聚糖和帕米膦酸双修饰的固体脂质纳米粒的制备

目的:制备壳聚糖和帕米膦酸双修饰的固体脂质纳米粒。方法:首先利用课题组发表的专利合成帕米膦酸修饰Brij78的新型非离子表面活性剂(Pa-Brij78),然后以壳聚糖(CS)溶液为水相,Pa-Brij78为乳化剂,E-Wax为油相,采用微乳法,利用修饰的帕米膦酸基团与壳聚糖分子链中质子化的氨基交联反应原理,通过一系列实验条件的探索,确定了最佳实验工艺条件,成功制备了壳聚糖和帕米膦酸双修饰的固体脂质纳米粒。通过动态光散射(DLS)粒径仪测定了纳米粒的粒径大小和Zeta电位;透射电子显微镜(TEM)对CS-Pa-Brij78-SLNs的形貌结构进行了表征。结果:实验结果显示,制备壳聚糖和帕米膦酸双修饰的固体脂质纳米粒的最佳条件为:p H=6.0,壳聚糖浓度分别为0.1%,0.2%;反应温度65℃,反应时间40 min,在该条件下,制备的壳聚糖和帕米膦酸双修饰的固体脂质纳米粒(CS-Pa-Brij78-SLNs)粒径分别为97.9±6.6 nm和182.4±62.2 nm,表面电位分别为(+5.21±1.4m V);(+7.94±0.80 m V),装载姜黄素时,载药量为10%,包封率在90%以上,透射电镜下观察其形态圆整,清晰可见壳聚糖包裹的电晕。结论:本文以壳聚糖(CS)溶液为水相,合成的新型非离子表面活性剂Pa-Brij78为乳化剂,E-Wax为油相,采用微乳化法,经过最佳实验条件的探索,通过一步法成功制备了稳定的壳聚糖和帕米膦酸双修饰的固体脂质纳米粒(CS-Pa-Brij78-SLNs)。     

载HCPT纳米粒的制备及其体外抗肿瘤活性研究

目的:制备载羟基喜树碱(HCPT)的PLGA-hyd-PEG-FA纳米粒(HCPT@PLGA-hyd-PEG-FA),并对其体外抗肿瘤活性进行研究。方法:采用乳化溶剂挥发法制备HCPT@PLGA-hyd-PEG-FA,通过单因素试验考察超声功率、聚合物浓度、PVA浓度、水相和油相体积比及投药量对纳米粒粒径的影响;采用zeta电位及激光粒度分析仪测定纳米粒的粒径及zeta电位,用透射电镜(TEM)观察其形态;采用透析法评价HCPT@PLGA-hyd-PEG-FA的体外释药特性;采用MTT法测定HCPT@PLGA-hyd-PEG-FA对HepG2细胞的细胞毒性。结果:HCPT@PLGA-hyd-PEG-FA平均粒径约为109±3 nm,zeta电位为-11.57 mV,载药量为5.6%,TEM显示其为球形;体外释药结果表明HCPT@PLGA-hyd-PEG-FA对HCPT的释放具有p H值依赖性;HCPT和HCPT@PLGA-hyd-PEG-FA的IC50值分别为474.6 ng/mL和286.0 ng/mL。结论:HCPT@PLGA-hyd-PEG-FA体外释药性能良好,HCPT@PLGA-hyd-PEG-FA的细胞毒性明显大于游离的HCPT,值得进一步研究。     

植物蛋白质O-糖基化修饰的研究进展

糖基化是最主要的蛋白质翻译后修饰方式之一,主要有N-糖基化、O-糖基化和糖基磷脂酰肌醇锚定修饰三种类型。在植物细胞中, O-糖基化修饰广泛发生,它不仅参与蛋白质转录调节、信号转导,还与细胞壁合成等生物学过程紧密相关。在多种O-糖基化修饰类型中, O-N-乙酰氨基葡萄糖(O-GlcNAc)糖基化修饰结构独特、易于检测和表征,因此已经有许多相关技术实现了对其的表征。然而,其他类型O-糖基化修饰蛋白的结构和功能仍有待更全面的研究。该文综述了植物蛋白中不同类型O-糖基化修饰的相关研究进展,总结了植物O-糖基化修饰蛋白检测技术的优缺点,最后展望了这些技术在植物蛋白质O-糖基化修饰研究中的应用前景。     

转铁蛋白修饰磁性纳米粒的制备及其体外抗肿瘤活性研究

目的:本研究旨在构建一种转铁蛋白修饰负载阿霉素(DOX)的磁纳米粒靶向递药系统,以提高阿霉素作用的靶向性。方法:采用化学共沉淀法制备转铁蛋白修饰负载阿霉素的磁性纳米粒(DOX@MNP),采用zeta电位及纳米粒度分析仪测定DOX@MNP的粒径及其zeta电位,透析法评价DOX@MNP的体外释药特征。通过MTT实验,研究DOX@MNP与游离DOX对A549细胞的细胞毒性,通过激光共聚焦显微镜和流式细胞仪观察A549细胞对DOX@MNP与游离DOX的摄取情况。结果:DOX@MNP的释药具有p H依赖性。MTT实验结果显示,DOX@MNP与游离DOX具有相当的细胞毒性;激光共聚焦显微镜和流式细胞仪检测结果显示A549细胞对DOX和DOX@MNP的摄取没有明显差异。结论:本文构建了一种转铁蛋白修饰包载阿霉素的磁纳米粒,体外结果显示其具有与游离DOX相当的细胞毒性,为进一步进行体内实验奠定了基础。     

磁性纳米颗粒作为基因转染载体的研究

通过扫描电子显微镜和Zeta电位仪对磁性纳米颗粒的形貌、粒径、表面电位等进行了表征。利用凝胶电泳阻滞试验分析磁性纳米颗粒与DNA的结合情况,研究磁性纳米颗粒对DNA的保护效果,运用MTT和流式细胞术分析磁性纳米颗粒对细胞的毒性。以绿色荧光蛋白基因为报告基因进行293T细胞的转染,研究磁性纳米颗粒与质粒DNA不同比例条件下对293T细胞的转染效率,并与脂质体(Lipofectamine2000)介导的转染进行比较分析。结果表明,磁性纳米颗粒与DNA可以稳定结合,可以保护DNA免受酶的消化作用,当磁性纳米颗粒与DNA比为1 1时,转染效率最高,优于脂质体(Lipotamine2000)介导的转染,且对细胞的毒害作用小于Lipotamine2000。     

纳米丝素蛋白微球的制备及性能研究

以家蚕丝素蛋白为原料,基于丝素自组装理论,通过酶解-干燥-溶解法制备不同尺寸的丝素蛋白微球,制备出的微球具有良好的水不溶性和稳定的分散性。对微球的形貌和结构表征结果表明,用该方法制备的丝素蛋白微球为纳米微球,当酶的添加量为2%且蛋白自组装时间为4 h时,丝素蛋白微球的平均粒径最小,仅为(32±11)nm。红外光谱(FT-IR)和X射线衍射(XRD)结果显示,微球中β-折叠结构的多少决定了微球晶体的大小,β-折叠越多,微球中晶体的体积越大。通过调控丝素蛋白自组装过程,可以制备平均粒径在30～140 nm之间的纳米丝素蛋白微球,且不引入任何有机溶剂和无机溶剂,制备过程绿色环保,制备出的丝素蛋白微球安全无毒。     

Intentional formation of a protein corona on nanoparticles: Serum concentration affects protein corona mass,surface charge,and nanoparticle–cell interaction

The protein corona, which immediately is formed after contact of nanoparticles and biological systems, plays a crucial role for the biological fate of nanoparticles. In the here presented study we describe a strategy to control the amount of corona proteins which bind on particle surface and the impact of such a protein corona on particle-cell interactions. For corona formation, polyethyleneimine (PEI) coated magnetic nanoparticles (MNP) were incubated in a medium consisting of fetal calf serum (FCS) and cell culture medium. To modulate the amount of proteins bind to particles, the composition of the incubation medium was varied with regard to the FCS content. The protein corona mass was estimated and the size distribution of the participating proteins was determined by means of sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS–PAGE). Additionally, the zeta potential of incubated particles was measured. Human blood–brain barrier-representing cell line HBMEC was used for in vitro incubation experiments. To investigate the consequences of the FCS dependent protein corona formation on the interaction of MNP and cells flow cytometry and laser scanning microscopy were used. Zeta potential as well as SDS–PAGE clearly reveal an increase in the amount of corona proteins on MNP with increasing amount of FCS in incubation medium. For MNP incubated with lower FCS concentrations especially medium-sized proteins of molecular weights between 30 kDa and 100 kDa could be found within the protein corona, whereas for MNP incubated within higher FCS concentrations the fraction of corona proteins of 30 kDa and less increased. The presence of the protein corona reduces the interaction of PEI-coated MNP with HBMEC cells within a 30 min-incubation.     

An integrative method for evaluating the biological effects of nanoparticle-protein corona

BackgroundNanoplastics in the environment can enter the human body through gastrointestinal intake, dermal contact, and pulmonary inhalation, posing a threat to human health. Protein molecules in body fluids will quickly adsorb on the surfaces of the nanoplastics, forming a protein corona, which has implications for the interaction of the nanoplastics with cells and the metabolic pathways of the nanoplastic within cells. For years, practical tools such as dynamic light scattering, transmission electron microscopy, and liquid chromatography have been developed to understand the protein corona of nanoparticles (NPs), either in vitro or in cellular or molecular level. However, an integrated approach to understand the nanoparticles-protein corona is still lacking.MethodsUsing the most frequently observed environmental nanoplastics, polystyrene nanoplastics (PS), as a standard, we established an integrative structural characterization platform, a biophysical and biochemical evaluation method to investigate the effect of surface charge on protein corona composition. The cellular and molecular mechanisms were also explored through in vitro cellular experiments.ResultsThe first integrative method for characterizing biological properties of NPs-protein corona has been established. This method comprehensively covers the critical aspects to understand NPs-protein corona interactions, from structure to function.ConclusionsThe integrative method for nanoplastics microstructure characterization can be applied to the structural characterization of nanoparticles in nanoscale, which is of universal significance from in vitro characterization to cellular experiments and then to molecular mechanism studies.General significanceThis strategy has high reliability and repeatability and can be applied both in environment and nanomedicine safety assessment.     

Heat Stability of Differently Stabilized Solid Lipid Nanoparticles in the Presence of Excess Bulk Phase Protein

In order to apply emulsion-based delivery systems to food, they have to be stable in a protein rich environment. This study investigated the stability of solid lipid nanoparticles (SLN) during heat treatment in the presence or absence of β-lactoglobulin (BLG). SLN were stabilized either by Tween 20 (TS) or by the protein itself (BS) and were enriched to a total BLG content of 56 mg/mL. The sizes of both types of SLN were initially in the range of 170 nm. The amount of free protein was determined before and after enrichment with BLG. As revealed by particle size and zeta potential measurements, a protein layer of BLG (hard corona) adsorbed on BS but not on TS. By contrast, a soft corona was formed around both BS and TS. SLN were heat treated in the presence and absence of protein and were characterized regarding size and zeta potential. According to transmission electron microscopy imaging, heating did not affect the shape of TS and BS: TS were platelets, whereas BS exhibited a spherical or platelet like shape. Upon heat treatment, the particle size of TS increased to about 3.5 fold of the initial size (to appr. 600 nm) in the presence and in the absence of excess protein. The cloudy protein layer (soft corona) around TS could thus not prevent coalescence of TS. By contrast, BS did not experience a change in particle size. Hence, by the choice of emulsifier, an encapsulation system that is stable against heat treatment can be obtained.

     

A hard-sphere model of protein corona formation on spherical and cylindrical nanoparticles

A nanoparticle (NP) immersed in biological media rapidly forms a corona of adsorbed proteins, which later controls the eventual fate of the particle and the route through which adverse outcomes may occur. The composition and timescale for the formation of this corona are both highly dependent on both the NP and its environment. The deposition of proteins on the surface of the NP can be imitated by a process of random sequential adsorption, and, based on this model, we develop a rate-equation treatment for the formation of a corona represented by hard spheres on spherical and cylindrical NPs. We find that the geometry of the NP significantly alters the composition of the corona through a process independent of the rate constants assumed for adsorption and desorption of proteins, with the radius and shape of the NP both influencing the corona. We further investigate the roles of protein mobility on the surface of the NP and changes in the concentration of proteins.     

Transferrin coated nanoparticles: study of the bionano interface in human plasma

It is now well established that the surface of nanoparticles (NPs) in a biological environment is immediately modified by the adsorption of biomolecules with the formation of a protein corona and it is also accepted that the protein corona, rather than the original nanoparticle surface, defines a new biological identity. Consequently, a methodology to effectively study the interaction between nanomaterials and the biological corona encountered within an organism is a key objective in nanoscience for understanding the impact of the nanoparticle-protein interactions on the biological response in vitro and in vivo. Here, we outline an integrated methodology to address the different aspects governing the formation and the function of the protein corona of polystyrene nanoparticles coated with Transferrin by different strategies. Protein-NP complexes are studied both in situ (in human plasma, full corona FC) and after washing (hard corona, HC) in terms of structural properties, composition and second-order interactions with protein microarrays. Human protein microarrays are used to effectively study NP-corona/proteins interactions addressing the growing demand to advance investigations of the extrinsic function of corona complexes. Our data highlight the importance of this methodology as an analysis to be used in advance of the application of engineered NPs in biological environments.     

A health concern regarding the protein corona,aggregation and disaggregation

Nanoparticle (NP)–protein complexes exhibit the “correct identity” of NP in biological media. Therefore, protein–NP interactions should be closely explored to understand and modulate the nature of NPs in medical implementations. This review focuses mainly on the physicochemical parameters such as dimension, surface chemistry, morphology of NPs, and influence of pH on the formation of protein corona and conformational changes of adsorbed proteins by different kinds of techniques. Also, the impact of protein corona on the colloidal stability of NPs is discussed. Uncontrolled protein attachment on NPs may bring unwanted impacts such as protein denaturation and aggregation. In contrast, controlled protein adsorption by optimal concentration, size, pH, and surface modification of NPs may result in potential implementation of NPs as therapeutic agents especially for disaggregation of amyloid fibrils. Also, the effect of NPs-protein corona on reducing the cytotoxicity and clinical implications such as drug delivery, cancer therapy, imaging and diagnosis will be discussed. Validated correlative physicochemical parameters for NP–protein corona formation frequently derived from protein corona fingerprints of NPs which are more valid than the parameters obtained only on the base of NP features. This review may provide useful information regarding the potency as well as the adverse effects of NPs to predict their behavior in vivo.     

Coevolution of the checkerspot butterfly Euphydryas chalcedona and its larval food plant Diplacus aurantiacus: larval response to protein and leaf resin

Summary Prediapause larvae of the checkerspot butterfly Euphydryas chalcedona were raised from hatch until entrance into diapause on artificial diets. The proportions of protein and host plant leaf resin differed among the diets. Larval size growth rates and mortality were monitored and overall rates and efficiencies of food use were computed.Larval survivorship, growth rate and size of larvae at idapause were significantly enhanced by increasing dietary protein content, particularly over the range found in leaves of the host plant. In contrast, an increasing dietary content of Diplacus aurantiacus leaf resin significantly depressed larval surviviorship, growth rates and size of larvae at diapause. A simple dosedependent interaction was observed between the effects of dietary leaf resin and protein on larval success. Dietary content of leaf resin and protein significantly influenced some measures of food utilization efficiency (ECI and ECD), but not others (AD and NUE).The negative interaction between the effects of dietary leaf resin and protein content suggests the leaf resin phenolic compounds reduce the availability of protein to the larvae. The results for efficiency indices of larval food use are potentially in conflict with this interpretation.The influence of host plant leaf resin and protein on larval success, coupled with the relation between photosynthesis and leaf nitrogen content, are consistent with the hypothesis that productivity can be enhanced by herbivore deterrence resulting from leaf resin production.     

Optimum leaf size predicted by a novel leaf energy balance model incorporating dependencies of photosynthesis on light and temperature

To clarify relationships between leaf size and the environment variables, we constructed an energy balance model for a single leaf incorporating Leuning’s stomatal conductance model and Farquhar’s leaf photosynthesis model. We ran this model for various environmental conditions paying particular attention to the leaf boundary layer. The leaf size maximizing the rate of photosynthesis per unit leaf area (A) at a high irradiance differed depending on the air temperature. In warm environments, A increased with decrease in leaf size, whereas in cool environments, there was the leaf size maximizing A. With the increase in leaf size, the CO₂ concentration inside the leaf (C _i) decreased and the leaf temperature increased, both due to lower boundary layer conductance. At low air temperatures, the negative effect of low C _i on A in large leaves was compensated by the increase in leaf temperature towards the optimum temperature for A. This balance determined the optimum leaf size for A at low air temperatures. With respect to water use efficiency, large leaves tended to be advantageous, especially in cool environments at low-to-medium irradiances. Some temperature-dependent trends in leaf size observed in nature are discussed based on the present results.     

Proteins responding to drought and high-temperature stress in <Emphasis Type="Italic">Populus </Emphasis>× <Emphasis Type="Italic">euramericana</Emphasis> cv. ‘74/76’

Proteomic analysis provides a powerful method of studying plant responses to stress at the protein level. In order to study stress-responsive molecular mechanisms for Populus × euramericana cv. ‘74/76’, one of the most important forest plantation tree species in subtropical and temperate regions, we analyzed the response of 2-year-old cuttings of P. × euramericana cv. ‘74/76’ to drought and high temperature using two-dimensional gel electrophoresis. More than 1,000 reproducible leaf proteins were detected in the controls and treatments, and 26 proteins were found to change notably in abundance. We identified 13 proteins affected by drought stress and 11 proteins affected by high temperature. These proteins are mainly involved in photosynthesis such as ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit and putative photosystem I reaction center subunit II precursor, and detoxification (manganese superoxide dismutase and methionine sulfoxide reductase A). Furthermore, the level of the photosynthesis proteins affected greatly by the imposed stress conditions was consistent with the observed noticeable decrease in net photosynthesis rate. These studies provides a fundamental data for future research on responses to drought and high temperature, two major factors limiting the growth of forest trees during summer under recent climatic warming.     

Proteomic analysis of Citrus sinensis roots and leaves in response to long-term magnesium-deficiency

Background

Magnesium (Mg)-deficiency is frequently observed in Citrus plantations and is responsible for the loss of productivity and poor fruit quality. Knowledge on the effects of Mg-deficiency on upstream targets is scarce. Seedlings of ‘Xuegan’ [Citrus sinensis (L.) Osbeck] were irrigated with Mg-deficient (0 mM MgSO₄) or Mg-sufficient (1 mM MgSO₄) nutrient solution for 16 weeks. Thereafter, we first investigated the proteomic responses of C. sinensis roots and leaves to Mg-deficiency using two-dimensional electrophoresis (2-DE) in order to (a) enrich our understanding of the molecular mechanisms of plants to deal with Mg-deficiency and (b) understand the molecular mechanisms by which Mg-deficiency lead to a decrease in photosynthesis.

Results

Fifty-nine upregulated and 31 downregulated protein spots were isolated in Mg-deficient leaves, while only 19 upregulated and 12 downregulated protein spots in Mg-deficient roots. Many Mg-deficiency-responsive proteins were involved in carbohydrate and energy metabolism, followed by protein metabolism, stress responses, nucleic acid metabolism, cell wall and cytoskeleton metabolism, lipid metabolism and cell transport. The larger changes in leaf proteome versus root one in response to Mg-deficiency was further supported by our observation that total soluble protein concentration was decreased by Mg-deficiency in leaves, but unaffected in roots. Mg-deficiency had decreased levels of proteins [i.e. ribulose-1,5-bisphosphate carboxylase (Rubisco), rubisco activase, oxygen evolving enhancer protein 1, photosynthetic electron transfer-like protein, ferredoxin-NADP reductase (FNR), aldolase] involved in photosynthesis, thus decreasing leaf photosynthesis. To cope with Mg-deficiency, C. sinensis leaves and roots might respond adaptively to Mg-deficiency through: improving leaf respiration and lowering root respiration, but increasing (decreasing) the levels of proteins related to ATP synthase in roots (leaves); enhancing the levels of proteins involved in reactive oxygen species (ROS) scavenging and other stress-responsive proteins; accelerating proteolytic cleavage of proteins by proteases, protein transport and amino acid metabolism; and upregulating the levels of proteins involved in cell wall and cytoskeleton metabolism.

Conclusions

Our results demonstrated that proteomics were more affected by long-term Mg-deficiency in leaves than in roots, and that the adaptive responses differed between roots and leaves when exposed to long-term Mg-deficiency. Mg-deficiency decreased the levels of many proteins involved in photosynthesis, thus decreasing leaf photosynthesis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1462-z) contains supplementary material, which is available to authorized users.