植物硝酸盐转运体的功能及其调控

NO-3不仅是植物从土壤中吸收的重要无机氮素形式,还是在植物体内转移的氮素形式,植物依赖硝酸盐转运体(Nitrate transporters,NRTs)参与吸收和转运NO-3.目前,许多学者主要对NRT1.1、NRT1.2、NRT2.1进行大量研究,而对其他硝酸盐转运体的功能及调控机制研究甚少.植物体作为一个整体,吸收、转运硝酸盐是一个连续的过程,在此过程中,各硝酸盐转运体间如何相互补充、相互协调,仍有待进一步研究.文章通过对NRTs蛋白的结构、生物学功能和调控机制进行综述,旨在阐明植物吸收、转运NO-3的生理机制,为通过基因工程手段提高作物氮素利用效率的研究提供理论依据.     

植物内生菌促进宿主氮吸收与代谢研究进展

内生菌与植物共生能够提高宿主的氮吸收与氮代谢水平,这可能是由于内生菌在植物体内引发的多种效应的综合结果.植物内生菌能够通过促进植物根系发育和固氮作用为宿主植物提供更多的无机氮素;能够通过分泌多种胞外酶系如漆酶、蛋白水解酶等使宿主植物更好地利用有机氮素;能够提高宿主氮代谢关键酶如硝酸还原酶(NR)、谷氨酰胺合成酶(GS)等酶的活性;能够提高宿主植物激素水平和维生素含量从而促进宿主氮代谢;能够通过影响宿主植物氮代谢促进宿主植物分蘖、提高宿主植物叶绿素含量和光合速率等等.综述了国内外关于植物内生菌促进宿主氮代谢的相关报道,归纳了植物内生菌影响宿主氮素吸收与代谢的可能机制,并展望了关于植物内生菌促进宿主氮代谢机制方面的研究方向.     

Physiological and Molecular Response of Wheat Roots to Nitrate Supply in Seedling Stage

The objective of this study was to understand the morphological, physiological, and molecular responses of wheat roots to nitrate supply at seedling stage. Two wheat genotypes, Jimai 22 and Shannong 15, were grown in Hoagland's nutrient solution with different nitrate levels at seedling stage. Results indicated that the plant dry weight and N accumulation increased with the increase of nitrate supply. The number of axial root, total uptake area (TUA), and active uptake area (AUA) increased with more nitrate supply. Correlation analysis indicated that significant positive correlations existed between N accumulation and dry weight, N accumulation and AUA, and N accumulation and AUA/TUA. Although, the expressions ofNRT2.1, NRT2.2, and NRT2.3 decreased with nitrate supply increased, the expressions of NRTI, NRT2.1,and NRT2.3 could maintain high level at N3 treatment. The free amino acid and NO3- content in shoot also increased with the increased nitrate application, but no significant difference was found in root among the treatments. These results implied that the increase of N uptake by nitrate supply was due to the morphological and physiological responses of wheat roots and the high expression level of TaNRT genes. Similarly, the contribution of morphological, physiological,and molecular parameters was different between two genotypes of wheat.     

水稻氮高效相关基因的研究进展

提高氮肥利用率,降低农业生产中的氮肥投入,对实现中国提出的"化肥零增长"目标至关重要.氮素可通过植物根部以硝态氮或者铵态氮的形式从土壤中被吸收,并在植物体内转运合成氨基酸、核苷酸等生命必需物质,是农作物生长和产量形成的必要性元素.然而,氮肥过量则会破坏土壤理化性质,导致土壤盐碱化、生态环境污染;减少氮肥用量难以发挥当前...     

植物干旱胁迫适应机制研究进展

干旱是影响植物正常生长发育的一个最重要的逆境因子,水资源日益短缺成为制约农业发展的严重问题.植物对干旱胁迫的响应和适应机制一直是学术研究的热点领域.从植物对干旱胁迫所作出的形态生理反应(植物的根系、叶片的变化、对光和作用的影响)及内部分子适应机制(渗透调节基因、保护酶体系、转录因子等)两方面综述了干旱胁迫下植物的抗旱机理,为我国节水抗旱农业的研究提供一些新的思路和手段.     

Overexpression of IbSnRK1 enhances nitrogen uptake and carbon assimilation in transgenic sweetpotato

Nitrogen is an important nutrient for plant development. Nitrogen and carbon metabolisms are tightly linked to physiological functions in plants. In this study, we found that the IbSnRK1 gene was induced by Ca(NO₃)₂. Its overexpression enhanced nitrogen uptake and carbon assimilation in transgenic sweetpotato. After Ca(¹⁵NO₃)₂ treatment, the ¹⁵N atom excess, ¹⁵N and total N content and nitrogen uptake efficiency (NUE) were significantly increased in the roots, stems, and leaves of transgenic plants compared with wild type (WT) and empty vector control (VC). After Ca(NO₃)₂ treatment, the increased nitrate N content, nitrate reductase (NR) activity, free amino acid content, and soluble protein content were found in the roots or leaves of transgenic plants. The photosynthesis and carbon assimilation were enhanced. These results suggest that the IbSnRK1 gene play a important role in nitrogen uptake and carbon assimilation of sweetpotato. This gene has the potential to be used for improving the yield and quality of sweetpotato.     

施硫对不结球白菜硝酸盐累积及氮硫同化关键基因表达的影响

【目的】确定降低不结球白菜硝酸盐累积效果最佳的硫素形态,从转录水平筛选影响不结球白菜硝酸盐累积的关键基因,为完善不结球白菜科学施硫技术及进一步揭示硝酸盐累积分子调控机制、指导分子育种奠定基础。【方法】选取4种硫素形态及3个施用浓度处理不结球白菜,测定其对植株叶片及叶柄中硝酸盐含量的影响;利用半定量PCR技术从转录水平分析施硫对氮及硫代谢同化网络中30个基因表达的影响。【结果】不同形态硫处理均显著增加了不结球白菜的地上生物量,其中30 mg·kg^-1 Na₂SO₄处理的增幅最大,比对照增加49.76%,以Na₂SO₄处理的增幅最大。在降低小白菜硝酸盐含量中,以Na₂SO₄、Na₂S₂O₃处理效果相对显著,其中Na₂SO₄降低叶片中硝酸盐12.23%-23.55%,叶柄中33.08%-41.98%,降幅与浓度呈正相关,30 mg·kg^-1 Na₂SO₄处理的降幅最大;Na₂S₂O₃处理降低植株叶片中硝酸盐15.34%-33.08%,叶柄中11.95%-19.68%。硫处理在一定程度上促进氮同化,对照叶片中NR-1、NADH-GOGAT-1、NADH-GOGAT-2、Cytoplasm-GS-4、Cytoplasm-GS-5、GDH-3表达量低于其他处理,对照叶柄中NR-1、NADH-GOGAT-2、Cytoplasm-GS-1、GDH-2表达量低于其他处理,其中,各处理NADH-GOGAT-2表达量与叶片及叶柄中硝酸盐含量变化呈现一定规律性。硫处理对植株硫同化基因也产生一定影响,对照叶片中ATPS-2、ATPS-3、ATPS-4、APSR-3、SIR、SAT1.1、SAT2.1表达量较低,而对照叶柄中仅SIR、OASTL-A表达量明显低于其他处理。【结论】Na₂SO₄是降低不结球白菜硝酸盐效果较为显著的硫素,且能够显著提高产量,30 mg·kg^-1的Na₂SO₄为较优处理。NADH-GOGAT-2表达量与不结球白菜内硝酸盐含量呈负相关,推测其可能是影响氮同化的关键基因。     

Interaction effect of nitrogen form and planting density on plant growth and nutrient uptake in maize seedlings

High planting density is essential to increasing maize grain yield.However,single plants suffer from insufficient light under high planting density.Ammonium(NH_4~+)assimilation consumes less energy converted from radiation than nitrateIt is hypothesized that a mixed NO_3~–/NH_4~+supply is more important to improving plant growth and population productivity under high vs.low planting density.Maize plants were grown under hydroponic conditions at two planting densities(low density:only).A significant interaction effect was found between planting density and N form on plant biomass.Compared to nitrate only,75/25NO_3~–/NH_4~+increased per-plant biomass by 44%under low density,but by 81%under high density.Treatment with 75/25NO_3~–/NH_4~+increased plant ATP,photosynthetic rate,and carbon amount per plant by 31,7,and 44%under low density,respectively,but by 51,23,and 95%under high density.Accordingly,carbon level per plant under 75/25NO_3~–/NH_4~+was improved,which increased leaf area,specific leaf weight and total root length,especially for high planting density,increased by 57,17 and 63%,respectively.Furthermore,under low density,75/25NO_3~–/NH_4~+increased nitrogen uptake rate,while under high density,75/25NO_3~–/NH_4~+increased nitrogen,phosphorus,copper and iron uptake rates.By increasing energy use efficiency,an optimum NO_3~–/NH_4~+ratio can improve plant growth and nutrient uptake efficiency,especially under high planting density.In summary,an appropriate supply of NH_4~+in addition to nitrate can greatly improve plant growth and promote population productivity of maize under high planting density,and therefore a mixed N form is recommended for high-yielding maize management in the field.     

The mitigation effects of exogenous dopamine on low nitrogen stress in Malus hupehensis

Dopamine plays numerous physiological roles in plants. We explored its role in the regulation of growth, nutrient absorption, and response to nitrogen (N) deficiency in Malus hupehensis Rehd. Under low N condition, plant growth slowed, and the net photosynthetic rates, chlorophyll contents, and maximal quantum yield of PSII (F_v/F_m) decreased significantly. However, the application of 100 μmol L⁻¹ exogenous dopamine significantly reduced the inhibition of low N stress on plant growth. In addition to modifying root system architecture under low N supply, exogenous dopamine also changed the uptake, transport, and distribution of N, P, and K. Furthermore, exogenous dopamine enhances the tolerance to low nitrogen stress by increasing the activity of enzymes (nitrate reductase, nitrite reductase, glutamic acid synthase and glutamine synthetase) involved in N metabolism. We also found that exogenous dopamine promoted the expression of ethylene signaling genes (ERF1, ERF2, EIL1, ERS2, ETR1, and EIN4) under low N stress. Therefore, we hypothesized that ethylene might be involved in dopamine response to low N stress in M. hupehensis. Our results suggest that exogenous dopamine can mitigate low N stress by regulating the absorption of mineral nutrients, possibly through the regulation of the ethylene signaling pathway.     

植物尿素代谢及稳态调节机制研究进展

尿素是农业生产中施用量最多的氮肥之一,也是植物体内重要的代谢中间产物。普遍认为,植物主要吸收土壤中经土壤微生物转化产生铵态氮和硝态氮,直接吸收尿素和内部水解作用并不显著, 但这一观点正受到挑战,因为植物拥有专用的尿素转运蛋白,能够利用尿素作为唯一氮源。本文通过概述尿素在不同生命系统中存在的基础生理意义及MIPs和DUR3系统在调控尿素吸收、转运以及库/源间氮循环过程的作用,讨论了脲酶在促进尿素氮的同化、信号传导,精氨酸途径和酰胺途径在维持C/N代谢平衡和激素信号网络调节机制,以及植物尿素代谢及稳态调节机制在农业运用方面的展望。通过阐述植物体内局部尿素浓度与整体的氮素状态信号的反馈调节调控氮素的吸收和再利用的复杂调控网络,为提高作物氮的吸收、利用及再分配和农作物遗传改良奠定理论基础。     

Nitrogen Dioxide-Induced Responses in Brassica campestris Seedlings： The Role of Hydrogen Peroxide in the Modulation of Antioxidative Level and Induced Resistance

This article investigates the responses of Brassica campestris seedlings to an acute level of nitrogen dioxide (NO₂) exposure in a plant growth chamber, and examines whether pretreating plants with hydrogen peroxide (H₂O₂) will alleviate NO₂-caused injury. Twenty-eight-day-old B. campestris plants sprayed with 10 mmol L⁻¹ H₂O₂ aqueous solution (corresponding to approximate 1.0 mg H₂O₂ per single plant) were exposed to different concentrations of NO₂ (0.25, 0.5, 1.0, and 2.0 μL L⁻¹, respectively) for 24 h under controlled environment. To measure the plant biomass, the plants were fumigated with the same NO₂ concentrations as mentioned above for 7 h per day (8.00-15.00) for 7 days. As a control, charcoal filtered air alone was applied. Data were collected on plant biomass, total chlorophyll, photosynthetic rate, stomatal conductance, nitrate and nitrate reductase (NR), antioxidative enzymes, ascorbate (ASA), and malondialdehyde (MDA), immediately after exposure. The results showed that exposure to a moderate dose of NO₂ (e.g., 0.25 μL L⁻¹) had a favorable effect on plants, and the dry weight of the above-ground part increased, whereas the exposure to high NO₂ concentrations (e.g., 0.5 μL L⁻¹ or higher) caused a reduction in the plant biomass and the total chlorophyll, when compared with the control. In addition, at 0.5 μL L⁻¹ or higher NO₂ concentrations, prominent increases in the MDA level and superoxide dismutase (SOD) and NR activities were observed. Exposure to 1 μL L⁻¹ and higher NO₂ resulted in necroses appearing on older leaves, and an increase in catalase (CAT) activity, decrease in ASA content, increased accumulation of NO₃, and reduction in photosynthesis, when compared with the controls. No changes were detected in stomatal conductance under NO₂ fumigation. The pretreatment with 10 mmol L⁻¹ H₂O₂ alleviated significantly NO₂-caused biomass decrease and photosynthetic inhibition when compared with H₂O₂-untreated plants. Under NO₂ fumigation, further induction in SOD and CAT activities occurred in H₂O₂ treated plants when compared with H₂O₂-untreated plants. The effect of NO₂ on the ASA and MDA contents was also absent in H₂O₂-treated plants. However, the H₂O₂ treatment did not alter the nitrate content and NR activity in plants under NO₂ fumigation. The H₂O₂ treatment caused a lower rate of stomatal conductance. Taken together, these data suggest that fumigation with an acute level of NO₂ causes oxidative damage to B. campestris seedlings. The H₂O₂ pretreatment markedly protects plants against NO₂ stress and this may be associated with inducible antioxidative level. NO₂ fumigation contributes, at least in part, to the enhanced levels of nitrate in B. campestris leaves.     

植物表皮毛发育分子调控机制的研究进展

植物表皮毛在环境和植物相互作用中起到缓冲区域的重要作用,而细胞发育分化的独特性使其成为研究细胞发育调控和细胞命运决定等过程的最佳体系。近年来,随着分子生物学等技术的快速发展,植物表皮毛发育分子调控机制的研究发展较快。特别是模式植物拟南芥的部分关键的调控基因已经被克隆并获得其功能信息,为其他植物复杂表皮毛的研究和农业应用提供了理论指导。该研究主要以表皮毛发育时间的先后顺序综述该领域的研究进展、影响因素和其他植物表皮毛研究的现状,以期为大众和研究者提供比较全面的有关植物非分泌型表皮毛分子调控研究的进展信息。     

施氮后蚯蚓对植物吸氮及微生物固氮的影响

为探讨尿素施用后蚯蚓对植物吸氮量及微生物固氮量的影响,通过盆栽试验,以威廉腔环蚓(Metaphire guillelmi)为试验材料,对比有、无蚯蚓作用下15N标记的尿素施入后植物氮素含量的差异及土壤微生物量的变化过程。结果表明:培养结束后对植物进行取样测定,发现不同处理间植株氮含量并无显著差异,但接种蚯蚓的处理增加了植株生物量,进而导致蚯蚓作用下的植株总吸氮量提高了约30.8%。从分配比例上看,接种蚯蚓显著增加了植物吸收土壤氮的比例,却显著降低了植物吸收肥料氮的比例。在整个试验过程中,两处理的全氮(TN)含量均无显著变化,但土壤中来源于肥料的氮却随着培养的进行逐渐降低,且接种蚯蚓使其下降速度更快。微生物生物量氮(M BN)先下降后上升,且接种蚯蚓处理的MBN含量在试验初期(第5d)与试验末期(第30d)较高,但MBN中固定的肥料氮含量始终低于不接种蚯蚓的对照处理。试验过程中,土壤可溶性有机氮(D ON)的含量先下降后上升,与MBN变化趋势一致。与对照处理相比,接种蚯蚓处理的铵态氮(N H4+-N)含量降低,硝态氮(N O-3-N)含量则差异不显著。综上,蚯蚓可通过调节微生物生物量形成氮素缓冲库,从而促进植株对土壤氮而非尿素氮的吸收。     

植物硝酸还原酶功能的研究进展

硝酸还原酶(Nitrate Reductase,简称NR)是高等植物氮素同化的限速酶,可直接调节硝酸盐还原.从而调节氮代谢,并影响到光合碳代谢.发掘NR新的生理功能并探讨其作用机理具有重要的理论和实际意义.随着分子生物学技术的迅猛发展.可以从分子水平上深入了解NR的生理功能及作用机制;此外还可能由此了解氮代谢及其与其他生理过程之间的关系;同时也深入了解NR、NO与植物抗逆性的关系;以及研究硝酸还原酶的展望.     

紫花苜蓿对Cd胁迫的响应及品种差异研究进展

为利用紫花苜蓿对Cd污染土壤进行修复和综合利用提供理论基础。综述了紫花苜蓿对Cd胁迫的响应,包括:紫花苜蓿的生长对Cd的响应存在"低促高抑"现象;紫花苜蓿对Cd吸收的可能途径包括根表皮质膜的H+交换、Ca~(2+)和Mg~(2+)阳离子通道,根际环境和Cd元素在土壤中的有效态等因素会影响紫花苜蓿对Cd的吸收;在Cd由根部向地上部转运的过程中,随着土壤Cd含量的增加,更多的Cd被累积在紫花苜蓿的根部;紫花苜蓿应对土壤Cd胁迫的调控机理包括信号分子调控、抗氧化系统调控、生物巯基化合物对Cd的螯合、调节Cd的亚细胞分布和耐Cd基因的表达等多个方面。总结了紫花苜蓿对Cd胁迫响应的品种差异,主要表现在:种子萌发和幼苗生长;根瘤生长、植株形态和生物量;生理指标;对Cd的吸收与累积等方面。今后的研究工作可重点关注品种差异评判标准的建立、差异显著品种的系统筛选、在分子水平上的响应机理及品种差异机理的分析等方面。     

脂质分析技术及其在植物种子脂质 代谢调控研究中的应用进展

脂质是一类具有独特生理功能活性的化合物,参与调节多种植物应答非生物胁迫过程,对维持植 物组织中生理动态平衡至关重要。脂质组学（Lipidomics）自 2003 年被提出后,已迅速发展成为对脂质整体系 统分析的一门新兴学科,为传统代谢组学注入新的技术支撑,有助于阐明脂类物质在植物中的代谢调控机制。 同时,质谱成像技术因其具有无标记、非特异性、高灵敏度、多物质同时分析等优势,被广泛应用到植物组织 中各类脂质分子的空间分布研究。介绍了脂质组学和质谱成像技术的研究现状,重点综述脂质分析技术在植物 种子脂质代谢调控研究中的最新进展,特别是新兴质谱成像技术在植物种子中脂类物质的成像应用。脂质组学 和质谱成像技术作为目前多组学技术的重要补充,将为植物代谢途径和调控机制的深入探究提供新的契机。亚 微米级高空间分辨率质谱成像技术的不断发展,将进一步推动植物在空间分辨水平的脂质代谢调控网络的深入 解析和前沿应用研究。     

苹果异三聚体G蛋白α亚基基因MdGPA1的克隆及功能鉴定

【目的】异三聚体G蛋白(Heterotrimeric G protein)作为植物生物体内重要的信号转导分子,在感受外界环境刺激、参与植物抗逆反应和跨膜信号转导等方面发挥着重要作用。克隆异三聚体G蛋白α亚基基因MdGPA1,并在烟草中过量表达MdGPA1,对其进行生物学功能鉴定和生理指标分析,为多年生木本植物响应环境因子信号转导过程中的分子机理研究提供参考。【方法】本研究以‘嘎拉’苹果(Malus×domestica‘Royal Gala’)为研究试材,利用同源序列比对和PCR技术,克隆获得MdGPA1。使用MEGA5.0构建GPA1物种间系统进化树;利用qRT-PCR方法检测该基因在苹果受非生物胁迫诱导表达及组织特异性表达情况。构建MdGPA1植物过表达载体,通过农杆菌介导法转化烟草叶片,比较干旱胁迫条件下野生型和转基因株系的表型与生理指标,验证MdGPA1在植物干旱胁迫条件下的生物学功能。【结果】克隆得到苹果异三聚体G蛋白α亚基基因MdGPA1(基因序列号:MDP0000881842),该基因长为1 173 bp,编码390个氨基酸。进化树分析表明MdGPA1与白梨Pb GPA1亲缘关系最近,同源性最高。基因表达分析显示MdGPA1主要在叶片中表达,在根系中的表达量次之,在茎和果实中的表达量较低。定量分析表明,该基因参与干旱、低温和盐等非生物逆境胁迫响应,在150 mmol·L~(-1)Na Cl、150 mmol·L~(-1)甘露醇、10%PEG和4℃胁迫条件下表达量明显下调,在5%H_2O_2胁迫处理下表达量明显上调。在烟草中过量表达MdGPA1,发现MdGPA1转基因烟草表现出对干旱敏感的表型特征,其叶片鲜重、叶绿素含量以及脯氨酸含量明显低于野生型烟草。在地下部,MdGPA1转基因烟草同样表现出对干旱敏感的表型特征;其根系形态相比于野生型较小,干重也明显低于野生型。【结论】MdGPA1参与了植物感受外界环境刺激的过程,对干旱、低温和盐等非生物逆境胁迫都存在着不同程度的响应。在烟草中异源表达MdGPA1后,提高了烟草对干旱的敏感性,转基因烟草表现出不耐干旱的表型,受干旱胁迫比野生型烟草更为严重,说明MdGPA1在响应植物抗旱胁迫中起着负调控作用。