光周期诱导植物成花的分子调控机制

开花是植物从营养生长向生殖生长的转变过程。开花相关基因的表达是实现这一转变的基础,环境因子以及细胞自身的生长状况对这些基因的表达起着调控作用。目前利用模式植物拟南芥、水稻和观赏植物矮牵牛和金鱼草等植物,已了解到光周期信号被植物成熟叶片接受和感知并产生开花信号物质,这种开花物质经过叶片到茎尖的长距离运输,最终引起茎顶端开花起始。对国内外光周期途径植物成花分子机制的研究进展进行综述,旨在为进一步深入研究光周期调控观赏植物成花分子机制提供参考。     

miRNAs调控植物生长发育的研究进展

植物miRNAs是广泛分布于植物基因组的非编码小分子RNA,主要在转录后通过介导靶mRNA降解或翻译抑制来调控基因的表达水平,从而影响植物器官发生和发育。该研究综述了植物miRNA生物发生过程及其作用机制,并重点阐述了miRNAs在植物器官发育的作用,以期为尽快全面揭示植物器官发育调控机理提供理论依据。     

《中国蔬菜》2012·12 学术论文导读

长距离运输信号FT的开花调控机制刘智宇等(西南大学园艺园林学院,南方山地园艺学教育部重点实验室,重庆市蔬菜学重点实验室,重庆400715)—《中国蔬菜》2012(12)FLOWERING LOCUST(FT)是长距离运输信号物质,调节营养生长与生殖发育的转变,对开花调控意义重大。FT主要在叶片中表达,受光周期等多个     

中国农大揭示植物在黑暗下的ABA信号转导机制

中国农业大学生物学院植物生理学与生物化学国家重点实验室李继刚课题组揭示了转录因子PHYTOCHROME-INTERACTING FACTORS(PIFs)通过直接结合ABI5基因的启动子并且激活ABI5的表达,在黑暗下特异调控植物的ABA信号途径;该研究还发现ABA受体PYL8/PYL9能够和PIFs直接相互作用,并且介导PIFs对ABI5的转录调控;此外,该研究进一步支持了某些ABA受体通过与转录因子互作,直接调控基因表达的工作模式;综上,研究证明了植物中存在黑暗下特异的ABA信号调控组分和途径,有助于进一步理解植物如何根据环境的光信号调整其内源的ABA信号途径,从而在自然界获得更好的生存能力,还为PIFs这类重要转录因子在植物中参与的信号途径及调控机制提供了新的见解。     

植物环状RNA研究进展

环状RNA(circularRNA,circRNA)是一类经反向剪接后、由3′末端和5′末端共价结合形成的单链非编码RNA分子,广泛存在于多种生物体中,具有结构稳定、细胞或组织特异性等特征。circRNA具有多种功能,可作为miRNA"海绵"调控miRNA表达;促进来源基因转录;通过与蛋白互作参与相关途径调控等。多种植物circRNA的研究结果暗示其在生物胁迫、非生物胁迫及生长发育中发挥重要作用。对植物circRNA分子特征和作用机制的研究现状进行综述,并结合动物中circRNA的研究进展,讨论植物circRNA的潜在作用机制,并提出植物中尚未解决的问题及其未来的应用前景。     

植物光敏色素的研究进展

简要综述了光敏色素的分子特性、亚细胞定位、感光性和它介导的光信号传导及调控作用等方面的研究进展。指出光敏色素是一种调节植物许多光反应的色素蛋白复合体,不同的光敏色素具有特异的亚细胞定位和感光性。光敏色素家族介导的光信号传导构成了一个复杂的网络系统。同时,还讨论了拟南芥光敏色素家族的研究成果。     

果树microRNA研究进展

micro RNA(mi RNA)是一类来自真核生物自身基因组的非编码小分子RNA,通过互补配对原则作用于靶基因,从而调控植物的生长发育、激素信号以及胁迫响应等生物过程。扼要总结了果树mi RNA的生物学功能,分析了果树作物与模式植物mi RNA保守性的差异,从mi RNA的分离鉴定、表达检测及靶基因验证等方面介绍了果树mi RNA的研究方法,同时对该领域的研究进展及存在的问题进行讨论。     

长距离运输信号FT的开花调控机制

FLOWERING LOCUST(FT)是长距离运输信号物质,调节营养生长与生殖发育的转变,对开花调控意义重大。FT主要在叶片中表达,受光周期等多个途径调控,并以FT蛋白而非mRNA转运到顶端分生组织处,激活一系列下游基因,从而诱导开花。本文就FT基因的表达机制、FT蛋白的长距离运输、及其在顶端分生组织中诱导成花的机理等进行了综述,并结合FT的研究现状展望了未来的研究方向。     

番茄中ABC转运蛋白SlABCG23调控茉莉酸信号途径

茉莉酸（jasmonic acid,JA）的运输依赖于转运蛋白的参与。ABC(ATP binding cassette)转运蛋白参与植物体内多种物质的运输。已知在番茄中存在4个与拟南芥中JA转运蛋白具有较高同源性的ABC转运蛋白。对其进行了Motif、蛋白质结构域和跨膜结构分析,并选取其中的SlABCG23进行功能初步鉴定,推测其可能与JA信号途径的调控有关。构建了SlABCG23的过表达载体,通过农杆菌侵染法得到3株过表达番茄植株。通过表型分析发现,SlABCG23过表达植株的花器官增大,花粉萌发受阻,果实内种子发育异常且体内JA含量降低。推测SlABCG23可能通过影响JA的含量参与调控JA信号途径。     

aiiA基因在植物软腐病研究中的应用进展

N-酰基高丝氨酸内酯（N-acyl-homoserine lactones,AHLs）是一类广泛存在于许多革兰氏阴性细菌群体感应系统中的信号分子,又称作自体诱导物（Autoinducer,AI）。aiiA基因编码的AiiA蛋白能降解细菌产生的AHLs信号分子,干扰该信号分子参与细菌群体感应的调控过程,抑制多种植物病原菌致病基因的诱导表达,从而减轻或消除病原菌的致病性。本文介绍了aiiA基因、AiiA蛋白的研究情况,以及aiiA基因在抗软腐病工程菌和转基因植物研究上的应用现状,并提出了提高植物抗软腐病的研究方向。     

Protocol: a highly sensitive RT-PCR method for detection and quantification of microRNAs

MicroRNAs (miRNAs) are a class of small non-coding RNAs with a critical role in development and environmental responses. Efficient and reliable detection of miRNAs is an essential step towards understanding their roles in specific cells and tissues. However, gel-based assays currently used to detect miRNAs are very limited in terms of throughput, sensitivity and specificity. Here we provide protocols for detection and quantification of miRNAs by RT-PCR. We describe an end-point and real-time looped RT-PCR procedure and demonstrate detection of miRNAs from as little as 20 pg of plant tissue total RNA and from total RNA isolated from as little as 0.1 μl of phloem sap. In addition, we have developed an alternative real-time PCR assay that can further improve specificity when detecting low abundant miRNAs. Using this assay, we have demonstrated that miRNAs are differentially expressed in the phloem sap and the surrounding vascular tissue. This method enables fast, sensitive and specific miRNA expression profiling and is suitable for facilitation of high-throughput detection and quantification of miRNA expression.     

Grafting and RNA transport via phloem tissue in horticultural plants

Grafting is a cultivation method that exploits a cooperative relationship between partner plants possessing different genomes. It is most commonly used for the propagation and cultivation of trees, shrubs, and fruit vegetables. In addition, as represented by florigen (flowering hormone) experiments, grafting has been utilized in the field of plant physiology to clarify the mechanism of long-distance transport by which signals arising in organs that perceive an environmental change are transmitted to response organs. Recent analytical technology has revealed that some specific RNA molecules are also transported through phloem tissue as genetic information to execute coordinated organ growth and development. Therefore, it is anticipated that the RNA transport system could be applied for the improvement of cultivars of various horticultural crops, if the mechanism were controllable by artificial means.     

黄瓜叶片和韧皮部汁液中碳水化合物及相关酶的日变化

 以黄瓜叶片和韧皮部汁液为对象, 研究1个昼夜周期中各种碳水化合物含量及相关酶活性的变化。结果表明夜间至上午10: 00, 葡萄糖和果糖是叶片中主要的可溶性糖, 而下午13: 00至16: 00,水苏糖成为成熟叶片中含量最高的可溶性糖, 这种变化主要由叶片中水苏糖含量剧烈的昼夜变化引起; 当黄瓜同化物从源叶向外运输时, 韧皮部汁液中的可溶性糖以水苏糖为主, 运输完毕后则以蔗糖为主; 黄瓜成熟叶片在夜间以淀粉、葡萄糖、果糖、水苏糖、蔗糖等各种形式贮藏尚未运出的同化物, 而此时韧皮部汁液中葡萄糖、果糖、水苏糖的含量极低, 可能有特定的源库调节机制阻止叶片中的可溶性糖在夜间进一步向韧皮部中装载。     

Changes in carbohydrate levels and their metabolic enzymes in leaves,phloem sap and mesocarp during cucumber (Cucumis sativus L.) fruit development

Levels of carbohydrates and activities of metabolic enzymes were examined in leaves (source), phloem sap (flow) and mesocarp tissues (sink) in the course of cucumber (Cucumis sativus L.) fruit development, from 2 days before anthesis to 20 days after anthesis. While total sugar levels increased in all the three sampling organs, starch levels declined in leaves and mesocarp tissues as fruit development progressed. Glucose and fructose were the primary contributors to the soluble sugar pools in mature leaves. Stachyose was found as the most important component of the phloem sap extracts, followed by sucrose and raffinose. However, the primary sugars accumulated in mesocarp tissues were glucose and fructose, not stachyose or sucrose. Activities of sucrose synthesizing enzymes (sucrose phosphate synthase plus sucrose synthase in the synthesizing direction) exceeded that of sucrose degrading enzymes (acid invertase, neutral invertase plus sucrose synthase in the degrading direction) in leaves, which might cause a sucrose pool utilized in raffinose and stachyose biosynthesis. While alkaline a-galactosidase form I activity declined, stachyose synthase activity showed a rapid increase until 12 days after anthesis and only subsequently decreased in leaves. Activities of sucrose degrading enzymes were always much higher than that of sucrose synthesizing enzymes in mesocarp tissues. Thus, sucrose accumulation could not occur in mesocarp tissues. While stachyose synthase activity steadily decreased, alkaline a-galactosidase form I activity showed a moderate increase before decrease in mesocarp tissues. The relationship between levels of soluble sugars and activities of relative enzymes was also discussed.     

Studies in the Development of the Strawberry: III. Flower-Bud Initiation and Development in Large-Fruited Perpetual (“Remontant”) Strawberries

Summary

Four N application rates generated a range of tree N status as indicated by leaf N concentrations in six year old trees of `Mission' almond (Prunus dulcis (Mill.) D. A. Webb). Leaf N concentrations were related positively with concentrations of amino acids - especially asparagine and glutamine - in phloem and xylem saps. A pulse of 1.25 kg N per tree was applied to trees previously receiving 0, 78, 157 or 313 g N per tree, annually. Apparent uptake of soil N into above-ground tree parts was determined over a 39 d period. N uptake was determined as the difference in the products of tree biomass and tissue N concentrations before and after the N pulse. Tissue N concentrations increased signi®cantly in trees previously receiving the two lowest N application rates, whereas trees previously receiving the high N treatments were unresponsive. Tree N contents (0 g N per year, and also 78 g N per year treatments) increased slightly in response to the N pulse, although statistical differences were not observed due possibly to high variability in biomass among trees. At the same time, the amino acid concentrations in phloem exudate and xylem sap were highest in trees grown under the highest N fertilization regime. We suggest that the high amino acid concentrations in the phloem and xylem saps are indicative of a larger pool of amino N cycling throughout the vasculature of high N-status trees. Our data indicate an inverse relationship between tree N status, amino acid concentrations in xylem and phloem saps and capacity for soil N uptake in ®eld-grown trees. These results represent the ®rst ®eld data to correlate the concentration of amino acids circulating in the plant vasculature with soil N uptake. A functional relationship between the amino acid concentrations cycling within the tree and the regulation of soil N uptake has, however, not yet been established.     

Water relations of lettuce. I. Internal physical aspects for two cultivars

Experiments were performed to assess physical aspects of internal water relations (reported in this paper), and the gas exchange properties as affected by drought (reported in a second paper). A Dutch cultivar (‘Amanda Plus’) and a French cultivar (‘Sucrine’) were used. Water was withheld from plants for 5 or 9 days, and the latter group was rewatered to observe the pattern of recovery 1 day after rewatering. Measurements were made of plant water potential (hygrometry), sap osmotic potential (hygrometry and cryoscopy), sap electrical conductivity, and plant relative water content (RWC). Hygrometry was found suitable for measurement of plant water and sap osmotic potentials, although equilibration time for the former parameter was long. With suspension of irrigation, all the parameters decreased except for the electrical conductivity which increased. Leaf water and osmotic potentials were lower in ‘Amanda Plus’ than in ‘Sucrine’, but pressure potential in the former was better maintained. Significant parabolic regressions existed for RWC and osmotic potential on plant water potential. The significant linear regressions of plant water and sap osmotic potentials on sap electrical conductivity were thought to provide easy methods for measurements of the 2 former parameters.     

硼、镁缺乏诱发柑橘叶片维管组织变化差异研究

 以尤溪金柑（Fortunella crassifolia Swingle）、纽荷尔脐橙[Citrus senisis（L.）]和琯溪蜜柚[C. grandis（L.）]一年生老熟春梢叶片为材料,结合等离子体发射光谱法（ICP）和常规石蜡切片法对缺硼和缺镁条件下叶片维管组织结构变化的差异进行了研究。结果表明：缺硼植株叶片中脉维管组织异常增生,早期纤维鞘结构成束状分离,但木质部与韧皮部之间界限分明,维管射线结构保持完整;后期主脉初生韧皮部及纤维鞘外层薄壁细胞坏死,侧脉初生韧皮部坏死并伴随韧皮部增生的同时海绵组织细胞增生。维管组织及维管束外周的薄壁细胞增生为缺硼典型组织异常。缺镁植株叶片,早期叶绿体的数量与结构发生明显改变,中脉纤维鞘成束状分布,后生木质部结构弥散,木射线结构不完整;后期中脉髓部与韧皮部细胞坏死,侧脉初生木质部导管内部产生大量侵填体,初生木质部退化,而木质部与韧皮增生。木质部的阻塞退化与不规则增生以及髓部细胞的退化为缺镁典型组织异常。     

桃果实维管束的分布及解剖研究

 为了解桃果实输导组织分布及结构特征, 以‘大久保’桃果实为试材, 观察了维管束系统的分支体系和分布状况, 并用石蜡切片技术对维管束组织的解剖结构进行了系统观察。结果表明, 桃果实中的维管束分为骨干、分支和毛细3级, 其中骨干维管束又分为种胚维管束、内果皮维管束和中果皮维管束(腹维管束、背维管束及分布在内果皮两侧着生于果柄的维管束) , 分别为种仁、内果皮、中果皮的物质运输通道。种胚维管束韧皮部极其发达, 并伴有三生结构; 内果皮中分布的维管束韧皮部发达; 腹维管束、背维管束粗大且分支较多, 兼具发达的韧皮部及木质部。分支维管束和毛细微管束主要分布在中果皮中。毛细维管束的特点是韧皮部处有腔, 腔体随着果实的发育不断扩大。形态和结构上的不同是与其功能相适应的, 由此推测种仁和内果皮发育需要的营养物质以有机营养为主, 中果皮发育需要的营养物质则涵括有机物、无机物、水分。     

丝瓜伤流量的测定

于2007~2009年,连续3 a采集丝瓜伤流液,测定了丝瓜的伤流量。结果表明:剪断丝瓜茎能采集相当数量的伤流液,无棱丝瓜单株伤流量最高值为1 719 mL,有棱丝瓜单株伤流量最高值为3 666 mL。丝瓜伤流液量不仅与植株生长健壮程度有关,还受其它因素的影响。     

田间苹果成熟组织RNA高效提取方法

针对田间苹果成熟组织富含多酚、多糖和大量次生代谢产物的特点,建立了适合田间苹果不同组织的高效RNA提取方法,以不同季节田间生长的苹果叶片和皮层为材料,用此方法均能在2 h左右完成超过10个样品的总RNA提取,质量高、完整性好的总RNA,可用于田间苹果病毒RT-PCR检测,获得良好效果.经反复大量试验证实,该方法适合田间...