Roles of Auxin and Cytokinin in Soybean Pod Setting

Abstract

Soybean plants differentiate abundant floral buds, but most of them fail to grow pods and abort during development. Many studies indicated promotive effects of exogenously applied cytokinin on pod setting, but the effects of auxin application on pod set are ambiguous. In this study, we examined the changes in the concentrations of endogenous auxin and cytokinin in racemes and the effects of application of the two hormones on pod setting to clarify the role of auxin and cytokinin in soybean pod setting. The long-raceme soybean genotype IX93-100 was grown in pots and in the field. The auxin (IAA, indoleacetic acid) concentration in racemes was high for a long period from pre-anthesis to 9 days after anthesis (DAA) of the first flower on a raceme, but the cytokinin concentration was high for a short period, with a peak at 9 DAA. The IAA concentration was higher in distal portions of racemes, but the cytokinin concentration was higher in basal portions of racemes. In pot-grown plants, IAA applied to racemes tended to reduce the number of flowers and pods. In contrast, 6-benzylaminopurine (BA) applied to racemes before anthesis tended to reduce the number of flowers and pods, and that applied around 7 DAA significantly increased the pod-set percentage. However, these effects of IAA and BA application were slight in field-grown plants. These results indicate that the concentration of endogenous auxin and cytokinin in racemes changes in a different manner, and that cytokinins have a positive, and auxin a negative effect on pod setting when respective hormones are applied to racemes after the anthesis stage.     

植物激素及其对水稻植株发育调控的研究进展

随着我国科技力量的飞速发展,科学家们在激素受体基因分离鉴定、激素控制株型以及激素间的相互作用等方面取得了突破性进展,其中生长素(IAA)在协调体内外调节机制中起着不可或缺的作用;细胞分裂素(CTK)可以通过对细胞分裂与分化的调节而参与对水稻生长发育的调控;赤霉素作为植物生长的必需激素之一,调控植物生长发育的各个方面,如:种子萌发,下胚轴的伸长,叶片的生长和水稻开花时间等;脱落酸(ABA)同样也是一种重要的植物激素,受到生物胁迫和非生物胁迫的调控,在水稻对胁迫耐受性和抗性中发挥着重要作用;乙烯(ETH)则是一种多功能的植物激素,它在水稻生长发育和应对生物及非生物胁迫过程中起着重要作用。本文着重阐述了近几年植物激素在生理学研究方面的研究进展,提出了我国在植物激素研究领域的未来发展方向与趋势,同时也展望了植物激素研究对水稻重要农业性状改良的意义。     

Metabolie Engineering of Flower Color in Ornamental Plants

Abstract

Advances in the knowledge of plant pigment pathways at genetic, biochemical and molecular levels, and the establishment of genetic transformation methods for an increasing number of plant species have paved the way to genetic engineering of flower and plant color for ornamental purposes. From trial-and-error approaches based on the available few genes, the trend is now to comprehensively study the target species, genotypes and pigment pathways to precisely address specific breeding goals. This review examines the state of the art in this field, from the pioneering stages to fundamental and applied research on flavonoids, which is being extended to carotenoids and is also likely to involve other pigments in the near future.     

Engineering for Drought Tolerance in Horticultural and Ornamental Plants

Abstract

Drought is one of the major factors limiting plant growth and productivity. Plant adaptation to drought is dependent on molecular networks for drought perception, signal transduction, expression of a subset of genes and production of metabolites that protect and maintain the structure of cellular components. In general, the drought response pathways can be classified into two categories: one is dependent on the stress hormone abscisic acid (ABA) and the other is ABA-independent. Many genes in these pathways have been identified, thereby providing guidance in choosing genes for engineering of drought tolerance. The review highlights the genes that mediate drought response and tolerance, and discusses lessons learned from engineering for drought tolerance in model plants, such as Arabidopsis, rice and tobacco. Because success of drought tolerance engineering is dependent on not only protein coding regions but also appropriate promoters, this article also reviews the promoters that are crucial for successful engineering of stress tolerance.     

Regulation of C/N Interaction in Model Plant Species

Summary

Carbon (C) and nitrogen (N) metabolisms are two major metabolic pathways which have been intensively studied in plants. Both N and C metabolisms are tightly linked in numerous plant biochemical pathways. Therefore the C to N ratio has to be carefully regulated to ensure proper functioning of the huge metabolic network. In order to maintain a viable C/N status under a large range of growth conditions plants have evolved complex mechanisms to regulate the delicate network of these two major assimilatory pathways. C and N metabolisms are both highly regulated. We will present the current knowledge on the regulation of N and C metabolisms by sugars and N metabolites. Players involved in these regulatory processes are just starting to be uncovered and possible signaling molecules involved in these regulations as well as known or potential candidate regulatory genes willbe discussed.     

Ornamental Plant Transformation

Abstract

Ornamental plant transformation has advanced considerably in the last decade. Now over 40 genera have been reported to be transformed. The primary methods of creating transgenic ornamental species have been Agrobacterium tumefaciens-medmtedtransformation and microprojectile bombardment. The vast majority of reports indicate the use of Agrobacteriummedmtedtransformation employing binary vectors and virhelper plasmids or supervirulence genes. Many reports are of transformation with the uidA reporter gene driven by the 35S cauliflower mosaic virus promoter, but recent efforts are now focusing on trait genes including disease resistance, flower color, flower longevity, floral scent and plant habit. Greater use of tissue specific and inducible promoters promises to enhance the functionality and usefulness of introduced trait genes. While technical challenges for production of transgenic ornamental plants still exist, the greatest challenges to realizing the potential benefits of transgenic ornamental plants are questionable public acceptance of transgenic plants and the prohibitive costs of generating environmental impact data needed to gain regulatory clearance.     

小麦生理型雄性不育系花药内源JA与ABA含量动态变化及其代谢通路差异基因表达研究

为了进一步阐明化学杂交剂SQ-1诱导小麦花粉败育的分子机制,以西农1376为材料,采用RNA-seq技术,对PHYMS-1376及其对照可育系CK-1376四分体、单核早期、单核晚期、二核期、三核期花药进行转录组测序,筛选出差异表达基因,进行GO富集、KEGG富集和GSEA富集分析,并利用高效液相法分别检测了PHYMS-1376及CK-1376上述五个时期花药中ABA和JA含量,通过qRT-PCR技术分析了ABA和JA通路关键差异基因的表达模式。结果发现,与CK-1376相比,在PHYMS-1376花药中共筛选出了 36 058个差异表达基因,主要富集到植物激素信号传导、苯丙素生物合成、淀粉和蔗糖代谢、氨基酸的生物合成4个通路;JA含量在PHYMS-1376四分体花药中显著降低（P<0.05）,至单核早期显著升高,单核晚期又显著降低,二核期显著升高,三核期显著降低;ABA含量在PHYMS-1376四分体至三核期花药中含量均高于CK-1376,其中在单核早期、单核晚期和二核期差异显著,可能与不育系各时期花药中PP2C关键基因TraesCS1D02G271000表达量过低相关,致使PP2C蛋白含量减少,进一步激活BIN2/BILs激酶,使SnRK2s磷酸化,促进ABA含量增加。上述结果表明：PHYMS-1376各发育时期花药中JA含量的异常波动与ABA含量的显著增加及上述2个通路关键基因的差异表达可能与SQ-1诱导小麦花粉败育密切相关。本研究为深入揭示SQ-1诱导小麦生理型雄性不育机理提供了一定的理论基础。     

水稻富含半胱氨酸类受体激酶家族基因对纹枯病菌和植物激素的响应特征分析

[目的]明确水稻富含半胱氨酸类受体激酶(Cysteine-rich receptor-like kinases,CRK)家族基因对纹枯病菌侵染和植物激素的响应特征,是解析CRK在水稻纹枯病抗性中的功能的重要前期工作.[方法]利用生物信息学方法构建了水稻45个CRK的系统发育树,并利用qPCR分析了它们对纹枯病菌和对植物...     

小麦 TaSPL17 基因在苗期对不同激素处理的响应

小麦TaSPL17基因在小麦株型调控中具有重要作用。为发掘TaSPL17基因在小麦育种中的应用价值,本研究采用不同浓度的独脚金内酯人工合成类似物GR24、生长素IAA和细胞分裂素6-BA分别处理三叶期的小麦,通过qRT-PCR技术检测小麦苗期根部和茎基部TaSPL17基因相对表达量的变化。结果发现,外源施加GR24、IAA和6-BA能显著下调小麦幼苗根部和茎基部TaSPL17基因的表达,并且在一定范围内施加的激素浓度越高,对TaSPL17基因表达的抑制作用越明显。以上结果表明,小麦株型相关基因TaSPL17的表达量可以被独脚金内酯、生长素和细胞分裂素调节,该基因可能通过参与这三种激素的信号途径发挥其在株型调控中的作用。     

Physiological regulation of potato tuber dormancy

At harvest, potato (Solanum tuberosum L.) tubers are dormant and will not sprout. As the period of postharvest storage is extended, tuber dormancy is broken and sprout growth commences. The loss of tuber dormancy and onset of sprout growth is accompanied by numerous biochemical changes, many of which are detrimental to the nutritional and processing qualities of potatoes. Endogenous hormones have been proposed to play a significant role in tuber dormancy regulation. The involvement of all major classes of endogenous hormones in tuber dormancy is reviewed. Based on available evidence, it is concluded that both ABA and ethylene are required for dormancy induction, but only ABA is needed to maintain bud dormancy. An increase in cytokinin sensitivity and content appear to be the principal factors leading to the loss of dormancy. Changes in endogenous IAA and GA content appear to be more closely related to the regulation of subsequent sprout growth.     

外源赤霉素信号对甘蔗分蘖及其内源激素的影响

前期研究发现,外源GA信号影响了甘蔗分蘖进程。为了解GA信号对甘蔗不同分蘖时期叶片内源激素含量的影响,以综合性状优良的甘蔗主栽品种‘桂糖42号’为材料,采用不同外源GA信号调节剂对蔗种进行浸种处理,并以清水处理为对照（CK）,分别测定分蘖初期、盛期和末期+1叶（主苗+分蘖苗）中内源激素吲哚乙酸（indole-3-acetic acid,IAA）、赤霉素（gibberellins,GA）、乙烯（ethylene,ETH）、细胞分裂素（cytokinin,CTK）、脱落酸（abscisic acid,ABA）和油菜素内脂（brassinosteroids, BR）的含量,并分析它们之间的相关关系。结果表明：外源GA₃（gibberellic acid 3;GA生物合成促进剂）对蔗种浸种处理后,增加了分蘖期甘蔗分蘖叶片中IAA、GA和CTK的总体含量,提高了分蘖前期ETH含量和后期ABA含量;多效唑（paclobutracol, PP₃₃₃;GA生物合成抑制剂）处理后却增加了分蘖前期内源GA和ABA含量,提高了后期分蘖叶片中ETH含量,同时降低了CTK和BR含量。进一步的相关性分析发现,利用外源赤霉素信号促进剂处理蔗种后,甘蔗叶片内源激素IAA与GA、CTK和BR、CTK与GA均呈显著正相关;而ABA与GA呈显著负相关,与ETH呈显著正相关。可见,外源GA信号影响了甘蔗分蘖期叶片内源激素系统,促进生长的激素与抑制生长的激素达到动态平衡状态,最终导致了甘蔗分蘖的差异。甘蔗分蘖与植物内源激素含量密切相关,可通过施用外源激素来影响内源激素的含量,调控激素之间的动态平衡,达到提高甘蔗分蘖形成及其成茎的目的。     

玉米光温敏无雄穗系植株多种植物激素含量的动态变化

以玉米光温敏无雄穗系I17及其正常系N17植株为试验材料,在春季和秋季种植条件下分别测定叶片与雄穗中生长素(IAA)、脱落酸(ABA)、赤霉素(GA3)和玉米素(ZT)的含量,研究植物激素对玉米光温敏无雄穗系植株雄穗发生及其育性的影响。结果表明,春季种植的无雄穗系I17与正常系N17的叶片和雄穗中IAA、GA3、ZT和ABA含量没有明显差异;秋季种植的无雄穗系I17叶片中IAA、GA3和ZT含量在苗期、抽雄期及花粒期均显著低于正常系N17,ABA含量显著高于N17。在植物激素平衡方面,秋季种植的无雄穗系I17叶片中IAA/ABA、GA3/ABA及ZT/ABA的比值均显著低于正常系N17的相应值。IAA、GA3和ZT的严重亏损与ABA的过量积累是引起玉米无雄穗的重要原因之一。     

Improvement of Horticultural and Ornamental Crops Through Transgenic Manipulation of the Phytochrome Family of Plant Photoreceptors

Abstract

Consumer demands drive continuous developments in the production of horticultural and ornamental crops. In addition to improvements in quality and nutritional content, crop producers must supply an increased variety of products to a year-round market. The availability of many horticultural and ornamental crop products is dependent on the timing of reproductive development. The time at which many plants initiate sexual or vegetative reproduction is governed by a number of interacting environmental factors such as daylength, light quality and temperature. Artificial manipulation of the growing environment is therefore frequently used to ensure production meets retailers' marketing programs, a strategy which can often result in high energy costs. An alternative approach involves the manipulation of genes encoding proteins responsible for perceiving and transducing environmental stimuli, in particular, the genes encoding the phytochrome family of plant photoreceptors. Alterations in the expression of genes encoding phytochromes can modulate not only the timing of reproductive development, but also plant architecture. Such approaches can therefore be used to modulate a variety of phenotypic traits such as height, lateral branching and harvest yield, while enabling growers to tailor crop reproduction to their marketing needs. In this review, we will discuss examples of crop improvement using transgenic manipulation of phytochrome expression, along with benefits and disadvantages of such approaches.     

Hormonal Mechanisms of Dormancy Induction in Developing Seeds

Summary

Primary dormancy develops in seeds during their maturation on the mother plant. In recent years, the use of hormone mutants and the manipulation of endogenous hormone levels by their biosynthetic inhibitors have led to a new approach of the hormonal regulation of the onset of dormancy. There is good evidence to show that ABA synthesis at axis level is an absolute requirement for the induction and maintenance of dormancy. This continued de novo synthesized ABA could positively control the expression of specific ABA-responsive genes. Among the set of late embryo abundant proteins, some appear to be good candidates as “dormancy proteins.” This review aims to correlate the preliminary results obtained by molecular biology with the recent advances in understanding the hormonal control of dormancy induction in developing seeds.     

Effects of high temperature and shading on grain abscisic acid content and grain filling pattern in rice (Oryza sativa L.)

ABSTRACT

Abscisic acid (ABA) is a key factor regulating starch biosynthesis genes and is involved in assimilate partitioning to individual spikelets. The objective of this study was to clarify the effects of high temperature and shading during grain filling on grain ABA content and the grain filling pattern of spikelets located at different positions in a panicle. We grew the rice cultivar ‘Koshihikari’ in pots in 2009 under two temperature regimes and two light conditions during grain filling. We periodically measured grain dry weight and grain ABA content (pmol per grain) and concentration (pmol per grain dry weight). Shading increased a grain weight difference between superior and inferior spikelets while high temperature decreased the difference regardless of light condition. High temperature decreased ABA content and concentration in grains. There was a close correlation between mean grain ABA content and mean grain-filling rate averaged over the first half of grain filling.     

Transgenic Approaches to Disease Resistance in Ornamental Crops

Abstract

Viral, bacterial, and fungal diseases of ornamental plants cause major losses in productivity and quality. Chemical methods are available for control of fungal diseases, and to a lesser extent for bacterial diseases, but there are no economically effective chemical controls for viral diseases except to control vector species. Host plant resistance is an effective means of controlling plant diseases, and minimizing the necessity for the application of pesticides; however, there are many ornamentals in which no natural disease resistance is available. It is possible to introduce resistance derived from other species, or even from the pathogen itself, by genetic engineering. This allows the introduction of specific, or in some instances broad spectrum, disease resistance into plant genotypes that have been selected for desirable horticultural characters; in contrast, introduction of natural resistance by traditional breeding may take many cycles of breeding to combine disease resistance with desirable ornamental quality. This article briefly reviews existing work on transformation systems for ornamentals, and discusses the various approaches to introducing resistance to viral, bacterial, and fungal diseases, and to nematode infestations. These include pathogen-related proteins, R genes, and general pathogen resistance; anti-microbial peptides; expression of anti-pathogen antibodies; viral sequences; ribozymes; antiviral peptides; ribonucleases; and ribosome-inactivating proteins. Examples are given of application of these approaches to disease resistance in other types of crop and model plant systems, and actual or potential application to disease resistance in ornamentals. Future prospects for obtaining plants with multiple pest and disease resistances are discussed.     

Problems and Challenges of Invasive Ornamental Plants and Molecular Tools to Control Their Spread

Abstract

Invasive plants, one of the most devastating ecological problems in the 21st century, cause an estimated $35 billion loss per year to the economy in the United States alone. More than 50% of all invasive plant species and 85% of invasive woody plant species were introduced originally for ornamental and landscape use. Because many non-native ornamentals are commercially important and widely utilized for various purposes, completely banning their use and prohibiting their import are unpractical solutions. On the other hand, currently used methods to control the spread of non-native plants are ineffective, expensive, or environmentally problematic. Recent advances in plant molecular biology and plant genetic transformation may enable us to create sterile cultivars of these non-native ornamental crops of high commercial value. The use of sterile cultivars should reduce or eliminate the undesirable spread of some non-native invasive plants into natural areas.     

Risk,Trust, and Consumer Acceptance of Plant Biotechnology

Abstract

This discussion summarizes current knowledge about rewards, risks, and reality surrounding the public's perception of genetically modified (GM) plants and foods. Differences in perception and acceptance of GM products between European and US publics are briefly described. The discussion includes recommendations for effective communication with the public. Pitfalls are identified that restrict credible discourse about the risks and benefits of GM ornamental plants and biotechnological products.

The U.S. gardening public is increasingly informed about technologies that influence their hobby interests, including plant biotechnology. Results of a preliminary and on-going survey of Tennessee Master Gardener Volunteers are presented that reveal consumer concerns similar to ones already voiced in the U.S. about GM foods. Discussion concludes by integrating these considerations, within the context of ongoing debate about GM foods, to provide implications about the success of novel GM ornamental plant introductions in the near future.