The regulation of assimilate allocation and transport

2000 ◽  
Vol 27 (6) ◽  
pp. 583 ◽  
Author(s):  
Hanjo Hellmann ◽  
Laurence Barker ◽  
Dietmar Funck ◽  
Wolf B. Frommer
Keyword(s):  
Higher Plants ◽  
Sugar Transport ◽  
Long Distance ◽  
Regulatory Pathways ◽  
Sugar Transporters ◽  
E Coli ◽  
Long Distance Transport ◽  
N Metabolism ◽  
C And N ◽  
And Storage

In higher plants, sugars possess multiplefunctions: transport and storage of carbon and energy as well as signalmolecules. A variety of sugar transporters have been cloned that showdifferential expression between source and sink tissues. Expression of thesetransporters is highly regulated, according to the local metabolic status andthe demands of long distance transport. Very little knowledge is available onmechanisms underlying the regulation of sugar transporter expression inplants. Studies in E. coli, yeast and mammals haveunravelled complex regulatory pathways with crosstalk between sugar transportand metabolism. Recent studies in plants provide increasing evidence for theexistence of similar regulatory mechanisms. In many cases, connections havebeen found between C-and N-metabolism, implicating a tight network of signaltransduction and metabolism. Some aspects of this network are presented inthis review, emphasising sugar transport and sugar signaltransduction.

Phloem long-distance transport of CmNACP mRNA: implications for supracellular regulation in plants

Development ◽  
1999 ◽  
Vol 126 (20) ◽  
pp. 4405-4419 ◽  
Author(s):  
R. Ruiz-Medrano ◽  
B. Xoconostle-Cazares ◽  
W.J. Lucas
Keyword(s):  
Higher Plants ◽  
Phloem Transport ◽  
The Body ◽  
Pcr Analysis ◽  
Rt Pcr ◽  
Long Distance ◽  
Rna Molecules ◽  
Long Distance Transport ◽  
Meristem Development

Direct support for the concept that RNA molecules circulate throughout the plant, via the phloem, is provided through the characterisation of mRNA from phloem sap of mature pumpkin (Cucurbita maxima) leaves and stems. One of these mRNAs, CmNACP, is a member of the NAC domain gene family, some of whose members have been shown to be involved in apical meristem development. In situ RT-PCR analysis revealed the presence of CmNACP RNA in the companion cell-sieve element complex of leaf, stem and root phloem. Longitudinal and transverse sections showed continuity of transcript distribution between meristems and sieve elements of the protophloem, suggesting CmNACP mRNA transport over long distances and accumulation in vegetative, root and floral meristems. In situ hybridization studies conducted on CmNACP confirmed the results obtained using in situ RT-PCR. Phloem transport of CmNACP mRNA was proved directly by heterograft studies between pumpkin and cucumber plants, in which CmNACP transcripts were shown to accumulate in cucumber scion phloem and apical tissues. Similar experiments were conducted with 7 additional phloem-related transcripts. Collectively, these studies established the existence of a system for the delivery of specific mRNA transcripts from the body of the plant to the shoot apex. These findings provide insight into the presence of a novel mechanism likely used by higher plants to integrate developmental and physiological processes on a whole-plant basis.

scholarly journals Regulation of Sulfur Homeostasis in Mycorrhizal Maize Plants Grown in a Fe-Limited Environment

2020 ◽  
Vol 21 (9) ◽  
pp. 3249
Author(s):  
Styliani N. Chorianopoulou ◽  
Petros P. Sigalas ◽  
Niki Tsoutsoura ◽  
Anastasia Apodiakou ◽  
Georgios Saridis ◽  
...  
Keyword(s):  
Higher Plants ◽  
Expression Patterns ◽  
Soluble Form ◽  
Mycorrhizal Symbiosis ◽  
Sulfur Deprivation ◽  
Long Distance ◽  
Sulfate Anion ◽  
Long Distance Transport ◽  
Maize Plants ◽  
Distance Transport

Sulfur is an essential macronutrient for growth of higher plants. The entry of the sulfate anion into the plant, its importation into the plastids for assimilation, its long-distance transport through the vasculature, and its storage in the vacuoles require specific sulfate transporter proteins. In this study, mycorrhizal and non-mycorrhizal maize plants were grown for 60 days in an S-deprived substrate, whilst iron was provided to the plants in the sparingly soluble form of FePO4. On day 60, sulfate was provided to the plants. The gene expression patterns of a number of sulfate transporters as well as sulfate assimilation enzymes were studied in leaves and roots of maize plants, both before as well as after sulfate supply. Prolonged sulfur deprivation resulted in a more or less uniform response of the genes’ expressions in the roots of non-mycorrhizal and mycorrhizal plants. This was not the case neither in the roots and leaves after the supply of sulfur, nor in the leaves of the plants during the S-deprived period of time. It is concluded that mycorrhizal symbiosis modified plant demands for reduced sulfur, regulating accordingly the uptake, distribution, and assimilation of the sulfate anion.

scholarly journals Characterization of a vacuolar sucrose transporter, HbSUT5, from Hevea brasiliensis: involvement in latex production through regulation of intracellular sucrose transport in the bark and laticifers

2019 ◽  
Author(s):  
xiangyu long ◽  
Heping Li ◽  
Jianghua Yang ◽  
Lusheng Xin ◽  
Bin He ◽  
...  
Keyword(s):  
Hevea Brasiliensis ◽  
Higher Plants ◽  
Transcript Level ◽  
Active Role ◽  
Sucrose Transporter ◽  
Sucrose Transport ◽  
Long Distance ◽  
Rubber Biosynthesis ◽  
Long Distance Transport ◽  
Latex Production

Abstract Background: Sucrose (Suc), as the precursor molecule for rubber biosynthesis in Hevea brasiliensis, is transported via phloem-mediated long-distance transport from leaves to laticifers in trunk bark, where latex (cytoplasm of laticifers) is tapped for rubber. Suc transporters (SUTs) play important roles during various steps of Suc transport in higher plants. Results: In our previous report, six SUT genes have been cloned in Hevea tree, among which HbSUT3 has been verified to play an active role in Suc loading to the laticifers. In this study, another latex-abundant SUT isoform, HbSUT5, with expressions only inferior to HbSUT3 was characterized especially for its roles in latex production. Both phylogenetic analysis and subcellular localization identify HbSUT5 as a SUT4-clade (=type III) vacuolar membrane SUT, suggesting its potential participation in Suc exchange between lutoids (polydispersed microvacuoles) and cytosol in latex. Suc uptake assay in yeast identifies HbSUT5 as a typical Suc-H+ symporter, but the high affinity of HbSUT5 for Suc (Km = 2.03 mM at pH 5.5) and its similar efficiency in transporting maltose making it a peculiar SUT under the SUT4-clade. At the transcript level, HbSUT5 is abundantly and preferentially expressed in Hevea barks. It is contrary to HbSUT3 that the transcripts of HbSUT5 are obviously decreased both in Hevea latex and bark during the treatments of tapping and ethephon, indicating it counteracts the yield-stimulating effects of two treatments. Conclusions: A vacuolar sucrose transporter, HbSUT5, may play an important role in Suc exchange between lutoids (polydispersed vacuoles) and latex in laticifers. It is better to understand that the whole HbSUT family regulate and control Suc accumulation in laticifers, influencing rubber yield formation in Hevea.

A study of phloem sieve element structure using electron, fluorescent, and confocal microscopy

1991 ◽  
Vol 49 ◽  
pp. 202-203
Author(s):  
Richard D. Sjolund ◽  
Chi Wang
Keyword(s):  
Cell Walls ◽  
Higher Plants ◽  
Post Injury ◽  
Long Distance ◽  
Callose Deposition ◽  
Sieve Elements ◽  
Long Distance Transport ◽  
P Protein ◽  
Sieve Tubes ◽  
Distance Transport

Phloem sieve elements are the cells responsible for the long distance transport of nutrients, primarily sugars and amino acids, in higher plants. The translocation of nutrients in these cells, joined together to form long sieve tubes, is dependent on the development of high hydrostatic pressures (20 bars or higher). The dissection of plant tissues containing these phloem cells which is necessary for microscopic study usually results in the cutting of the sieve elements and a resultant loss of phloem contents due to the explosive release of the hydrostatic pressure. Wound-sealing mechanisms involving P-protein filaments and callose deposition in the cell walls rapidly seal off wound sites and prevent the loss of translocates, especially in Angiosperms. As a result, most electron microscope images of sieve elements obtained from plant organs reveal post-injury structure following wounding.

scholarly journals Plasma membrane-localized SlSWEET7a and SlSWEET14 regulate sugar transport and storage in tomato fruits

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Xinsheng Zhang ◽  
Chaoyang Feng ◽  
Manning Wang ◽  
Tianlai Li ◽  
Xin Liu ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Sugar Content ◽  
Sugar Transport ◽  
Invertase Activity ◽  
Vascular Bundles ◽  
Tomato Fruits ◽  
Sugar Transporters ◽  
Potential Strategy ◽  
And Storage

AbstractSugars, especially glucose and fructose, contribute to the taste and quality of tomato fruits. These compounds are translocated from the leaves to the fruits and then unloaded into the fruits by various sugar transporters at the plasma membrane. SWEETs, are sugar transporters that regulate sugar efflux independently of energy or pH. To date, the role of SWEETs in tomato has received very little attention. In this study, we performed functional analysis of SlSWEET7a and SlSWEET14 to gain insight into the regulation of sugar transport and storage in tomato fruits. SlSWEET7a and SlSWEET14 were mainly expressed in peduncles, vascular bundles, and seeds. Both SlSWEET7a and SlSWEET14 are plasma membrane-localized proteins that transport fructose, glucose, and sucrose. Apart from the resulting increase in mature fruit sugar content, silencing SlSWEET7a or SlSWEET14 resulted in taller plants and larger fruits (in SlSWEET7a-silenced lines). We also found that invertase activity and gene expression of some SlSWEET members increased, which was consistent with the increased availability of sucrose and hexose in the fruits. Overall, our results demonstrate that suppressing SlSWEET7a and SlSWEET14 could be a potential strategy for enhancing the sugar content of tomato fruits.

scholarly journals Chloride as a Beneficial Macronutrient in Higher Plants: New Roles and Regulation

2019 ◽  
Vol 20 (19) ◽  
pp. 4686 ◽  
Author(s):  
José M. Colmenero-Flores ◽  
Juan D. Franco-Navarro ◽  
Paloma Cubero-Font ◽  
Procopio Peinado-Torrubia ◽  
Miguel A. Rosales
Keyword(s):  
Higher Plants ◽  
Optimal Growth ◽  
Long Distance ◽  
Root Cells ◽  
Long Distance Transport ◽  
New Genes ◽  
Genes Encoding ◽  
Cell Turgor ◽  
Use Efficiency ◽  
High Concentrations

Chloride (Cl−) has traditionally been considered a micronutrient largely excluded by plants due to its ubiquity and abundance in nature, its antagonism with nitrate (NO3−), and its toxicity when accumulated at high concentrations. In recent years, there has been a paradigm shift in this regard since Cl− has gone from being considered a harmful ion, accidentally absorbed through NO3− transporters, to being considered a beneficial macronutrient whose transport is finely regulated by plants. As a beneficial macronutrient, Cl− determines increased fresh and dry biomass, greater leaf expansion, increased elongation of leaf and root cells, improved water relations, higher mesophyll diffusion to CO2, and better water- and nitrogen-use efficiency. While optimal growth of plants requires the synchronic supply of both Cl− and NO3− molecules, the NO3−/Cl− plant selectivity varies between species and varieties, and in the same plant it can be modified by environmental cues such as water deficit or salinity. Recently, new genes encoding transporters mediating Cl− influx (ZmNPF6.4 and ZmNPF6.6), Cl− efflux (AtSLAH3 and AtSLAH1), and Cl− compartmentalization (AtDTX33, AtDTX35, AtALMT4, and GsCLC2) have been identified and characterized. These transporters have proven to be highly relevant for nutrition, long-distance transport and compartmentalization of Cl−, as well as for cell turgor regulation and stress tolerance in plants.

scholarly journals Genome-Wide Identification and Expression Analysis of Sugar Transporter (ST) Gene Family in Longan (Dimocarpus longan L.)

Plants ◽  
2020 ◽  
Vol 9 (3) ◽  
pp. 342 ◽  
Author(s):  
Ting Fang ◽  
Yuan Peng ◽  
Ya Rao ◽  
Shenghao Li ◽  
Lihui Zeng
Keyword(s):  
Higher Plants ◽  
Expression Profiles ◽  
Pcr Analysis ◽  
Sugar Accumulation ◽  
Signal Molecules ◽  
Sugar Transporter ◽  
Flower Bud ◽  
Long Distance ◽  
Sugar Transporters ◽  
Dimocarpus Longan

Carbohydrates are nutrients and important signal molecules in higher plants. Sugar transporters (ST) play important role not only in long-distance transport of sugar, but also in sugar accumulations in sink cells. Longan (Dimocarpus longan L.) is one of the most important commercial tropical/subtropical evergreen fruit species in Southeast Asia. In this study, a total of 52 longan sugar transporter (DlST) genes were identified and they were divided into eight clades according to phylogenetic analysis. Out of these 52 DlST genes, many plant hormones (e.g., MeJA and gibberellin), abiotic (e.g., cold and drought), and biotic stress responsive element exist in their promoter region. Gene structure analysis exhibited that each of the clades have closely associated gene architectural features based on similar number or length of exons. The numbers of DlSTs, which exhibited alternative splicing (AS) events, in flower bud is more than that in other tissues. Expression profile analysis revealed that ten DlST members may regulate longan flowerbud differentiation. In silico expression profiles in nine longan organs indicated that some DlST genes were tissue specificity and further qRT-PCR analysis suggested that the transcript level of seven DlSTs (DlINT3, DlpGlcT1, DlpGlcT2, DlPLT4, DlSTP1, DlVGT1 and DlVGT2) was consistent with sugar accumulation in fruit, indicating that they might be involved in sugar accumulations during longan fruit development. Our findings will contribute to a better understanding of sugar transporters in woody plant.

scholarly journals Evolution and palaeophysiology of the vascular system and other means of long-distance transport

2017 ◽  
Vol 373 (1739) ◽  
pp. 20160497 ◽  
Author(s):  
John A. Raven
Keyword(s):  
Mass Flow ◽  
Vascular System ◽  
Terrestrial Ecosystem ◽  
Arbuscular Mycorrhizas ◽  
Organic Solutes ◽  
Long Distance ◽  
Long Distance Transport ◽  
Structural Details ◽  
Flow Through ◽  
And Storage

Photolithotrophic growth on land using atmospheric CO 2 inevitably involves H 2 O vapour loss. Embryophytes greater than or equal to 100 mm tall are homoiohydric and endohydric with mass flow of aqueous solution through the xylem in tracheophytes. Structural details in Rhynie sporophytes enable modelling of the hydraulics of H 2 O supply to the transpiring surface, and the potential for gas exchange with the Devonian atmosphere. Xylem carrying H 2 O under tension involves programmed cell death, rigid cell walls and embolism repair; fossils provide little evidence on these functions other than the presence of lignin. The phenylalanine ammonia lyase essential for lignin synthesis came from horizontal gene transfer. Rhynie plants lack endodermes, limiting regulation of the supply of soil nutrients to shoots. The transfer of organic solutes from photosynthetic sites to growing and storage tissues involves mass flow through phloem in extant tracheophytes. Rhynie plants show little evidence of phloem; possible alternatives for transport of organic solutes are discussed. Extant examples of the arbuscular mycorrhizas found in Rhynie plants exchange soil-derived nutrients (especially P) for plant-derived organic matter, involving bidirectional mass flow along the hyphae. The aquatic cyanobacteria and the charalean Palaeonitella at Rhynie also have long-distance (relative to the size of the organism) transport. This article is part of a discussion meeting issue ‘The Rhynie cherts: our earliest terrestrial ecosystem revisited’.

scholarly journals The influence of transport time and storage of smoked meat by traditional method on the content of a total four-aelative hydrocarbon aromatic hydrocarbons

2018 ◽  
Vol 19 (6) ◽  
pp. 83-86
Author(s):  
Karolina Choroszy ◽  
Krzysztof Tereszkiewicz
Keyword(s):  
Storage Time ◽  
Food Product ◽  
Long Distance ◽  
Transport Time ◽  
Safety Practices ◽  
Eu Legislation ◽  
Long Distance Transport ◽  
Food Transport ◽  
And Storage ◽  
Distance Transport

The transport of food products is one of the main stages in the food chain. Each type of food product needs to be adjusted to the conditions of transport of its specific. Traditionally smoked meats are products that should receive special care during rotation due to the fast evaporating water which, after prolonged transport and storage, may lead to an increase in the content of harmful PAH compounds. One of the factors determining their formation are time and conditions of storage and transport. EU legislation clearly specifies the amount of total benzo (a) pyrene, chrysene, benzo (a) anthracene, benzo (b) fluoranthene and benzo (a) pyrene and the safety practices of food transport companies. Despite high achievements and improvement of food safety, there are exceeded maximum limits of PAH compounds due to too long transport and storage time. The article discusses the risks of increased contamination with compounds from the PAH group in transport and during storage. It is shown that long-distance transport and storage of smoked sausages traditionally causes a slight increase in the concentration of the sum of 4 PAHs and BaP. The time of transport and storage of cold meats in refrigeration conditions also causes water loss, which results in drying of the surface and loss of the bar weight

The Fine Structure of Phloem Cells

1985 ◽  
Vol 43 ◽  
pp. 632-635
Author(s):  
James Cronshaw
Keyword(s):  
Structural Studies ◽  
High Concentration ◽  
Long Distance ◽  
Phloem Tissue ◽  
Sieve Elements ◽  
Long Distance Transport ◽  
P Protein ◽  
Companion Cells ◽  
Electron Microscopical ◽  
Distance Transport

Long distance transport in plants takes place in phloem tissue which has characteristic cells, the sieve elements. At maturity these cells have sieve areas in their end walls with specialized perforations. They are associated with companion cells, parenchyma cells, and in some species, with transfer cells. The protoplast of the functioning sieve element contains a high concentration of sugar, and consequently a high hydrostatic pressure, which makes it extremely difficult to fix mature sieve elements for electron microscopical observation without the formation of surge artifacts. Despite many structural studies which have attempted to prevent surge artifacts, several features of mature sieve elements, such as the distribution of P-protein and the nature of the contents of the sieve area pores, remain controversial.

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