Phosphoglucoisomerase Is an Important Regulatory Enzyme in Partitioning Carbon out of the Calvin-Benson Cycle

Phosphoglucoisomerase (PGI) isomerizes fructose 6-phosphate (F6P) and glucose 6-phosphate (G6P) in starch and sucrose biosynthesis. Both plastidic and cytosolic isoforms are found in plant leaves. Using recombinant enzymes and isolated chloroplasts, we have characterized the plastidic and cytosolic isoforms of PGI. We have found that the Arabidopsis plastidic PGI Km for G6P is three-fold greater compared to that for F6P and that erythrose 4-phosphate is a key regulator of PGI activity. Additionally, the Km of spinach plastidic PGI can be dynamically regulated in the dark compared to the light and increases by 200% in the dark. We also found that targeting Arabidopsis cytosolic PGI into plastids of Nicotiana tabacum disrupts starch accumulation and degradation. Our results, in combination with the observation that plastidic PGI is not in equilibrium, indicates that PGI is an important regulatory enzyme that restricts flow and acts as a one-way valve preventing backflow of G6P into the Calvin-Benson cycle. We propose the PGI may be manipulated to improve flow of carbon to desired targets of biotechnology.

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Différenciation de boutons floraux, de bourgeons végétatifs, de racines et de cal à partir de l'assise sous-épidermique des ramifications florales de Nicotiana tabacum Wisc. 38. Etude infrastructurale

Canadian Journal of Botany ◽

10.1139/b76-212 ◽

1976 ◽

Vol 54 (17) ◽

pp. 1979-1996 ◽

Cited By ~ 22

Author(s):

M. Tran Thanh Van ◽

A. Chlyah

Keyword(s):

Endoplasmic Reticulum ◽

Nicotiana Tabacum ◽

Callus Formation ◽

Starch Accumulation ◽

Mitochondrial Activity ◽

Cell Level ◽

Flower Buds ◽

Ultrastructural Studies ◽

Different Types ◽

General Activation

Ultrastructural studies of different types of differentiation, organogenetic (formation of flower buds, vegetative buds, or roots) or nonorganogenetic (callus formation), show important modifications at the subepidermal cell level. Besides the changes showing general activation leading to the first mitosis such as an increase of the ribosomes density, a more laboured endoplasmic reticulum, and a denser nucleus located near the centre, other changes seem to be related to a particular differentiation: for the flower program, an early starch accumulation and a higher mitochondrial activity in the cells take place and for the callus program important pinocytosis phenomena occur at the plasmalemma level.

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Characterisation of virus-related red tip disease in pineapple (Ananas comosus)

Research Journal of Biotechnology ◽

10.25303/1612rjbt1017 ◽

2021 ◽

Vol 16 (12) ◽

pp. 10-17

Author(s):

Kassim Faizah Abu ◽

Ganesan Vadamalai ◽

Khalid H. Alobaidi ◽

Nor Azlina Hasbullah ◽

Sarah Thaer ◽

...

Keyword(s):

Electron Microscope ◽

Nicotiana Tabacum ◽

Protein Identification ◽

Average Diameter ◽

Ananas Comosus ◽

Tropical Fruits ◽

Plant Leaves ◽

Transmission Electron ◽

Sds Page ◽

Domestic Use

Pineapple (Ananas comosus) is one of the tropical fruits that is cultivated in Malaysia for export as well as domestic use. Unfortunately, the production is heavily affected by the red tip disease which was detected in the southern part of Malaysia 3 decades ago. Despite the identification of this disease, causal agent receives less attention from researchers. Nevertheless, symptoms associated with this infection and the mode of transference inside the plantations indicate viral-like disease. RNA extracted from the pineapple infected leaves introduced to Nicotiana tabacum cv. Coker by kneading the plant leaves to extract fresh sap. Yellowish necrosis was detected three weeks after artificial inoculation. The staining of the fresh diseased sample and inoculated Nicotiana tabacum cv. Coker showed the existence of round particles with an average diameter of 94.25nm under the transmission electron microscope. SDS-PAGE analysis revealed proteins bands similar to those of tospovirus at 25, 55 and 128 kDa. Further protein identification and validation suggested for molecular confirmation of the disease causative agent.

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bHLH Transcription Factor NtMYC2a Regulates Carbohydrate Metabolism during the Pollen Development of Tobacco (Nicotiana tabacum L. cv. TN90)

Plants ◽

10.3390/plants11010017 ◽

2021 ◽

Vol 11 (1) ◽

pp. 17

Author(s):

Shiquan Bian ◽

Tian Tian ◽

Yongqiang Ding ◽

Ning Yan ◽

Chunkai Wang ◽

...

Keyword(s):

Transcription Factor ◽

Nicotiana Tabacum ◽

Transgenic Plants ◽

Carbohydrate Metabolism ◽

Pollen Development ◽

Starch Accumulation ◽

Bhlh Transcription Factor ◽

Pollen Maturation ◽

Nicotiana Tabacum L

Basic helix-loop-helix (bHLH) transcription factor MYC2 regulates plant growth and development in many aspects through the jasmonic acid (JA) signaling pathway, while the role of MYC2 in plant carbohydrate metabolism has not been reported. Here, we generated NtMYC2a-overexpressing (NtMYC2a-OE) and RNA-interference-mediated knockdown (NtMYC2a-RI) transgenic plants of tobacco (Nicotiana tabacum L. cv. TN90) to investigate the role of NtMYC2a in carbohydrate metabolism and pollen development. Results showed that NtMYC2a regulates the starch accumulation and the starch-sugar conversion of floral organs, especially in pollen. The RT-qPCR analysis showed that the expression of starch-metabolic-related genes, AGPs, SS2 and BAM1, were regulated by NtMYC2a in the pollen grain, anther wall and ovary of tobacco plants. The process of pollen maturation was accelerated in NtMYC2a-OE plants and was delayed in NtMYC2a-RI plants, but the manipulation of NtMYC2a expression did not abolish the pollen fertility of the transgenic plants. Intriguingly, overexpression of NtMYC2a also enhanced the soluble carbohydrate accumulation in tobacco ovaries. Overall, our results demonstrated that the bHLH transcription factor NtMYC2a plays an important role in regulating the carbohydrate metabolism during pollen maturation in tobacco.

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Ectodesmata as Revealed By Freeze-Etch Preparations of Plant Epidermal Cell Walls

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100072782 ◽

1973 ◽

Vol 31 ◽

pp. 468-469

Author(s):

N.C. Lyon ◽

W. C. Mueller

Keyword(s):

Electron Microscopy ◽

Acetic Acid ◽

Nitric Acid ◽

Oxalic Acid ◽

Light Microscopy ◽

Epidermal Cell ◽

Cell Walls ◽

Plant Viruses ◽

Plant Leaves ◽

Thin Sections

Schumacher and Halbsguth first demonstrated ectodesmata as pores or channels in the epidermal cell walls in haustoria of Cuscuta odorata L. by light microscopy in tissues fixed in a sublimate fixative (30% ethyl alcohol, 30 ml:glacial acetic acid, 10 ml: 65% nitric acid, 1 ml: 40% formaldehyde, 5 ml: oxalic acid, 2 g: mecuric chloride to saturation 2-3 g). Other workers have published electron micrographs of structures transversing the outer epidermal cell in thin sections of plant leaves that have been interpreted as ectodesmata. Such structures are evident following treatment with Hg++ or Ag+ salts and are only rarely observed by electron microscopy. If ectodesmata exist without such treatment, and are not artefacts, they would afford natural pathways of entry for applied foliar solutions and plant viruses.

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Tobacco Mosaic Virus-Infected Tissue

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100119375 ◽

1985 ◽

Vol 43 ◽

pp. 510-511

Author(s):

Egbert W. Henry

Keyword(s):

Nicotiana Tabacum ◽

Tobacco Mosaic Virus ◽

Chlorogenic Acid ◽

Mosaic Virus ◽

Host Resistance ◽

Oxidative Metabolism ◽

Leaf Tissue ◽

Vein Clearing ◽

Basal Septum ◽

Concentration Levels

Tobacco mosaic virus (TMV) infection has been studied in several investigations of Nicotiana tabacum leaf tissue. Earlier studies have suggested that TMV infection does not have precise infective selectivity vs. specific types of tissues. Also, such tissue conditions as vein banding, vein clearing, liquification and suberization may result from causes other than direct TMV infection. At the present time, it is thought that the plasmodesmata, ectodesmata and perhaps the plasmodesmata of the basal septum may represent the actual or more precise sites of TMV infection.TMV infection has been implicated in elevated levels of oxidative metabolism; also, TMV infection may have a major role in host resistance vs. concentration levels of phenolic-type enzymes. Therefore, enzymes such as polyphenol oxidase, peroxidase and phenylalamine ammonia-lyase may show an increase in activity in response to TMV infection. It has been reported that TMV infection may cause a decrease in o-dihydric phenols (chlorogenic acid) in some tissues.

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