scholarly journals The T-DNA Oncogene A4-orf8 from Agrobacterium rhizogenes A4 Induces Abnormal Growth in Tobacco

2005 ◽  
Vol 18 (3) ◽  
pp. 205-211 ◽  
Author(s):  
Marie Umber ◽  
Bernadette Clément ◽  
Léon Otten
Keyword(s):  
Agrobacterium Rhizogenes ◽  
Soluble Sugars ◽  
Starch Accumulation ◽  
Wild Type ◽  
Abnormal Growth ◽  
Regenerated Plants ◽  
Physical Linkage ◽  
Dark Green ◽  
Characteristic Growth ◽  
Fad Binding

The related orf8 and iaaM T-DNA genes from Agrobacterium are each composed of two distinct parts. The 5′ parts (called Norf8 or NiaaM) encode a 200-amino-acid (aa) sequence with homology to various T-DNA oncoproteins such as RolB, RolC, and 6b. The 3′ parts (Corf8 or CiaaM) encode a 550-aa sequence with homology to IaaM proteins from Pseudomonas and Pantoea spp. Whereas iaaM genes encode flavin adenine dinucleotide (FAD)-dependent tryptophan 2-monooxygenases that catalyze the synthesis of indole-3-acetamide (IAM), A4-orf8 from Agrobacterium rhizogenes A4 does not. Plants expressing a 2x35S-A4-Norf8 construct accumulate soluble sugars and starch. We now have regenerated plants that express the full-size 2x35S-A4-orf8 and the truncated 2x35S-A4-Corf8 gene. 2x35S-A4-Corf8 plants accumulate starch and show reduced growth like 2x35SA4-Norf8 plants but, in addition, display a novel set of characteristic growth modifications. These consist of leaf hypertrophy and hyperplasia (blisters); thick, dark-green leaves; thick stems; and swollen midveins. Mutations in the putative FAD-binding site of A4-Orf8 did not affect the blister syndrome. Plants expressing 2x35S-A4-Corf8 had a normal phenotype but contained less starch and soluble sugars than did wild-type plants. When 2x35S-A4-Corf8 plants were crossed to starch-accumulating 2x35S-A4-Norf8 plants with reduced growth, A4-Corf8 partially restored growth and reduced starch accumulation. A4-Corf8xA4-Norf8 crosses did not lead to the blister syndrome, suggesting that this requires physical linkage of the A4-NOrf8 and A4-COrf8 sequences.

scholarly journals Shifting carbon flux from non-transient starch to lipid allows oil accumulation in transgenic tobacco leaves

2020 ◽  
Author(s):  
Kevin L. Chu ◽  
Lauren M. Jenkins ◽  
Sally R. Bailey ◽  
Shrikaar Kambhampati ◽  
Somnath Koley ◽  
...  
Keyword(s):  
Transgenic Tobacco ◽  
Carbon Flux ◽  
Soluble Sugars ◽  
Dry Weight ◽  
Starch Accumulation ◽  
Leaf Biomass ◽  
Wild Type ◽  
Oil Accumulation ◽  
Tobacco Leaves ◽  
Source Sink

AbstractPlant leaf biomass is composed predominantly of carbohydrate and protein with less than 5% dry weight allocated to lipid and less than 1% of total lipid in the form of triacylglycerols (TAGs). The combined overexpression of multiple genes involved in different aspects of TAG synthesis and stabilization can result in TAG accumulation to over 30% dry weight in tobacco leaves, presumably requiring many metabolic adjustments within plant cells. The metabolic consequences to the combined source and sink capacities of high oil accumulating transgenic tobacco leaves compared to wild-type were inspected across development and photoperiod by utilizing foliar biomass components and 13CO2 flux through central carbon intermediates. Lipid biosynthesis was investigated through assessment of acyl-acyl carrier protein (ACP) pools using a recently derived quantification method that was extended to accommodate isotopic labeling. Lipids accumulated stepwise over plant development in the high-oil leaves, with 13CO2-labeling studies confirming increased carbon flux to lipids. The large increase in lipid content was concurrent with a decrease in foliar starch, with limited contribution from non-sucrose soluble sugars, indicating a redirection of carbon from starch to lipids. Starch accumulated non-transiently with plant age in wild-type leaves, suggesting an inherent capacity for a developmentally-regulated carbon sink in tobacco leaves that may have enabled the programmed altered carbon partitioning to lipids in transgenics. These studies provide insight into the metabolic plasticity of dual source-sink leaves over development and may in part explain recent successful leaf lipid engineering efforts in tobacco.One sentence summaryEngineering high oil accumulation in tobacco leaves is enabled by inherent source-sink plasticity associated with non-transient foliar starch accumulation over development.

ELONGATED HYPOCOTYL 5 mediates blue light-induced starch degradation in tomato

2020 ◽  
Author(s):  
Han Dong ◽  
Chaoyi Hu ◽  
Chaochao Liu ◽  
Jiachun Wang ◽  
Yanhong Zhou ◽  
...  
Keyword(s):  
Blue Light ◽  
Soluble Sugars ◽  
Light Signal ◽  
Starch Accumulation ◽  
Starch Degradation ◽  
Sugar Accumulation ◽  
Wild Type ◽  
Mobility Shift ◽  
Storage Carbohydrate ◽  
In The Wild

Abstract Starch is the major storage carbohydrate in plants, and its metabolism in chloroplasts depends mainly on light. However, the mechanism through which photoreceptors regulate starch metabolism in chloroplasts is unclear. In this study, we found that the cryptochrome 1a (CRY1a)-mediated blue light signal is critical for regulating starch accumulation by inducing starch degradation through the HY5 transcription factor in the chloroplasts in tomato. cry1a mutants and HY5-RNAi plants accumulated more starch and presented lower transcript levels of starch degradation-related genes in their leaves than did the wild-type (WT) plants. Blue light significantly induced the transcription of starch degradation-related genes in the wild-type and CRY1a- or HY5-overexpressing plants but had little effect in the cry1a and HY5-RNAi plants. Dual-luciferase assays, electrophoretic mobility shift assays (EMSA) and chromatin immunoprecipitation (ChIP)-qPCR revealed that HY5 could activate the starch degradation-related genes PWD, BAM1, BAM3, BAM8, MEX1 and DPE1 by directly binding to their promoters. Silencing of HY5 and these starch degradation-related genes in CRY1a-overexpressing plants led to increased accumulation of starch and decreased accumulation of soluble sugars. These findings presented here not only deepen our understanding of how light control starch degradation and sugar accumulation but also allow us to explore potential targets for improving crop quality.

scholarly journals SEC3 Mutations Are Synthetically Lethal With Profilin Mutations and Cause Defects in Diploid-Specific Bud-Site Selection

Genetics ◽  
1996 ◽  
Vol 144 (2) ◽  
pp. 495-510 ◽  
Author(s):  
B K Haarer ◽  
A Corbett ◽  
Y Kweon ◽  
A S Petzold ◽  
P Silver ◽  
...  
Keyword(s):  
Site Selection ◽  
Secretory Pathway ◽  
Wild Type ◽  
Synthetic Lethal ◽  
Abnormal Growth ◽  
Colony Color ◽  
Synthetically Lethal ◽  
Homozygous Diploid ◽  
Bud Site ◽  
Wild Type Yeast

Abstract Replacement of the wild-type yeast profilin gene (PFY1) with a mutated form (pfy1-111) that has codon 72 changed to encode glutamate rather than arginine results in defects similar to, but less severe than, those that result from complete deletion of the profilin gene. We have used a colony color-sectoring assay to identify mutations that cause pfy1-111, but not wild-type, cells to be inviable. These profilin synthetic lethal (psl) mutations result in various degrees of abnormal growth, morphology, and temperature sensitivity in PFY1 cells. We have examined psl1 strains in the most detail. Interestingly, these strains display a diploid-specific defect in bud-site selection; haploid strains bud normally, while homozygous diploid strains show a dramatic increase in random budding. We discovered that PSL1 is the late secretory gene, SEC3, and have found that mutations in several other late secretory genes are also synthetically lethal with pfy1-111. Our results are likely to reflect an interdependence between the actin cytoskeleton and secretory processes in directing cell polarity and growth. Moreover, they indicate that the secretory pathway is especially crucial for maintaining budding polarity in diploids.

scholarly journals Identification of genes associated with productivity traits and salinity tolerance from activation tagged lines of rice

2021 ◽  
Author(s):  
Kota Vamsee Raja ◽  
Kalva Madhanasekhar ◽  
Vudem Dashavantha Reddy ◽  
Attipalli Ramachandra Reddy ◽  
Khareedu Venkateswara Rao
Keyword(s):  
Stress Tolerance ◽  
Salinity Stress ◽  
Soluble Sugars ◽  
Crop Productivity ◽  
Antioxidant Systems ◽  
Wild Type ◽  
Stress Symptoms ◽  
Effective Antioxidant ◽  
Use Efficiency ◽  
Tolerance To Salinity

AbstractWorld-wide crop productivity is hugely impacted by diverse eco-environmental conditions. In the present investigation, activation tagged (AT) lines of rice endowed with improved agronomic attributes have been analyzed for tolerance to salinity stress besides identification of genes associated with these attributes. Under salinity stress conditions, AT lines exhibited increased seed germination rates, improved plant growth and development at vegetative and reproductive stages as compared to wild-type (WT) plants. Furthermore, AT lines disclosed enhanced plant water content, photosynthetic efficiency, stomatal conductance, water use efficiency and maximum quantum yield when compared to WT plants, leading to improved yields and delayed onset of stress symptoms. Moreover, AT lines revealed effective antioxidant systems causing decreased accumulation of reactive oxygen species and delayed salinity stress symptoms compared to WT plants. Reduced accumulation of malondialdehyde with concomitant increases in proline and soluble sugars of AT lines further endorsing their improved stress tolerance levels. TAIL and qRT-PCR analyses of AT lines revealed Ds element integrations at different loci and respective overexpression of identified candidate genes involved in various aspects of plant development and stress tolerance. Accordingly, the AT lines plausibly serve as a rare genetic resource for fortifying stress tolerance and productivity traits of elite rice cultivars.HighlightActivation tagged lines of rice endowed with improved agronomic attributes have been analyzed for tolerance to salinity stress besides identification and expression analysis of genes associated with these attributes.

scholarly journals Role of the SUT1 and SUT2 sugar transporters during stolbur phytoplasma infection in tomato

2020 ◽  
Author(s):  
Federica De Marco ◽  
Brigitte Batailler ◽  
Michael R. Thorpe ◽  
Frédérique Razan ◽  
Rozenn Le Hir ◽  
...  
Keyword(s):  
Redox Homeostasis ◽  
Sugar Transport ◽  
Transcriptional Analysis ◽  
Starch Accumulation ◽  
Metabolic Switch ◽  
Sieve Elements ◽  
Sugar Transporters ◽  
Abnormal Growth ◽  
Sucrose Transporters ◽  
Phytoplasma Infection

SummaryPhytoplasmas inhabit phloem sieve elements and cause abnormal growth and altered sugar partitioning. But how they interact with phloem functions is not clearly known. The phloem responses were investigated in tomato infected by ‘Candidatus Phytoplasma solani’, at the beginning of the symptomatic stage of infection, both in symptomatic and asymptomatic leaves, the first symptoms appearing in the sink top leaf at the stem apex. Antisense lines impaired in the phloem sucrose transporters SUT1 and SUT2 were included. The infection in source leaves was not associated with symptoms. In the symptomatic, sink leaf, yellowing and leaf curling was associated with higher starch accumulation and expression of defense genes. The transcriptional analysis of symptomatic leaf midribs indicated that transcript levels for genes acting in the glycolysis and peroxisome metabolism in infected plants differed from these in non-infected plants. Phytoplasma multiplied actively in at least three additional lower leaves although they were symptomless, with no sign of activation of defense markers, although the rate of exudation of sucrose from these symptomless, source leaves was lower for infected plants. A few metabolites in phloem-enriched exudate were affected by the infection, such as glycolate and aspartate, and some of them were also affected in the control SUT1- and SUT2- antisense lines, in which sucrose retrieval or release in the sieve elements are impaired. A metabolic switch could explain the delivery of more glycolate into the sieve elements of infected plants. The findings suggest a link between sugar transport and redox homeostasis.One sentence summaryAn impairment of sucrose retrieval and release in the sieve elements occurs during phytoplasma infection, associated with changes in sugar and peroxisome metabolism

scholarly journals The dissociation mechanism of processive cellulases

2019 ◽  
Vol 116 (46) ◽  
pp. 23061-23067 ◽  
Author(s):  
Josh V. Vermaas ◽  
Riin Kont ◽  
Gregg T. Beckham ◽  
Michael F. Crowley ◽  
Mikael Gudmundsson ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Molecular Mechanisms ◽  
Soluble Sugars ◽  
Dissociation Rate ◽  
Replica Exchange ◽  
Wild Type ◽  
Replica Exchange Molecular Dynamics ◽  
Hamiltonian Replica Exchange ◽  
Biochemical Measurements ◽  
Rate Limiting

Cellulase enzymes deconstruct recalcitrant cellulose into soluble sugars, making them a biocatalyst of biotechnological interest for use in the nascent lignocellulosic bioeconomy. Cellobiohydrolases (CBHs) are cellulases capable of liberating many sugar molecules in a processive manner without dissociating from the substrate. Within the complete processive cycle of CBHs, dissociation from the cellulose substrate is rate limiting, but the molecular mechanism of this step is unknown. Here, we present a direct comparison of potential molecular mechanisms for dissociation via Hamiltonian replica exchange molecular dynamics of the model fungal CBH, Trichoderma reesei Cel7A. Computational rate estimates indicate that stepwise cellulose dethreading from the binding tunnel is 4 orders of magnitude faster than a clamshell mechanism, in which the substrate-enclosing loops open and release the substrate without reversing. We also present the crystal structure of a disulfide variant that covalently links substrate-enclosing loops on either side of the substrate-binding tunnel, which constitutes a CBH that can only dissociate via stepwise dethreading. Biochemical measurements indicate that this variant has a dissociation rate constant essentially equivalent to the wild type, implying that dethreading is likely the predominant mechanism for dissociation.

scholarly journals Transcriptomic Analysis of Starch Biosynthesis in the Developing Grain of Hexaploid Wheat

2009 ◽  
Vol 2009 ◽  
pp. 1-23 ◽  
Author(s):  
Boryana S. Stamova ◽  
Debbie Laudencia-Chingcuanco ◽  
Diane M. Beckles
Keyword(s):  
Gene Expression ◽  
Dna Microarrays ◽  
Expression Profiles ◽  
Expression Patterns ◽  
Soluble Sugars ◽  
Starch Synthesis ◽  
Gene Families ◽  
Starch Accumulation ◽  
Protein Accumulation ◽  
High Accumulation

The expression of genes involved in starch synthesis in wheat was analyzed together with the accumulation profiles of soluble sugars, starch, protein, and starch granule distribution in developing caryopses obtained from the same biological materials used for profiling of gene expression using DNA microarrays. Multiple expression patterns were detected for the different starch biosynthetic gene isoforms, suggesting their relative importance through caryopsis development. Members of the ADP-glucose pyrophosphorylase, starch synthase, starch branching enzyme, and sucrose synthase gene families showed different expression profiles; expression of some members of these gene families coincided with a period of high accumulation of starch while others did not. A biphasic pattern was observed in the rates of starch and protein accumulation which paralleled changes in global gene expression. Metabolic and regulatory genes that show a pattern of expression similar to starch accumulation and granule size distribution were identified, suggesting their coinvolvement in these biological processes.

Seed development in relation to desiccation tolerance: A comparison between desiccation-sensitive (recalcitrant) seeds of Avicennia marina and desiccation-tolerant types

1993 ◽  
Vol 3 (1) ◽  
pp. 1-13 ◽  
Author(s):  
Jill M. Farrant ◽  
N. W. Pammenter ◽  
Patricia Berjak
Keyword(s):  
Seed Development ◽  
Seedling Establishment ◽  
Soluble Sugars ◽  
Avicennia Marina ◽  
Sensu Stricto ◽  
Starch Accumulation ◽  
Recalcitrant Seeds ◽  
Recalcitrant Seed ◽  
Orthodox Seeds

AbstractDevelopment of the highly desiccation-sensitive (recalcitrant) seeds of primarily one species, Avicennia marina, is reviewed and compared with the ontogeny of desiccation-tolerant (orthodox) seeds. A. marina seeds undergo no maturation drying and remain metabolically active throughout development, which grades almost imperceptibly into germination. While PGR control of histodifferentiation is essentially similar to that characterizing desiccation-tolerant seeds, the phase of growth and reserve deposition is characterized by exceedingly high cytokinin levels which, it is proposed, promote a sink for assimilate import. While some starch accumulation does occur, the predominant reserves are soluble sugars which are readily available for the immediate onset of seedling establishment upon shedding. ABA levels are negligible in the embryo tissues during seed maturation, but increase in the pericarp, which imposes a constraint upon germination until these outer coverings are sloughed or otherwise removed. The pattern of proteins synthesized remains qualitatively similar throughout seed development in A. marina, and no LEA proteins are produced. This suggests both that seedling establishment is independent of maturation proteins and that the absence of LEAs and desiccation sensitivity might be causally related. The study on A. marina reveals that for this recalcitrant seed-type, germination per se cannot be defined: rather, it is considered as the continuation of development temporarily constrained by the pericarp ABA levels. This leads to a reexamination of the role of rehydration as key event sensu stricto, in the germination processes in desiccation-tolerant (orthodox) seeds.

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