ACHT4-driven oxidation of APS1 attenuates starch synthesis under low light intensity in Arabidopsis plants

The regulatory mechanisms that use signals of low levels of reactive oxygen species (ROS) could be obscured by ROS produced under stress and thus are better investigated under homeostatic conditions. Previous studies showed that the chloroplastic atypical thioredoxin ACHT1 is oxidized by 2-Cys peroxiredoxin (2-Cys Prx) in Arabidopsis plants illuminated with growth light and in turn transmits a disulfide-based signal via yet unknown target proteins in a feedback regulation of photosynthesis. Here, we studied the role of a second chloroplastic paralog, ACHT4, in plants subjected to low light conditions. Likewise, ACHT4 reacted in planta with 2-Cys Prx, indicating that it is oxidized by a similar disulfide exchange reaction. ACHT4 further reacted uniquely with the small subunit (APS1) of ADP-glucose pyrophosphorylase (AGPase), the first committed enzyme of the starch synthesis pathway, suggesting that it transfers the disulfides it receives from 2-Cys Prx to APS1 and turns off AGPase. In accordance, ACHT4 participated in an oxidative signal that quenched AGPase activity during the diurnal transition from day to night, and also in an attenuating oxidative signal of AGPase in a dynamic response to small fluctuations in light intensity during the day. Increasing the level of expressed ACHT4 or of ACHT4ΔC, a C terminus-deleted form that does not react with APS1, correspondingly decreased or increased the level of reduced APS1 and decreased or increased transitory starch content. These findings imply that oxidative control mechanisms act in concert with reductive signals to fine tune starch synthesis during daily homeostatic conditions.

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Decreased-activity mutants of phosphoglucose isomerase in the cytosol and chloroplast of Clarkia xantiana. Impact on mass-action ratios and fluxes to sucrose and starch, and estimation of Flux Control Coefficients and Elasticity Coefficients

Biochemical Journal ◽

10.1042/bj2610457 ◽

1989 ◽

Vol 261 (2) ◽

pp. 457-467 ◽

Cited By ~ 79

Author(s):

A L Kruckeberg ◽

H E Neuhaus ◽

R Feil ◽

L D Gottlieb ◽

M Stitt

Keyword(s):

Light Intensity ◽

Starch Synthesis ◽

Phosphoglucose Isomerase ◽

Wild Type ◽

Low Light ◽

Subcellular Compartment ◽

Flux Control Coefficients ◽

Substrate Ratio ◽

Control Coefficients ◽

Clarkia Xantiana

1. Subcellular-compartment-specific decreased-activity mutants of phosphoglucose isomerase in Clarkia xantiana were used to analyse the control of sucrose and starch synthesis during photosynthesis. Mutants were available in which the plastid phosphoglucose isomerase complement is decreased to 75% or 50% of the wild-type level, and the cytosol complement to 64%, 36% or 18% of the wild-type level. 2. The effects on the [product]/[substrate] ratio and on fluxes to sucrose or starch and the rate of photosynthesis were studied with the use of saturating or limiting light intensity to impose a high or low flux through these pathways. 3. Removal of a small fraction of either phosphoglucose isomerase leads to a significant shift of the [product]/[substrate] ratio away, from equilibrium. We conclude that there is no ‘excess’ of enzyme over that needed to maintain its reactants reasonably close to equilibrium. 4. Decreased phosphoglucose isomerase activity can also alter the fluxes to starch or sucrose. However, the effect on flux does not correlate with the extent of disequilibrium, and also varies depending on the subcellular compartment and on the conditions. 5. The results were used to estimate Flux Control Coefficients for the chloroplast and cytosolic phosphoglucose isomerases. The chloroplast isoenzyme exerts control on the rate of starch synthesis and on photosynthesis in saturating light intensity and CO2, but not at low light intensity. The cytosolic enzyme only exerts significant control when its complement is decreased 3-5-fold, and differs from the plastid isoenzyme in exerting more control in low light intensity. It has a positive Control Coefficient for sucrose synthesis, and a negative Control Coefficient for starch synthesis. 6. The Elasticity Coefficients in vivo of the cytosolic phosphoglucose isomerase were estimated to lie between 5 and 8 in the wild-type. They decrease in mutants with a lowered complement of cytosolic phosphoglucose isomerase. 7. The implications of these results for regulation and for evolution are discussed.

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Expression of bacterial starch-binding domains in Arabidopsis increases starch granule size

Functional Plant Biology ◽

10.1071/fp05277 ◽

2006 ◽

Vol 33 (3) ◽

pp. 257 ◽

Cited By ~ 6

Author(s):

Crispin A. Howitt ◽

Sadequr Rahman ◽

Matthew K. Morell

Keyword(s):

Starch Granule ◽

Starch Content ◽

Starch Synthesis ◽

Length Distribution ◽

Renewable Resource ◽

Granule Size ◽

Parental Line ◽

In Planta ◽

Chain Length Distribution ◽

Binding Domains

Starch is a readily renewable resource that is very widely used for food and industrial purposes; however, greater variation in the functional properties of starch would further extend the use of this biodegradable polymer. Genetic engineering may provide a way to produce designer starches that have the desired properties. Starch-binding domains (SBD) from bacterial enzymes that catabolise starches have the ability to bind two helices of starch and thus have the potential to crosslink starch and / or to be used as anchors for other enzymes that can modify starch properties. In a first step towards novel modification of starch we have investigated the effect of expressing SBDs, singly and in tandem, in planta, and targeting them to the chloroplast in the model plant Arabidopsis thaliana (L.) Heynh. Transgenic plants that contained the SBD from the cyclomaltodextrin glucanotransferase (CGTase) of Thermoanaerobacterium thermosulfurigenes in the chloroplast were produced in both the wild type and the starch excess mutant (sex 1-1) backgrounds. Analysis of starch isolated from the chloroplasts of these lines revealed no significant changes in the amylose : amylopectin ratio, the chain-length distribution of debranched amylopectin or the gelatinisation temperature when compared to the parental line. However, significant changes were observed in the starch granule size with the plants expressing the construct having larger granules. The effect was more pronounced in the sex 1-1 background, and expression of two starch-binding domains linked in tandem had an even greater effect. Despite the starch granules being larger in lines expressing the starch-binding domain, no difference was seen in the starch content of the leaves when compared to parental lines. As the presence of the SBDs in the starch granule only altered granule size, and not other granule properties, they may provide an ideal anchor for targeting starch-modifying enzymes to the site of starch synthesis. This will allow the development of novel modifications of starch during synthesis.

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A mutant of rice lacking the leaf large subunit of ADP-glucose pyrophosphorylase has drastically reduced leaf starch content but grows normally

Functional Plant Biology ◽

10.1071/fp06257 ◽

2007 ◽

Vol 34 (6) ◽

pp. 480 ◽

Cited By ~ 37

Author(s):

Sandrine Rösti ◽

Brendan Fahy ◽

Kay Denyer

Keyword(s):

Environmental Conditions ◽

No Reduction ◽

Starch Content ◽

Large Subunit ◽

Starch Synthesis ◽

Small Subunit ◽

Wild Type ◽

Gene Encoding ◽

Subunit Protein ◽

Adp Glucose Pyrophosphorylase

A mutant of rice was identified with a Tos17 insertion in OsAPL1, a gene encoding a large subunit (LSU) of ADP-glucose pyrophosphorylase (AGPase). The insertion prevents production of a normal transcript from OsAPL1. Characterisation of the mutant (apl1) showed that the LSU encoded by OsAPL1 is required for AGPase activity in rice leaf blades. In mutant leaf blades, the AGPase small subunit protein is not detectable and the AGPase activity and starch content are reduced to <1 and <5% of that in wild type blades, respectively. The mutation also leads to a reduction in starch content in the leaf sheaths but does not significantly affect AGPase activity or starch synthesis in other parts of the plant. The sucrose, glucose and fructose contents of the leaves are not affected by the mutation. Despite the near absence of starch in the leaf blades, apl1 mutant rice plants grow and develop normally under controlled environmental conditions and show no reduction in productivity.

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Starch synthesis in potato tubers transformed with the wheat genes for ADPglucose pyrophosphorylase

Functional Plant Biology ◽

10.1071/pp01161 ◽

2002 ◽

Vol 29 (8) ◽

pp. 975 ◽

Cited By ~ 7

Author(s):

Kathryn A. Vardy ◽

Michael J. Emes ◽

Michael M. Burrell

Keyword(s):

Solanum Tuberosum L ◽

Starch Content ◽

Starch Synthesis ◽

Small Subunit ◽

Starch Biosynthesis ◽

Potato Tubers ◽

Potato Plants ◽

Adpglucose Pyrophosphorylase ◽

Plastid Targeting

The aim of this work was to study the role of ADPglucose pyrophosphorylase (AGPase) in starch biosynthesis of non-photosynthetic organs. Agrobacterium tumefaciens was used to transform potato plants (Solanum tuberosum L. cv. Desire�) with the wheat AGPase genes (AGP-S and AGP-L, coding for the small and large subunits, respectively). Neither of these genes contains a recognisable plastid targeting sequence. Southern analysis and analysis of starch content identified four lines that contained both wheat sequences. Immunoblotting indicated that, in the tubers, three lines expressed the wheat small subunit (AGP-S), but AGP-L cross-reacting protein was not apparent. The fourth transgenic line had reduced AGPase activity. AGPase activity in the AGP-transgenic tubers ranged from 15 to 165% of that found in β-glucuronidase (GUS) control lines.

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Pendugaan Parameter Genetik Kedelai Generasi F4 pada Intensitas Cahaya Rendah

Agrotek ◽

10.30862/agt.v2i3.472 ◽

2018 ◽

Vol 2 (3) ◽

Author(s):

Yohanis Amos Mustamu ◽

Trikoesoemaningtyas Trikoesoemaningtyas ◽

Desta Wirnas ◽

Didy Sopandie ◽

Darman M. Arsyad

Keyword(s):

Light Intensity ◽

Genetic Parameter ◽

Design Experiment ◽

Low Light ◽

Experimental Field ◽

High Heritability ◽

Intensity Condition ◽

Augmented Design ◽

Genetic Coefficient ◽

The University

The objective of this study was to collect information on genetic parameter and agronomy character of soybean F4 generation in the low light intensity condition. The parameter was tested to 130 lines F4 which are produced by Balai Besar Pengkajian dan Pengembangan Teknologi Pertanian (BBP2TP) Boor and the genotype of Sibayak, Tegal, Tanggamus, and Argomulyo were used as controls. The experiment was conducted in the university�s experimental field in Cikabayan, from September to December 2007. A total of 130 advance (F4) soybean lines were evaluated under shading in an augmented design experiment. The result of this study showed that all character has low genetic coefficient. The weight character of 25 grains has a considerably high heritability number in low li

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Sweet Corn Research around the World 2015–2020

Agronomy ◽

10.3390/agronomy11030534 ◽

2021 ◽

Vol 11 (3) ◽

pp. 534

Author(s):

Pedro Revilla ◽

Calli M. Anibas ◽

William F. Tracy

Keyword(s):

Sweet Corn ◽

Starch Content ◽

Starch Synthesis ◽

Environmental Care ◽

Research Activities ◽

The Us ◽

The World ◽

The Usa ◽

Basic Biology ◽

Endosperm Starch

Modern sweet corn is distinguished from other vegetable corns by the presence of one or more recessive alleles within the maize endosperm starch synthesis pathway. This results in reduced starch content and increased sugar concentration when consumed fresh. Fresh sweet corn originated in the USA and has since been introduced in countries around the World with increasing popularity as a favored vegetable choice. Several reviews have been published recently on endosperm genetics, breeding, and physiology that focus on the basic biology and uses in the US. However, new questions concerning sustainability, environmental care, and climate change, along with the introduction of sweet corn in other countries have produced a variety of new uses and research activities. This review is a summary of the sweet corn research published during the five years preceding 2021.

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Growth of Haematococcus pluvialis on a Small-Scale Angled Porous Substrate Photobioreactor for Green Stage Biomass

Applied Sciences ◽

10.3390/app11041788 ◽

2021 ◽

Vol 11 (4) ◽

pp. 1788

Author(s):

Thanh-Tri Do ◽

Binh-Nguyen Ong ◽

Tuan-Loc Le ◽

Thanh-Cong Nguyen ◽

Bich-Huy Tran-Thi ◽

...

Keyword(s):

Light Intensity ◽

Algal Biomass ◽

Haematococcus Pluvialis ◽

Biomass Productivity ◽

Pilot Scale ◽

Small Scale ◽

Porous Substrate ◽

Low Light ◽

Green Algal ◽

Green Stage

In the production of astaxanthin from Haematococcus pluvialis, the process of growing algal biomass in the vegetative green stage is an indispensable step in both suspended and immobilized cultivations. The green algal biomass is usually cultured in a suspension under a low light intensity. However, for astaxanthin accumulation, the microalgae need to be centrifuged and transferred to a new medium or culture system, a significant difficulty when upscaling astaxanthin production. In this research, a small-scale angled twin-layer porous substrate photobioreactor (TL-PSBR) was used to cultivate green stage biomass of H. pluvialis. Under low light intensities of 20–80 µmol photons m−2·s−1, algae in the biofilm consisted exclusively of non-motile vegetative cells (green palmella cells) after ten days of culturing. The optimal initial biomass density was 6.5 g·m−2, and the dry biomass productivity at a light intensity of 80 µmol photons m−2·s−1 was 6.5 g·m−2·d−1. The green stage biomass of H. pluvialis created in this small-scale angled TL-PSBR can be easily harvested and directly used as the source of material for the inoculation of a pilot-scale TL-PSBR for the production of astaxanthin.

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Transfer of photosynthetically fixed carbon between the prokaryotic green alga Prochloron and its ascidian host

Marine and Freshwater Research ◽

10.1071/mf9830431 ◽

1983 ◽

Vol 34 (3) ◽

pp. 431 ◽

Cited By ~ 21

Author(s):

DJ Griffiths ◽

L Thinh

Keyword(s):

Light Intensity ◽

Green Alga ◽

Host Tissue ◽

Total Carbon ◽

Symbiotic Association ◽

Fixed Carbon ◽

Low Light ◽

Ascidian Species ◽

Dark Fixation ◽

Efficient Transfer

In the symbiotic association between the prokaryotic green alga Prochloron and three didemnid host species (Diplosoma similis, Lissoclinum bistratum, Trididemnum cyclops), between 6 and 51 % of the total carbon fixed during exposure for 1 h to H14CO3- in the light (150 �E m-2 s-1) becomes associated with the host tissue. Dark fixation of 14CO2 in these ascidian species and in Lissoclinum punctatum never exceeds 6% of photosynthetic fixation at saturating light intensity. The corresponding values for dark fixation of 14CO2 in isolated Prochloron cells fall within the same range. There is very little excretion of photosynthate from whole colonies of the above ascidian species nor from Didemnum molle, Lissoclinum voeltzkowi and Trididemnum miniatum (usually less than 1 % of total photosynthate at saturation light intensity), suggesting an efficient transfer mechanism from Prochloron to host. Evidence from pulse-chase experiments suggests that transfer probably involves the early products of photosynthesis. The extent of transfer of photosynthate between Prochloron and T. cyclops varies with the rate of photosynthetic 14CO2 fixation into the whole colony but there is some transfer even at low light intensities, which strongly limit photosynthesis.

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A UV-Induced Mutation in Neurospora That Affects Translational Regulation in Response to Arginine

Genetics ◽

10.1093/genetics/142.1.117 ◽

1996 ◽

Vol 142 (1) ◽

pp. 117-127 ◽

Cited By ~ 3

Author(s):

Michael Freitag ◽

Nelima Dighde ◽

Matthew S Sachs

Keyword(s):

Translational Control ◽

Translational Regulation ◽

Fusion Gene ◽

Mrna Translation ◽

Small Subunit ◽

Upstream Open Reading Frame ◽

Control Mechanisms ◽

Carbamoyl Phosphate ◽

Altered Expression ◽

Reading Frame

The Neurospora crmsu arg-2 gene encodes the small subunit of arginine-specific carbamoyl phosphate synthetase. The levels of arg-2 mRNA and mRNA translation are negatively regulated by arginine. An upstream open reading frame (uORF) in the transcript’s 5′ region has been implicated in arginine-specific control. An arg-2-hph fusion gene encoding hygromycin phosphotransferase conferred arginine-regulated resistance to hygromycin when introduced into N. crassa. We used an arg-2-hph strain to select for UV-induced mutants that grew in the presence of hygromycin and arginine, and we isolated 46 mutants that had either of two phenotypes. One phenotype indicated altered expression of both arg-2-hph and urg-2 genes; the other, altered expression of urg-2-hph but not arg-2. One of the latter mutations, which was genetically closely linked to arg-2-hph, was recovered from the 5′ region of the arg-2-hph gene using PCR. Sequence analyses and transformation experiments revealed a mutation at uORF codon 12 (Asp to Asn) that abrogated negative regulation. Examination of the distribution of ribosomes on arg-2-hph transcripts showed that loss of regulation had a translational component, indicating the uORF sequence was important for Arg-specific translational control. Comparisons with other uORFS suggest common elements in translational control mechanisms.

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Response of Photosynthesis and Chlorophyll Fluorescence Parameters of Castanopsis kawakamii Seedlings to Forest Gaps

Forests ◽

10.3390/f11010021 ◽

2019 ◽

Vol 11 (1) ◽

pp. 21

Author(s):

Zhong-sheng He ◽

Rong Tang ◽

Meng-jia Li ◽

Meng-ran Jin ◽

Cong Xin ◽

...

Keyword(s):

Chlorophyll Fluorescence ◽

Light Intensity ◽

Seedling Growth ◽

Group Treatment ◽

Control Group ◽

Low Light ◽

Chlorophyll Fluorescence Parameters ◽

Forest Gaps ◽

Low Light Intensity ◽

Weak Light

Light is a major environmental factor limiting the growth and survival of plants. The heterogeneity of the light environment after gap formation in forest influences the leaf chlorophyll contents, net photosynthetic rate (Pn), and chlorophyll fluorescence, thus influencing the growth and regeneration of Castanopsis kawakamii seedlings. The aim of this study was to explore the effects of weak light on the photosynthetic physiology of C. kawakamii seedlings in forest gaps and non-gaps. The results showed that (1) the contents of chlorophyll a (Chl-a), chlorophyll b (Chl-b), and total chlorophyll (Chl-T) in forest gaps were lower than in non-gaps. Seedlings tended to increase chlorophyll content to absorb light energy to adapt to low light intensity in non-gap environments. (2) The Pn values of C. kawakamii seedlings in forest gaps were significantly higher than in non-gaps, and forest gaps could improve the seedlings’ photosynthetic capacity. (3) The C. kawakamii seedlings in forest gaps were more sensitive to weak light and control group treatment, especially the tall seedlings, indicating that seedlings require more light to satisfy their growth needs in the winter. The seedlings in non-gaps demonstrated better adaptability to low light intensity. The light intensity was not adequate in weak light conditions and limited seedling growth. We suggest that partial forest selection cutting could improve light intensity in non-gaps, thus promoting seedling growth and regeneration of C. kawakamii more effectively in this forest.

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