Mobilizing Vacuolar Sugar Increases Vegetative Triacylglycerol Accumulation

Photosynthetically derived sugars provide carbon skeletons for metabolism and carbon signals that favor anabolism. The amount of sugar available for fatty acid (FA) and triacylglycerol (TAG) synthesis depends on sugar compartmentation, transport, and demands from competing pathways. We are exploring the influence of sugar partitioning between the vacuole and cytoplasm on FA synthesis in Arabidopsis by building on our previous finding that reduced leaf sugar export in the sucrose-proton symporter2 (suc2) mutant, in combination with impaired starch synthesis in the ADP-glucose pyrophosphorylase (adg1) mutant, accumulates higher sugar levels and increased total FA and TAG compared to the wild type parent. Here we sought to relocalize sugar from the vacuole to the cytoplasm to drive additional FA/TAG synthesis and growth. Arabidopsis suc2 adg1 was therefore crossed with tonoplast monosaccharide transporter mutants tmt1 and tmt2 and overexpression of the sucrose/proton cotransporter SUC4 in which tmt1 tmt2 impairs sugar transport to the vacuole from the cytoplasm and SUC4 overexpression enhances sugar transport in the reverse direction from the vacuole to the cytoplasm. A resulting homozygous suc2 adg1 tmt1 tmt2 SUC4 line was used to test the hypothesis that increased intracellular carbon supply in the form of sugars would increase both FA and TAG accumulation. The data shows that relative to suc2 adg1, suc2 adg1 tmt1 tmt2 SUC4 significantly increases leaf total FA content by 1.29-fold to 10.9% of dry weight and TAG by 2.4-fold to 2.88%, supporting the hypothesis that mobilizing vacuolar sugar is a valid strategy for increasing vegetative oil accumulation.

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Ectopic Expression of OLEOSIN 1 and Inactivation of GBSS1 Have a Synergistic Effect on Oil Accumulation in Plant Leaves

Plants ◽

10.3390/plants10030513 ◽

2021 ◽

Vol 10 (3) ◽

pp. 513

Author(s):

Zhiyang Zhai ◽

Hui Liu ◽

John Shanklin

Keyword(s):

Synergistic Effect ◽

Oil Content ◽

Ectopic Expression ◽

Dry Weight ◽

Oil Accumulation ◽

Transgenic Lines ◽

Leaf Oil ◽

The Individual ◽

Mutant Lines ◽

Tag Accumulation

During the transformation of wild-type (WT) Arabidopsis thaliana, a T-DNA containing OLEOSIN-GFP (OLE1-GFP) was inserted by happenstance within the GBSS1 gene, resulting in significant reduction in amylose and increase in leaf oil content in the transgenic line (OG). The synergistic effect on oil accumulation of combining gbss1 with the expression of OLE1-GFP was confirmed by transforming an independent gbss1 mutant (GABI_914G01) with OLE1-GFP. The resulting OLE1-GFP/gbss1 transgenic lines showed higher leaf oil content than the individual OLE1-GFP/WT or single gbss1 mutant lines. Further stacking of the lipogenic factors WRINKLED1, Diacylglycerol O-Acyltransferase (DGAT1), and Cys-OLEOSIN1 (an engineered sesame OLEOSIN1) in OG significantly elevated its oil content in mature leaves to 2.3% of dry weight, which is 15 times higher than that in WT Arabidopsis. Inducible expression of the same lipogenic factors was shown to be an effective strategy for triacylglycerol (TAG) accumulation without incurring growth, development, and yield penalties.

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Faculty Opinions recommendation of Molecular identification and physiological characterization of a novel monosaccharide transporter from Arabidopsis involved in vacuolar sugar transport.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1060881.512822 ◽

2007 ◽

Author(s):

Ulf-Ingo Flugge

Keyword(s):

Molecular Identification ◽

Sugar Transport ◽

Monosaccharide Transporter ◽

Physiological Characterization

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The Barley HvSTP13GR mutant triggers resistance against biotrophic fungi

10.1101/2021.09.16.460598 ◽

2021 ◽

Author(s):

Caroline Ines Skoppek ◽

Wilko Punt ◽

Marleen Heinrichs ◽

Frank Ordon ◽

Gwendolin Wehner ◽

...

Keyword(s):

Plant Protection ◽

Rust Fungus ◽

Durable Resistance ◽

Sugar Transport ◽

Gene Promoter ◽

Monosaccharide Transporter ◽

Base Editing ◽

Biological Stress ◽

Biotrophic Fungi ◽

Promoter Studies

High-yielding and stress resistant crops are essential to ensure future food supply. Barley is an important crop to feed livestock and to produce malt, but the annual yield is threatened by pathogen infections. Pathogens can trigger an altered sugar partitioning in the host plant, that possibly leads to an advantage for the pathogen. Hampering these processes represents a promising strategy to potentially increase resistance. We analyzed the response of the barley monosaccharide transporter HvSTP13 towards biotic stress and its potential use for plant protection. The expression of HvSTP13 increased upon bacterial and fungal PAMP application, suggesting a PAMP-triggered signaling that converged on the transcriptional induction of the gene. Promoter studies indicate a region that is likely targeted by transcription factors downstream of PAMP-triggered immunity pathways. We confirmed that the non-functional HvSTP13GR variant confers resistance against an economically relevant biotrophic rust fungus, in barley. In addition, we established targeted CRISPR/Cas9 cytosine base editing in barley protoplasts to generate alternative HvSTP13 mutants and characterized the sugar transport activity and subcellular localization of the proteins. These mutants represent promising variants for future resistance analysis. Our experimental setup provides basal prerequisites to further decode the role of HvSTP13 in response to biological stress. Moreover, in line with other studies, our experiments indicate that the alteration of sugar partitioning pathways, in a host pathogen interaction, is a promising approach to achieve broad and durable resistance in plants.

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The Rhodococcus opacus PD630 Heparin-Binding Hemagglutinin Homolog TadA Mediates Lipid Body Formation

Applied and Environmental Microbiology ◽

10.1128/aem.00985-10 ◽

2010 ◽

Vol 76 (21) ◽

pp. 7217-7225 ◽

Cited By ~ 36

Author(s):

Daniel P. MacEachran ◽

M. E. Prophete ◽

A. J. Sinskey

Keyword(s):

Kinetic Studies ◽

Lipid Body ◽

Dry Weight ◽

Rhodococcus Opacus ◽

Lipid Bodies ◽

Heparin Binding ◽

Tag Biosynthesis ◽

Tag Accumulation

ABSTRACT Generally, prokaryotes store carbon as polyhydroxyalkanoate, starch, or glycogen. The Gram-positive actinomycete Rhodococcus opacus strain PD630 is noteworthy in that it stores carbon in the form of triacylglycerol (TAG). Several studies have demonstrated that R. opacus PD630 can accumulate up to 76% of its cell dry weight as TAG when grown under nitrogen-limiting conditions. While this process is well studied, the underlying molecular and biochemical mechanisms leading to TAG biosynthesis and subsequent storage are poorly understood. We designed a high-throughput genetic screening to identify genes and their products required for TAG biosynthesis and storage in R. opacus PD630. We identified a gene predicted to encode a putative heparin-binding hemagglutinin homolog, which we have termed tadA (triacylglycerol accumulation deficient), as being important for TAG accumulation. Kinetic studies of TAG accumulation in both the wild-type (WT) and mutant strains demonstrated that the tadA mutant accumulates 30 to 40% less TAG than the parental strain (WT). We observed that lipid bodies formed by the mutant strain were of a different size and shape than those of the WT. Characterization of TadA demonstrated that the protein is capable of binding heparin and of agglutinating purified lipid bodies. Finally, we observed that the TadA protein localizes to lipid bodies in R. opacus PD630 both in vivo and in vitro. Based on these data, we hypothesize that the TadA protein acts to aggregate small lipid bodies, found in cells during early stages of lipid storage, into larger lipid bodies and thus plays a key role in lipid body maturation in R. opacus PD630.

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Heat Stress During Grain Filling in Maize: Effects on Carbohydrate Storage and Metabolism

Functional Plant Biology ◽

10.1071/pp9940829 ◽

1994 ◽

Vol 21 (6) ◽

pp. 829 ◽

Cited By ~ 54

Author(s):

GW Singletary ◽

R Banisadr ◽

PL Keeling

Keyword(s):

Heat Stress ◽

Seed Size ◽

Starch Synthesis ◽

Dry Weight ◽

Grain Filling ◽

Soluble Starch ◽

Effect Of Temperature ◽

Starch Accumulation ◽

Maize Kernels

Heat stress during maize seed development can interfere with endosperm starch biosynthesis and reduce seed size, an important component of yield. Our objectives were to evaluate the direct influence of temperature during grain filling on kernel growth, carbohydrate accumulation, and corresponding endosperm metabolism. Kernels of maize were grown in vitro at 25�C until 15 or 16 days after pollination and then subjected to various temperatures for the remainder of their development. Mature kernel dry weight declined 45% in a linear fashion between 22 and 36�C. The rate of starch accumulation reached a maximum at approximately 32�C, and when measured at frequent intervals, declined only slightly with further temperature increase to 35�C. Reduced seed size resulted from an abbreviated duration of starch-related metabolism, which did not appear to be limited by endogenous sugars. Instead, a survey of 12 enzymes of sugar and starch metabolism indicated that ADP glucose pyrophosphorylase and soluble starch synthase were unique in displaying developmental peaks of activity which were compressed both in amount and time, similar to the effect of temperature on starch accumulation. We conclude that decreased starch synthesis in heat-stressed maize kernels results from a premature decline in the activity of these enzymes.

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Effects of Elevated Temperature and Reduced Water Uptake on Enzymes of Starch Synthesis in Developing Wheat Grains

Functional Plant Biology ◽

10.1071/pp9900431 ◽

1990 ◽

Vol 17 (4) ◽

pp. 431 ◽

Cited By ~ 14

Author(s):

CY Caley ◽

CM Duffus ◽

B Jeffcoat

Keyword(s):

Elevated Temperatures ◽

Starch Content ◽

Starch Synthesis ◽

Dry Weight ◽

Endosperm Development ◽

Starch Synthase ◽

Temperature Regimes ◽

Endosperm Starch ◽

Rate Limiting ◽

Reduced Water

The mechanism of temperature regulation of endosperm development has been investigated by studying the effects of two temperature regimes on starch deposition and starch synthase activity during grain development in two cultivars of wheat. Most of the starch synthase activity was present throughout development as the granule-bound form using ADPglucose as the principal substrate. That starch synthase may be a rate-limiting enzyme for accumulation of starch, and hence dry weight, is suggested by: (1) rates are proportionately less in the cultivar with the lower final endosperm dry weight; (2) at elevated temperatures when starch content and dry weight are reduced, starch synthase activity falls; (3) the rate of starch deposition calculated to be possible from measured rates of starch synthase activity is close to the observed rate of starch deposition. On the other hand, it was concluded that it is not lack of starch synthase activity that causes termination of starch deposition, since activity is maintained well after starch deposition has ceased. Using the same two wheat cultivars, grown as detached ears in liquid culture, the effects of reduced endosperm water content, induced by the presence of polyethylene glycol in the culture medium, were investigated. Endosperm starch synthase activity was unaffected but ADPglucose pyrophosphorylase activity was greatly reduced, suggesting a possible role in the termination of starch synthesis.

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Expression of Chlamydomonas reinhardtii chloroplast diacylglycerol acyltransferase-3 is activated by light in concert with triacylglycerol accumulation

10.1101/2021.01.17.426997 ◽

2021 ◽

Author(s):

María de las Mercedes Carro ◽

Débora Soto ◽

Leandro Mamone ◽

Gabriela Gonorazky ◽

Carolina Bagnato ◽

...

Keyword(s):

Chlamydomonas Reinhardtii ◽

Diacylglycerol Acyltransferase ◽

Industrial Applications ◽

Wild Type ◽

Low Light ◽

Future Studies ◽

Promising Target ◽

Regulatory Loop ◽

Triacylglycerol Accumulation ◽

Tag Accumulation

AbstractConsiderable progress has been made towards the understanding of triacylglycerol (TAG) accumulation in algae. One key aspect is finding conditions that trigger TAG production without reducing cell division. Previously, we identified a soluble diacylglycerol acyltransferase (DGAT), related to plant DGAT3, with heterologous DGAT activity. In this work, we demonstrate that Chlamydomonas reinhardtii DGAT3 localizes to the chloroplast and its expression is activated by light, in correspondence with TAG accumulation. Dgat3 mRNAs and TAGs increased in both wild type and starch-deficient cells grown with acetate upon transferring them from dark or low light to higher light. Light-activated DGAT3 expression and TAG accumulation depended on the preexisting levels of TAGs, suggesting the existence of a regulatory loop. These results indicate that DGAT3 could be responsible, at least in part, for light-dependent TAG accumulation. Moreover, our results present DGAT3 as a promising target of future studies oriented to the industrial applications of TAGs.

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An Evaluation of the Oil Concentration in Sesame Seeds in Relation to Developmental Stage, Node Position and Capsule Age

Experimental Agriculture ◽

10.1017/s0014479700003240 ◽

1984 ◽

Vol 20 (2) ◽

pp. 129-134

Author(s):

S. N. Saha ◽

S. C. Bhargava

Keyword(s):

Seed Oil ◽

Dry Weight ◽

Yield Potential ◽

Main Shoot ◽

Oil Accumulation ◽

Sesame Seeds ◽

Oil Concentration ◽

Sesame Genotypes ◽

Node Position ◽

Oil Formation

SUMMARYWeekly measurements were made of the seed oil concentration (% dry weight) in five sesame genotypes (Sesamum indicum) from flowering to maturity. During early but not late development the oil concentration of main shoot capsules was less variable than that in capsules taken from branches. The oil concentration of seeds from capsules at different nodes decreased from 67 to 22% between the lowest (oldest) capsule at node 8 and the youngest one at the uppermost node (25) in 1976, and from 65 to 19% for the same nodes in 1977. Variations in oil accumulation in relation to capsule age revealed that oil formation begins within 5 days after fertilization and maximum accumulation (52% oil) was achieved after 30 days. The implications of these findings for the assessment of oil yield potential are discussed.

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The Arabidopsis MYB96 Transcription Factor Mediates ABA-Dependent Triacylglycerol Accumulation in Vegetative Tissues under Drought Stress Conditions

Plants ◽

10.3390/plants8090296 ◽

2019 ◽

Vol 8 (9) ◽

pp. 296 ◽

Cited By ~ 5

Author(s):

Hong Gil Lee ◽

Mid-Eum Park ◽

Bo Yeon Park ◽

Hyun Uk Kim ◽

Pil Joon Seo

Keyword(s):

Transcription Factor ◽

Drought Stress ◽

Molecular Networks ◽

Plant Fitness ◽

Plant Tolerance ◽

Adaptive Responses ◽

Vegetative Tissues ◽

Tag Biosynthesis ◽

Triacylglycerol Accumulation ◽

Tag Accumulation

Triacylglycerols (TAGs), a major lipid form of energy storage, are involved in a variety of plant developmental processes. While carbon reserves mainly accumulate in seeds, significant amounts of TAG have also been observed in vegetative tissues. Notably, the accumulation of leaf TAGs is influenced by environmental stresses such as drought stress, although underlying molecular networks remain to be fully elucidated. In this study, we demonstrate that the R2R3-type MYB96 transcription factor promotes TAG biosynthesis in Arabidopsis thaliana seedlings. Core TAG biosynthetic genes were up-regulated in myb96-ox seedlings, but down-regulated in myb96-deficient seedlings. In particular, ABA stimulates TAG accumulation in the vegetative tissues, and MYB96 plays a fundamental role in this process. Considering that TAG accumulation contributes to plant tolerance to drought stress, MYB96-dependent TAG biosynthesis not only triggers plant adaptive responses but also optimizes energy metabolism to ensure plant fitness under unfavorable environmental conditions.

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