Fructan: More Than a Reserve Carbohydrate?1

Vijn, I.; Smeekens, Sjef

doi:10.1104/pp.120.2.351

Cited by 494 publications

(376 citation statements)

References 36 publications

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“…7). Coexpression of HvSUT2 and the fructan biosynthesis genes Hv6-SFT and Hv1-FEH suggests a concerted role for an intermediate carbon storage in vacuoles to provide sink strength of the caryopsis (Vijn and Smeekens, 1999). The positive correlation of Hv6-SFT and Hv1-FEH and Suc further indicates that these genes are Suc inducible also in sink organs, as described previously for leaves (Nagaraj et al, 2005).…”

Section: Sugar Signaling Network May Cause Diurnal Regulation Of a Lmentioning

confidence: 53%

Significance of Light, Sugar, and Amino Acid Supply for Diurnal Gene Regulation in Developing Barley Caryopses

et al. 2010

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The caryopses of barley (Hordeum vulgare), as of all cereals, are complex sink organs optimized for starch accumulation and embryo development. While their early to late development has been studied in great detail, processes underlying the caryopses' diurnal adaptation to changes in light, temperature, and the fluctuations in phloem-supplied carbon and nitrogen have remained unknown. In an attempt to identify diurnally affected processes in developing caryopses at the early maturation phase, we monitored global changes of both gene expression and metabolite levels. We applied the 22 K Barley1 GeneChip microarray and identified 2,091 differentially expressed (DE) genes that were assigned to six major diurnal expression clusters. Principal component analysis and other global analyses demonstrated that the variability within the data set relates to genes involved in circadian regulation, storage compound accumulation, embryo development, response to abiotic stress, and photosynthesis. The correlation of amino acid and sugar profiles with expression trajectories led to the identification of several hundred potentially metabolite-regulated DE genes. A comparative analysis of our data set and publicly available microarray data disclosed suborgan-specific expression of almost all diurnal DE genes, with more than 350 genes specifically expressed in the pericarp, endosperm, or embryo tissues. Our data reveal a tight linkage between day/night cycles, changes in light, and the supply of carbon and nitrogen. We present a model that suggests several phases of diurnal gene expression in developing barley caryopses, summarized as starvation and priming, energy collection and carbon fixation, light protection and chaperone activity, storage and growth, and embryo development.

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Section: Sugar Signaling Network May Cause Diurnal Regulation Of a Lmentioning

confidence: 53%

Significance of Light, Sugar, and Amino Acid Supply for Diurnal Gene Regulation in Developing Barley Caryopses

et al. 2010

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“…In general, fructans are thought to be localized in the vacuole (Pollock et al, 1996;Vijn and Smeekens, 1999), although an apoplastic localization of fructans and 1-FEH activity was reported (Livingston and Henson, 1998;Kawakami et al, 2005). There are two possible explanations for tissue specificity and unexpected apoplastic localization in developing barley grains.…”

Section: Localization Of Inulin-type Oligofructansmentioning

confidence: 91%

Spatio-Temporal Dynamics of Fructan Metabolism in Developing Barley Grains

et al. 2014

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Barley (Hordeum vulgare) grain development follows a series of defined morphological and physiological stages and depends on the supply of assimilates (mainly sucrose) from the mother plant. Here, spatio-temporal patterns of sugar distributions were investigated by mass spectrometric imaging, targeted metabolite analyses, and transcript profiling of microdissected grain tissues. Distinct spatio-temporal sugar balances were observed, which may relate to differentiation and grain filling processes. Notably, various types of oligofructans showed specific distribution patterns. Levan-and graminan-type oligofructans were synthesized in the cellularized endosperm prior to the commencement of starch biosynthesis, while during the storage phase, inulin-type oligofructans accumulated to a high concentration in and around the nascent endosperm cavity. In the shrunken endosperm mutant seg8, with a decreased sucrose flux toward the endosperm, fructan accumulation was impaired. The tight partitioning of oligofructan biosynthesis hints at distinct functions of the various fructan types in the young endosperm prior to starch accumulation and in the endosperm transfer cells that accomplish the assimilate supply toward the endosperm at the storage phase.

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“…It has long been established that fructan biosynthetic enzymes such as Suc:Suc 1-fructosyltransferase and fructan:fructan 1-fructosyltransferase show some invertase activity (transfer of fructosyl residues to water rather than to Suc or fructan). Conversely, many invertases are able to produce shortchain fructans when incubated at very high Suc concentrations (for review, see Vijn and Smeekens, 1999;Van Laere and Van den Ende, 2002). At the molecular level, fructosyltransferases showed very high homologies to vacuolar-type acid invertases (Van Laere and Van den Ende, 2002;Van den Ende et al, 2003), similar to GGT showing high homologies to different plant acid a-Gals (Fig.…”

Section: Discussionmentioning

confidence: 99%

Cloning, Functional Expression, and Characterization of the Raffinose Oligosaccharide Chain Elongation Enzyme, Galactan:Galactan Galactosyltransferase, from Common Bugle Leaves

2004

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Galactan:galactan galactosyltransferase (GGT) is a unique enzyme of the raffinose family oligosaccharide (RFO) biosynthetic pathway. It catalyzes the chain elongation of RFOs without using galactinol (a-galactosyl-myoinositol) by simply transferring a terminal a-galactosyl residue from one RFO molecule to another one. Here, we report the cloning and functional expression of a cDNA encoding GGT from leaves of the common bugle (Ajuga reptans), a winter-hardy long-chain RFO-storing Lamiaceae. The cDNA comprises an open reading frame of 1215 bp. Expression in tobacco (Nicotiana plumbaginifolia) protoplasts resulted in a functional recombinant protein, which showed GGT activity like the previously described purified, native GGT enzyme. At the amino acid level, GGT shows high homologies ([60%) to acid plant a-galactosidases of the family 27 of glycosylhydrolases. It is clearly distinct from the family 36 of glycosylhydrolases, which harbor galactinol-dependent raffinose and stachyose synthases as well as alkaline a-galactosidases. Physiological studies on the role of GGT confirmed that GGT plays a key role in RFO chain elongation and carbon storage. When excised leaves were exposed to chilling temperatures, levels of GGT transcripts, enzyme activities, and long-chain RFO concentrations increased concomitantly. On a whole-plant level, chilling temperatures induced GGT expression mainly in the roots and fully developed leaves, both known RFO storage organs of the common bugle, indicating an adaptation of the metabolism from active growth to transient storage in the cold.

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Fructan: More Than a Reserve Carbohydrate?1

Cited by 494 publications

References 36 publications

Significance of Light, Sugar, and Amino Acid Supply for Diurnal Gene Regulation in Developing Barley Caryopses

Significance of Light, Sugar, and Amino Acid Supply for Diurnal Gene Regulation in Developing Barley Caryopses

Spatio-Temporal Dynamics of Fructan Metabolism in Developing Barley Grains

Cloning, Functional Expression, and Characterization of the Raffinose Oligosaccharide Chain Elongation Enzyme, Galactan:Galactan Galactosyltransferase, from Common Bugle Leaves

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