The role of amylomaltase in maltose metabolism in the cytosol of photosynthetic cells

Lu, Yan; Sharkey, Thomas D.

doi:10.1007/s00425-003-1127-z

Cited by 165 publications

(217 citation statements)

References 43 publications

(48 reference statements)

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“…Many of the data presented in this study in potato are extremely similar to those found in the studies of the Arabidopsis dpe2 mutants (Lu and Sharkey, 2004;Chia et al, 2004). Those mutants showed both a maltose-and a starch-excess phenotype, something that we also found.…”

Section: The Protein Is Present In Potato Chloroplastssupporting

confidence: 88%

“…The mutation studied by Critchley et al (2001) was in a gene lying on chromosome 5 (At5g64860), with the other putative isoform being on chromosome 2 (At2g40840). Recently two studies have identified Arabidopsis plants mutated in the gene coding for this second isoform (Lu and Sharkey, 2004;Chia et al, 2004). In this article, we describe the analysis of the role of this isoform in starch metabolism in potato.…”

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confidence: 99%

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Repression of a Novel Isoform of Disproportionating Enzyme (stDPE2) in Potato Leads to Inhibition of Starch Degradation in Leaves But Not Tubers Stored at Low Temperature

et al. 2004

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A potato (Solanum tuberosum) cDNA encoding an isoform of disproportionating enzyme (stDPE2) was identified in a functional screen in Escherichia coli. The stDPE2 protein was demonstrated to be present in chloroplasts and to accumulate at times of active starch degradation in potato leaves and tubers. Transgenic potato plants were made in which its presence was almost completely eliminated. It could be demonstrated that starch degradation was repressed in leaves of the transgenic plants but that cold-induced sweetening was not affected in tubers stored at 48C. No evidence could be found for an effect of repression of stDPE2 on starch synthesis. The malto-oligosaccharide content of leaves from the transgenic plants was assessed. It was found that the amounts of malto-oligosaccharides increased in all plants during the dark period and that the transgenic lines accumulated up to 10-fold more than the control. Separation of these malto-oligosaccharides by high-performance anionexchange chromatography with pulsed-amperometric detection showed that the only one that accumulated in the transgenic plants in comparison with the control was maltose. stDPE2 was purified to apparent homogeneity from potato tuber extracts and could be demonstrated to transfer glucose from maltose to oyster glycogen.Disproportionating enzyme (D-enzyme; 4-a-glucanotransferase, EC 2.4.1.25) catalyzes the transfer (disproportionation) of a-1,4 bonds between different glucans. It is located in plastids and has always been presumed to be involved in starch metabolism. Mutant and transgenic plants, which lack its activity almost entirely, have been isolated (Takaha et al., 1998;Colleoni et al., 1999aColleoni et al., , 1999bCritchley et al., 2001;Wattebled et al., 2003), and based on studies on these, two contradictory proposals have been made as to its role. Following analysis of the Chlamydomonas reinhardtii sta11 mutant, it was suggested that D-enzyme is involved directly in the synthesis of the amylopectin fraction of starch (Colleoni et al., 1999a(Colleoni et al., , 1999bWattebled et al., 2003); however, no evidence for this could be found in an Arabidopsis D-enzyme mutant (dpe1; Critchley et al., 2001). It was demonstrated in this mutant that starch degradation was impaired, and it was proposed that the main role of D-enzyme is in malto-oligosaccharide metabolism during mobilization of starch in the dark period. In addition, transgenic potato (Solanum tuberosum) plants have been produced in which 99% of D-enzyme activity was repressed, but no influence on either amylopectin synthesis or starch degradation was reported (Takaha et al., 1998).In all of the above studies, only one isoform of D-enzyme was repressed. Analysis of the Arabidopsis genome, however, has revealed that it contains two genes that appear to code for different D-enzyme isoforms. The mutation studied by Critchley et al. (2001) was in a gene lying on chromosome 5 (At5g64860), with the other putative isoform being on chromosome 2 (At2g40840). Recently two studies have identified ...

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Section: The Protein Is Present In Potato Chloroplastssupporting

confidence: 88%

mentioning

confidence: 99%

Repression of a Novel Isoform of Disproportionating Enzyme (stDPE2) in Potato Leads to Inhibition of Starch Degradation in Leaves But Not Tubers Stored at Low Temperature

et al. 2004

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“…However, their expression patterns were different in the endosperm. While ISA3 transcripts were more abundant during early endosperm development, with an expression maximum around 4 to 6 DAF, ISA1 transcripts began to accumu- Lu and Sharkey (2004) late from 6 DAF and remained abundant until desiccation (Fig. 2D).…”

Section: Distinct Genes Are Involved In Starch Biosynthesis In Pericamentioning

confidence: 99%

“…ISA3 (Wattebled et al, 2005;Delatte et al, 2006) is also capable of degrading transient starch to maltooligosaccharides, which are further converted either to Glc by plastidial disproportionating enzyme 1 (DPE1; Critchley et al, 2001) or by BAM to maltose. Produced maltose is metabolized to Glc in cytosol by DPE2 (Lu and Sharkey, 2004).…”

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confidence: 99%

Spatiotemporal Profiling of Starch Biosynthesis and Degradation in the Developing Barley Grain

Borisjuk²,

et al. 2009

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Barley (Hordeum vulgare) grains synthesize starch as the main storage compound. However, some starch is degraded already during caryopsis development. We studied temporal and spatial expression patterns of genes coding for enzymes of starch synthesis and degradation. These profiles coupled with measurements of selected enzyme activities and metabolites have allowed us to propose a role for starch degradation in maternal and filial tissues of developing grains. Early maternal pericarp functions as a major short-term starch storage tissue, possibly ensuring sink strength of the young caryopsis. Gene expression patterns and enzyme activities suggest two different pathways for starch degradation in maternal tissues. One pathway possibly occurs via a-amylases 1 and 4 and b-amylase 1 in pericarp, nucellus, and nucellar projection, tissues that undergo programmed cell death. Another pathway is deducted for living pericarp and chlorenchyma cells, where transient starch breakdown correlates with expression of chloroplast-localized b-amylases 5, 6, and 7, glucan, water dikinase 1, phosphoglucan, water dikinase, isoamylase 3, and disproportionating enzyme. The suite of genes involved in starch synthesis in filial starchy endosperm is much more complex than in pericarp and involves several endosperm-specific genes. Transient starch turnover occurs in transfer cells, ensuring the maintenance of sink strength in filial tissues and the reallocation of sugars into more proximal regions of the starchy endosperm. Starch is temporally accumulated also in aleurone cells, where it is degraded during the seed filling period, to be replaced by storage proteins and lipids.

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“…One mutant constitutively lacks the functional cytosolic transglucosidase (also designated as disproportionating enzyme2; DPE2) and, therefore, the cytosolic route of starch-derived maltose metabolism is impaired (Chia et al, 2004;Lu and Sharkey, 2004). The other mutant does not express the plastidial maltose transporter MEX1, resulting in a massively enlarged maltose pool (Niittylä et al, 2004).…”

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Double Knockout Mutants of Arabidopsis Grown under Normal Conditions Reveal that the Plastidial Phosphorylase Isozyme Participates in Transitory Starch Metabolism

et al. 2013

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In leaves of two starch-related single-knockout lines lacking either the cytosolic transglucosidase (also designated as disproportionating enzyme 2, DPE2) or the maltose transporter (MEX1), the activity of the plastidial phosphorylase isozyme (PHS1) is increased. In both mutants, metabolism of starch-derived maltose is impaired but inhibition is effective at different subcellular sites. Two constitutive double knockout mutants were generated (designated as dpe2-1 × phs1a and mex1 × phs1b) both lacking functional PHS1. They reveal that in normally grown plants, the plastidial phosphorylase isozyme participates in transitory starch degradation and that the central carbon metabolism is closely integrated into the entire cell biology. All plants were grown either under continuous illumination or in a light-dark regime. Both double mutants were compromised in growth and, compared with the single knockout plants, possess less average leaf starch when grown in a light-dark regime. Starch and chlorophyll contents decline with leaf age. As revealed by transmission electron microscopy, mesophyll cells degrade chloroplasts, but degradation is not observed in plants grown under continuous illumination. The two double mutants possess similar but not identical phenotypes. When grown in a light-dark regime, mesophyll chloroplasts of dpe2-1 × phs1a contain a single starch granule but under continuous illumination more granules per chloroplast are formed. The other double mutant synthesizes more granules under either growth condition. In continuous light, growth of both double mutants is similar to that of the parental single knockout lines. Metabolite profiles and oligoglucan patterns differ largely in the two double mutants.

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The role of amylomaltase in maltose metabolism in the cytosol of photosynthetic cells

Cited by 165 publications

References 43 publications

Repression of a Novel Isoform of Disproportionating Enzyme (stDPE2) in Potato Leads to Inhibition of Starch Degradation in Leaves But Not Tubers Stored at Low Temperature

Repression of a Novel Isoform of Disproportionating Enzyme (stDPE2) in Potato Leads to Inhibition of Starch Degradation in Leaves But Not Tubers Stored at Low Temperature

Spatiotemporal Profiling of Starch Biosynthesis and Degradation in the Developing Barley Grain

Double Knockout Mutants of Arabidopsis Grown under Normal Conditions Reveal that the Plastidial Phosphorylase Isozyme Participates in Transitory Starch Metabolism

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