The Role of Pea Chloroplast [alpha]-Glucosidase in Transitory Starch Degradation

Abstract This study aimed to gain insights into the molecular mechanisms underlying the role of ethylene in regulating germination and seedling growth in wheat by combining pharmacological, molecular, and metabolomics approaches. Our study showed that ethylene does not affect radicle protrusion but controls post-germination endospermic starch degradation through transcriptional regulation of specific α-amylase and α-glucosidase genes, and this effect is mediated by alteration of endospermic bioactive gibberellin (GA) levels, and GA sensitivity via expression of the GA signaling gene, TaGAMYB. Our data implicated ethylene as a positive regulator of embryo axis and coleoptile growth through transcriptional regulation of specific TaEXPA genes. These effects were associated with modulation of GA levels and sensitivity, through expression of GA metabolism (TaGA20ox1, TaGA3ox2, and TaGA2ox6) and signaling (TaGAMYB) genes, respectively, and/or the abscisic acid (ABA) level and sensitivity, via expression of specific ABA metabolism (TaNCED2 or TaCYP707A1) and signaling (TaABI3) genes, respectively. Ethylene appeared to regulate the expression of TaEXPA3 and thereby root growth through its control of coleoptile ABA metabolism, and root ABA signaling via expression of TaABI3 and TaABI5. These results show that spatiotemporal modulation of ABA/GA balance mediates the role of ethylene in regulating post-germination storage starch degradation and seedling growth in wheat.

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Starch branching enzymes as putative determinants of postharvest quality in horticultural crops

BMC Plant Biology ◽

10.1186/s12870-021-03253-6 ◽

2021 ◽

Vol 21 (1) ◽

Author(s):

Jingwei Yu ◽

Keyun Wang ◽

Diane M. Beckles

Keyword(s):

Sugar Content ◽

Postharvest Quality ◽

Starch Accumulation ◽

Starch Degradation ◽

Published Data ◽

Horticultural Crops ◽

Starch Branching Enzymes ◽

Branching Enzymes ◽

End Use

AbstractStarch branching enzymes (SBEs) are key determinants of the structure and amount of the starch in plant organs, and as such, they have the capacity to influence plant growth, developmental, and fitness processes, and in addition, the industrial end-use of starch. However, little is known about the role of SBEs in determining starch structure-function relations in economically important horticultural crops such as fruit and leafy greens, many of which accumulate starch transiently. Further, a full understanding of the biological function of these types of starches is lacking. Because of this gap in knowledge, this minireview aims to provide an overview of SBEs in horticultural crops, to investigate the potential role of starch in determining postharvest quality. A systematic examination of SBE sequences in 43 diverse horticultural species, identified SBE1, 2 and 3 isoforms in all species examined except apple, olive, and Brassicaceae, which lacked SBE1, but had a duplicated SBE2. Among our findings after a comprehensive and critical review of published data, was that as apple, banana, and tomato fruits ripens, the ratio of the highly digestible amylopectin component of starch increases relative to the more digestion-resistant amylose fraction, with parallel increases in SBE2 transcription, fruit sugar content, and decreases in starch. It is tempting to speculate that during the ripening of these fruit when starch degradation occurs, there are rearrangements made to the structure of starch possibly via branching enzymes to increase starch digestibility to sugars. We propose that based on the known action of SBEs, and these observations, SBEs may affect produce quality, and shelf-life directly through starch accumulation, and indirectly, by altering sugar availability. Further studies where SBE activity is fine-tuned in these crops, can enrich our understanding of the role of starch across species and may improve horticulture postharvest quality.

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Digestive proteases and carbohydrases along the alimentary tract of the stargazer, Uranoscopus scaber Linnaeus, 1753

Mediterranean Marine Science ◽

10.12681/mms.173 ◽

2006 ◽

Vol 7 (1) ◽

pp. 5

Author(s):

E.S. PAPOUTSOGLOU ◽

A.R. LYNDON

Keyword(s):

Digestive Tract ◽

Protease Activity ◽

Digestive Enzyme ◽

Large Molecular Weight ◽

Anterior Intestine ◽

Total Capacity ◽

Alpha Glucosidase ◽

Carbohydrate Digestion ◽

Uranoscopus Scaber

Digestive enzyme activity and capacity (activity x tissue weight) for protein (total protease assay, 25° C) and carbohydrates (total carbohydrase and alpha-glucosidase assay at 5, 18 and 25° C) was investigated for the carnivorous stargazer, Uranoscopus scaber along its digestive tract. Results indicated that whole gut total protease activity was highest at pH 1.5 (P<0.05) (25° C) in U. scaber, (6.64±2.55 mg tyrosine per g digestive tract per minute, pH 1.5). Total protease activity was apparent mainly in the stomach at pH 1.5 (9.73±3.3), and to a lesser degree in the anterior intestine (11.15±1.5, pH 10.0) and pyloric caeca (4.92±2.06, pH 10.0), especially at pH 9.0 and 10.0. Furthermore, 60% of total capacity for protein digestion derives from the stomach region, which takes up 65% of the digestive tract. Total carbohydrase activity and capacity levels were very low compared to other carnivorous teleosts, indicating very low tendency for complex, large molecular weight carbohydrate digestion. However, alpha-glucosidase levels were higher, a fact which combined with relevant data for other marine carnivorous teleosts suggests a possible role of disaccharide in relation to marine carnivorous fish dietary carbohydrate inclusion.

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Comparison between 1-deoxynojirimycin and N-methyl-1-deoxynojirimycin as inhibitors of oligosaccharide processing in intestinal epithelial cells

Biochemical Journal ◽

10.1042/bj2260733 ◽

1985 ◽

Vol 226 (3) ◽

pp. 733-740 ◽

Cited By ~ 52

Author(s):

P A Romero ◽

B Saunier ◽

A Herscovics

Keyword(s):

Epithelial Cells ◽

Intestinal Epithelial Cells ◽

Intestinal Epithelial ◽

Glucose Residue ◽

Jack Bean ◽

Canavalia Ensiformis ◽

Glucosidase Inhibitor ◽

Oligosaccharide Processing ◽

Alpha Glucosidase

The alpha-glucosidase inhibitor N-methyl-1-deoxynojirimycin (MDJN) inhibits the synthesis of N-linked complex oligosaccharides in rat intestinal epithelial cells to the same extent as reported previously for 1-deoxynojirimycin (DJN) [Saunier, Kilker, Tkacz, Quaroni & Herscovics (1982) J. Biol. Chem. 257, 14155-14161]. Analysis of each of the endo-beta-N-acetylglucosaminidase H (endo H)-sensitive oligosaccharides separated by h.p.l.c. with yeast glucosidase I, which specifically removes the terminal glucose residue from oligosaccharides containing three glucose residues, and with jack-bean (Canavalia ensiformis) alpha-mannosidase, indicates that both inhibitors cause the accumulation of a mixture of glucosylated oligosaccharides containing one to three glucose residues and seven to nine, and even possibly six, mannose residues. About 70% of the endo H-sensitive oligosaccharides formed in the presence of MDJN contain three glucose residues, compared with only about 20% of the corresponding oligosaccharides of the DJN treated cells. It is concluded that both compounds inhibit the formation of N-linked complex oligosaccharides by interfering with the processing glucosidases. These compounds are valuable in the study of the role of oligosaccharides in glycoproteins.

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Influence de la température d'endurcissement sur la tolérance au gel de la luzerne et sa teneur en sucres, amidon et proline

Canadian Journal of Plant Science ◽

10.4141/cjps91-107 ◽

1991 ◽

Vol 71 (3) ◽

pp. 737-747 ◽

Cited By ~ 5

Author(s):

Annick Bertrand ◽

Roger Paquin

Keyword(s):

Medicago Sativa ◽

Cold Tolerance ◽

Sugar Content ◽

Frost Tolerance ◽

Proline Content ◽

Starch Degradation ◽

Limiting Factor ◽

Total Sugar Content ◽

Medicago Sativa L

The increased sugar and starch in crowns and roots during hardening is considered a limiting factor for the acquisition of cold tolerance in alfalfa (Medicago sativa L.). We wanted to determine the effect of a decrease in carbohydrate on cold tolerance. Alfalfa plants (Medicago sativa L.) were hardened at 1 °C or −2 °C during the day and at 10 °C or 15 °C during the dark while control plants were kept continuously at 1 °C or −2 °C. Hardening alfalfa at 10 °C and 15 °C during darkness decreased the total sugar content while it increased at 1 °C and −2 °C. However, frost tolerance and growth of the plants were not changed by raising the night temperature to 10 and 15 °C. The sugar increase corresponded in general to a starch degradation, mainly in the crowns. In plants hardened at −2 °C the proline content was higher in the leaves and lower in crowns. The opposite was observed in plants hardened at 10 and 15 °C during darkness. However, during hardening at −2 °C, we observed the desiccation of leaves and an increase in the proline content. We discuss the role of sugars as promoting agents for the acquisition of frost tolerance. Key words: Alfalfa, frost tolerance, sugars, starch, proline, hardening

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