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Concerted suppression of all starch branching enzyme genes in barley produces amylose-only starch granules

BACKGROUND: Starch is stored in higher plants as granules composed of semi-crystalline amylopectin and amorphous amylose. Starch granules provide energy for the plant during dark periods and for germination of seeds and tubers. Dietary starch is also a highly glycemic carbohydrate being degraded to...

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Autores principales: Carciofi, Massimiliano, Blennow, Andreas, Jensen, Susanne L, Shaik, Shahnoor S, Henriksen, Anette, Buléon, Alain, Holm, Preben B, Hebelstrup, Kim H
Formato: Online Artículo Texto
Lenguaje:English
Publicado: BioMed Central 2012
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3537698/
https://www.ncbi.nlm.nih.gov/pubmed/23171412
http://dx.doi.org/10.1186/1471-2229-12-223
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author Carciofi, Massimiliano
Blennow, Andreas
Jensen, Susanne L
Shaik, Shahnoor S
Henriksen, Anette
Buléon, Alain
Holm, Preben B
Hebelstrup, Kim H
author_facet Carciofi, Massimiliano
Blennow, Andreas
Jensen, Susanne L
Shaik, Shahnoor S
Henriksen, Anette
Buléon, Alain
Holm, Preben B
Hebelstrup, Kim H
author_sort Carciofi, Massimiliano
collection PubMed
description BACKGROUND: Starch is stored in higher plants as granules composed of semi-crystalline amylopectin and amorphous amylose. Starch granules provide energy for the plant during dark periods and for germination of seeds and tubers. Dietary starch is also a highly glycemic carbohydrate being degraded to glucose and rapidly absorbed in the small intestine. But a portion of dietary starch, termed “resistant starch” (RS) escapes digestion and reaches the large intestine, where it is fermented by colonic bacteria producing short chain fatty acids (SCFA) which are linked to several health benefits. The RS is preferentially derived from amylose, which can be increased by suppressing amylopectin synthesis by silencing of starch branching enzymes (SBEs). However all the previous works attempting the production of high RS crops resulted in only partly increased amylose-content and/or significant yield loss. RESULTS: In this study we invented a new method for silencing of multiple genes. Using a chimeric RNAi hairpin we simultaneously suppressed all genes coding for starch branching enzymes (SBE I, SBE IIa, SBE IIb) in barley (Hordeum vulgare L.), resulting in production of amylose-only starch granules in the endosperm. This trait was segregating 3:1. Amylose-only starch granules were irregularly shaped and showed peculiar thermal properties and crystallinity. Transgenic lines retained high-yield possibly due to a pleiotropic upregualtion of other starch biosynthetic genes compensating the SBEs loss. For gelatinized starch, a very high content of RS (65 %) was observed, which is 2.2-fold higher than control (29%). The amylose-only grains germinated with same frequency as control grains. However, initial growth was delayed in young plants. CONCLUSIONS: This is the first time that pure amylose has been generated with high yield in a living organism. This was achieved by a new method of simultaneous suppression of the entire complement of genes encoding starch branching enzymes. We demonstrate that amylopectin is not essential for starch granule crystallinity and integrity. However the slower initial growth of shoots from amylose-only grains may be due to an important physiological role played by amylopectin ordered crystallinity for rapid starch remobilization explaining the broad conservation in the plant kingdom of the amylopectin structure.
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spelling pubmed-35376982013-01-10 Concerted suppression of all starch branching enzyme genes in barley produces amylose-only starch granules Carciofi, Massimiliano Blennow, Andreas Jensen, Susanne L Shaik, Shahnoor S Henriksen, Anette Buléon, Alain Holm, Preben B Hebelstrup, Kim H BMC Plant Biol Research Article BACKGROUND: Starch is stored in higher plants as granules composed of semi-crystalline amylopectin and amorphous amylose. Starch granules provide energy for the plant during dark periods and for germination of seeds and tubers. Dietary starch is also a highly glycemic carbohydrate being degraded to glucose and rapidly absorbed in the small intestine. But a portion of dietary starch, termed “resistant starch” (RS) escapes digestion and reaches the large intestine, where it is fermented by colonic bacteria producing short chain fatty acids (SCFA) which are linked to several health benefits. The RS is preferentially derived from amylose, which can be increased by suppressing amylopectin synthesis by silencing of starch branching enzymes (SBEs). However all the previous works attempting the production of high RS crops resulted in only partly increased amylose-content and/or significant yield loss. RESULTS: In this study we invented a new method for silencing of multiple genes. Using a chimeric RNAi hairpin we simultaneously suppressed all genes coding for starch branching enzymes (SBE I, SBE IIa, SBE IIb) in barley (Hordeum vulgare L.), resulting in production of amylose-only starch granules in the endosperm. This trait was segregating 3:1. Amylose-only starch granules were irregularly shaped and showed peculiar thermal properties and crystallinity. Transgenic lines retained high-yield possibly due to a pleiotropic upregualtion of other starch biosynthetic genes compensating the SBEs loss. For gelatinized starch, a very high content of RS (65 %) was observed, which is 2.2-fold higher than control (29%). The amylose-only grains germinated with same frequency as control grains. However, initial growth was delayed in young plants. CONCLUSIONS: This is the first time that pure amylose has been generated with high yield in a living organism. This was achieved by a new method of simultaneous suppression of the entire complement of genes encoding starch branching enzymes. We demonstrate that amylopectin is not essential for starch granule crystallinity and integrity. However the slower initial growth of shoots from amylose-only grains may be due to an important physiological role played by amylopectin ordered crystallinity for rapid starch remobilization explaining the broad conservation in the plant kingdom of the amylopectin structure. BioMed Central 2012-11-21 /pmc/articles/PMC3537698/ /pubmed/23171412 http://dx.doi.org/10.1186/1471-2229-12-223 Text en Copyright ©2012 Carciofi et al.; licensee BioMed Central Ltd. http://creativecommons.org/licenses/by/2.0 This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
spellingShingle Research Article
Carciofi, Massimiliano
Blennow, Andreas
Jensen, Susanne L
Shaik, Shahnoor S
Henriksen, Anette
Buléon, Alain
Holm, Preben B
Hebelstrup, Kim H
Concerted suppression of all starch branching enzyme genes in barley produces amylose-only starch granules
title Concerted suppression of all starch branching enzyme genes in barley produces amylose-only starch granules
title_full Concerted suppression of all starch branching enzyme genes in barley produces amylose-only starch granules
title_fullStr Concerted suppression of all starch branching enzyme genes in barley produces amylose-only starch granules
title_full_unstemmed Concerted suppression of all starch branching enzyme genes in barley produces amylose-only starch granules
title_short Concerted suppression of all starch branching enzyme genes in barley produces amylose-only starch granules
title_sort concerted suppression of all starch branching enzyme genes in barley produces amylose-only starch granules
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3537698/
https://www.ncbi.nlm.nih.gov/pubmed/23171412
http://dx.doi.org/10.1186/1471-2229-12-223
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