The structure of starch can be manipulated by changing the expression levels of starch branching enzyme IIb in rice endosperm

Tanaka, Naoki; Fujita, Naoko; Nishi, Aiko; Satoh, Hiroyuki; Hosaka, Yuko; Ugaki, Masashi; Kawasaki, Shinji; Nakamura, Yasunori

doi:10.1111/j.1467-7652.2004.00097.x

Cited by 187 publications

(160 citation statements)

References 38 publications

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“…When GBE is incubated with amylose, the resulting glucan products resemble glycogen with respect to chain distribution (13), compatible with the irregular branching model of Hizukuri (31). Overexpression of SBEIIb in an SBEIIb-deficient mutant of rice produced a disorganized, highly branched hydrosoluble polyglucan (56), highlighting the importance of coordination and balance between SBE and SS activities in the plastid (see "Regulation of SBEs by Protein Phosphorylation" section). Amylopectin defines the structure of the starch granule, and granule architecture is remarkably conserved in the plant kingdom (32).…”

Section: Tablementioning

confidence: 59%

A review of starch‐branching enzymes and their role in amylopectin biosynthesis

2014

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Starch-branching enzymes (SBEs) are one of the four major enzyme classes involved in starch biosynthesis in plants and algae, and their activities play a crucial role in determining the structure and physical properties of starch granules. SBEs generate a-1,6-branch linkages in a-glucans through cleavage of internal a-1,4 bonds and transfer of the released reducing ends to C-6 hydroxyls. Starch biosynthesis in plants and algae requires multiple isoforms of SBEs and is distinct from glycogen biosynthesis in both prokaryotes and eukaryotes which uses a single branching enzyme (BE) isoform. One of the unique characteristics of starch structure is the grouping of a-1,6-branch points in clusters within amylopectin. This is a feature of SBEs and their interplay with other starch biosynthetic enzymes, thus facilitating formation of the compact water-insoluble semicrystalline starch granule. In this respect, the activity of SBE isoforms is pivotal in starch granule assembly. SBEs are structurally related to the aamylase superfamily of enzymes, sharing three domains of secondary structure with prokaryotic Bes: the central (b/a) 8 -barrel catalytic domain, an NH 2 -terminal domain involved in determining the size of a-glucan chain transferred, and the C-terminal domain responsible for catalytic capacity and substrate preference. In addition, SBEs have conserved plant-specific domains, including phosphorylation sites which are thought to be involved in regulating starch metabolism. SBEs form heteromeric protein complexes with other SBE isoforms as well as other enzymes involved in starch synthesis, and assembly of these protein complexes is regulated by protein phosphorylation. Phosphorylated SBEIIb is found in multienzyme complexes with isoforms of glucan-elongating starch synthases, and these protein complexes are implicated in amylopectin cluster formation. This review presents a comparative overview of plant SBEs and includes a review of their properties, structural and functional characteristics, and recent developments on their posttranslational regulation.

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Section: Tablementioning

confidence: 59%

A review of starch‐branching enzymes and their role in amylopectin biosynthesis

2014

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“…The 2.9 kb mRNA band previously reported to be the normal mRNA of the OsSSI gene (Tanaka et al, 2004) was detected in wild-type and 1/1 lines, and the intensity of the band decreased gradually in the order i42/2 . i2-22/2 .…”

Section: Production Of Ssi-deficient Mutant Linesmentioning

confidence: 87%

Function and Characterization of Starch Synthase I Using Mutants in Rice

et al. 2006

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(A.M., H.H.) Four starch synthase I (SSI)-deficient rice (Oryza sativa) mutant lines were generated using retrotransposon Tos17 insertion. The mutants exhibited different levels of SSI activities and produced significantly lower amounts of SSI protein ranging from 0% to 20% of the wild type. The mutant endosperm amylopectin showed a decrease in chains with degree of polymerization (DP) 8 to 12 and an increase in chains with DP 6 to 7 and DP 16 to 19. The degree of change in amylopectin chain-length distribution was positively correlated with the extent of decrease in SSI activity in the mutants. The structural changes in the amylopectin increased the gelatinization temperature of endosperm starch. Chain-length analysis of amylopectin in the SSI band excised from native-polyacrylamide gel electrophoresis/SS activity staining gel showed that SSI preferentially synthesized DP 7 to 11 chains by elongating DP 4 to 7 short chains of glycogen or amylopectin. These results show that SSI distinctly generates DP 8 to 12 chains from short DP 6 to 7 chains emerging from the branch point in the A or B 1 chain of amylopectin. SSI seemingly functions from the very early through the late stage of endosperm development. Yet, the complete absence of SSI, despite being a major SS isozyme in the developing endosperm, had no effect on the size and shape of seeds and starch granules and the crystallinity of endosperm starch, suggesting that other SS enzymes are probably capable of partly compensating SSI function. In summary, this study strongly suggested that amylopectin chains are synthesized by the coordinated actions of SSI, SSIIa, and SSIIIa isoforms.

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“…Butardo et al (2011) reported that amylose content and amylopectin long chains (DP $ 36) were promoted more markedly but amylopectin short chains decreased more significantly in transgenic lines with more pronounced decrease of SBEIIb. Tanaka et al (2004) further detected that SBEIIb dosage was positively related to amylopectin short chains and negatively related to amylopectin long chains. Therefore, the question about whether the different molecular structures in TRS heterogeneous starch granules originated from the different dosages of the three SBE isoforms was raised.…”

Section: Dynamic Deposition Of Amylopectin Biosynthetic Enzymes In Thmentioning

confidence: 98%

Gradually Decreasing Starch Branching Enzyme Expression Is Responsible for the Formation of Heterogeneous Starch Granules

Wang

Lin

et al. 2017

Plant Physiol.

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Rice (Oryza sativa) endosperm is mainly occupied by homogeneous polygonal starch from inside to outside. However, morphologically different (heterogeneous) starches have been identified in some rice mutants. How these heterogeneous starches form remains unknown. A high-amylose rice line (TRS) generated through the antisense inhibition of starch branching synthase I (SBEI) and SBEIIb contains four heterogeneous starches: polygonal, aggregate, elongated, and hollow starch; these starches are regionally distributed in the endosperm from inside to outside. Here, we investigated the relationship between SBE dosage and the morphological architecture of heterogeneous starches in TRS endosperm from the view of the molecular structure of starch. The results indicated that their molecular structures underwent regular changes, including gradually increasing true amylose content but decreasing amylopectin content and gradually increasing the ratio of amylopectin long chain but decreasing the ratio of amylopectin short chain. Granule-bound starch synthase I (GBSSI) amounts in the four heterogeneous starches were not significantly different from each other, but SBEI, SBEIIa, and SBEIIb showed a gradually decreasing trend. Further immunostaining analysis revealed that the gradually decreasing SBEs acting on the formation of the four heterogeneous granules were mainly due to the spatial distribution of the three SBEs in the endosperm. It was suggested that the decreased amylopectin in starch might remove steric hindrance and provide extra space for abundant amylose accumulation when the GBSSI amount was not elevated. Furthermore, extra amylose coupled with altered amylopectin structure possibly led to morphological changes in heterogeneous granules.

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The structure of starch can be manipulated by changing the expression levels of starch branching enzyme IIb in rice endosperm

Cited by 187 publications

References 38 publications

A review of starch‐branching enzymes and their role in amylopectin biosynthesis

A review of starch‐branching enzymes and their role in amylopectin biosynthesis

Function and Characterization of Starch Synthase I Using Mutants in Rice

Gradually Decreasing Starch Branching Enzyme Expression Is Responsible for the Formation of Heterogeneous Starch Granules

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