Amylopectin biosynthetic enzymes from developing rice seed form enzymatically active protein complexes

Crofts, Naoko; Abe, Natsuko; Oitome, Naoko F.; Matsushima, Ryoka; Hayashi, Makio; Tetlow, Ian J.; Emes, Michael J.; Nakamura, Yasunori

doi:10.1093/jxb/erv212

Cited by 125 publications

(164 citation statements)

References 72 publications

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“…Based on our findings in this work and published results (32)(33)(34)(35), we now propose a RS biosynthetic pathway (Fig. 6).…”

Section: Discussionsupporting

confidence: 74%

“…It is known that the SSIIIa protein is associated with other proteins in developing rice endosperm (32), and in maize a proportion of SSIIIa is also present in a large complex including ADP-glucose pyrophosphorylase (AGPase), pyruvate orthophosphate dikinase (PPDK), SSIIa, and SBEIIa and SBEIIb (33). The enzyme PPDK catalyzes a reversible reaction from pyruvate, ATP, and Pi to phosphoenolpyruvate (PEP), AMP, and PPi (34), but in photosynthesis, it operates in the direction of PEP formation, driven by the hydrolysis of PPi (34).…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Critical roles of soluble starch synthase SSIIIa and granule-bound starch synthase Waxy in synthesizing resistant starch in rice

Zhou

Wang

Liu

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

178

172

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Changes in human lifestyle and food consumption have resulted in a large increase in the incidence of type-2 diabetes, obesity, and colon disease, especially in Asia. These conditions are a growing threat to human health, but consumption of foods high in resistant starch (RS) can potentially reduce their incidence. Strategies to increase RS in rice are limited by a lack of knowledge of its molecular basis. Through map-based cloning of a RS locus in indica rice, we have identified a defective soluble starch synthase gene (SSIIIa) responsible for RS production and further showed that RS production is dependent on the high expression of the Waxy a (Wx a ) allele, which is prevalent in indica varieties. The resulting RS has modified granule structure; high amylose, lipid, and amylose-lipid complex; and altered physicochemical properties. This discovery provides an opportunity to increase RS content of cooked rice, especially in the indica varieties, which predominates in southern Asia.diabetes | resistant starch biosynthesis | soluble starch synthase | granule-bound starch synthase | amylose-lipid complex I ncreases in the incidence of type-2 diabetes are being observed throughout the world. This increase is thought to be due to changes in both diet and lifestyle (1, 2) and is increasingly apparent in Asia. Consumption of foods high in resistant starch (RS) can help to control type-2 diabetes, because its slow digestion and absorption by the small intestine decreases postprandial glucose and insulin responses (3). Foods high in RS also potentially protect against pathogen infection, diarrhea, inflammatory bowel disease, colon cancer, and chronic renal and hepatic diseases. Consumption of RS can increase satiety and reduce calorie intake to help weight management (3). Thus, improvement of the amounts and properties of RS in foods is an important goal.Rice (Oryza sativa L.) is consumed by more than half the world's population (4), and for many, it is the primary source of nutrients and carbohydrates for energy. Consumption of 18-20 g of RS (5, 6) is recommended per day for health benefits, but hot cooked rice typically contains <3% RS (7). Rice varieties or mutants with improved RS have been identified, such as Goami No. 2, Gongmi No. 3, RS111, and Jiangtangdao 1 (7-10).A high-RS, high-amylose transgenic rice line has been developed by suppressing the expression of starch branching enzymes (SBEs) (11) and a mutation of SBEIIb cosegregated with RS content in rice (8). In other cereals, down-regulation of soluble starch synthase (SS) SSIIa and of SBE results in greater RS in barley (12, 13) and wheat (14)(15)(16)(17)(18)(19)(20). Because the molecular basis underlying RS production is largely unknown, discovery of new RS genes is vital both for the elucidation of RS biosynthesis and for the breeding of high-RS varieties. We therefore screened a mutagenized population of the hybrid-rice restorer line R7954 for mutants with high RS in hot cooked rice. This strategy was designed to identify new RS genes of practical value ...

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“…Based on our findings in this work and published results (32)(33)(34)(35), we now propose a RS biosynthetic pathway (Fig. 6).…”

Section: Discussionsupporting

confidence: 74%

Section: Discussionmentioning

confidence: 99%

Critical roles of soluble starch synthase SSIIIa and granule-bound starch synthase Waxy in synthesizing resistant starch in rice

Zhou

Wang

Liu

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

178

172

View full text Add to dashboard Cite

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“…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. In addition, the fact that SBEs were inhibited gradually along with endosperm development in TRS supported this idea again ( A series of biochemical evidence has shown that SBEs are prone to forming a great variety of multisubunit complexes with SSs, DBEs, and Pho1 in the soluble fraction of amyloplasts in order to function (Hennen-Bierwagen et al, 2008Crofts et al, 2015). This fact, coupled with the complexity of starch development, makes it difficult to quantity SBEs that act directly on starch formation in TRS heterogeneous granules.…”

Section: Dynamic Deposition Of Amylopectin Biosynthetic Enzymes In Thmentioning

confidence: 86%

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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“…However, the loss of SBEI in a SBEIIb-deficient background in maize caused increased branching of amylopectin [287], and the researchers postulated that this result was suggestive of a regulatory role for SBEI in influencing the catalytic activity of other SBE isoforms. Indeed, physical interactions between SBEI and SBEIIb have been reported in endosperm amyloplasts from a number of sources [288][289][290][291]. SBEI's role in determination of amylopectin structure may be rather more subtle, as suggested by one recent study showing reduced germination efficiency of SBEI-deficient maize kernels [292].…”

Section: Branch Linkage Formation By Starch Branching Enzymesmentioning

confidence: 99%

Starch Biosynthesis in the Developing Endosperms of Grasses and Cereals

Tetlow

Emes

2017

Agronomy

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Abstract:The starch-rich endosperms of the Poaceae, which includes wild grasses and their domesticated descendents the cereals, have provided humankind and their livestock with the bulk of their daily calories since the dawn of civilization up to the present day. There are currently unprecedented pressures on global food supplies, largely resulting from population growth, loss of agricultural land that is linked to increased urbanization, and climate change. Since cereal yields essentially underpin world food and feed supply, it is critical that we understand the biological factors contributing to crop yields. In particular, it is important to understand the biochemical pathway that is involved in starch biosynthesis, since this pathway is the major yield determinant in the seeds of six out of the top seven crops grown worldwide. This review outlines the critical stages of growth and development of the endosperm tissue in the Poaceae, including discussion of carbon provision to the growing sink tissue. The main body of the review presents a current view of our understanding of storage starch biosynthesis, which occurs inside the amyloplasts of developing endosperms.

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Amylopectin biosynthetic enzymes from developing rice seed form enzymatically active protein complexes

Abstract: HighlightStarch biosynthetic enzymes in rice endosperm are physically associated with each other and form enzymatically active multiple protein–protein complexes, several of which were common to cereals while others were unique.

Cited by 125 publications

References 72 publications

Critical roles of soluble starch synthase SSIIIa and granule-bound starch synthase Waxy in synthesizing resistant starch in rice

Critical roles of soluble starch synthase SSIIIa and granule-bound starch synthase Waxy in synthesizing resistant starch in rice

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

Starch Biosynthesis in the Developing Endosperms of Grasses and Cereals

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