MutMapPlus identified novel mutant alleles of a rice <i>starch branching enzyme <scp>II</scp>b</i> gene for fine‐tuning of cooked rice texture

Nakata, Masaru; Miyashita, Tomomi; Kimura, Rieko; Nakata, Yuriko; Takagi, Hiroki; Kuroda, Masaharu; Yamaguchi, Takeshi; Umemoto, Takayuki; Yamakawa, Hiromoto

doi:10.1111/pbi.12753

Cited by 49 publications

(33 citation statements)

References 56 publications

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“…Besides GBSSI , we did not detect the QTNs from candidates involved in starch biosynthesis, namely starch synthase IIa ( SSIIa ) (Umemoto et al, 2002 ; Nakamura et al, 2005 ), starch branching enzyme ( SBE IIb ) (Nishi et al, 2001 ; Tanaka et al, 2004 ; Nakata et al, 2018 ), as the RDP panel employed in the present study belongs to indica population. From the past studies, variation in SSIIa alleles were identified by exploring inter species genetic variation between indica compared to japonica , due to enrichment of the intermediate amylopectin chains (DP 12–24) (Umemoto et al, 2002 , 2004 ).…”

Section: Discussionmentioning

confidence: 62%

Deciphering the Genetic Architecture of Cooked Rice Texture

et al. 2018

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The textural attributes of cooked rice determine palatability and consumer acceptance. Henceforth, understanding the underlying genetic basis is pivotal for the genetic improvement of preferred textural attributes in breeding programs. We characterized diverse set of 236 Indica accessions from 37 countries for textural attributes, which includes adhesiveness (ADH), hardness (HRD), springiness (SPR), and cohesiveness (COH) as well as amylose content (AC). A set of 147,692 high quality SNPs resulting from genotyping data of 700K high Density Rice Array (HDRA) derived from the Indica diversity panels of 218 lines were retained for marker-trait associations of textural attributes using single-locus (SL) genome wide association studies (GWAS) which resulted in identifying hotspot on chromosome 6 for AC and ADH attributes. Four independent multi-locus approaches (ML-GWAS) including FASTmrEMMA, pLARmEB, mrMLM, and ISIS_EM-BLASSO were implemented to dissect additional loci of major/minor effects influencing the rice texture and to overcome limitations of SL-based GWAS approach. In total 224 significant quantitative trait nucleotide (QTNs) were identified using ML-GWAS, of which 97 were validated with at least two out of the four multi-locus methods. The GWAS results were in accordance with the very significant negative correlation (r = −0.83) observed between AC and ADH, and the significant correlation exhibited by AC (r < 0.4) with HRD, SPR, and COH. The novel haplotypes and putative candidate genes influencing textural properties beyond AC will be a useful resource for deployment into the marker assisted program to capture consumer preferences influencing rice texture and palatability.

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Section: Discussionmentioning

confidence: 62%

Deciphering the Genetic Architecture of Cooked Rice Texture

et al. 2018

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“…Rice be2b single mutant plants produce opaque seeds that weigh less than wild-type (WT) seeds (Nishi et al 2001;Matsushima et al 2012). Amylopectin chain length distribution analyses show that the be2b single mutants produce signi cantly less short amylopectin chains, with degree of polymerization (DP) = 6-12 (Nishi et al 2001;Asai et al 2014;Nakata et al 2018); therefore, BEIIb is thought to produce branch points of A and B 1 chains of amylopectin. The reduction of starch synthase I (SSI) activity is accompanied by the loss of BEIIb in rice (Nishi et al 2001).…”

Section: Introductionmentioning

confidence: 99%

Generation and Starch Characterization of Non-Transgenic BEI and BEIIb Double Mutant Rice (Oryza sativa) with Ultra-high Level of Resistant Starch

Miura¹,

Koyama²,

Crofts³

et al. 2020

Preprint

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Background Cereals high in resistant starch (RS) are gaining popularity, as their intake is thought to help manage diabetes and prediabetes. Number of patients suffering from diabetes is also increasing in Asian countries where people consume rice as a staple food, hence generation of practically growable high RS rice line has been anticipated. It is known that suppression of starch branching enzyme (BE) IIb increases RS content in cereals. To further increase RS content and for more practical use, we generated a non-transgenic be1 be2b double mutant rice (Oryza sativa) line, which completely lacked both proteins, by crossing a be1 mutant with a be2b mutant. Results The be1 be2b mutant showed a decrease in intermediate amylopectin chains and an increase in long amylopectin chains compared with be2b. The amylose content of be1 be2b mutant (51.7%) was the highest among all pre-existing non-transgenic rice lines. To understand the effects of chewing steamed rice and cooking rice flour on RS content, RS content of mashed and un-mashed steamed rice as well as raw and gelatinized rice flour were measured using be1 be2b and its parent mutant lines. The RS contents of mashed steamed rice and raw rice flour of be1 be2b mutant (28.4% and 35.1%, respectively) were 3-fold higher than those of be2b mutant. Gel-filtration analyses of starch treated with digestive enzymes showed that the RS in be1 be2b mutant was composed of the degradation products of amylose and long amylopectin chains. Seed weight of be1 be2b mutant was approximately 60% of the wild type and rather heavier than that of be2b mutant. Conclusions The endosperm starch in be1 be2b double mutant rice were enriched with long amylopectin chains. This led to a great increase in RS content in steamed rice grains and rice flour in be1 be2b compared with be2b single mutant. be1 be2b generated in this study must serve as a good material for an ultra-high RS rice cultivar.

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“…When BEIIb activity is absent, regardless of the presence or absence of BEIIb, amylopectin structure is drastically altered such that the number of short chains (DP < 17), particularly DP 8–12, is reduced and the number of long chains is increased (Nishi et al, 2001; Tanaka et al, 2004; Matsushima et al, 2010; Butardo et al, 2011; Nakata et al, 2018). In addition, the absence or reduction of BEIIb changes the crystallinity of starch, increases its gelatinization temperature, and lowers solubility in alkaline solutions (Nishi et al, 2001; Tanaka et al, 2004; Matsushima et al, 2010; Butardo et al, 2011; Nakata et al, 2018). Furthermore, the absence of both SSI and BEIIb proteins in japonica rice leads to sterility although a double mutant with reduced SSI levels and lacking BEIIb is able to generate seeds (Abe et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

Rice Mutants Lacking Starch Synthase I or Branching Enzyme IIb Activity Altered Starch Biosynthetic Protein Complexes

et al. 2018

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Amylopectin, the major component of starch, is synthesized by synergistic activity of multiple isozymes of starch synthases (SSs) and branching enzymes (BEs). The frequency and length of amylopectin branches determine the functionality of starch. In the rice endosperm, BEIIb generates short side chains of amylopectin and SSI elongates those branches, which can be further elongated by SSIIa. Absence of these enzymes greatly affects amylopectin structure. SSI, SSIIa, and BEIIb associate with each other and with other starch biosynthetic enzymes although SSIIa is low activity in japonica rice. The aim of the current study was to understand how the activity of starch biosynthetic enzyme complexes is compensated in the absence of SSI or BEIIb, and whether the compensatory effects are different in the absence of BEIIb or in the presence of inactive BEIIb. Interactions between starch biosynthetic enzymes were analyzed using one ss1 null mutant and two be2b japonica rice mutants (a mutant producing inactive BEIIb and a mutant that did not produce BEIIb). Soluble proteins extracted from the developing rice seeds were separated by gel filtration chromatography. In the absence of BEIIb activity, BEIIa was eluted in a broad molecular weight range (60–700 kDa). BEIIa in the wild-type was eluted with a mass below 300 kDa. Further, majority of inactive BEIIb co-eluted with SSI, SSIIa, and BEI, in a mass fraction over 700 kDa, whereas only small amounts of these isozymes were found in the wild-type. Compared with the be2b lines, the ss1 mutant showed subtle differences in protein profiles, but the amounts of SSIIa, SSIVb, and BEI in the over-700–kDa fraction were elevated. Immunoprecipitation revealed reduced association of SSIIa and BEIIb in the ss1 mutant, while the association of BEIIb with SSI, SSIIa, SSIVb, BEI, and BEIIa were more pronounced in the be2b mutant that produced inactive BEIIb enzyme. Mass spectrometry and western blotting revealed that SSI, SSIIa, SSIIIa, BEI, BEIIa, starch phosphorylase 1, and pullulanase were bound to the starch granules in the be2b mutants, but not in the wild-type and ss1 mutant. These results will aid the understanding of the mechanism of amylopectin biosynthesis.

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MutMapPlus identified novel mutant alleles of a rice starch branching enzyme IIb gene for fine‐tuning of cooked rice texture

Cited by 49 publications

References 56 publications

Deciphering the Genetic Architecture of Cooked Rice Texture

Deciphering the Genetic Architecture of Cooked Rice Texture

Generation and Starch Characterization of Non-Transgenic BEI and BEIIb Double Mutant Rice (Oryza sativa) with Ultra-high Level of Resistant Starch

Rice Mutants Lacking Starch Synthase I or Branching Enzyme IIb Activity Altered Starch Biosynthetic Protein Complexes

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