Development and characterization of a new rice cultivar, 'Chikushi-kona 85', derived from a starch-branching enzyme IIb-deficient mutant line.

A new super-hard rice cultivar, 'Chikushi-kona 85', which was derived from a cross between 'Fukei 2032' and 'EM129', was developed via bulk method breeding. 'Chikushi-kona 85' showed a higher content of resistant starch than the normal non-glutinous rice cultivar, 'Nishihomare', and a higher grain yield than the first super-hard rice cultivar, 'EM10'. The amylopectin chain length of 'Chikushi-kona 85' and its progenitor line 'EM129' was longer than that of 'Nishihomare', and was similar to that of 'EM10'.

Rice Endosperm Starch Phosphorylase (Pho1) Assembles with Disproportionating Enzyme (Dpe1) to Form a Protein Complex That Enhances Synthesis of Malto-oligosaccharides.

Starch synthesis in cereal grain endosperm is dependent on the concerted actions of many enzymes. The starch plastidial phosphorylase (Pho1) plays an important role in the initiation of starch synthesis and in the maturation of starch granule in developing rice seeds. Prior evidence has suggested that the rice enzyme, OsPho1, may have a physical/functional interaction with other starch biosynthetic enzymes.

Development and evaluation of rice giant embryo mutants for high oil content originated from a high-yielding cultivar 'Mizuhochikara'.

Rice bran oil is a byproduct of the milling of rice (Oryza sativa L.). It offers various health benefits and has a beneficial fatty acid composition.

Analysis of the Rice ADP-Glucose Transporter (OsBT1) Indicates the Presence of Regulatory Processes in the Amyloplast Stroma That Control ADP-Glucose Flux into Starch.

Previous studies showed that efforts to further elevate starch synthesis in rice (Oryza sativa) seeds overproducing ADP-glucose (ADPglc) were prevented by processes downstream of ADPglc synthesis. Here, we identified the major ADPglc transporter by studying the shrunken3 locus of the EM1093 rice line, which harbors a mutation in the BRITTLE1 (BT1) adenylate transporter (OsBt1) gene. Despite containing elevated ADPglc levels (approximately 10-fold) compared with the wild-type, EM1093 grains are small and shriveled due to the reduction in the amounts and size of starch granules.

The plastidial starch phosphorylase from rice endosperm: catalytic properties at low temperature.

Consistent with its essential role in starch biosynthesis at low temperatures, the plastidial starch phosphorylase from rice endosperm is highly active at low temperature. Moreover, contrary to results on other higher plant phosphorylases, the L80 peptide, a domain unique to plant phosphorylases and not present in orthologous phosphorylases from other organisms, is not involved in enzyme catalysis. Starch phosphorylase (Pho) is an essential enzyme in starch synthesis in developing rice endosperm as the enzyme plays a critical role in both the early and maturation phases of starch granule formation especially at low temperature.

Development of formulae for estimating amylose content, amylopectin chain length distribution, and resistant starch content based on the iodine absorption curve of rice starch.

Not only amylose but also amylopectin greatly affects the gelatinization properties of rice starch and the quality of cooked rice grains. We here characterized the starches of 32 rice cultivars and evaluated the relationship between their iodine absorption curve, apparent amylose content (AAC), pasting property, resistant starch (RS) content, and chain length distribution of amylopectin. We found that the iodine absorption curve differed among the various sample rice cultivars.

Influence of single-nucleotide polymorphisms in the gene encoding granule-bound starch synthase I on amylose content in Vietnamese rice cultivars.

Amylose content is one of the most important factors influencing the physical and chemical properties of starch in rice. Analysis of 352 Vietnamese rice cultivars revealed a wide range of variation in apparent amylose content and the expression level of granule-bound starch synthase. On the basis of single-nucleotide polymorphisms (SNP) at the splicing donor site of the first intron and in the coding region of the granule-bound starch synthase I gene, Waxy gene, alleles can be classified into seven groups that reflect differences in apparent amylose content.

The rice endosperm ADP-glucose pyrophosphorylase large subunit is essential for optimal catalysis and allosteric regulation of the heterotetrameric enzyme.

Although an alternative pathway has been suggested, the prevailing view is that starch synthesis in cereal endosperm is controlled by the activity of the cytosolic isoform of ADPglucose pyrophosphorylase (AGPase). In rice, the cytosolic AGPase isoform is encoded by the OsAGPS2b and OsAGPL2 genes, which code for the small (S2b) and large (L2) subunits of the heterotetrameric enzyme, respectively. In this study, we isolated several allelic missense and nonsense OsAGPL2 mutants by N-methyl-N-nitrosourea (MNU) treatment of fertilized egg cells and by TILLING (Targeting Induced Local Lesions in Genomes).

Improved palatability and bio-functionality of super-hard rice by soaking in a barley-koji miso suspension.

Cooked grains of ae rice cultivars are too hard and non-sticky due to the presence of long-chain amylopectin, and ae rice cultivars are therefore called ``super-hard rice'' and cannot be used as table rice. However, they are promising in terms of their bio-functionality such as preventing diabetes. Miso (soybean paste) is a yeast-fermented food, made from steamed soybeans, salt, and inoculated cereals known as koji, made from rice, barley, or soybeans.

Hepatic steatosis with relation to increased expression of peroxisome proliferator-activated receptor-γ in insulin resistant mice.

We have isolated insulin resistant mice (ddY-H mice) which are spontaneously induced even if fed with the standard chow pellets. Since marked accumulation of triglycerides (TG) in liver was observed, the present study investigated causes of hepatic TG accumulation in ddY-H mice fed with the standard chow pellets. In ddY-H mice, hepatic TG content increased from seven-weeks of age, and further marked accumulation of TG was observed at 20-weeks of age.

Wx/ae double-mutant brown rice prevents the rise in plasma lipid and glucose levels in mice.

A wx/ae double-mutant rice is generated by crossing waxy mutant and amylose-extender mutant in rice. Wx/ae brown rice contains highly beneficial nutrients for lipid and glucose metabolism, including resistant starch, dietary fiber, and γ-oryzanol, when compared to Koshihikari brown rice, the non-waxy japonica cultivar. To examine the effects of wx/ae brown rice on glucose and lipid metabolism, type 2 diabetic NSY/Hos mice were fed a high-fat diet containing 25% of wx/ae brown rice or Koshihikari brown rice for 10 weeks.

The OsGEN-L protein from Oryza sativa possesses Holliday junction resolvase activity as well as 5'-flap endonuclease activity.

OsGEN-L has a 5'-flap endonuclease activity and plays an essential role in rice microspore development. The Class 4 RAD2/XPG family nucleases, including OsGEN-L, were recently found to have resolving activity for the Holliday junction (HJ), the intermediate of DNA strand recombination. In this study, we performed a detailed characterization of OsGEN-L, as a structure-specific endonuclease.

RNA targeting to a specific ER sub-domain is required for efficient transport and packaging of α-globulins to the protein storage vacuole in developing rice endosperm.

Studies focusing on the targeting of RNAs that encode rice storage proteins, prolamines and glutelins to specific sub-domains of the endoplasmic reticulum (ER), as well as mis-localization studies of other storage protein RNAs, indicate a close relationship between the ER site of RNA translation and the final site of protein deposition in the endomembrane system in developing rice endosperm. In addition to prolamine and glutelin, rice accumulates smaller amounts of α-globulins, which are deposited together with glutelin in the protein storage vacuole (PSV). In situ RT-PCR analysis revealed that α-globulin RNAs are not distributed to the cisternal ER as expected for a PSV-localized protein, but instead are targeted to the protein body-ER (PB-ER) by a regulated process requiring cis-sorting sequences.

Characteristics of pregelatinized ae mutant rice flours prepared by boiling after preroasting.

As ae mutant rice, such as EM10, lacks the starch branching enzyme IIb, its amylopectin contains more long-chain glucans than that of ordinary Indica and Japonica rice grains. Although boiled grains of ae rice cultivars are too hard and nonsticky for table rice, they are promising in terms of biofunctionality, such as prevention of diabetes. The present paper investigates the characterization of a novel group of four ae mutant rice cultivars (EM72, EM145, EM174, and EM189).

Genetic analysis of cysteine-poor prolamin polypeptides reduced in the endosperm of the rice esp1 mutant.

The esp1 mutant CM21 specifically exhibits reduced levels of cysteine-poor (CysP) prolamin bands with pIs of 6.65, 6.95, 7.

Crystal structure of the branching enzyme I (BEI) from Oryza sativa L with implications for catalysis and substrate binding.

Starch-branching enzyme catalyzes the cleavage of α-1, 4-linkages and the subsequent transfer of α-1,4 glucan to form an α-1,6 branch point in amylopectin. Sequence analysis of the rice-branching enzyme I (BEI) indicated a modular structure in which the central α-amylase domain is flanked on each side by the N-terminal carbohydrate-binding module 48 and the α-amylase C-domain. We determined the crystal structure of BEI at a resolution of 1.

A novel factor FLOURY ENDOSPERM2 is involved in regulation of rice grain size and starch quality.

Rice (Oryza sativa) endosperm accumulates a massive amount of storage starch and storage proteins during seed development. However, little is known about the regulatory system involved in the production of storage substances. The rice flo2 mutation resulted in reduced grain size and starch quality.

Protein disulfide isomerase like 1-1 participates in the maturation of proglutelin within the endoplasmic reticulum in rice endosperm.

The rice esp2 mutation was previously characterized by the abnormal accumulation of elevated levels of proglutelin and the absence of an endosperm-specific protein disulfide isomerase like (PDIL1-1). Here we show that Esp2 is the structural gene for PDIL1-1 and that this lumenal chaperone is asymmetrically distributed within the cortical endoplasmic reticulum (ER) and largely restricted to the cisternal ER. Temporal studies indicate that PDIL1-1 is essential for the maturation of proglutelin only when its rate of synthesis significantly exceeds its export from the ER, a condition resulting in its build up in the ER lumen and the induction of ER quality control processes which lower glutelin levels as well as those of the other storage proteins.

Palatable and bio-functional wheat/rice products developed from pre-germinated brown rice of super-hard cultivar EM10.

It became possible to produce high-quality and bio-functional wheat/rice bread and wheat/rice noodles by blending, pre-germinated and cooked brown rice of a super-hard cultivar with wheat flour. Super-hard rice (SHR) is not suitable for table rice because of its low palatability. Nevertheless, it was found to be suitable as a blending material for bread-making or noodle-making due to its hard texture and high content of resistant starch.

Structure, physical, and digestive properties of starch from wx ae double-mutant rice.

Amylopectin is the principal component of starch. The amylose extender (ae) gene encodes the starch-branching enzyme IIb, which is critical in determining the fine structure of endosperm starch. To determine the relationship between the fine structure of amylopectin and its physical properties, rice mutant lines defective in the ae function with altered fine structure of amylopectin and in combination with the waxy (wx) background were selected for comparative studies with primary wild-type and ae starches.

Development of coenzyme Q10-enriched rice using sugary and shrunken mutants.

Coenzyme Q10 (CoQ10) is a popular food supplement. Earlier, we successfully produced CoQ10 in rice, which normally produces predominately CoQ9. Here we developed efficient production of CoQ10 in rice by introducing the gene for decaprenyl diphosphate synthase into rice sugary and shrunken mutants.

Rice endosperm-specific plastidial alpha-glucan phosphorylase is important for synthesis of short-chain malto-oligosaccharides.

Previous genetic studies have indicated that the type L alpha-glucan phosphorylase (Pho1) has an essential role during the initiation process of starch biosynthesis during rice seed development. To gain insight into its role in starch metabolism, we characterized the enzymatic properties of the Pho1 recombinant form. Pho1 has significantly higher catalytic efficiency toward both linear and branched alpha-glucans in the synthesis direction than in the degradation direction with equilibrium constants for the various substrates ranging from 13 to 45.

Vacuolar processing enzyme plays an essential role in the crystalline structure of glutelin in rice seed.

To identify the function of genes that regulate the processing of proglutelin, we performed an analysis of glup3 mutants, which accumulates excess amounts of proglutelin and lack the vacuolar processing enzyme (VPE). VPE activity in developing seeds from glup3 lines was reduced remarkably compared with the wild type. DNA sequencing of the VPE gene in glup3 mutants revealed either amino acid substitutions or the appearance of a stop codon within the coding region.

The action of rice branching enzyme I (BEI) on starches.

The rice branching enzyme I (BEI) overproduced in Escherichia coli cells was investigated with respect to action on starches. BEI treatment decreased the turbidity of starch suspensions with distinct pasting behaviors from a native starch. This result suggests the great potential of BEI as a molecular tool for the production of a novel glucan polymer.

The ADAXIALIZED LEAF1 gene functions in leaf and embryonic pattern formation in rice.

The adaxial-abaxial axis in leaf primordia is thought to be established first and is necessary for the expansion of the leaf lamina along the mediolateral axis. To understand axis information in leaf development, we isolated the adaxialized leaf1 (adl1) mutant in rice, which forms abaxially rolled leaves. adl1 leaves are covered with bulliform-like cells, which are normally distributed only on the adaxial surface.