Floury Endosperm Research Articles

A deleterious Sar1c variant in rice inhibits export of seed storage proteins from the endoplasmic reticulum.

We identified a dosage-dependent dominant negative form of Sar1c, which confirms the essential role of COPII system in mediating ER export of storage proteins in rice endosperm. Higher plants accumlate large amounts of seed storage proteins (SSPs). However, mechanisms underlying SSP trafficking are largely unknown, especially the ER-Golgi anterograde process. Here, we showed that a rice glutelin precursor accumulation13 (gpa13) mutant exhibited floury endosperm and overaccumulated glutelin precursors, which phenocopied the reported RNAi-Sar1abc line. Molecular cloning revealed that the gpa13 allele encodes a mutated Sar1c (mSar1c) with a deletion of two conserved amino acids Pro134 and Try135. Knockdown or knockout of Sar1c alone caused no obvious phenotype, while overexpression of mSar1c resulted in seedling lethality similar to the gpa13 mutant. Transient expression experiment in tobacco combined with subcellular fractionation experiment in gpa13 demonstrated that the expression of mSar1c affects the subcellular distribution of all Sar1 isoforms and Sec23c. In addition, mSar1c failed to interact with COPII component Sec23. Conversely, mSar1c competed with Sar1a/b/d to interact with guanine nucleotide exchange factor Sec12. Together, we identified a dosage-dependent dominant negative form of Sar1c, which confirms the essential role of COPII system in mediating ER export of storage proteins in rice endosperm.

Early Maturing Rice Variety “Baromi2” with a Floury Endosperm and Suitable for Dry-Milling of Rice Grain

Su Kyung Ha, Bo-Kyeong Kim, Woon-Ha Hwang, Young-Jun Mo, Jong-Min Jeong, Dong-Kyu Lee, Woo-Jae Kim, Jeong-Ju Kim, and Ji-Ung Jeung. Korean J. Breed. Sci. 2022;54:433-41. https://doi.org/10.9787/KJBS.2022.54.4.433

Physical and Chemical Characteristics of Native Maize from the Jalisco Highlands and Their Influence on the Nixtamalization Process

From a cultural point of view, Maize is the most important crop in Mexico, and is also an essential food in the Mexican diet. This study aimed to evaluate the physical and chemical characteristics of maize grain and their influence on the quality of dough and tortillas produced with three native maize cultivars from western Mexico. Physical, structural, and chemical characteristics of the grain were evaluated, including hectolitric weight, 100-grain weight, flotation index, grain structure, grain color, pedicel, pericarp, germ, and floury endosperm, vitreous endosperm, ethereal extract, and protein. Nixtamal and tortilla quality include nixtamal moisture, dough moisture, freshly made tortilla moisture, total soluble solids, pericarp remnant, dough yield, and hot tortilla yield. In general, statistical differences (p ≤ 0.05) were found in almost all variables analyzed. The principal component analysis (PCA) showed that two principal components (PCs), described approximately 79% of the variation, and a positive correlation between the characteristics of freshly made tortilla moisture (FMTM), dough yield (DY), and nixtamal moisture (NM), as well as dough moisture (DM) and hot tortilla yield (HTY). Future studies on these and other native maize cultivars of western Mexico must be conducted to assess the physicochemical and phytochemical characteristics of maize grains that may be useful for food and pharmaceutical applications, contributing to the conservation, propagation, and use of natural and ancient resources.

Biochemical analysis of a novel allele of the OsPPDKB gene associated with floury endosperm

Here we isolated and characterized floTR1, a new floury endosperm rice mutant. Whole genome sequence and analysis of a cleaved amplified polymorphic sequence marker found that the FloTR1 gene encodes a pyruvate orthophosphate dikinase B (OsPPDKB). The floTR1 mutant has a single G to A base substitution in the OsPPDKB gene, which results in a missense glycine to aspartate mutation. Although there was little change in the mRNA expression levels of OsPPDKB between floTR1 and the original variety (WT) plants, PPDK activity in the floTR1 developing endosperm was null. Recombinant enzyme analysis also found that aspartate replacement, as found in floTR1, resulted in the complete loss of PPDK activity in vitro. Analysis of other recombinant enzymes suggested that the spatial configuration such as size and direction of the side chain in the replaced amino acids predominantly affected its activity. The rice flour of floTR1 showed not only smaller particle size distribution and lower damaged starch content but also higher specific rice bread loaf volume than WT. Our data provides new insights into effects on OsPPDK activity caused by a SNP mutation and suggests applications for this new floury rice mutant.

Dynamic Transcriptome-Based Weighted Gene Co-expression Network Analysis Reveals Key Modules and Hub Genes Associated With the Structure and Nutrient Formation of Endosperm for Wax Corn.

The endosperm of corn kernel consists of two components, a horny endosperm, and a floury endosperm. In the experiment, a kind of floury endosperm corn was identified. The result of phenotypic trait analysis and determination of amino acid content showed that the floury endosperm filled with the small, loose, and scattered irregular spherical shape starch granules and contained higher content of amino acid. The starch biochemical properties are similar between floury corns and regular flint corn. By using dynamically comparative transcriptome analysis of endosperm at 20, 25, and 30 DAP, a total of 113.42 million raw reads and 50.508 thousand genes were obtained. By using the weighted gene co-expression network analysis, 806 genes and six modules were identified. And the turquoise module with 459 genes was proved to be the key module closely related to the floury endosperm formation. Nine zein genes in turquoise module, including two zein-alpha A20 (Zm00001d019155 and Zm00001d019156), two zein-alpha A30 (Zm00001d048849 and Zm00001d048850), one 50 kDa gamma-zein (Zm00001d020591), one 22 kDa alpha-zein 14 (Zm00001d048817), one zein-alpha 19D1 (Zm00001d030855), one zein-alpha 19B1 (Zm00001d048848), and one FLOURY 2 (Zm00001d048808) were identified closely related the floury endosperm formation. Both zein-alpha 19B1 (Zm00001d048848) and zein-alpha A30 (Zm00001d048850) function as source genes with the highest expression level in floury endosperm. These results may provide the supplementary molecular mechanism of structure and nutrient formation for the floury endosperm of maize.

Substandard starch grain4 may function in amyloplast development by influencing starch and lipid metabolism in rice endosperm

The amyloplast is a specialized plastid in rice endosperm cells where starch is synthesized and stored as starch granules (SGs). However, little is known about the molecular mechanism underlying amyloplast and SG development. In this study, a novel mutant (c134) demonstrating a floury endosperm with enlarged SGs and amyloplasts was identified. The floury endosperm was caused by rounder, loosely packed SG. Grain-quality profile and expression analysis showed reduced contents of total starch and amylose in the c134 mutant, as well as reduced expression of a number of genes involved in starch biosynthesis. Galactosyldiacylglycerol (GDG) content and fatty acid synthesis play important roles in plastid development, and in the c134 endosperm, an obvious decrease in GDG and various fatty acids was observed, with down-regulated expression of various genes involved in lipid biosynthesis. Furthermore, map-based cloning revealed an amino acid substitution (glycine to aspartic acid) in the substandard starch grain4 (SSG4) protein. The results of this study suggest that SSG4 influences the regulation of starch and lipid metabolism as well as amyloplast development, a finding that is useful for potential genetic improvement of rice grain quality in future starch and lipid breeding and biotechnology.

The induced mutant allele flo4-303 confers floury characteristics on the japonica rice cultivar 'Hoshinoko'.

Rice flour is useful as a substitute for wheat flour, however, to obtain fine flour, millers need special milling facilities, which increase the cost of milling. To reduce the milling cost, we developed a floury mutant line by irradiating gamma-rays to dry seeds of the japonica cultivar 'Hoshinoyume'. The line was registered as a new cultivar, 'Hoshinoko'. Genetical analysis of the floury trait was conducted using an F2 population derived from a cross between 'Hoshinoko' and 'Corbetti' (a japonica rice cultivar with normal endosperm), which indicated the involvement of a single recessive gene located near the RM163 marker on the long arm of rice chromosome 5, flanking flo4 identified by Kang et al. (2005). Sequence analysis of flo4 showed a two-bp (CA) insertion in the eighth exon of in 'Hoshinoko' compared to that of 'Hoshinoyume', which led to a frameshift mutation. The CAPS-based genotype of flo4 gene completely correlated to the phenotype of endosperm in two populations. This CAPS marker could be helpful for rice breeders to develop new cultivars harboring floury endosperm of the flo4-303 gene.

Structure of heteroxylans from vitreous and floury endosperms of maize grain and impact on the enzymatic degradation

Heteroxylans (HX) from vitreous and floury parts of maize endosperm were isolated. Structural analysis showed a xylan backbone with few unsubstituted xylose residues (<9%) demonstrating the high content in side chains in both fractions. HX from floury endosperm contained more arabinose and galactose than vitreous HX. The mono-substitution rate was 15% higher in the vitreous endosperm HX. Similar amounts of uronic acids were present in both fractions (~7% DM). Galactose in the floury endosperm HX was present exclusively in terminal position. A xylanase preparation solubilized more material from floury (40.5%) than from vitreous endosperm cell walls (15%). This could be a consequence of the structural differences between the two fractions and/or of the impact of structure on the interaction abilities of these fractions with other cell wall polysaccharides.Our study advances the understanding of cell wall polysaccharides in maize endosperm and their role in enzymatic susceptibility of maize grain.

Plastidic pyruvate dehydrogenase complex E1 component subunit Alpha1 is involved in galactolipid biosynthesis required for amyloplast development in rice.

SummaryStarch accounts for over 80% of the total dry weight in cereal endosperm and determines the kernel texture and nutritional quality. Amyloplasts, terminally differentiated plastids, are responsible for starch biosynthesis and storage. We screened a series of rice mutants with floury endosperm to clarify the mechanism underlying amyloplast development and starch synthesis. We identified the floury endosperm19 (flo19) mutant which shows opaque of the interior endosperm. Abnormal compound starch grains (SGs) were present in the endosperm cells of the mutant. Molecular cloning revealed that the FLO19 allele encodes a plastid‐localized pyruvate dehydrogenase complex E1 component subunit α1 (ptPDC‐E1‐α1) that is expressed in all rice tissues. In vivo enzyme assays demonstrated that the flo19 mutant showed decreased activity of the plastidic pyruvate dehydrogenase complex. In addition, the amounts of monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG) were much lower in the developing flo19 mutant endosperm, suggesting that FLO19 participates in fatty acid supply for galactolipid biosynthesis in amyloplasts. FLO19 overexpression significantly increased seed size and weight, but did not affect other important agronomic traits, such as panicle length, tiller number and seed setting rate. An analysis of single nucleotide polymorphism data from a panel of rice accessions identified that the pFLO19L haplotype was positively associated with grain length, implying a potential application in rice breeding. In summary, our study demonstrates that FLO19 is involved in galactolipid biosynthesis which is essential for amyloplast development and starch biosynthesis in rice.

The CBM48 domain-containing protein FLO6 regulates starch synthesis by interacting with SSIVb and GBSS in rice.

FLO6 is involved in starch synthesis by interacting with SSIVb and GBSS in rice. Starch synthesized and stored in plastids including chloroplasts and amyloplasts plays a vital role in plant growth and provides the major energy for human diet. However, the molecular mechanisms by which regulate starch synthesis remain largely unknown. In this study, we identified and characterized a rice floury endosperm mutant M39, which exhibited defective starch granule formation in pericarp and endosperm, accompanied by the decreased starch content and amylose content. The abnormal starch accumulation in M39 pollen grains caused a significant decrease in plant fertility. Chloroplasts in M39 leaves contained no or only one large starch granule. Positional cloning combined with complementary experiment demonstrated that the mutant phenotypes were restored by the FLOURY ENDOSPERM6 (FLO6). FLO6 was generally expressed in various tissues, including leaf, anther and developing endosperm. FLO6 is a chloroplast and amyloplast-localized protein that is able to bind to starch by its carbohydrate-binding module 48 (CBM48) domain. Interestingly, we found that FLO6 interacted with starch synthase IVb (SSIVb) and granule-bound starch synthase (GBSSI and GBSSII). Together, our results suggested that FLO6 plays a critical role in starch synthesis through cooperating with several starch synthesis enzymes throughout plant growth and development.

Screening and identification of genes affecting grain quality and spikelet fertility during high-temperature treatment in grain filling stage of rice

BackgroundRecent temperature increases due to rapid climate change have negatively affected rice yield and grain quality. Particularly, high temperatures during right after the flowering stage reduce spikelet fertility, while interfering with sugar energy transport, and cause severe damage to grain quality by forming chalkiness grains. The effect of high-temperature on spikelet fertility and grain quality during grain filling stage was evaluated using a double haploid line derived from another culture of F1 by crossing Cheongcheong and Nagdong cultivars. Quantitative trait locus (QTL) mapping identifies candidate genes significantly associated with spikelet fertility and grain quality at high temperatures.ResultsOur analysis screened OsSFq3 that contributes to spikelet fertility and grain quality at high-temperature. OsSFq3 was fine-mapped in the region RM15749-RM15689 on chromosome 3, wherein four candidate genes related to the synthesis and decomposition of amylose, a starch component, were predicted. Four major candidate genes, including OsSFq3, and 10 different genes involved in the synthesis and decomposition of amylose and amylopectin, which are starch constituents, together with relative expression levels were analyzed. OsSFq3 was highly expressed during the initial stage of high-temperature treatment. It exhibited high homology with FLOURY ENDOSPERM 6 in Gramineae plants and is therefore expected to function similarly.ConclusionThe QTL, major candidate genes, and OsSFq3 identified herein could be effectively used in breeding rice varieties to improve grain quality, while tolerating high temperatures, to cope with climate changes. Furthermore, linked markers can aid in marker-assisted selection of high-quality and -yield rice varieties tolerant to high temperatures.

Effects of corn grain endosperm type and conservation method on feed intake, feeding behavior, and productive performance of lactating dairy cows

Our objective was to evaluate the effects of corn grain varying in endosperm type and conserved as high-moisture or dry ground corn on dry matter intake (DMI), feeding behavior, ruminal fermentation, and yields of milk and milk components of cows in early to mid-lactation. Seven ruminally and duodenally cannulated Holstein cows (73 ± 39 d in milk; mean ± SD) were used in a duplicated 4 × 4 Latin square design with 21-d periods. A 2 × 2 factorial arrangement of treatments was used with main effects of corn grain endosperm type (floury or vitreous) conserved as high-moisture corn (HMC) or dry ground corn (DGC). Rations were formulated to contain 27.0% starch, 26.6% neutral detergent fiber (NDF), 19.1% forage NDF, and 16.5% crude protein. Corn grain treatments supplied 86.6% of dietary starch and contained alfalfa silage as the sole forage. Dry matter intake was increased 1.3 kg/d by DGC compared with HMC. The increase in DMI by DGC was related to a shorter intermeal interval (104.4 vs. 118.2 min/d), and meal size was not affected by treatment. Dry ground corn decreased rumination bout length and number of chews per bout compared with HMC. No differences were detected between endosperm treatments for DMI, yields of milk, 3.5% fat-corrected milk (FCM), milk fat, protein, lactose, or solids-not-fat (SNF). Mean yield of 3.5% FCM across treatments was 47.5 kg/d. However, a tendency for an interaction was observed for feed efficiency; floury endosperm increased efficiency 0.05 kg 3.5% FCM per kg of DMI for DGC but decreased it by 0.14 kg 3.5% FCM per kg of DMI for HMC relative to vitreous endosperm. Vitreous compared with floury corn tended to increase true protein concentration in milk when conserved as DGC (2.68% vs. 2.62%) but not as HMC. Concentration of SNF was increased by DGC compared with HMC (8.45 vs. 8.37%) due, in part, to the effect of treatment on milk protein concentration. Body weight was not affected by treatment, but vitreous endosperm tended to increase loss of body condition compared with floury endosperm. Corn endosperm type and conservation method had little effect on productive performance of high-producing cows.

Rice FLOURY ENDOSPERM 18 encodes a pentatricopeptide repeat protein required for 5' processing of mitochondrial nad5 messenger RNA and endosperm development.

Pentatricopeptide repeat (PPR) proteins, composing one of the largest protein families in plants, are involved in RNA binding and regulation of organelle RNA metabolism at the post-transcriptional level. Although several PPR proteins have been implicated in endosperm development in rice (Oryza sativa), the molecular functions of many PPRs remain obscure. Here, we identified a rice endosperm mutant named floury endosperm 18 (flo18) with pleiotropic defects in both reproductive and vegetative development. Map-based cloning and complementation tests showed that FLO18 encodes a mitochondrion-targeted P-type PPR protein with 15 PPR motifs. Mitochondrial function was disrupted in the flo18 mutant, as evidenced by decreased assembly of Complex I in the mitochondrial electron transport chain and altered mitochondrial morphology. Loss of FLO18 function resulted in defective 5'-end processing of mitochondrial nad5 transcripts encoding subunit 5 of nicotinamide adenine dinucleotide hydrogenase. These results suggested that FLO18 is involved in 5'-end processing of nad5 messenger RNA and plays an important role in mitochondrial function and endosperm development.

Effect of Transplanting Date on the Growth, Yield, and Occurrence of Viviparity in Floury Endosperm Rice Cultivars in the Chungbuk Province

Effect of Transplanting Date on the Growth, Yield, and Occurrence of Viviparity in Floury Endosperm Rice Cultivars in the Chungbuk Province

Feature selection, artificial neural network prediction and experimental testing for predicting breakage rate of maize kernels based on mechanical properties

AbstractThe kernel breakage in harvest process is a significant problem which causes massive grain losses. In order to solve this problem, a possible solution is to predict the breakage rate and give suitable harvest time thus reducing grain losses. This study focused on using mechanical properties to predict breakage rate. Compression tests, compression–relaxation tests, insertion–retraction and stretch tests were conducted and 20 parameters were derived. Threshing tests were conducted to get breakage rate. As these parameters might be related and it is not practical to use massive parameters for prediction, the feature selection using neighborhood component analysis (FSNCA) was used for picking important parameters. The variables were compacted to an acceptable level by the FSNCA while various aspects of mechanical properties were included. The FSNCA determined the hardness of floury endosperm, rupture energy in vertical direction (x‐axis), allowable stress in lateral direction (z‐axis), hysteresis in x‐axis and elastic modulus in z‐axis as predictors. The artificial neural network (ANN) was built for prediction. The built ANN model showed an agreement in prediction results and real breakage rate (R = 0.98). The prediction error was ±1.7%.Practical ApplicationsThe mechanical properties were illustrated as potential indexes which can be utilized for predicting breakage rate of maize kernels in threshing process. The selection method reduced the dimension of predictors, which means fewer tests are required for prediction. As a result, this research proposed a possible solution for the prediction of maize breakage in harvest. Moreover, the prediction model can give guidance for optimal harvest time and thus reduce breakage rate in harvest.

Qualitative and Quantitative Analysis of Sorghum Grain Composition Including Protein and Tannins Using ATR-FTIR Spectroscopy

Chemical composition and grain quality traits are important factors related to the end-use quality of sorghum. Thus, rapid and non-destructive analytical methods for screening sorghum for desirable grain quality traits benefit the industries using sorghum for food, feed, and biofuels as well as sorghum breeders and seed companies working to improve the grain quality of sorghum. In the present study, a method based on Fourier-transform infrared spectroscopy (FTIR) was developed to characterize the major chemical components in sorghum flour. Sorghum flour had three major FTIR active regions from 1800 to 800 cm−1. As expected, FTIR spectra revealed that starch was the primary compound in sorghum flour, followed by protein with only minor amounts of lipids and phenolic acids. Phenolic acids were characterized by a peak at 1709 cm−1, which varied in intensity across sorghum varieties. Tannin sorghum could be discriminated from non-tannin sorghum by a shift in O–H stretch band around 3300 cm−1 and their C=C absorption peaks at 1608 and 1522 cm−1. Flour from the outer part of the kernel (corneous endosperm) had greater protein and lipid absorbance while the inner kernel (floury endosperm) had stronger starch absorbance. Pearson’s correlation analyses between FTIR peak intensities and protein/starch content showed that starch content did not have a significant correlation with infrared peaks, whereas the amide I peak at 1652 cm−1 (C=O stretching group), highly correlated with protein content (P ≤ 0.05). A calibration curve (Y = 127.79X-14.345, R2 = 0.9454) was built using peak height at 1652 cm−1 to predict protein content and this was applied to determining protein digestibility.

Mitochondrion-targeted PENTATRICOPEPTIDE REPEAT5 is required for cis-splicing of nad4 intron 3 and endosperm development in rice

Endosperm as the storage organ of starch and protein in cereal crops largely determines grain yield and quality. Despite the fact that several pentatricopeptide repeat (PPR) proteins required for endosperm development have been identified in rice, the molecular mechanisms of many P-type PPR proteins in endosperm development remains unclear. Here, we isolated a rice floury endosperm mutant ppr5 that developed small starch grains and an abnormal aleurone layer, accompanied by decreased starch, protein, and amylose contents. Map-based cloning combined with a complementation test demonstrated that PPR5 encodes a P-type PPR protein that is localized to the mitochondria. The mutation in PPR5 caused reduced splicing efficiency of mitochondrial NADH dehydrogenase 4 (nad4) gene intron 3 and reduced complex I assembly and activity. Loss of PPR5 function greatly up-regulated expression of alternative oxidases (AOXs), reduced ATP production, and affected mitochondrial morphology. We demonstrate that PPR5, as a P-type PPR protein, is required for mitochondrial function and endosperm development by controlling the cis-splicing of mitochondrial nad4 intron 3.

Effects of drying temperature and genotype on morphology and technological, thermal, and pasting properties of corn starch

The objective of this study was to evaluate the effects of drying temperature (30, 50, 70, and 90 °C) and genotype (yellow floury corn, white floury corn, and yellow flint corn) on the morphology and technological and thermal properties of corn starch. The white and yellow genotypes with floury endosperm (soft) had spherical starch granules, while the granules of the yellow flint genotype were polyhedral. White floury corn showed higher extraction yield, higher resistance during granules' swelling before the physical collapse, as it was not affected by the increase in drying temperature, and at 90 °C it presented higher breakdown and energy necessary for gelatinization. There were peak viscosity and gelatinization enthalpy reduction on starch from yellow floury corn and yellow flint corn according to the increase in drying temperature. Drying temperatures below 50 °C are indicated for all genotypes studied. White floury corn is indicated due to the higher extraction yield presented. Yellow floury corn is indicated for application in chilled and frozen products due to lower starch retrogradation. The yellow flint corn is indicated for application as a thickening agent due to higher gel hardness.

The composition of floury and vitreous endosperm affects starch digestibility kinetics of the whole maize kernel

Maize grain starch is the major energy source in animal nutrition, and its high digestion and utilization largely depend on endosperm traits and the structure of the starch-lipoprotein matrix. The aim of this work was to determine floury and vitreous endosperm traits and its relation to starch digestibility rate. In total, kernels of 30 hybrids were manually dissected, and amylose, total zein and starch and non-starch lipids were determined in both vitreous and floury endosperm. Starch digestibility of the whole kernel was determined based on glucose released during a two-step in vitro pig model of enzymatic digestion, and starch digestibility rate was calculated according to the first-order kinetics. The vitreous endosperm of tested hybrids had higher contents of amylose (204.6 vs 190.4 g/kg), zein (63.2 vs 40.4 k/kg) and starch lipids (5.6 vs 4.9 g/kg), and lower content of non-starch lipids (7.3 vs 9.6 g/kg) than floury endosperm. Digestibility coefficients varied among hybrids, and starch digestibility rate varied from 0.73 to 1.63 1/h. Lipids in both vitreous and floury endosperm negatively correlated with the most of digestion coefficients, whereas zein correlated in vitreous and amylose in the floury endosperm (P < 0.05). Starch digestibility rate negatively correlated with all traits, except amylose content in vitreous endosperm. As a result, a linear regression model with four variables including contents of zein and starch lipids in vitreous and zein and amylose in floury endosperm can predict more than 65% variability of starch digestibility rate of tested hybrids.

Relationship between the corneous and floury endosperm content and the popped sorghum quality

Popcorn is a healthy snack suggested by nutritionists. However, some countries in Europe, Asia, and South America have evaluated the use of sorghum as a popped cereal. Therefore, this study aims to evaluate the content of corneous and floury endosperm of sorghum and its influence in the popped sorghum quality. Five red varieties and three white varieties were evaluated. The physical and microstructural characteristics of the raw varieties were evaluated. The correlation matrix showed that physical properties such as the pericarp thickness, the hectoliter weight, and the type of endosperm are crucial to obtain popped sorghum. A high percentage of corneous endosperm and the size distribution of starch granules in the floury endosperm determine the popping ability of sorghum. The analysis of the principal components showed that the Paloma variety was the most suitable to obtain popped sorghum.