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Morphology of the seed endosperm in the flo5 mutants (b, d) and their respective wild type controls (a, c). Left panels dehusked seeds of Dongjin a, flo5-1 b, Hwayoung c, and flo5-2 d placed on an illuminator. Notably, in the flo5-1 and flo5-2 seed endosperms, a dark central portion is commonly evident and is characteristic of a white-core floury endosperm. Right panels horizontal and longitudinal sections of polished seed endosperms of flo5 mutants (b, d) and wild type rice plants (a, c). A central white-core floury endosperm is prominent in the flo5 mutants. Bar 2 mm
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To elucidate the role of SSIIIa during starch synthesis in rice (Oryza sativa L.) endosperm, we characterized null mutants of this gene, generated by T-DNA insertions. Scanning electron microscope (SEM) analysis revealed that the starch granules in these mutants are smaller and rounder compared with the wild type controls, and that the mutant endos...
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... central portion of the husked rice grains derived from the flo5-1 and flo5-2 mutant plants displays a white-core floury endosperm (Fig. 2b, d, left panel), which manifests as a sort of opaque phenotype, whereas the respective wild type control cultivars dis- play a transparent normal endosperm on an illuminator (Fig. 2a, c, left panel). Cross sectioning of the mature mutant rice grains further revealed that the central portion of the endosperm is indeed floury-like, whereas the exterior appears normal (Fig. 2b, d, right panel). This indicates that the disrupted process of starch synthesis resulting from the OsSSIIIa/Flo5 lesion leads to a deformity of the starch granules. In addition, we examined the effects of the flo5 mutations on grain weight but did not observe significant differences be- tween the wild type and flo5 mutant rice (data not shown). Morphology of the starch granules in the flo5 mutants To examine starch granule morphology, we performed SEM analysis using cut seed endosperm and purified starch granules (Fig. 3). In these experiments, cross- sectioned endosperm of polished rice grains revealed that the flo5 mutants have a loosely packed central portion (Fig. 3b, d, top and middle panels), probably due to their abnormal starch granule morphology. In contrast, the wild type control endosperm was found to be occupied by densely packed starch granules in the central portion (Fig. 3a, c, top and middle panels). The starch of both Dongjin and Hwayoung wild type cul- tivars was found to form as polygonal granules with a sharp edge, characteristic of the typical starch granule morphology in normal rice endosperm (Fig. 3a, c, bottom panel). In contrast, in the flo5-1 and flo5-2 mutants, the starch granules were observed to be smaller than that of the parental controls, and did not display the sharp edge seen in the wild type starch granules (Fig. 3b, d, bottom ...
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... central portion of the husked rice grains derived from the flo5-1 and flo5-2 mutant plants displays a white-core floury endosperm (Fig. 2b, d, left panel), which manifests as a sort of opaque phenotype, whereas the respective wild type control cultivars dis- play a transparent normal endosperm on an illuminator (Fig. 2a, c, left panel). Cross sectioning of the mature mutant rice grains further revealed that the central portion of the endosperm is indeed floury-like, whereas the exterior appears normal (Fig. 2b, d, right panel). This indicates that the disrupted process of starch synthesis resulting from the OsSSIIIa/Flo5 lesion leads to a deformity of the starch granules. In addition, we examined the effects of the flo5 mutations on grain weight but did not observe significant differences be- tween the wild type and flo5 mutant rice (data not shown). Morphology of the starch granules in the flo5 mutants To examine starch granule morphology, we performed SEM analysis using cut seed endosperm and purified starch granules (Fig. 3). In these experiments, cross- sectioned endosperm of polished rice grains revealed that the flo5 mutants have a loosely packed central portion (Fig. 3b, d, top and middle panels), probably due to their abnormal starch granule morphology. In contrast, the wild type control endosperm was found to be occupied by densely packed starch granules in the central portion (Fig. 3a, c, top and middle panels). The starch of both Dongjin and Hwayoung wild type cul- tivars was found to form as polygonal granules with a sharp edge, characteristic of the typical starch granule morphology in normal rice endosperm (Fig. 3a, c, bottom panel). In contrast, in the flo5-1 and flo5-2 mutants, the starch granules were observed to be smaller than that of the parental controls, and did not display the sharp edge seen in the wild type starch granules (Fig. 3b, d, bottom ...
Context 3
... central portion of the husked rice grains derived from the flo5-1 and flo5-2 mutant plants displays a white-core floury endosperm (Fig. 2b, d, left panel), which manifests as a sort of opaque phenotype, whereas the respective wild type control cultivars dis- play a transparent normal endosperm on an illuminator (Fig. 2a, c, left panel). Cross sectioning of the mature mutant rice grains further revealed that the central portion of the endosperm is indeed floury-like, whereas the exterior appears normal (Fig. 2b, d, right panel). This indicates that the disrupted process of starch synthesis resulting from the OsSSIIIa/Flo5 lesion leads to a deformity of the starch granules. In addition, we examined the effects of the flo5 mutations on grain weight but did not observe significant differences be- tween the wild type and flo5 mutant rice (data not shown). Morphology of the starch granules in the flo5 mutants To examine starch granule morphology, we performed SEM analysis using cut seed endosperm and purified starch granules (Fig. 3). In these experiments, cross- sectioned endosperm of polished rice grains revealed that the flo5 mutants have a loosely packed central portion (Fig. 3b, d, top and middle panels), probably due to their abnormal starch granule morphology. In contrast, the wild type control endosperm was found to be occupied by densely packed starch granules in the central portion (Fig. 3a, c, top and middle panels). The starch of both Dongjin and Hwayoung wild type cul- tivars was found to form as polygonal granules with a sharp edge, characteristic of the typical starch granule morphology in normal rice endosperm (Fig. 3a, c, bottom panel). In contrast, in the flo5-1 and flo5-2 mutants, the starch granules were observed to be smaller than that of the parental controls, and did not display the sharp edge seen in the wild type starch granules (Fig. 3b, d, bottom ...
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Gelatinisation temperature (GT) is one of the key traits measured in programs for breeding rice (Oryza sativa L.). It is commonly estimated by the alkali spreading value (ASV), and less commonly by differential scanning calorimetry (DSC). Using a diverse set of germplasm, it was determined that DSC values associate poorly with ASV, are not correlat...
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Abstract Background Resistant starch (RS) is beneficial for human health. Loss of starch branching enzyme IIb (BEIIb) increases the proportion of amylopectin long chains, which greatly elevates the RS content. Although high RS content cereals are desired, an increase in RS content is often accompanied by a decrease in seed weight. To further increa...
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... Furthermore, amylose is synthesized by granule-bound starch synthases (GBSSs; Martin & Smith, 1995;Hanashiro et al., 2008), whereas amylopectin biosynthesis is catalyzed by starch synthases (SSs), starch branching enzymes (BEs) and starch debranching enzymes (DBEs; James et al., 1995;Ball et al., 1996;Myers et al., 2000). Mutations in starch synthesis enzyme-encoding genes lead to disrupted starch biosynthesis and thus often produce chalky, floury or even shrunken endosperm (Nishi et al., 2001;Satoh et al., 2003;Kawagoe et al., 2005;Fujita et al., 2007Fujita et al., , 2011Ryoo et al., 2007;Toyosawa et al., 2016;Huang et al., 2021;Zhao et al., 2022). Despite this substantial knowledge, more regulators required for starch biosynthesis remain to be identified. ...
Endosperm is the main storage organ in cereal grain and determines grain yield and quality. The molecular mechanisms of heat shock proteins in regulating starch biosynthesis and endosperm development remain obscure.
Here, we report a rice floury endosperm mutant flo24 that develops abnormal starch grains in the central starchy endosperm cells. Map‐based cloning and complementation test showed that FLO24 encodes a heat shock protein HSP101, which is localized in plastids. The mutated protein FLO24T296I dramatically lost its ability to hydrolyze ATP and to rescue the thermotolerance defects of the yeast hsp104 mutant.
The flo24 mutant develops more severe floury endosperm when grown under high‐temperature conditions than normal conditions. And the FLO24 protein was dramatically induced at high temperature. FLO24 physically interacts with several key enzymes required for starch biosynthesis, including AGPL1, AGPL3 and PHO1. Combined biochemical and genetic evidence suggests that FLO24 acts cooperatively with HSP70cp‐2 to regulate starch biosynthesis and endosperm development in rice.
Our results reveal that FLO24 acts as an important regulator of endosperm development, which might function in maintaining the activities of enzymes involved in starch biosynthesis in rice.
... Mutations or changes in their expression can affect starch accumulation in the seed endosperm, resulting in a sugar endosperm phenotype [23]. Seven rice endosperm mutant genes have been reported: Flo1 [24], Flo2 [25], Flo3 [26], Flo4 [27], Flo5 [28,29], Flo6 [30], and Flo7 [31,32]. Among them, Flo3 produces a floury endosperm and reduces the 16 KD globulin content [26]. ...
... Among them, Flo3 produces a floury endosperm and reduces the 16 KD globulin content [26]. Flo5 causes the missing of the starch synthesis gene OsSSIIIa [28,29]. Flo6 encodes a protein that combines with starch isomerase to regulate starch synthesis and cooperates with isoamylase 1 (ISA1) in the amylopectin synthesis [30]. ...
The eating and cooking quality (ECQ) directly affects the taste of rice, being closely related to factors such as gelatinization temperature (GT), gel consistency (GC) and amylose content (AC). Mining the quantitative trait loci (QTLs), and gene loci controlling ECQ-related traits is vital. A genome-wide association study on ECQ-related traits was conducted, combining 1.2 million single nucleotide polymorphisms (SNPs) with the phenotypic data of 173 rice accessions. Two QTLs for GT, one for GC and five for AC were identified, of which two were found in previously reported genes, and six were newly found. There were 28 positional candidate genes in the region of qAC11. Based on a linkage disequilibrium (LD) analysis, three candidate genes were screened within the LD region associated with AC. There were significant differences between the haplotypes of LOC_Os11g10170, but no significant differences were found for the other two genes. The qRT-PCR results showed that the gene expression levels in the accessions with high ACs were significantly larger than those in the accessions with low ACs at 35d and 42d after flowering. Hap 2 and Hap 3 of LOC_Os11g10170 reduced the AC by 13.09% and 10.77%, respectively. These results provide a theoretical and material basis for improving the ECQ of rice.
... In this study, eight different floury endosperm mutants with different FD were used to analyze the changes in rice appearance quality, CEQ, and starch granule morphology compared to the wild-type. Previous studies have identified many floury endosperm mutants with different FD, including white-core mutants (OsSSIIIa/Flo5, flo19, flo15) [38][39][40], white belly endosperm mutants (gif1, bzip58) [41,42], floury mutants (ssg4, gpa8, fgr1, flo16) [7,11,43,44] and white periphery endosperm mutants (flo7) [45], which combined with this study indicate that starch synthesis is a complex and finely regulated process involving multiple genes. In this study, variations in FD were observed among z2 and q2 grains of the same panicle. ...
Besides increasing grain yield, improving rice (Oryza sativa L.) quality has been paid more and more attention recently. Cooking and eating quality (CEQ) is an important indicator of rice quality. Since CEQs are quantitative traits and challenging for measurement, efforts have mainly focused on two major genes, Wx and SSIIa. Chalkiness and floury endosperm significantly affect the eating quality of rice, leading to noticeable changes in CEQ. Due to the easily observable phenotype of floury endosperm, cloning single gene mutations that cause floury endosperm and evaluating changes in CEQs indirectly facilitate the exploration of the minor genes controlling CEQ. In this study, eight mutants with different degrees of floury endosperm, generated through ethylmethane sulfonate (EMS) mutagenesis, were analyzed. These mutants exhibited wide variation in starch morphology and CEQs. Particularly, the z2 mutant showed spherical starch granules significantly increased rapid visco analyzer (RVA) indexes and urea swelling, while the z4 mutant displayed extremely sharp starch granules and significantly decreased RVA indexes and urea swelling compared to the wild type. Additionally, these mutants still maintained correlations with certain RVA profiles, suggesting that the genes PUL, which affect these indexes, may not undergo mutation. Cloning these mutated genes in the future, especially in z2 and z4, will enhance the genetic network of rice eating quality and hold significant importance for molecular marker-assisted breeding to improve rice quality.
... Recent studies have identified eight known alleles of the Waxy gene, which control the amylose content of rice at various degrees. It is reported that there are three floury endosperm genes including Flo4, Flo5, and Flo6, involved in starch synthesis pathways of rice (Wang et al. 1990; Kang et al. 2005;Ryoo et al. 2007). Flo4 encodes a pyruvate phosphate dikinase (PPDK). ...
... This activity is enhanced in the SSIIIa mutant (G to A in an exon) by releasing PPDK and AGPase, and could increase lipid synthesis (Kang et al. 2005). AGPase is encoded by Flo6 (Ryoo et al. 2007). Additionally, the loss of SSIIIa activity can redirect the carbon flow necessary for amylose synthesis by GBSSI (encoded by Wx), thereby disrupting the balance between lipid and amylose, both of which are crucial components of RS (Zhang et al. 2012;Ordonio and Matsuoka 2016). ...
... In the case of AGPase, a single nucleotide polymorphism (SNP) in the open reading frame (ORF) region of Flo6 (osagpl-3) could potentially hinder the functionality of the domain responsible for interacting with ADP-Glc. This mutation's impact is particularly evident during the endosperm development stage and results in the mutant floury endosperm phenotype (Ryoo et al. 2007). Another gene, named OsGIF1, whose overexpression in rice resulting in an increase in the size of leaves, stem, and seeds, while the loss-of-function of OsGIF1 leads to the development of smaller plants (Zhou et al. 2016). ...
Rice is one of the major crops in the world. In the twenty-first century, due to the development and popularity of Japanese food culture, the consumption of rice increased dramatically not only in Asia but also in European and American countries. Thus, the demand for rice quality also increased, especially in terms of taste. In this study, the localization of Quantitative Trait Locus (QTL) related to qualities of rice appearance, taste, and palatability of cooked rice was performed in a recombinant inbred population of LD4 and Ha068142 by using high-density single nucleotide polymorphisms genetic mapping. Fourteen QTLs (qFV-5–1, qFV-5 –2, qFV-10, qRAV.7, qRAV.9, qRTV.1, qPGWC.5-1, qPGWC.5-2, qPGWC.11, qGWC.11, qPC.1, qPC.7, qAC.1, qAC.5) related to qualities of rice appearance and taste were detected based on seven traits. Three QTLs (qFV-5–1, qFV-5–2, qFV-10) on chromosomes 5 and 10 were identified utilizing rice foodstuff value. Concurrently, the interaction effect between genes was also detected. The three QTLs can improve rice foodstuff value by 9.8 points. The findings of this study thus lay the foundation for the molecular breeding of rice with high-quality appearance and taste.
... The chalky trait in rice is primarily governed by genetics and influenced by environmental factors [7]. In recent years, researchers have unveiled several genetic mechanisms related to chalkiness, including pathways for energy production, as exemplified by FLO10 [17], FLO12 [18], and FLO13 [19]; energy substance allocation, which is represented by NFYB1, GIF1 [10]; starch synthesis, as exemplified by GBSS [20], SS [21], SBE [22], FLO6 [23], RSR1, and bZIP58 [10]; and starch granule accumulation, as exemplified by CHALK5 [24], BIP [25,26], and PDIL1-1 [27]. By analyzing FLO2 interactions, chalkiness-related genes, and the expression pattern of OsFIF3 in the reproductive phase and early grain-filling stage, we identified OsFIF3 as a contributor to the chalky phenotype in rice. ...
Chalkiness is a key determinant that directly affects the appearance and cooking quality of rice grains. Previously, Floury endosperm 2 (FLO2) was reported to be involved in the formation of rice chalkiness; however, its regulation mechanism is still unclear. Here, FLO2 interaction factor 3 (OsFIF3), a bHLH transcription factor, was identified and analyzed in Oryza sativa. A significant increase in chalkiness was observed in OsFIF3-overexpressed grains, coupled with a round, hollow filling of starch granules and reduced grain weight. OsFIF3 is evolutionarily conserved in monocotyledons, but variable in dicotyledons. Subcellular localization revealed the predominant localization of OsFIF3 in the nucleus. The DAP-seq (DNA affinity purification sequencing) results showed that OsFIF3 could affect the transcriptional accumulation of β-amylase 1, α-amylase isozyme 2A-like, pectinesterase 11, β-glucosidase 28 like, pectinesterase, sucrose transport protein 1 (SUT1), and FLO2 through the binding of the CACGTG motif on their promoters. Moreover, FLO2 and SUT1 with abundant OsFIF3 binding signals showed significant expression reduction in OsFIF3 overexpression lines, further confirming OsFIF3’s role in starch metabolism regulation and energy material allocation. Taken together, these findings show that the overexpression of OsFIF3 inhibits the expression of FLO2 and SUT1, thereby increasing grain chalkiness and affecting grain weight.
... It is reported that these isoforms can belong to five different enzyme sets, denoted as amylopectin enzyme set i-iii and amylose enzyme set i-ii [101,103]. For instance, SS (SSI, SSII-2, SSII-3, SSIII-2, SSIV-1 and SSIV-2), SBEI and GBSSI can form amylopectin enzyme set i; amylopectin enzyme set ii is formed by SSII-1, SSII-2, SSII-3, SSIII-1, SSIII-2, SSIV-1 and GBSSI; the components of some amylopectin enzyme sets are relatively simple, comprising SSII-3 and GBSSI; furthermore, SS (SSI, SSII-3, SSIII-1 and SSIII-2), SBEII and GBSSI can form amylose enzyme set i, and SS (SSI, SSIII-1 and SSIII-2), SBE (SBEI and SBEII) and GBSSI form amylose enzyme set ii [8,70,72,76,83,[88][89][90][91][92]98,99,101,[103][104][105][106][107][108][109][110][111]. Table 1 shows which isoforms belong to which enzyme sets and the effects of the enzyme sets on the structural features of starch. ...
Starch provides approximately half of humans’ food energy, and its structural features influence human health. The most important structural feature is the chain length distribution (CLD), which affects properties such as the digestibility of starch-containing foods. The rate of digestion of such foods has a strong correlation with the prevalence and treatment of diseases such as diabetes, cardiovascular disease and obesity. Starch CLDs can be divided into multiple regions of degrees of polymerization, wherein the CLD in a given region is predominantly, but not exclusively, formed by a particular set of starch biosynthesis enzymes: starch synthases, starch branching enzymes and debranching enzymes. Biosynthesis-based models have been developed relating the ratios of the various enzyme activities in each set to the CLD component produced by that set. Fitting the observed CLDs to these models yields a small number of biosynthesis-related parameters, which, taken together, describe the entire CLD. This review highlights how CLDs can be measured and how the model-based parameters obtained from fitting these distributions are related to the properties of starch-based foods significant for health, and it considers how this knowledge could be used to develop plant varieties to provide foods with improved properties.
... To date, over 20 endosperm mutants named flo (floury) have been characterized [7,16]. These include induced mutations in genes that are directly involved in starch accumulation, such as SSIIIa (flo5), encoding a soluble starch synthase [17]; AGPL2 (flo6), encoding an ADP-glucose pyrophosphorylase [18]; Ugp1 (flo8), encoding a UDP-glucose pyrophosphorylase [19]; and GLYI7 (flo15) encoding a glyoxylase I [20]. While most flo mutants exhibit a milky-white appearance in the entire or partial region of the endosperm, their effects on grain quality traits, such as amylose content, amylopectin chain length distribution, protein, and lipid contents, as well as agronomic traits, such as plant height and grain yield components, are highly variable [7]. ...
Rice cultivars with floury endosperm provide a useful raw material for producing dry-milled rice flour, helping to enhance the processed rice food industry. To expand the genetic resources for breeding floury endosperm rice cultivars, we developed Samkwang(SA)-flo3 (SK-flo3), a floury endosperm mutant line derived from the chemical mutagenesis of Samkwang, an elite Korean japonica rice cultivar. Compared with Samkwang, SK-flo3 showed significantly lower grain hardness, which is suitable for producing dry-milled flour without the soaking and drying processes required in regular wet rice milling. The dry-milled flour of SK-flo3 exhibited excellent physicochemical properties with less damaged starch and finer flour particles relative to Samkwang. Genetic analyses revealed a G-to-A point mutation in exon 7 of cyOsPPDKB, substituting glycine with aspartic acid as a causative mutation for the floury endosperm of SK-flo3. We named this allele flo4-6 and developed a molecular marker to efficiently transfer it to commercial rice cultivars. Our results provide useful genetic resources and information for developing specialty rice cultivars for high-quality rice flour production with reduced milling costs.
... It was reported that the starch content was not altered in the flag leaf of T-DNA insertion mutant ssIIIa/flo5 in the japonica cultivars of the Dongjin background (30). As SSIIIb was highly expressed in leaves (Fig. 2C), we analyzed the starch contents in leaves using 5-week-old plants grown in field conditions. ...
The sedentary lifestyle and refined food consumption significantly lead to obesity, type 2 diabetes, and related complications, which have become one of the major threats to global health. This incidence could be potentially reduced by daily foods rich in resistant starch (RS). However, it remains a challenge to breed high-RS rice varieties. Here, we reported a high-RS mutant rs4 with an RS content of ~10.8% in cooked rice. The genetic study revealed that the loss-of-function SSIIIb and SSIIIa together with a strong Wx allele in the background collaboratively contributed to the high-RS phenotype of the rs4 mutant. The increased RS contents in ssIIIa and ssIIIa ssIIIb mutants were associated with the increased amylose and lipid contents. SSIIIb and SSIIIa proteins were functionally redundant, whereas SSIIIb mainly functioned in leaves and SSIIIa largely in endosperm owing to their divergent tissue-specific expression patterns. Furthermore, we found that SSIII experienced duplication in different cereals, of which one SSIII paralog was mainly expressed in leaves and another in the endosperm. SSII but not SSIV showed a similar evolutionary pattern to SSIII. The copies of endosperm-expressed SSIII and SSII were associated with high total starch contents and low RS levels in the seeds of tested cereals, compared with low starch contents and high RS levels in tested dicots. These results provided critical genetic resources for breeding high-RS rice cultivars, and the evolutionary features of these genes may facilitate to generate high-RS varieties in different cereals.
... In this study, it was found that, compared with the CK treatment, the ST treatment significantly down-regulated the expression level of the SSIIIa gene ( Figure 2E,e) and the contents of B2 and B3 chains decreased accordingly ( Figure 7C,D,c,d). The SSIIIa gene contributes to the extension of B2−B4 chains [29,52,53]. Zhang et al. [54] inhibited the expression of SSIIa and SSIIIa genes by RNA interference, then found that amylopectin content decreased. ...
The source strength and sink demand as well as their interaction have been demonstrated to co-regulate the synthesis of starch and determine the grain quality, but the knowledge of the underlying physiological mechanisms is limiting. An indica variety, Yangdao 6, and a japonica variety, Jinxiangyu 1, were planted with three treatments, including normal growth plant (CK), leaf-cutting (LC) and spikelet-thinning (ST). The transcript levels of starch metabolic genes, physicochemical characteristics of starch and appearance, milling, cooking and tasting qualities of rice under different treatments were determined. The ST treatment increased the relative expression of genes related to the synthesis of short branch-chains of amylopectin (SSI, BEI, BEIIb) and amylose (GBSSI) and reduced the relative expression of medium-long to long branch-chains of amylopectin synthesis genes (SSIIa, SSIIIa, SSIIIb, ISA1). When comparing ST with the CK treatment, starch granules became smoother with higher contents of short branch-chains and lower ratios of medium-long and long branch-chains of amylopectin; the crystallinity and the value of 1045/1022 cm−1 was decreased; for pasting properties, the setback and pasting temperature were decreased; the peak viscosity, hot viscosity, breakdown and final viscosity were significantly increased. Meanwhile, the ST treatment improved the appearance, milling and cooking and tasting qualities. The opposite results were observed under the LC treatment. These results indicated that source strength and sink size would regulate expression levels of starch metabolic genes, which is pivotal for the contents of amylose and short/long branch chains ratio of amylopectin, thus changing the structure and physicochemical properties of starch and grain quality. Here, we speculated that the improved source strength in terms of higher leaf/canopy photosynthesis and small sink size, such as small panicle size, would be preferred traits in high grain quality rice breeding.
... Four isoforms of SS have been identified in cereal endosperm: SSI, SSII, SSIII, and SSIV (Jeon et al., 2010). Mutants defective in these genes (such as SSIIa and SSIIIa) show abnormalities in endosperm-stored starch, leading to grain chalkiness and poor grain filling (Ryoo et al., 2007;Zhang et al., 2011). Cereals contain three isoforms of SBE: SBEI, SBEIIa, and SBEIIb. ...
During grain filling, starch and other nutrients accumulate in the endosperm; this directly determines grain yield and grain quality in crops such as rice (Oryza sativa), maize (Zea mays), and wheat (Triticum aestivum). Grain filling is a complex trait affected by both intrinsic and environmental factors, making it difficult to explore the underlying genetics, molecular regulation, and the application of these genes for breeding. With the development of powerful genetic and molecular techniques, much has been learned about the genes and molecular networks related to grain filling over the past decades. In this review, we highlight the key factors affecting grain filling, including both biological and abiotic factors. We then summarize the key genes controlling grain filling and their roles in this event, including regulators of sugar translocation and starch biosynthesis, phytohormone‐related regulators, and other factors. Finally, we discuss how the current knowledge of valuable grain filling genes could be integrated with strategies for breeding cereal varieties with improved grain yield and quality.
