International Journal of Molecular Sciences

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16 pages, 3349 KiB

Open AccessArticle

Serine 31 Phosphorylation-Driven Regulation of AGPase Activity: Potential Implications for Enhanced Starch Yields in Crops

by Guowu Yu, Yuewei Mou, Noman Shoaib, Xuewu He, Lun Liu, Runze Di, Nishbah Mughal, Na Zhang and Yubi Huang

Int. J. Mol. Sci. 2023, 24(20), 15283; https://doi.org/10.3390/ijms242015283 - 18 Oct 2023

Cited by 1 | Viewed by 862

Abstract

ADP-Glc pyrophosphorylase (AGPase), which catalyzes the transformation of ATP and glucose-1-phosphate (Glc-1-P) into adenosine diphosphate glucose (ADP-Glc), acts as a rate-limiting enzyme in crop starch biosynthesis. Prior research has hinted at the regulation of AGPase by phosphorylation in maize. However, the identification and [...] Read more.

ADP-Glc pyrophosphorylase (AGPase), which catalyzes the transformation of ATP and glucose-1-phosphate (Glc-1-P) into adenosine diphosphate glucose (ADP-Glc), acts as a rate-limiting enzyme in crop starch biosynthesis. Prior research has hinted at the regulation of AGPase by phosphorylation in maize. However, the identification and functional implications of these sites remain to be elucidated. In this study, we identified the phosphorylation site (serine at the 31st position of the linear amino acid sequence) of the AGPase large subunit (Sh2) using iTRAQ^TM. Subsequently, to ascertain the impact of Sh2 phosphorylation on AGPase, we carried out site-directed mutations creating Sh2-S31A (serine residue replaced with alanine) to mimic dephosphorylation and Sh2-S31D (serine residue replaced with aspartic acid) or Sh2-S31E (serine residue replaced with glutamic acid) to mimic phosphorylation. Preliminary investigations were performed to determine Sh2 subcellular localization, its interaction with Bt2, and the resultant AGPase enzymatic activity. Our findings indicate that phosphorylation exerts no impact on the stability or localization of Sh2. Furthermore, none of these mutations at the S31 site of Sh2 seem to affect its interaction with Bt2 (smaller subunit). Intriguingly, all S31 mutations in Sh2 appear to enhance AGPase activity when co-transfected with Bt2, with Sh2-S31E demonstrating a substantial five-fold increase in AGPase activity compared to Sh2. These novel insights lay a foundational groundwork for targeted improvements in AGPase activity, thus potentially accelerating the production of ADP-Glc (the primary substrate for starch synthesis), promising implications for improved starch biosynthesis, and holding the potential to significantly impact agricultural practices. Full article

(This article belongs to the Special Issue Advances in Starch: Molecular Structure, Functionalities and Biosynthesis)

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19 pages, 12956 KiB

Open AccessArticle

Changes in Structural and Thermodynamic Properties of Starch during Potato Tuber Dormancy

by Lyubov A. Wasserman, Oksana O. Kolachevskaya, Alexey V. Krivandin, Anna G. Filatova, Oleg V. Gradov, Irina G. Plashchina and Georgy A. Romanov

Int. J. Mol. Sci. 2023, 24(9), 8397; https://doi.org/10.3390/ijms24098397 - 7 May 2023

Cited by 1 | Viewed by 1609

Abstract

The main reserve polysaccharide of plants—starch—is undoubtedly important for humans. One of the main sources of starch is the potato tuber, which is able to preserve starch for a long time during the so-called dormancy period. However, accumulated data show that this dormancy [...] Read more.

The main reserve polysaccharide of plants—starch—is undoubtedly important for humans. One of the main sources of starch is the potato tuber, which is able to preserve starch for a long time during the so-called dormancy period. However, accumulated data show that this dormancy is only relative, which raises the question of the possibility of some kind of starch restructuring during dormancy periods. Here, the effect of long-term periods of tuber rest (at 2–4 °C) on main parameters of starches of potato tubers grown in vivo or in vitro were studied. Along with non-transgenic potatoes, Arabidopsis phytochrome B (AtPHYB) transformants were investigated. Distinct changes in starch micro and macro structures—an increase in proportion of amorphous lamellae and of large-sized and irregular-shaped granules, as well as shifts in thickness of the crystalline lamellae—were detected. The degree of such alterations, more pronounced in AtPHYB-transgenic tubers, increased with the longevity of tuber dormancy. By contrast, the polymorphic crystalline structure (B-type) of starch remained unchanged regardless of dormancy duration. Collectively, our data support the hypothesis that potato starch remains metabolically and structurally labile during the entire tuber life including the dormancy period. The revealed starch remodeling may be considered a process of tuber preadaptation to the upcoming sprouting stage. Full article

(This article belongs to the Special Issue Advances in Starch: Molecular Structure, Functionalities and Biosynthesis)

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19 pages, 3689 KiB

Open AccessArticle

Three Starch Synthase IIa (SSIIa) Alleles Reveal the Effect of SSIIa on the Thermal and Rheological Properties, Viscoelasticity, and Eating Quality of Glutinous Rice

by Tsukine Nakano, Naoko Crofts, Satoko Miura, Naoko F. Oitome, Yuko Hosaka, Kyoko Ishikawa and Naoko Fujita

Int. J. Mol. Sci. 2023, 24(4), 3726; https://doi.org/10.3390/ijms24043726 - 13 Feb 2023

Cited by 2 | Viewed by 1318

Abstract

Glutinous rice accumulates amylose-free starch and is utilized for rice cakes and crackers, owing to the loss of the Waxy gene which encodes granule-bound starch synthase I (GBSSI). Starch synthase IIa (SSIIa) elongates amylopectin chains with a degree of polymerization (DP) of 6–12 [...] Read more.

Glutinous rice accumulates amylose-free starch and is utilized for rice cakes and crackers, owing to the loss of the Waxy gene which encodes granule-bound starch synthase I (GBSSI). Starch synthase IIa (SSIIa) elongates amylopectin chains with a degree of polymerization (DP) of 6–12 to 13–24 and greatly influences starch properties. To elucidate the relationship between the branch length of amylopectin and the thermal and rheological properties, viscoelasticity, and eating quality of glutinous rice, three allelic near isogenic lines with high, low, or no SSIIa activity were generated (designated as SS2a wx, ss2a^L wx, and ss2a wx, respectively). Chain length distribution analyses revealed that ss2a wx exhibited the highest short chain (DP < 12) number and lowest gelatinization temperature, whereas SS2a wx showed the opposite results. Gel filtration chromatography showed that the three lines contained essentially no amylose. Viscoelasticity analyses of rice cakes stored at low temperature for different durations revealed that ss2a wx maintained softness and elasticity for up to 6 days, while SS2a wx hardened within 6 h. Sensory evaluation was consistent with mechanical evaluation. The relationship of amylopectin structure with the thermal and rheological properties, viscoelasticity, and eating quality of glutinous rice is discussed. Full article

(This article belongs to the Special Issue Advances in Starch: Molecular Structure, Functionalities and Biosynthesis)

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18 pages, 1892 KiB

Open AccessArticle

Understanding the Potential Gene Regulatory Network of Starch Biosynthesis in Tartary Buckwheat by RNA-Seq

by Juan Huang, Bin Tang, Rongrong Ren, Min Wu, Fei Liu, Yong Lv, Taoxiong Shi, Jiao Deng and Qingfu Chen

Int. J. Mol. Sci. 2022, 23(24), 15774; https://doi.org/10.3390/ijms232415774 - 12 Dec 2022

Cited by 2 | Viewed by 1299

Abstract

Starch is a major component of crop grains, and its content affects food quality and taste. Tartary buckwheat is a traditional pseudo-cereal used in food as well as medicine. Starch content, granule morphology, and physicochemical properties have been extensively studied in Tartary buckwheat. [...] Read more.

Starch is a major component of crop grains, and its content affects food quality and taste. Tartary buckwheat is a traditional pseudo-cereal used in food as well as medicine. Starch content, granule morphology, and physicochemical properties have been extensively studied in Tartary buckwheat. However, the complex regulatory network related to its starch biosynthesis needs to be elucidated. Here, we performed RNA-seq analyses using seven Tartary buckwheat varieties differing in starch content and combined the RNA-seq data with starch content by weighted correlation network analysis (WGCNA). As a result, 10,873 differentially expressed genes (DEGs) were identified and were functionally clustered to six hierarchical clusters. Fifteen starch biosynthesis genes had higher expression level in seeds. Four trait-specific modules and 3131 hub genes were identified by WGCNA, with the lightcyan and brown modules positively correlated with starch-related traits. Furthermore, two potential gene regulatory networks were proposed, including the co-expression of FtNAC70, FtPUL, and FtGBSS1-3 in the lightcyan module and FtbHLH5, C3H, FtBE2, FtISA3, FtSS3-5, and FtSS1 in the brown. All the above genes were preferentially expressed in seeds, further suggesting their role in seed starch biosynthesis. These results provide crucial guidance for further research on starch biosynthesis and its regulatory network in Tartary buckwheat. Full article

(This article belongs to the Special Issue Advances in Starch: Molecular Structure, Functionalities and Biosynthesis)

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16 pages, 4642 KiB

Open AccessArticle

Screening of Induced Mutants Led to the Identification of Starch Biosynthetic Genes Associated with Improved Resistant Starch in Wheat

by Ahsan Irshad, Huijun Guo, Shoaib Ur Rehman, Jiayu Gu, Chaojie Wang, Hongchun Xiong, Yongdun Xie, Shirong Zhao and Luxiang Liu

Int. J. Mol. Sci. 2022, 23(18), 10741; https://doi.org/10.3390/ijms231810741 - 15 Sep 2022

Cited by 5 | Viewed by 1844

Abstract

Several health benefits are obtained from resistant starch, also known as healthy starch. Enhancing resistant starch with genetic modification has huge commercial importance. The variation of resistant starch content is narrow in wheat, in relation to which limited improvement has been attained. Hence, [...] Read more.

Several health benefits are obtained from resistant starch, also known as healthy starch. Enhancing resistant starch with genetic modification has huge commercial importance. The variation of resistant starch content is narrow in wheat, in relation to which limited improvement has been attained. Hence, there is a need to produce a wheat population that has a wide range of variations in resistant starch content. In the present study, stable mutants were screened that showed significant variation in the resistant starch content. A megazyme kit was used for measuring the resistant starch content, digestible starch, and total starch. The analysis of variance showed a significant difference in the mutant population for resistant starch. Furthermore, four diverse mutant lines for resistant starch content were used to study the quantitative expression patterns of 21 starch metabolic pathway genes; and to evaluate the candidate genes for resistant starch biosynthesis. The expression pattern of 21 starch metabolic pathway genes in two diverse mutant lines showed a higher expression of key genes regulating resistant starch biosynthesis (GBSSI and their isoforms) in the high resistant starch mutant lines, in comparison to the parent variety (J411). The expression of SBEs genes was higher in the low resistant starch mutants. The other three candidate genes showed overexpression (BMY, Pho1, Pho2) and four had reduced (SSIII, SBEI, SBEIII, ISA3) expression in high resistant starch mutants. The overexpression of AMY and ISA1 in the high resistant starch mutant line JE0146 may be due to missense mutations in these genes. Similarly, there was a stop_gained mutation for PHO2; it also showed overexpression. In addition, the gene expression analysis of 21 starch metabolizing genes in four different mutants (low and high resistant starch mutants) shows that in addition to the important genes, several other genes (phosphorylase, isoamylases) may be involved and contribute to the biosynthesis of resistant starch. There is a need to do further study about these new genes, which are responsible for the fluctuation of resistant starch in the mutants. Full article

(This article belongs to the Special Issue Advances in Starch: Molecular Structure, Functionalities and Biosynthesis)

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18 pages, 5704 KiB

Open AccessArticle

Low Light Stress Increases Chalkiness by Disturbing Starch Synthesis and Grain Filling of Rice

by Qiuping Li, Fei Deng, Yuling Zeng, Bo Li, Chenyan He, Youyun Zhu, Xing Zhou, Zinuo Zhang, Li Wang, Youfeng Tao, Yu Zhang, Wei Zhou, Hong Cheng, Yong Chen, Xiaolong Lei and Wanjun Ren

Int. J. Mol. Sci. 2022, 23(16), 9153; https://doi.org/10.3390/ijms23169153 - 15 Aug 2022

Cited by 6 | Viewed by 1577

Abstract

Low light stress increases the chalkiness of rice; however, this effect has not been fully characterized. In this study, we demonstrated that low light resulted in markedly decreased activity of ADP-glucose pyrophosphorylase in the grains and those of sucrose synthase and soluble starch [...] Read more.

Low light stress increases the chalkiness of rice; however, this effect has not been fully characterized. In this study, we demonstrated that low light resulted in markedly decreased activity of ADP-glucose pyrophosphorylase in the grains and those of sucrose synthase and soluble starch synthase in the early period of grain filling. Furthermore, low light also resulted in decreased activities of granule-bound starch synthase and starch branching enzyme in the late period of grain filling. Therefore, the maximum and mean grain filling rates were reduced but the time to reach the maximum grain filling rates and effective grain filling period were increased by low light. Thus, it significantly decreased the grain weight at the maximum grain filling rate and grain weight and retarded the endosperm growth and development, leading to a loose arrangement of the amyloplasts and an increase in the chalkiness of the rice grains. Compared to the grains at the top panicle part, low light led to a greater decrease in the grain weight at the maximum grain filling rate and time to reach the grain weight at the maximum grain filling rate at the bottom panicle part, which contributed to an increase in chalkiness by increasing the rates of different chalky types at the bottom panicle part. In conclusion, low light disturbed starch synthesis in grains, thereby impeding the grain filling progress and increasing chalkiness, particularly for grains at the bottom panicle part. Full article

(This article belongs to the Special Issue Advances in Starch: Molecular Structure, Functionalities and Biosynthesis)

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12 pages, 2085 KiB

Open AccessArticle

EfABI4 Transcription Factor Is Involved in the Regulation of Starch Biosynthesis in Euryale ferox Salisb Seeds

by Peng Wu, Yue Zhu, Ailian Liu, Yuhao Wang, Shuping Zhao, Kai Feng and Liangjun Li

Int. J. Mol. Sci. 2022, 23(14), 7598; https://doi.org/10.3390/ijms23147598 - 8 Jul 2022

Cited by 2 | Viewed by 1474

Abstract

Starch is the final product of photosynthesis and the main storage form in plants. Studies have shown that there is a close synergistic regulatory relationship between ABA signal transduction and starch biosynthesis. In this study, we employed RNA sequencing (RNA-Seq) to investigate transcriptomic [...] Read more.

Starch is the final product of photosynthesis and the main storage form in plants. Studies have shown that there is a close synergistic regulatory relationship between ABA signal transduction and starch biosynthesis. In this study, we employed RNA sequencing (RNA-Seq) to investigate transcriptomic changes of the Euryale ferox seeds treated by exogenous ABA. The differentially expressed genes engaged in the “Starch and sucrose” and “TCA cycle” pathway. Furthermore, the key transcription factor EfABI4 in ABA signaling pathway and the key genes of starch biosynthesis (EfDBE1, EfSBE2, EfSS1, EfSS2, EfSS3, EfSS4 and EfGBSS1) were significantly up-regulated. Further, the Euryale ferox plant was treated with ABA, it was found that the total starch content of Euryale ferox seeds at different development stages was significantly higher than that of the control, and the key genes of starch synthesis in Euryale ferox seeds were also significantly up-regulated. Finally, yeast one-hybrid and dual luciferase assay proved that EfABI4 can promote the expression of EfSS1 by directly binding to its promoter. Subcellular localization results showed that EfABI4 protein was located at the nucleus and EfSS1 protein was located in the cytomembrane. These findings revealed that ABA promotes starch synthesis and accumulation by mediating EfABI4 to directly promote EfSS1 gene expression, which is helpful for understanding starch synthesis in seeds. Full article

(This article belongs to the Special Issue Advances in Starch: Molecular Structure, Functionalities and Biosynthesis)

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Review

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23 pages, 1954 KiB

Open AccessReview

Genetic Engineering of Starch Biosynthesis in Maize Seeds for Efficient Enzymatic Digestion of Starch during Bioethanol Production

by Liangjie Niu, Liangwei Liu, Jinghua Zhang, Monica Scali, Wei Wang, Xiuli Hu and Xiaolin Wu

Int. J. Mol. Sci. 2023, 24(4), 3927; https://doi.org/10.3390/ijms24043927 - 15 Feb 2023

Viewed by 4273

Abstract

Maize accumulates large amounts of starch in seeds which have been used as food for human and animals. Maize starch is an importantly industrial raw material for bioethanol production. One critical step in bioethanol production is degrading starch to oligosaccharides and glucose by [...] Read more.

Maize accumulates large amounts of starch in seeds which have been used as food for human and animals. Maize starch is an importantly industrial raw material for bioethanol production. One critical step in bioethanol production is degrading starch to oligosaccharides and glucose by α-amylase and glucoamylase. This step usually requires high temperature and additional equipment, leading to an increased production cost. Currently, there remains a lack of specially designed maize cultivars with optimized starch (amylose and amylopectin) compositions for bioethanol production. We discussed the features of starch granules suitable for efficient enzymatic digestion. Thus far, great advances have been made in molecular characterization of the key proteins involved in starch metabolism in maize seeds. The review explores how these proteins affect starch metabolism pathway, especially in controlling the composition, size and features of starch. We highlight the roles of key enzymes in controlling amylose/amylopectin ratio and granules architecture. Based on current technological process of bioethanol production using maize starch, we propose that several key enzymes can be modified in abundance or activities via genetic engineering to synthesize easily degraded starch granules in maize seeds. The review provides a clue for developing special maize cultivars as raw material in the bioethanol industry. Full article

(This article belongs to the Special Issue Advances in Starch: Molecular Structure, Functionalities and Biosynthesis)

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