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Kamble NU, Makhamadjonov F, Fahy B, Martins C, Saalbach G, Seung D. Initiation of B-type starch granules in wheat endosperm requires the plastidial α-glucan phosphorylase PHS1. THE PLANT CELL 2023; 35:4091-4110. [PMID: 37595145 PMCID: PMC10615211 DOI: 10.1093/plcell/koad217] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2023] [Revised: 07/24/2023] [Accepted: 07/28/2023] [Indexed: 08/20/2023]
Abstract
The plastidial α-glucan phosphorylase (PHS1) can elongate and degrade maltooligosaccharides (MOSs), but its exact physiological role in plants is poorly understood. Here, we discover a specialized role of PHS1 in establishing the unique bimodal characteristic of starch granules in wheat (Triticum spp.) endosperm. Wheat endosperm contains large A-type granules that initiate at early grain development and small B-type granules that initiate in later grain development. We demonstrate that PHS1 interacts with B-GRANULE CONTENT1 (BGC1), a carbohydrate-binding protein essential for normal B-type granule initiation. Mutants of tetraploid durum wheat (Triticum turgidum) deficient in all homoeologs of PHS1 had normal A-type granules but fewer and larger B-type granules. Grain size and starch content were not affected by the mutations. Further, by assessing granule numbers during grain development in the phs1 mutant and using a double mutant defective in both PHS1 and BGC1, we demonstrate that PHS1 is exclusively involved in B-type granule initiation. The total starch content and number of starch granules per chloroplast in leaves were not affected by loss of PHS1, suggesting that its role in granule initiation in wheat is limited to the endosperm. We therefore propose that the initiation of A- and B-type granules occurs via distinct biochemical mechanisms, where PHS1 plays an exclusive role in B-type granule initiation.
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Affiliation(s)
| | | | - Brendan Fahy
- John Innes Centre, Norwich Research Park, Norwich, NR4 7UH,UK
| | - Carlo Martins
- John Innes Centre, Norwich Research Park, Norwich, NR4 7UH,UK
| | | | - David Seung
- John Innes Centre, Norwich Research Park, Norwich, NR4 7UH,UK
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Sharma S, Friberg M, Vogel P, Turesson H, Olsson N, Andersson M, Hofvander P. Pho1a (plastid starch phosphorylase) is duplicated and essential for normal starch granule phenotype in tubers of Solanum tuberosum L. FRONTIERS IN PLANT SCIENCE 2023; 14:1220973. [PMID: 37636090 PMCID: PMC10450146 DOI: 10.3389/fpls.2023.1220973] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/11/2023] [Accepted: 07/18/2023] [Indexed: 08/29/2023]
Abstract
Reserve starch from seeds and tubers is a crucial plant product for human survival. Much research has been devoted to quantitative and qualitative aspects of starch synthesis and its relation to abiotic factors of importance in agriculture. Certain aspects of genetic factors and enzymes influencing carbon assimilation into starch granules remain elusive after many decades of research. Starch phosphorylase (Pho) can operate, depending on metabolic conditions, in a synthetic and degradative pathway. The plastidial form of the enzyme is one of the most highly expressed genes in potato tubers, and the encoded product is imported into starch-synthesizing amyloplasts. We identified that the genomic locus of a Pho1a-type starch phosphorylase is duplicated in potato. Our study further shows that the enzyme is of importance for a normal starch granule phenotype in tubers. Null mutants created by genome editing display rounded starch granules in an increased number that contained a reduced ratio of apparent amylose in the starch.
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Affiliation(s)
- Shrikant Sharma
- Department of Plant Breeding, Swedish University of Agricultural Sciences, Alnarp, Sweden
| | | | | | | | | | | | - Per Hofvander
- Department of Plant Breeding, Swedish University of Agricultural Sciences, Alnarp, Sweden
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3
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Dong X, Chen L, Yang H, Tian L, Dong F, Chai Y, Qu LQ. Pho1 cooperates with DPE1 to control short maltooligosaccharide mobilization during starch synthesis initiation in rice endosperm. TAG. THEORETICAL AND APPLIED GENETICS. THEORETISCHE UND ANGEWANDTE GENETIK 2023; 136:47. [PMID: 36912930 DOI: 10.1007/s00122-023-04250-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2022] [Accepted: 10/18/2022] [Indexed: 06/18/2023]
Abstract
Plastidial α-glucan phosphorylase is a key factor that cooperates with plastidial disproportionating enzyme to control short maltooligosaccharide mobilization during the initiation process of starch molecule synthesis in developing rice endosperm. Storage starch synthesis is essential for grain filling. However, little is known about how cereal endosperm controls starch synthesis initiation. One of core events for starch synthesis initiation is short maltooligosaccharide (MOS) mobilization consisting of long MOS primer production and excess MOS breakdown. By mutant analyses and biochemical investigations, we present here functional identifications of plastidial α-glucan phosphorylase (Pho1) and disproportionating enzyme (DPE1) during starch synthesis initiation in rice (Oryza sativa) endosperm. Pho1 deficiency impaired MOS mobilization, triggering short MOS accumulation and starch synthesis reduction during early seed development. The mutant seeds differed significantly in MOS level and starch content at 15 days after flowering and exhibited diverse endosperm phenotypes during mid-late seed development: ranging from pseudonormal to shrunken (Shr), severely or excessively Shr. The level of DPE1 was almost normal in the PN seeds but significantly reduced in the Shr seeds. Overexpression of DPE1 in pho1 resulted in plump seeds only. DPE1 deficiency had no obvious effects on MOS mobilization. Knockout of DPE1 in pho1 completely blocked MOS mobilization, resulting in severely and excessively Shr seeds only. These findings show that Pho1 cooperates with DPE1 to control short MOS mobilization during starch synthesis initiation in rice endosperm.
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Affiliation(s)
- Xiangbai Dong
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing, 100093, China
| | - Liangke Chen
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing, 100093, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Huifang Yang
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing, 100093, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Lihong Tian
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing, 100093, China
| | - Fengqin Dong
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing, 100093, China
| | - Yaru Chai
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing, 100093, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Le Qing Qu
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing, 100093, China.
- University of Chinese Academy of Sciences, Beijing, 100049, China.
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Yu G, Shoaib N, Xie Y, Liu L, Mughal N, Li Y, Huang H, Zhang N, Zhang J, Liu Y, Hu Y, Liu H, Huang Y. Comparative Study of Starch Phosphorylase Genes and Encoded Proteins in Various Monocots and Dicots with Emphasis on Maize. Int J Mol Sci 2022; 23:ijms23094518. [PMID: 35562912 PMCID: PMC9104829 DOI: 10.3390/ijms23094518] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2022] [Revised: 04/10/2022] [Accepted: 04/12/2022] [Indexed: 01/27/2023] Open
Abstract
Starch phosphorylase (PHO) is a multimeric enzyme with two distinct isoforms: plastidial starch phosphorylase (PHO1) and cytosolic starch phosphorylase (PHO2). PHO1 specifically resides in the plastid, while PHO2 is found in the cytosol. Both play a critical role in the synthesis and degradation of starch. This study aimed to report the detailed structure, function, and evolution of genes encoding PHO1 and PHO2 and their protein ligand-binding sites in eight monocots and four dicots. "True" orthologs of PHO1 and PHO2 of Oryza sativa were identified, and the structure of the enzyme at the protein level was studied. The genes controlling PHO2 were found to be more conserved than those controlling PHO1; the variations were mainly due to the variable sequence and length of introns. Cis-regulatory elements in the promoter region of both genes were identified, and the expression pattern was analyzed. The real-time quantitative polymerase chain reaction indicated that PHO2 was expressed in all tissues with a uniform pattern of transcripts, and the expression pattern of PHO1 indicates that it probably contributes to the starch biosynthesis during seed development in Zea mays. Under abscisic acid (ABA) treatment, PHO1 was found to be downregulated in Arabidopsis and Hordeum vulgare. However, we found that ABA could up-regulate the expression of both PHO1 and PHO2 within 12 h in Zea mays. In all monocots and dicots, the 3D structures were highly similar, and the ligand-binding sites were common yet fluctuating in the position of aa residues.
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Affiliation(s)
- Guowu Yu
- National Demonstration Center for Experimental Crop Science Education, College of Agronomy, Sichuan Agricultural University, Chengdu 611130, China; (G.Y.); (N.S.); (Y.X.); (L.L.); (N.M.); (H.H.)
- State Key Laboratory of Crop Gene Exploration and Utilization in Southwest China, Sichuan Agricultural University, Chengdu 611130, China; (Y.L.); (Y.H.)
| | - Noman Shoaib
- National Demonstration Center for Experimental Crop Science Education, College of Agronomy, Sichuan Agricultural University, Chengdu 611130, China; (G.Y.); (N.S.); (Y.X.); (L.L.); (N.M.); (H.H.)
| | - Ying Xie
- National Demonstration Center for Experimental Crop Science Education, College of Agronomy, Sichuan Agricultural University, Chengdu 611130, China; (G.Y.); (N.S.); (Y.X.); (L.L.); (N.M.); (H.H.)
| | - Lun Liu
- National Demonstration Center for Experimental Crop Science Education, College of Agronomy, Sichuan Agricultural University, Chengdu 611130, China; (G.Y.); (N.S.); (Y.X.); (L.L.); (N.M.); (H.H.)
| | - Nishbah Mughal
- National Demonstration Center for Experimental Crop Science Education, College of Agronomy, Sichuan Agricultural University, Chengdu 611130, China; (G.Y.); (N.S.); (Y.X.); (L.L.); (N.M.); (H.H.)
| | - Yangping Li
- State Key Laboratory of Crop Gene Exploration and Utilization in Southwest China, Sichuan Agricultural University, Chengdu 611130, China; (Y.L.); (Y.H.)
| | - Huanhuan Huang
- National Demonstration Center for Experimental Crop Science Education, College of Agronomy, Sichuan Agricultural University, Chengdu 611130, China; (G.Y.); (N.S.); (Y.X.); (L.L.); (N.M.); (H.H.)
| | - Na Zhang
- College of Science, Sichuan Agricultural University, Chengdu 611130, China;
| | - Junjie Zhang
- College of Life Science, Sichuan Agricultural University, Ya’an 625014, China;
| | - Yinghong Liu
- Maize Research Institute, Sichuan Agricultural University, Chengdu 611130, China;
| | - Yufeng Hu
- State Key Laboratory of Crop Gene Exploration and Utilization in Southwest China, Sichuan Agricultural University, Chengdu 611130, China; (Y.L.); (Y.H.)
| | - Hanmei Liu
- College of Life Science, Sichuan Agricultural University, Ya’an 625014, China;
- Correspondence: (H.L.); (Y.H.)
| | - Yubi Huang
- National Demonstration Center for Experimental Crop Science Education, College of Agronomy, Sichuan Agricultural University, Chengdu 611130, China; (G.Y.); (N.S.); (Y.X.); (L.L.); (N.M.); (H.H.)
- State Key Laboratory of Crop Gene Exploration and Utilization in Southwest China, Sichuan Agricultural University, Chengdu 611130, China; (Y.L.); (Y.H.)
- Correspondence: (H.L.); (Y.H.)
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Shoaib N, Liu L, Ali A, Mughal N, Yu G, Huang Y. Molecular Functions and Pathways of Plastidial Starch Phosphorylase (PHO1) in Starch Metabolism: Current and Future Perspectives. Int J Mol Sci 2021; 22:ijms221910450. [PMID: 34638789 PMCID: PMC8509025 DOI: 10.3390/ijms221910450] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Revised: 09/22/2021] [Accepted: 09/23/2021] [Indexed: 12/17/2022] Open
Abstract
Starch phosphorylase is a member of the GT35-glycogen-phosphorylase superfamily. Glycogen phosphorylases have been researched in animals thoroughly when compared to plants. Genetic evidence signifies the integral role of plastidial starch phosphorylase (PHO1) in starch biosynthesis in model plants. The counterpart of PHO1 is PHO2, which specifically resides in cytosol and is reported to lack L80 peptide in the middle region of proteins as seen in animal and maltodextrin forms of phosphorylases. The function of this extra peptide varies among species and ranges from the substrate of proteasomes to modulate the degradation of PHO1 in Solanum tuberosum to a non-significant effect on biochemical activity in Oryza sativa and Hordeum vulgare. Various regulatory functions, e.g., phosphorylation, protein–protein interactions, and redox modulation, have been reported to affect the starch phosphorylase functions in higher plants. This review outlines the current findings on the regulation of starch phosphorylase genes and proteins with their possible role in the starch biosynthesis pathway. We highlight the gaps in present studies and elaborate on the molecular mechanisms of phosphorylase in starch metabolism. Moreover, we explore the possible role of PHO1 in crop improvement.
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Affiliation(s)
- Noman Shoaib
- College of Agronomy, Sichuan Agricultural University, Chengdu 611130, China; (N.S.); (L.L.); (N.M.)
| | - Lun Liu
- College of Agronomy, Sichuan Agricultural University, Chengdu 611130, China; (N.S.); (L.L.); (N.M.)
| | - Asif Ali
- State Key Laboratory of Crop Gene Exploration and Utilization in Southwest China, Rice Research Institute, Sichuan Agricultural University, Chengdu 611130, China;
| | - Nishbah Mughal
- College of Agronomy, Sichuan Agricultural University, Chengdu 611130, China; (N.S.); (L.L.); (N.M.)
| | - Guowu Yu
- College of Agronomy, Sichuan Agricultural University, Chengdu 611130, China; (N.S.); (L.L.); (N.M.)
- Correspondence: (G.Y.); (Y.H.); Tel.: +86-180-0803-9351 (G.Y.); +86-028-8629-0868 (Y.H.)
| | - Yubi Huang
- College of Agronomy, Sichuan Agricultural University, Chengdu 611130, China; (N.S.); (L.L.); (N.M.)
- State Key Laboratory of Crop Gene Exploration and Utilization in Southwest China, Sichuan Agricultural University, Chengdu 611130, China
- Correspondence: (G.Y.); (Y.H.); Tel.: +86-180-0803-9351 (G.Y.); +86-028-8629-0868 (Y.H.)
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Tappiban P, Ying Y, Xu F, Bao J. Proteomics and Post-Translational Modifications of Starch Biosynthesis-Related Proteins in Developing Seeds of Rice. Int J Mol Sci 2021; 22:5901. [PMID: 34072759 PMCID: PMC8199009 DOI: 10.3390/ijms22115901] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Revised: 05/26/2021] [Accepted: 05/28/2021] [Indexed: 12/25/2022] Open
Abstract
Rice (Oryza sativa L.) is a foremost staple food for approximately half the world's population. The components of rice starch, amylose, and amylopectin are synthesized by a series of enzymes, which are responsible for rice starch properties and functionality, and then affect rice cooking and eating quality. Recently, proteomics technology has been applied to the establishment of the differentially expressed starch biosynthesis-related proteins and the identification of posttranslational modifications (PTMs) target starch biosynthesis proteins as well. It is necessary to summarize the recent studies in proteomics and PTMs in rice endosperm to deepen our understanding of starch biosynthesis protein expression and regulation, which will provide useful information to rice breeding programs and industrial starch applications. The review provides a comprehensive summary of proteins and PTMs involved in starch biosynthesis based on proteomic studies of rice developing seeds. Starch biosynthesis proteins in rice seeds were differentially expressed in the developing seeds at different developmental stages. All the proteins involving in starch biosynthesis were identified using proteomics methods. Most starch biosynthesis-related proteins are basically increased at 6-20 days after flowering (DAF) and decreased upon the high-temperature conditions. A total of 10, 14, 2, 17, and 7 starch biosynthesis related proteins were identified to be targeted by phosphorylation, lysine acetylation, succinylation, lysine 2-hydroxyisobutyrylation, and malonylation, respectively. The phosphoglucomutase is commonly targeted by five PTMs types. Research on the function of phosphorylation in multiple enzyme complex formation in endosperm starch biosynthesis is underway, while the functions of other PTMs in starch biosynthesis are necessary to be conducted in the near future.
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Affiliation(s)
- Piengtawan Tappiban
- Key Laboratory of Nuclear Agricultural Sciences of Ministry of Agriculture and Zhejiang Province, Institute of Nuclear Agricultural Sciences, College of Agriculture and Biotechnology, Zhejiang University, Zijingang Campus, Hangzhou 310058, China; (P.T.); (Y.Y.); (F.X.)
| | - Yining Ying
- Key Laboratory of Nuclear Agricultural Sciences of Ministry of Agriculture and Zhejiang Province, Institute of Nuclear Agricultural Sciences, College of Agriculture and Biotechnology, Zhejiang University, Zijingang Campus, Hangzhou 310058, China; (P.T.); (Y.Y.); (F.X.)
| | - Feifei Xu
- Key Laboratory of Nuclear Agricultural Sciences of Ministry of Agriculture and Zhejiang Province, Institute of Nuclear Agricultural Sciences, College of Agriculture and Biotechnology, Zhejiang University, Zijingang Campus, Hangzhou 310058, China; (P.T.); (Y.Y.); (F.X.)
| | - Jinsong Bao
- Key Laboratory of Nuclear Agricultural Sciences of Ministry of Agriculture and Zhejiang Province, Institute of Nuclear Agricultural Sciences, College of Agriculture and Biotechnology, Zhejiang University, Zijingang Campus, Hangzhou 310058, China; (P.T.); (Y.Y.); (F.X.)
- Hainan Institute of Zhejiang University, Yazhou Bay Science and Technology City, Yazhou District, Sanya 572025, China
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Koper K, Hwang SK, Wood M, Singh S, Cousins A, Kirchhoff H, Okita TW. The Rice Plastidial Phosphorylase Participates Directly in Both Sink and Source Processes. ACTA ACUST UNITED AC 2020; 62:125-142. [DOI: 10.1093/pcp/pcaa146] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2020] [Accepted: 11/11/2020] [Indexed: 12/19/2022]
Abstract
Abstract
The plastidial starch phosphorylase (Pho1) functions in starch metabolism. A distinctive structural feature of the higher Pho1 is a 50–82-amino-acid long peptide (L50–L82), which is absent in phosphorylases from non-plant organisms. To study the function of the rice Pho1 L80 peptide, we complemented a pho1− rice mutant (BMF136) with the wild-type Pho1 gene or with a Pho1 gene lacking the L80 region (Pho1ΔL80). While expression of Pho1 in BMF136 restored normal wild-type phenotype, the introduction of Pho1ΔL80 enhanced the growth rate and plant productivity above wild-type levels. Mass spectrometry analysis of proteins captured by anti-Pho1 showed the surprising presence of PsaC, the terminal electron acceptor/donor subunit of photosystem I (PSI). This unexpected interaction was substantiated by reciprocal immobilized protein pull-down assays of seedling extracts and supported by the presence of Pho1 on isolated PSI complexes resolved by blue-native gels. Spectrophotometric studies showed that Pho1ΔL80 plants exhibited modified PSI and enhanced CO2 assimilation properties. Collectively, these findings indicate that the higher plant Pho1 has dual roles as a potential modulator of source and sink processes.
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Affiliation(s)
- Kaan Koper
- Institute of Biological Chemistry, Washington State University, Pullman, WA 99164, USA
| | - Seon-Kap Hwang
- Institute of Biological Chemistry, Washington State University, Pullman, WA 99164, USA
| | - Magnus Wood
- Institute of Biological Chemistry, Washington State University, Pullman, WA 99164, USA
| | - Salvinder Singh
- Department of Agricultural Biotechnology, Assam Agricultural University, Jorhat, Assam 785013, India
| | - Asaph Cousins
- School of Biological Sciences, Washington State University, Pullman, WA 99164, USA
| | - Helmut Kirchhoff
- Institute of Biological Chemistry, Washington State University, Pullman, WA 99164, USA
| | - Thomas W Okita
- Institute of Biological Chemistry, Washington State University, Pullman, WA 99164, USA
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Hwang SK, Koper K, Okita TW. The plastid phosphorylase as a multiple-role player in plant metabolism. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2020; 290:110303. [PMID: 31779913 DOI: 10.1016/j.plantsci.2019.110303] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2019] [Revised: 10/04/2019] [Accepted: 10/07/2019] [Indexed: 05/11/2023]
Abstract
The physiological roles of the plastidial phosphorylase in starch metabolism of higher plants have been debated for decades. While estimated physiological substrate levels favor a degradative role, genetic evidence indicates that the plastidial phosphorylase (Pho1) plays an essential role in starch initiation and maturation of the starch granule in developing rice grains. The plastidial enzyme contains a unique peptide domain, up to 82 residues in length depending on the plant species, not found in its cytosolic counterpart or glycogen phosphorylases. The role of this extra peptide domain is perplexing, as its complete removal does not significantly affect the in vitro catalytic or enzymatic regulatory properties of rice Pho1. This peptide domain may have a regulatory function as it contains potential phosphorylation sites and, in some plant Pho1s, a PEST motif, a substrate for proteasome-mediated degradation. We discuss the potential roles of Pho1 and its L80 domain in starch biosynthesis and photosynthesis.
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Affiliation(s)
- Seon-Kap Hwang
- Institute of Biological Chemistry, Washington State University, Pullman, WA, 99164, USA
| | - Kaan Koper
- Institute of Biological Chemistry, Washington State University, Pullman, WA, 99164, USA
| | - Thomas W Okita
- Institute of Biological Chemistry, Washington State University, Pullman, WA, 99164, USA.
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Wang MQ, Zeng QH, Huang QX, Lin P, Li Y, Liu QL, Zhang L. Transcriptomic Analysis of Verbena bonariensis Leaves Under Low-Temperature Stress. DNA Cell Biol 2019; 38:1233-1248. [PMID: 31532241 DOI: 10.1089/dna.2019.4707] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Verbena bonariensis is a valuable plant for both ornament and flower border. As a major constraint, low temperature affects the growing development and survival of V. bonariensis. However, there are few systematic studies in terms of molecular mechanism on the tolerance of low temperature in V. bonariensis. In this study, Illumina sequencing technology was applied to analyze the cold resistance mechanism of plants. Six cDNA libraries were obtained from two samples of two groups, the cold-treated group and the control group. A total of 271,920 unigenes were produced from 406,641 assembled transcripts. Among these, 19,003 differentially expressed genes (DEGs) (corrected p-value <0.01, |log2(fold change) | >3) were obtained, including 9852 upregulated and 9151 downregulated genes. The antioxidant enzyme system, photosynthesis, plant hormone signal transduction, fatty acid metabolism, starch and sucrose metabolism pathway, and transcription factors were analyzed. Based on these results, series of candidate genes related to cold stress were screened out and discussed. The physiological indexes related to response mechanism of low temperature were tested. Eleven upregulated DEGs were validated by Quantitative Real-time PCR. In this study, we provided the transcriptome sequence resource of V. bonariensis and used these data to realize its molecular mechanism under cold stress. The results contributed to valuable clues for genetic studies and helped to screen candidate genes for cold-resistance breeding.
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Affiliation(s)
- Meng-Qi Wang
- Department of Ornamental Horticulture, Sichuan Agricultural University, Chengdu, China
| | - Qin-Han Zeng
- Department of Ornamental Horticulture, Sichuan Agricultural University, Chengdu, China
| | - Qiu-Xiang Huang
- Department of Ornamental Horticulture, Sichuan Agricultural University, Chengdu, China
| | - Ping Lin
- Department of Ornamental Horticulture, Sichuan Agricultural University, Chengdu, China
| | - Yan Li
- The Key Laboratory of Plant Resources Conservation and Germplasm Innovation in Mountainous Region (Ministry of Education), Institute of Agro-Bioengineering and College of Life Sciences, Guizhou University, Guiyang, China
| | - Qing-Lin Liu
- Department of Ornamental Horticulture, Sichuan Agricultural University, Chengdu, China
| | - Lei Zhang
- Department of Ornamental Horticulture, Sichuan Agricultural University, Chengdu, China
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Panigrahi R, Kariali E, Panda BB, Lafarge T, Mohapatra PK. Controlling the trade-off between spikelet number and grain filling: the hierarchy of starch synthesis in spikelets of rice panicle in relation to hormone dynamics. FUNCTIONAL PLANT BIOLOGY : FPB 2019; 46:507-523. [PMID: 30961785 DOI: 10.1071/fp18153] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Accepted: 02/13/2019] [Indexed: 06/09/2023]
Abstract
The advent of dwarf statured rice varieties enabled a major breakthrough in yield and production, but raising the ceiling of genetically determined yield potential even further has been the breeding priority. Grain filling is asynchronous in the rice panicle; the inferior spikelets particularly on secondary branches of the basal part do not produce grains of a quality suitable for human consumption. Of the various strategies being considered, the control of ethylene production at anthesis has been a valuable route to potentially enhance genetic yield level of rice. The physiology underlying spikelet development has revealed spikelet position-specific ethylene levels determine the extent of grain filling, with higher levels resulting in ill-developed spikelet embodying poor endosperm starch content. To break the yield barrier, breeders have increased spikelet number per panicle in new large-panicle rice plants. However, the advantage of panicles with numerous spikelets has not resulted in enhanced yield because of poor filling of inferior spikelets. High spikelet number stimulates ethylene production and downgrading of starch synthesis, suggesting a trade-off between spikelet number and grain filling. High ethylene production in inferior spikelets suppresses expression of genes encoding endosperm starch synthesising enzymes. Hence, ethylene could be a retrograde signal that dictates the transcriptome dynamics for the cross talk between spikelet number and grain filling in the rice panicle, so attenuation of its activity may provide a solution to the problem of poor grain filling in large-panicle rice. This physiological linkage that reduces starch biosynthesis of inferior kernels is not genetically constitutive and amenable for modification through chemical, biotechnological, surgical and allelic manipulations. Studies on plant genotypes with different panicle architecture have opened up possibilities of selectively improving starch biosynthesis of inferior spikelets and thereby increasing grain yield through a physiological route.
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Affiliation(s)
- Rashmi Panigrahi
- School of Life Sciences, Sambalpur University, Jyoti vihar, Sambalpur, 768019, India
| | - Ekamber Kariali
- School of Life Sciences, Sambalpur University, Jyoti vihar, Sambalpur, 768019, India
| | - Binay Bhusan Panda
- Environmental Biotechnology Laboratory, Institute of Life Science, Bhubaneswar, 751023, India
| | - Tanguy Lafarge
- CIRAD, UMR AGAP, F-34398 Montpellier, France; and AGAP, University of Montpellier, CIRAD, INRA, INRIA, Montpellier SupAgro, Montpellier, France
| | - Pravat Kumar Mohapatra
- School of Life Sciences, Sambalpur University, Jyoti vihar, Sambalpur, 768019, India; and Corresponding author. Emails:
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Hwang SK, Singh S, Maharana J, Kalita S, Tuncel A, Rath T, Panda D, Modi MK, Okita TW. Mechanism Underlying Heat Stability of the Rice Endosperm Cytosolic ADP-Glucose Pyrophosphorylase. FRONTIERS IN PLANT SCIENCE 2019; 10:70. [PMID: 30804963 PMCID: PMC6378277 DOI: 10.3389/fpls.2019.00070] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2018] [Accepted: 01/17/2019] [Indexed: 05/22/2023]
Abstract
Rice grains accumulate starch as their major storage reserve whose biosynthesis is sensitive to heat. ADP-glucose pyrophosphorylase (AGPase) is among the starch biosynthetic enzymes severely affected by heat stress during seed maturation. To increase the heat tolerance of the rice enzyme, we engineered two dominant AGPase subunits expressed in developing endosperm, the large (L2) and small (S2b) subunits of the cytosol-specific AGPase. Bacterial expression of the rice S2b with the rice L2, potato tuber LS (pLS), or with the mosaic rice-potato large subunits, L2-pLS and pLS-L2, produced heat-sensitive recombinant enzymes, which retained less than 10% of their enzyme activities after 5 min incubation at 55°C. However, assembly of the rice L2 with the potato tuber SS (pSS) showed significantly increased heat stability comparable to the heat-stable potato pLS/pSS. The S2b assembled with the mosaic L2-pLS subunit showed 3-fold higher sensitivity to 3-PGA than L2/S2b, whereas the counterpart mosaic pLS-L2/S2b showed 225-fold lower sensitivity. Introduction of a QTC motif into S2b created an N-terminal disulfide linkage that was cleaved by dithiothreitol reduction. The QTC enzyme showed moderate heat stability but was not as stable as the potato AGPase. While the QTC AGPase exhibited approximately fourfold increase in 3-PGA sensitivity, its substrate affinities were largely unchanged. Random mutagenesis of S2bQTC produced six mutant lines with elevated production of glycogen in bacteria. All six lines contained a L379F substitution, which conferred enhanced glycogen production in bacteria and increased heat stability. Modeled structure of this mutant enzyme revealed that this highly conserved leucine residue is located in the enzyme's regulatory pocket that provides interaction sites for activators and inhibitors. Our molecular dynamic simulation analysis suggests that introduction of the QTC motif and the L379F mutation improves enzyme heat stability by stabilizing their backbone structures possibly due to the increased number of H-bonds between the small subunits and increased intermolecular interactions between the two SSs and two LSs at elevated temperature.
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Affiliation(s)
- Seon-Kap Hwang
- Institute of Biological Chemistry, Washington State University, Pullman, WA, United States
| | - Salvinder Singh
- Department of Agricultural Biotechnology, Assam Agricultural University, Jorhat, India
| | - Jitendra Maharana
- Distributed Information Centre (DIC), Department of Agricultural Biotechnology, Assam Agricultural University, Jorhat, India
| | - Samhita Kalita
- Department of Agricultural Biotechnology, Assam Agricultural University, Jorhat, India
| | - Aytug Tuncel
- Institute of Biological Chemistry, Washington State University, Pullman, WA, United States
| | - Tanmayee Rath
- Distributed Information Centre (DIC), Department of Agricultural Biotechnology, Assam Agricultural University, Jorhat, India
| | - Debashish Panda
- Distributed Information Centre (DIC), Department of Agricultural Biotechnology, Assam Agricultural University, Jorhat, India
| | - Mahendra Kumar Modi
- Department of Agricultural Biotechnology, Assam Agricultural University, Jorhat, India
| | - Thomas W. Okita
- Institute of Biological Chemistry, Washington State University, Pullman, WA, United States
- *Correspondence: Thomas W. Okita,
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12
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Jiang J, Yao C, Cao X, Liu Y, Xue S. Characterization of starch phosphorylase from the marine green microalga (Chlorophyta) Tetraselmis subcordiformis reveals its potential role in starch biosynthesis. JOURNAL OF PLANT PHYSIOLOGY 2017; 218:84-93. [PMID: 28787650 DOI: 10.1016/j.jplph.2017.07.019] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2017] [Revised: 07/04/2017] [Accepted: 07/26/2017] [Indexed: 06/07/2023]
Abstract
In a marine green starch-producing microalga Tetraselmis subcordiformis, the role of starch phosphorylase (SP) in the starch biosynthesis was disclosed by characterizing the enzyme properties and activity variations during the starch accumulation process. TsSP4, a SP isoform accounting for the major SP activity in T. subcordiformis, was unique to be active in a monomer form with a molecular weight of approximately 110kDa. It resembled one of the chloroplast-located SPs (PhoA) in Chlamydomonas reinhardtii with a similarity of 63.3% in sequence, though it possessed the typical L78/80 domain found in the plastidial SPs (Pho1) of higher plants that was absent in PhoA. TsSP4 exhibited moderate sensitivity to ADP-Glc inhibition and had a high activity for longer-chain linear maltooligosacchride (MOS) and amylopectin against highly branched glycogen as the substrates. TsSP4 had 2-fold higher affinity for Glc-1-P in the synthetic direction than for Pi in the phosphorolytic direction, and the catalytic constant kcat for Glc-1-P was 2-fold of that for Pi. Collectively, TsSP4 preferred synthetic rather than phosphorolytic direction. TsSP4 could elongate MOSs even initially with Pi alone in the absence of Glc-1-P, which further supported its synthetic role in the starch biosynthesis. TsSP4 displayed increased activities in the developing and mature stage of starch biosynthesis under nitrogen-starvation conditions, indicating its possible contribution to the amylopectin amplification.
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Affiliation(s)
- Junpeng Jiang
- Marine Bioengineering Group, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China; University of Chinese Academy of Sciences, Beijing 100039, China
| | - Changhong Yao
- Department of Pharmaceutical & Biological Engineering, School of Chemical Engineering, Sichuan University, Chengdu, Sichuan 610065, China.
| | - Xupeng Cao
- Marine Bioengineering Group, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
| | - Yinghui Liu
- Marine Bioengineering Group, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
| | - Song Xue
- Marine Bioengineering Group, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China.
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13
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Nakamura Y, Ono M, Sawada T, Crofts N, Fujita N, Steup M. Characterization of the functional interactions of plastidial starch phosphorylase and starch branching enzymes from rice endosperm during reserve starch biosynthesis. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2017; 264:83-95. [PMID: 28969805 DOI: 10.1016/j.plantsci.2017.09.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2016] [Revised: 09/02/2017] [Accepted: 09/05/2017] [Indexed: 05/28/2023]
Abstract
Functional interactions of plastidial phosphorylase (Pho1) and starch branching enzymes (BEs) from the developing rice endosperm are the focus of this study. In the presence of both Pho1 and BE, the same branched primer molecule is elongated and further branched almost simultaneously even at very low glucan concentrations present in the purified enzyme preparations. By contrast, in the absence of any BE, glucans are not, to any significant extent, elongated by Pho1. Based on our in vitro data, in the developing rice endosperm, Pho1 appears to be weakly associated with any of the BE isozymes. By using fluorophore-labeled malto-oligosaccharides, we identified maltose as the smallest possible primer for elongation by Pho1. Linear dextrins act as carbohydrate substrates for BEs. By functionally interacting with a BE, Pho1 performs two essential functions during the initiation of starch biosynthesis in the rice endosperm: First, it elongates maltodextrins up to a degree of polymerization of at least 60. Second, by closely interacting with BEs, Pho1 is able to elongate branched glucans efficiently and thereby synthesizes branched carbohydrates essential for the initiation of amylopectin biosynthesis.
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Affiliation(s)
- Yasunori Nakamura
- Faculty of Bioresource Sciences, Akita Prefectural University, Akita-City, Akita 010-0195, Japan; Akita Natural Science Laboratory, 25-44 Oiwake-Nishi, Tennoh, Katagami, Akita 010-0101, Japan.
| | - Masami Ono
- Faculty of Bioresource Sciences, Akita Prefectural University, Akita-City, Akita 010-0195, Japan
| | - Takayuki Sawada
- Faculty of Bioresource Sciences, Akita Prefectural University, Akita-City, Akita 010-0195, Japan
| | - Naoko Crofts
- Faculty of Bioresource Sciences, Akita Prefectural University, Akita-City, Akita 010-0195, Japan
| | - Naoko Fujita
- Faculty of Bioresource Sciences, Akita Prefectural University, Akita-City, Akita 010-0195, Japan
| | - Martin Steup
- Institute of Biochemistry and Biology, University of Potsdam, Karl-Liebknecht Strasse 24-25, Potsdam, Germany; Peter Gilgen Centre for Research and Learning, The Hospital for Sick Children, 72 Elm St., Toronto ON M5G 1×8, Canada; University of Toronto, Canada
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14
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Crofts N, Nakamura Y, Fujita N. Critical and speculative review of the roles of multi-protein complexes in starch biosynthesis in cereals. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2017; 262:1-8. [PMID: 28716405 DOI: 10.1016/j.plantsci.2017.05.007] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2016] [Revised: 05/01/2017] [Accepted: 05/11/2017] [Indexed: 05/08/2023]
Abstract
Starch accounts for the majority of edible carbohydrate resources generated through photosynthesis. Amylopectin is the major component of starch and is one of highest-molecular-weight biopolymers. Rapid and systematic synthesis of frequently branched hydro-insoluble amylopectin and efficient accumulation into amyloplasts of cereal endosperm is crucial. The functions of multiple starch biosynthetic enzymes, including elongation, branching, and debranching enzymes, must be temporally and spatially coordinated. Accordingly, direct evidence of protein-protein interactions of starch biosynthetic enzymes were first discovered in developing wheat endosperm in 2004, and they have since been shown in the developing seeds of other cereals. This review article describes structural characteristics of starches as well as similarities and differences in protein complex formation among different plant species and among mutant plants that are deficient in specific starch biosynthetic enzymes. In addition, evidence for protein complexes that are involved in the initiation stages of starch biosynthesis is summarized. Finally, we discuss the significance of protein complexes and describe new methods that may elucidate the mechanisms and roles of starch biosynthetic enzyme complexes.
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Affiliation(s)
- Naoko Crofts
- Department of Biological Production, Akita Prefectural University, Akita 010-0195, Japan
| | - Yasunori Nakamura
- Department of Biological Production, Akita Prefectural University, Akita 010-0195, Japan
| | - Naoko Fujita
- Department of Biological Production, Akita Prefectural University, Akita 010-0195, Japan.
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Rossi GB, Valentim-Neto PA, Blank M, Faria JCD, Arisi ACM. Comparison of Grain Proteome Profiles of Four Brazilian Common Bean (Phaseolus vulgaris L.) Cultivars. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2017; 65:7588-7597. [PMID: 28777559 DOI: 10.1021/acs.jafc.7b03220] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Common bean (Phaseolus vulgaris L.) is a source of proteins for about one billion people worldwide. In Brazil, 'BRS Sublime', 'BRS Vereda', 'BRS Esteio', and 'BRS Estilo' cultivars were developed by Embrapa to offer high yield to farmers and excellent quality to final consumers. In this work, grain proteomes of these common bean cultivars were compared based on two-dimensional gel electrophoresis (2-DE) and tandem mass spectrometry (MS/MS). Principal component analysis (PCA) was applied to compare 349 matched spots in these cultivars proteomes, and all cultivars were clearly separated in PCA plot. Thirty-two differentially accumulated proteins were identified by MS. Storage proteins such as phaseolins, legumins, and lectins were the most abundant, and novel proteins were also identified. We have built a useful platform that could be used to analyze other Brazilian cultivars and genotypes of common beans.
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Affiliation(s)
| | | | | | - Josias Correa de Faria
- Embrapa Arroz e Feijão, Caixa Postal 179, 75375-000 Santo Antônio de Goiás, Goiás, Brazil
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16
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Affiliation(s)
- Yasunori Nakamura
- Akita Natural Science Laboratory; Tennoh, Katagami, Akita Japan
- Faculty of Bioresource Sciences; Akita Prefectural University; Shimoshinjo-Nakano, Akita Japan
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17
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Functional and structural characterization of plastidic starch phosphorylase during barley endosperm development. PLoS One 2017; 12:e0175488. [PMID: 28407006 PMCID: PMC5391026 DOI: 10.1371/journal.pone.0175488] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Accepted: 03/27/2017] [Indexed: 12/03/2022] Open
Abstract
The production of starch is essential for human nutrition and represents a major metabolic flux in the biosphere. The biosynthesis of starch in storage organs like barley endosperm operates via two main pathways using different substrates: starch synthases use ADP-glucose to produce amylose and amylopectin, the two major components of starch, whereas starch phosphorylase (Pho1) uses glucose-1-phosphate (G1P), a precursor for ADP-glucose production, to produce α-1,4 glucans. The significance of the Pho1 pathway in starch biosynthesis has remained unclear. To elucidate the importance of barley Pho1 (HvPho1) for starch biosynthesis in barley endosperm, we analyzed HvPho1 protein production and enzyme activity levels throughout barley endosperm development and characterized structure-function relationships of HvPho1. The molecular mechanisms underlying the initiation of starch granule biosynthesis, that is, the enzymes and substrates involved in the initial transition from simple sugars to polysaccharides, remain unclear. We found that HvPho1 is present as an active protein at the onset of barley endosperm development. Notably, purified recombinant protein can catalyze the de novo production of α-1,4-glucans using HvPho1 from G1P as the sole substrate. The structural properties of HvPho1 provide insights into the low affinity of HvPho1 for large polysaccharides like starch or amylopectin. Our results suggest that HvPho1 may play a role during the initiation of starch biosynthesis in barley.
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18
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Qin S, Tang Y, Chen Y, Wu P, Li M, Wu G, Jiang H. Overexpression of the Starch Phosphorylase-Like Gene (PHO3) in Lotus japonicus has a Profound Effect on the Growth of Plants and Reduction of Transitory Starch Accumulation. FRONTIERS IN PLANT SCIENCE 2016; 7:1315. [PMID: 27630651 PMCID: PMC5005325 DOI: 10.3389/fpls.2016.01315] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Accepted: 08/16/2016] [Indexed: 05/25/2023]
Abstract
Two isoforms of starch phosphorylase (PHO; EC 2.4.1.1), plastidic PHO1 and cytosolic PHO2, have been found in all plants studied to date. Another starch phosphorylase-like gene, PHO3, which is an ortholog of Chlamydomonas PHOB, has been detected in some plant lineages. In this study, we identified three PHO isoform (LjPHO) genes in the Lotus japonicus genome. Expression of the LjPHO3 gene was observed in all tissues tested in L. japonicus, and the LjPHO3 protein was located in the chloroplast. Overexpression of LjPHO3 in L. japonicus resulted in a drastic decline in starch granule sizes and starch content in leaves. The LjPHO3 overexpression transgenic seedlings were smaller, and showed decreased pollen fertility and seed set rate. Our results suggest that LjPHO3 may participate in transitory starch metabolism in L. japonicus leaves, but its catalytic properties remain to be studied.
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Affiliation(s)
- Shanshan Qin
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of SciencesGuangzhou, China
- University of Chinese Academy of SciencesBeijing, China
| | - Yuehui Tang
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of SciencesGuangzhou, China
- University of Chinese Academy of SciencesBeijing, China
| | - Yaping Chen
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of SciencesGuangzhou, China
| | - Pingzhi Wu
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of SciencesGuangzhou, China
| | - Meiru Li
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of SciencesGuangzhou, China
| | - Guojiang Wu
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of SciencesGuangzhou, China
| | - Huawu Jiang
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of SciencesGuangzhou, China
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19
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Hwang SK, Koper K, Satoh H, Okita TW. Rice Endosperm Starch Phosphorylase (Pho1) Assembles with Disproportionating Enzyme (Dpe1) to Form a Protein Complex That Enhances Synthesis of Malto-oligosaccharides. J Biol Chem 2016; 291:19994-20007. [PMID: 27502283 DOI: 10.1074/jbc.m116.735449] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Indexed: 11/06/2022] Open
Abstract
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. Pulldown experiments showed that OsPho1 as well as OsPho1 devoid of its L80 region, a peptide unique to higher plant phosphorylases, captures disproportionating enzyme (OsDpe1). Interaction of the latter enzyme form with OsDpe1 indicates that the putative regulatory L80 is not responsible for multienzyme assembly. This heterotypic enzyme complex, determined at a molar ratio of 1:1, was validated by reciprocal co-immunoprecipitation studies of native seed proteins and by co-elution chromatographic and co-migration electrophoretic patterns of these enzymes in rice seed extracts. The OsPho1-OsDpe1 complex utilized a broader range of substrates for enhanced synthesis of larger maltooligosaccharides than each individual enzyme and significantly elevated the substrate affinities of OsPho1 at 30 °C. Moreover, the assembly with OsDpe1 enables OsPho1 to utilize products of transglycosylation reactions involving G1 and G3, sugars that it cannot catalyze directly.
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Affiliation(s)
- Seon-Kap Hwang
- From the Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164-6340 and
| | - Kaan Koper
- From the Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164-6340 and
| | - Hikaru Satoh
- Faculty of Agriculture, Kyushu University, Fukuoka, 812-8581, Japan
| | - Thomas W Okita
- From the Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164-6340 and
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