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Lin Q, Huang B, Zhang M, Zhang X, Rivenbark J, Lappe RL, James MG, Myers AM, Hennen-Bierwagen TA. Functional interactions between starch synthase III and isoamylase-type starch-debranching enzyme in maize endosperm. PLANT PHYSIOLOGY 2012; 158:679-92. [PMID: 22193705 PMCID: PMC3271759 DOI: 10.1104/pp.111.189704] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2011] [Accepted: 12/20/2011] [Indexed: 05/09/2023]
Abstract
This study characterized genetic interactions between the maize (Zea mays) genes dull1 (du1), encoding starch synthase III (SSIII), and isa2, encoding a noncatalytic subunit of heteromeric isoamylase-type starch-debranching enzyme (ISA1/ISA2 heteromer). Mutants lacking ISA2 still possess the ISA1 homomeric enzyme. Eight du1(-) mutations were characterized, and structural changes in amylopectin resulting from each were measured. In every instance, the same complex pattern of alterations in discontinuous spans of chain lengths was observed, which cannot be explained solely by a discrete range of substrates preferred by SSIII. Homozygous double mutants were constructed containing the null mutation isa2-339 and either du1-Ref, encoding a truncated SSIII protein lacking the catalytic domain, or the null allele du1-R4059. In contrast to the single mutant parents, double mutant endosperms affected in both SSIII and ISA2 were starch deficient and accumulated phytoglycogen. This phenotype was previously observed only in maize sugary1 mutants impaired for the catalytic subunit ISA1. ISA1 homomeric enzyme complexes assembled in both double mutants and were enzymatically active in vitro. Thus, SSIII is required for normal starch crystallization and the prevention of phytoglycogen accumulation when the only isoamylase-type debranching activity present is ISA1 homomer, but not in the wild-type condition, when both ISA1 homomer and ISA1/ISA2 heteromer are present. Previous genetic and biochemical analyses showed that SSIII also is required for normal glucan accumulation when the only isoamylase-type debranching enzyme activity present is ISA1/ISA heteromer. These data indicate that isoamylase-type debranching enzyme and SSIII work in a coordinated fashion to repress phytoglycogen accumulation.
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Cheng J, Khan MA, Qiu WM, Li J, Zhou H, Zhang Q, Guo W, Zhu T, Peng J, Sun F, Li S, Korban SS, Han Y. Diversification of genes encoding granule-bound starch synthase in monocots and dicots is marked by multiple genome-wide duplication events. PLoS One 2012; 7:e30088. [PMID: 22291904 PMCID: PMC3264551 DOI: 10.1371/journal.pone.0030088] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2011] [Accepted: 12/13/2011] [Indexed: 11/18/2022] Open
Abstract
Starch is one of the major components of cereals, tubers, and fruits. Genes encoding granule-bound starch synthase (GBSS), which is responsible for amylose synthesis, have been extensively studied in cereals but little is known about them in fruits. Due to their low copy gene number, GBSS genes have been used to study plant phylogenetic and evolutionary relationships. In this study, GBSS genes have been isolated and characterized in three fruit trees, including apple, peach, and orange. Moreover, a comprehensive evolutionary study of GBSS genes has also been conducted between both monocots and eudicots. Results have revealed that genomic structures of GBSS genes in plants are conserved, suggesting they all have evolved from a common ancestor. In addition, the GBSS gene in an ancestral angiosperm must have undergone genome duplication ∼251 million years ago (MYA) to generate two families, GBSSI and GBSSII. Both GBSSI and GBSSII are found in monocots; however, GBSSI is absent in eudicots. The ancestral GBSSII must have undergone further divergence when monocots and eudicots split ∼165 MYA. This is consistent with expression profiles of GBSS genes, wherein these profiles are more similar to those of GBSSII in eudicots than to those of GBSSI genes in monocots. In dicots, GBSSII must have undergone further divergence when rosids and asterids split from each other ∼126 MYA. Taken together, these findings suggest that it is GBSSII rather than GBSSI of monocots that have orthologous relationships with GBSS genes of eudicots. Moreover, diversification of GBSS genes is mainly associated with genome-wide duplication events throughout the evolutionary course of history of monocots and eudicots.
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Affiliation(s)
- Jun Cheng
- Key Laboratory of Plant Germplasm Enhancement and Specialty Agriculture, Wuhan Botanical Garden of the Chinese Academy of Sciences, Wuhan, Hubei, China
| | - Muhammad Awais Khan
- Department of Natural Resources and Environmental Sciences, University of Illinois, Urbana, Illinois, United States of America
| | - Wen-Ming Qiu
- Key Laboratory of Horticultural Plant Biology (Ministry of Education), Huazhong Agricultural University, Wuhan, Hubei, China
| | - Jing Li
- Key Laboratory of Plant Germplasm Enhancement and Specialty Agriculture, Wuhan Botanical Garden of the Chinese Academy of Sciences, Wuhan, Hubei, China
| | - Hui Zhou
- Key Laboratory of Plant Germplasm Enhancement and Specialty Agriculture, Wuhan Botanical Garden of the Chinese Academy of Sciences, Wuhan, Hubei, China
| | - Qiong Zhang
- Key Laboratory of Plant Germplasm Enhancement and Specialty Agriculture, Wuhan Botanical Garden of the Chinese Academy of Sciences, Wuhan, Hubei, China
| | - Wenwu Guo
- Key Laboratory of Horticultural Plant Biology (Ministry of Education), Huazhong Agricultural University, Wuhan, Hubei, China
| | - Tingting Zhu
- Key Laboratory of Plant Germplasm Enhancement and Specialty Agriculture, Wuhan Botanical Garden of the Chinese Academy of Sciences, Wuhan, Hubei, China
| | - Junhua Peng
- Key Laboratory of Plant Germplasm Enhancement and Specialty Agriculture, Wuhan Botanical Garden of the Chinese Academy of Sciences, Wuhan, Hubei, China
| | - Fengjie Sun
- School of Science and Technology, Georgia Gwinnett College, Lawrenceville, Georgia, United States of America
| | - Shaohua Li
- Key Laboratory of Plant Germplasm Enhancement and Specialty Agriculture, Wuhan Botanical Garden of the Chinese Academy of Sciences, Wuhan, Hubei, China
| | - Schuyler S. Korban
- Department of Natural Resources and Environmental Sciences, University of Illinois, Urbana, Illinois, United States of America
- * E-mail: (SK); (YH)
| | - Yuepeng Han
- Key Laboratory of Plant Germplasm Enhancement and Specialty Agriculture, Wuhan Botanical Garden of the Chinese Academy of Sciences, Wuhan, Hubei, China
- * E-mail: (SK); (YH)
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Myers AM, James MG, Lin Q, Yi G, Stinard PS, Hennen-Bierwagen TA, Becraft PW. Maize opaque5 encodes monogalactosyldiacylglycerol synthase and specifically affects galactolipids necessary for amyloplast and chloroplast function. THE PLANT CELL 2011; 23:2331-47. [PMID: 21685260 PMCID: PMC3160020 DOI: 10.1105/tpc.111.087205] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
The maize (Zea mays) opaque5 (o5) locus was shown to encode the monogalactosyldiacylglycerol synthase MGD1. Null and point mutations of o5 that affect the vitreous nature of mature endosperm engendered an allelic series of lines with stepwise reductions in gene function. C(18:3)/C(18:2) galactolipid abundance in seedling leaves was reduced proportionally, without significant effects on total galactolipid content. This alteration in polar lipid composition disrupted the organization of thylakoid membranes into granal stacks. Total galactolipid abundance in endosperm was strongly reduced in o5(-) mutants, causing developmental defects and changes in starch production such that the normal simple granules were replaced with compound granules separated by amyloplast membrane. Complete loss of MGD1 function in a null mutant caused kernel lethality owing to failure in both endosperm and embryo development. The data demonstrate that low-abundance galactolipids with five double bonds serve functions in plastid membranes that are not replaced by the predominant species with six double bonds. Furthermore, the data identify a function of amyloplast membranes in the development of starch granules. Finally, the specific changes in lipid composition suggest that MGD1 can distinguish the constituency of acyl groups on its diacylglycerol substrate based upon the degree of desaturation.
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Affiliation(s)
- Alan M. Myers
- Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, Iowa 50011
| | - Martha G. James
- Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, Iowa 50011
| | - Qiaohui Lin
- Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, Iowa 50011
| | - Gibum Yi
- Department of Genetics, Development, and Cell Biology, Iowa State University, Ames, Iowa 50011
| | - Philip S. Stinard
- U.S. Department of Agriculture/Agricultural Research Service, Maize Genetics Cooperation Stock Center, Urbana, Illinois 61801
| | | | - Philip W. Becraft
- Department of Genetics, Development, and Cell Biology, Iowa State University, Ames, Iowa 50011
- Address correspondence to
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Utsumi Y, Utsumi C, Sawada T, Fujita N, Nakamura Y. Functional diversity of isoamylase oligomers: the ISA1 homo-oligomer is essential for amylopectin biosynthesis in rice endosperm. PLANT PHYSIOLOGY 2011; 156:61-77. [PMID: 21436381 PMCID: PMC3091037 DOI: 10.1104/pp.111.173435] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Rice (Oryza sativa) endosperm has two isoamylase (ISA) oligomers, ISA1 homo-oligomer and ISA1-ISA2 hetero-oligomer. To examine their contribution to starch synthesis, expression of the ISA1 or ISA2 gene was differently regulated in various transgenic plants. Although suppression of ISA2 gene expression caused the endosperm to have only the homo-oligomer, no significant effects were detected on the starch phenotypes. In contrast, ISA2 overexpression led to endosperm having only the hetero-oligomer, and starch synthesis in the endosperm was drastically impaired, both quantitatively and qualitatively, because the starch was devoid of typical starch features, such as thermal and x-ray diffraction properties, and water-soluble highly branched maltodextrins were accumulated. In the ISA2 overexpressed line, about 60% to 70% of the ISA1-ISA2 hetero-oligomer was bound to starch, while the ISA homo- and hetero-oligomers from the wild type were mostly present in the soluble form at the early milking stage of the endosperm. Detailed analysis of the relative amounts of homo- and hetero-oligomers in various lines also led us to the conclusion that the ISA1 homo-oligomer is essential, but not the ISA1-ISA2 oligomer, for starch production in rice endosperm. The relative amounts of ISA1 and ISA2 proteins were shown to determine the ratio of both oligomers and the stoichiometry of both ISAs in the hetero-oligomer. It was noted when compared with the homo-oligomer that all the hetero-oligomers from rice endosperm and leaf and potato (Solanum tuberosum) tuber were much more stable at 40°C. This study provides substantial data on the structural and functional diversity of ISA oligomers between plant tissues and species.
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