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Chachar Z, Lai R, Ahmed N, Lingling M, Chachar S, Paker NP, Qi Y. Cloned genes and genetic regulation of anthocyanin biosynthesis in maize, a comparative review. FRONTIERS IN PLANT SCIENCE 2024; 15:1310634. [PMID: 38328707 PMCID: PMC10847539 DOI: 10.3389/fpls.2024.1310634] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Accepted: 01/02/2024] [Indexed: 02/09/2024]
Abstract
Anthocyanins are plant-based pigments that are primarily present in berries, grapes, purple yam, purple corn and black rice. The research on fruit corn with a high anthocyanin content is not sufficiently extensive. Considering its crucial role in nutrition and health it is vital to conduct further studies on how anthocyanin accumulates in fruit corn and to explore its potential for edible and medicinal purposes. Anthocyanin biosynthesis plays an important role in maize stems (corn). Several beneficial compounds, particularly cyanidin-3-O-glucoside, perlagonidin-3-O-glucoside, peonidin 3-O-glucoside, and their malonylated derivatives have been identified. C1, C2, Pl1, Pl2, Sh2, ZmCOP1 and ZmHY5 harbored functional alleles that played a role in the biosynthesis of anthocyanins in maize. The Sh2 gene in maize regulates sugar-to-starch conversion, thereby influencing kernel quality and nutritional content. ZmCOP1 and ZmHY5 are key regulatory genes in maize that control light responses and photomorphogenesis. This review concludes the molecular identification of all the genes encoding structural enzymes of the anthocyanin pathway in maize by describing the cloning and characterization of these genes. Our study presents important new understandings of the molecular processes behind the manufacture of anthocyanins in maize, which will contribute to the development of genetically modified variants of the crop with increased color and possible health advantages.
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Affiliation(s)
- Zaid Chachar
- College of Agriculture and Biology, Zhongkai University of Agriculture and Engineering, Guangzhou, China
- Guangdong Laboratory for Lingnan Modern Agriculture, Guangzhou, China
| | - RuiQiang Lai
- College of Agriculture and Biology, Zhongkai University of Agriculture and Engineering, Guangzhou, China
- Guangdong Laboratory for Lingnan Modern Agriculture, Guangzhou, China
| | - Nazir Ahmed
- College of Horticulture and Landscape Architecture, Zhongkai University of Agriculture and Engineering, Guangzhou, China
| | - Ma Lingling
- College of Agriculture, Jilin Agricultural University, Changchun, Jilin, China
| | - Sadaruddin Chachar
- College of Horticulture and Landscape Architecture, Zhongkai University of Agriculture and Engineering, Guangzhou, China
| | | | - YongWen Qi
- College of Agriculture and Biology, Zhongkai University of Agriculture and Engineering, Guangzhou, China
- Guangdong Laboratory for Lingnan Modern Agriculture, Guangzhou, China
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Wang Y, Shi D, Zhu H, Yin H, Wang G, Yang A, Song Z, Jing Q, Shuai B, Xu N, Yang J, Chen H, Wang G. Revisiting maize Brittle endosperm-2 reveals new insights in BETL development and starchy endosperm filling. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2023; 332:111727. [PMID: 37149228 DOI: 10.1016/j.plantsci.2023.111727] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2023] [Revised: 03/18/2023] [Accepted: 05/03/2023] [Indexed: 05/08/2023]
Abstract
Rerouting the starch biosynthesis pathway in maize can generate specialty types, like sweet corn and waxy corn, with a drastically increasing global demand. Hence, a fine-tuning of starch metabolism is relevant to create diverse maize cultivars for end-use applications. Here, we characterized a new maize brittle endosperm mutant, referred to as bt1774, which exhibited decreased starch content but a dramatic increase of soluble sugars at maturity. Both endosperm and embryo development was impaired in bt1774 relative to the wild-type (WT), with a prominently arrested basal endosperm transfer layer (BETL). Map-based cloning revealed that BRITTLE ENDOSPERM2 (Bt2), which encodes a small subunit of ADP-glucose pyrophosphorylase (AGPase), is the causal gene for bt1774. A MuA2 element was found to be inserted into intron 2 of Bt2, leading to a severe decrease of its expression, in bt1774. This is in line with the irregular and loosely packed starch granules in the mutant. Transcriptome of endosperm at grain filling stage identified 1, 013 differentially expressed genes in bt1774, which were notably enriched in the BETL compartment, including ZmMRP1, Miniature1, MEG1, and BETLs. Gene expression of the canonical starch biosynthesis pathway was marginally disturbed in Bt1774. Combined with the residual 60% of starch in this nearly null mutant of Bt2, this data strongly suggests that an AGPase-independent pathway compensates for starch synthesis in the endosperm. Consistent with the BETL defects, zein accumulation was impaired in bt1774. Co-expression network analysis revealed that Bt2 probably has a role in intracellular signal transduction, besides starch synthesis. Altogether, we propose that Bt2 is likely involved in carbohydrate flux and balance, thus regulating both the BETL development and the starchy endosperm filling.
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Affiliation(s)
- Yongyan Wang
- National Key Laboratory of Wheat and Maize Crops Science, CIMMYT-China (Henan) Joint Center of Wheat and Maize, Collaborative Innovation Center of Henan Grain Crops, College of Agronomy, Henan Agricultural University, Zhengzhou 450002, China
| | - Dongsheng Shi
- School of Environmental and Rural Science, University of New England, Armidale, New South Wales, Australia
| | - Hui Zhu
- National Key Laboratory of Wheat and Maize Crops Science, CIMMYT-China (Henan) Joint Center of Wheat and Maize, Collaborative Innovation Center of Henan Grain Crops, College of Agronomy, Henan Agricultural University, Zhengzhou 450002, China
| | - Hanxue Yin
- National Key Laboratory of Wheat and Maize Crops Science, CIMMYT-China (Henan) Joint Center of Wheat and Maize, Collaborative Innovation Center of Henan Grain Crops, College of Agronomy, Henan Agricultural University, Zhengzhou 450002, China
| | - Gaoyang Wang
- National Key Laboratory of Wheat and Maize Crops Science, CIMMYT-China (Henan) Joint Center of Wheat and Maize, Collaborative Innovation Center of Henan Grain Crops, College of Agronomy, Henan Agricultural University, Zhengzhou 450002, China
| | - Anqi Yang
- National Key Laboratory of Wheat and Maize Crops Science, CIMMYT-China (Henan) Joint Center of Wheat and Maize, Collaborative Innovation Center of Henan Grain Crops, College of Agronomy, Henan Agricultural University, Zhengzhou 450002, China
| | - Zhixuan Song
- National Key Laboratory of Wheat and Maize Crops Science, CIMMYT-China (Henan) Joint Center of Wheat and Maize, Collaborative Innovation Center of Henan Grain Crops, College of Agronomy, Henan Agricultural University, Zhengzhou 450002, China
| | - Qingquan Jing
- National Key Laboratory of Wheat and Maize Crops Science, CIMMYT-China (Henan) Joint Center of Wheat and Maize, Collaborative Innovation Center of Henan Grain Crops, College of Agronomy, Henan Agricultural University, Zhengzhou 450002, China
| | - Bilian Shuai
- Shanghai Key Laboratory of Bio-Energy Crops, School of Life Sciences, Shanghai University, Shanghai 200444, China
| | - Ningkun Xu
- National Key Laboratory of Wheat and Maize Crops Science, CIMMYT-China (Henan) Joint Center of Wheat and Maize, Collaborative Innovation Center of Henan Grain Crops, College of Agronomy, Henan Agricultural University, Zhengzhou 450002, China
| | - Jianping Yang
- National Key Laboratory of Wheat and Maize Crops Science, CIMMYT-China (Henan) Joint Center of Wheat and Maize, Collaborative Innovation Center of Henan Grain Crops, College of Agronomy, Henan Agricultural University, Zhengzhou 450002, China
| | - Hongyu Chen
- National Key Laboratory of Wheat and Maize Crops Science, CIMMYT-China (Henan) Joint Center of Wheat and Maize, Collaborative Innovation Center of Henan Grain Crops, College of Agronomy, Henan Agricultural University, Zhengzhou 450002, China.
| | - Guifeng Wang
- National Key Laboratory of Wheat and Maize Crops Science, CIMMYT-China (Henan) Joint Center of Wheat and Maize, Collaborative Innovation Center of Henan Grain Crops, College of Agronomy, Henan Agricultural University, Zhengzhou 450002, China.
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Ajayo BS, Li Y, Wang Y, Dai C, Gao L, Liu H, Yu G, Zhang J, Huang Y, Hu Y. The novel ZmTCP7 transcription factor targets AGPase-encoding gene ZmBt2 to regulate storage starch accumulation in maize. FRONTIERS IN PLANT SCIENCE 2022; 13:943050. [PMID: 35909761 PMCID: PMC9335043 DOI: 10.3389/fpls.2022.943050] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Accepted: 06/28/2022] [Indexed: 05/27/2023]
Abstract
The process of starch biosynthesis is a major developmental event that affects the final grain yield and quality in maize (Zea mays L.), and transcriptional regulation plays a key role in modulating the expression of the main players in the pathway. ZmBt2, which encodes the small subunits of AGPase, is a rate-controlling gene of the pathway; however, much remains unknown about its transcriptional regulation. Our earlier study identifies a short functional fragment of ZmBt2 promoter (394-bp), and further shows it contains multiple putative cis-acting regulatory elements, demonstrating that several transcription factors may govern ZmBt2 expression. Here, we identified a novel TCP transcription factor (TF), ZmTCP7, that interacted with the functional fragment of the ZmBt2 promoter in a yeast one hybrid screening system. We further showed that ZmTCP7 is a non-autonomous TF targeted to the nucleus and predominantly expressed in maize endosperm. Using promoter deletion analyzes by transient expression in maize endosperm protoplasts combined with electrophoretic mobility shift assays, we found that ZmTCP7 bound to GAACCCCAC elements on the ZmBt2 promoter to suppress its expression. Transgenic overexpression of ZmTCP7 in maize caused a significant repression of ZmBt2 transcription by ~77.58%, resulting in a 21.51% decrease in AGPase activity and a 9.58% reduction in the endosperm starch content of transgenic maize. Moreover, the expressions of ZmBt1, ZmSSI, ZmSSIIa, and ZmSSIIIa were increased, while those of ZmSh2 and ZmSSIV reduced significantly in the endosperm of the transgenic maize. Overall, this study shows that ZmTCP7 functions as a transcriptional repressor of ZmBt2 and a negative regulator of endosperm starch accumulation, providing new insights into the regulatory networks that govern ZmBt2 expression and starch biosynthesis pathway in maize.
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Affiliation(s)
- Babatope Samuel Ajayo
- State Key Laboratory of Crop Gene Resource Exploration and Utilization in Southwest China, Chengdu, China
- College of Agronomy, Sichuan Agricultural University, Chengdu, China
| | - Yangping Li
- State Key Laboratory of Crop Gene Resource Exploration and Utilization in Southwest China, Chengdu, China
- College of Agronomy, Sichuan Agricultural University, Chengdu, China
| | - Yayun Wang
- State Key Laboratory of Crop Gene Resource Exploration and Utilization in Southwest China, Chengdu, China
- College of Agronomy, Sichuan Agricultural University, Chengdu, China
| | - Chengdong Dai
- State Key Laboratory of Crop Gene Resource Exploration and Utilization in Southwest China, Chengdu, China
- College of Agronomy, Sichuan Agricultural University, Chengdu, China
| | - Lei Gao
- State Key Laboratory of Crop Gene Resource Exploration and Utilization in Southwest China, Chengdu, China
- College of Agronomy, Sichuan Agricultural University, Chengdu, China
| | - Hanmei Liu
- College of Agronomy, Sichuan Agricultural University, Chengdu, China
- College of Life Science, Sichuan Agricultural University, Ya’an, China
| | - Guowu Yu
- State Key Laboratory of Crop Gene Resource Exploration and Utilization in Southwest China, Chengdu, China
- College of Agronomy, Sichuan Agricultural University, Chengdu, China
| | - Junjie Zhang
- College of Agronomy, Sichuan Agricultural University, Chengdu, China
- College of Life Science, Sichuan Agricultural University, Ya’an, China
| | - Yubi Huang
- State Key Laboratory of Crop Gene Resource Exploration and Utilization in Southwest China, Chengdu, China
- College of Agronomy, Sichuan Agricultural University, Chengdu, China
| | - Yufeng Hu
- State Key Laboratory of Crop Gene Resource Exploration and Utilization in Southwest China, Chengdu, China
- College of Agronomy, Sichuan Agricultural University, Chengdu, China
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Boehlein SK, Shaw JR, Boehlein TJ, Boehlein EC, Hannah LC. Fundamental differences in starch synthesis in the maize leaf, embryo, ovary and endosperm. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2018; 96:595-606. [PMID: 30062763 DOI: 10.1111/tpj.14053] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Accepted: 07/23/2018] [Indexed: 05/25/2023]
Abstract
Enzymological and starch analyses of various ADP-glucose pyrophosphorylase (AGPase) null mutants point to fundamental differences in the pathways for starch synthesis in the maize leaf, embryo, ovary and endosperm. Leaf starch is synthesized via the AGPase encoded by the small and large subunits shown previously to be expressed at abundant levels in the leaf, whereas more than one AGPase isoform functions in the embryo and in the ovary. Embryo starch content is also dependent on genes functioning in the leaf and in the endosperm. AGPase encoded by shrunken-2 and brittle-2 synthesizes ~75% of endosperm starch. The gene, agpsemzm, previously shown to encode the small subunit expressed in the embryo, and agpllzm, the leaf large subunit gene, are here shown to encode the endosperm, plastid-localized AGPase. Loss of this enzyme does not reduce endosperm starch. Rather, the data suggest that AGPase-independent starch synthesis accounts for ~25% of endosperm starch. Three maize genes encode the small subunit of the AGPase. Data here show that the triple mutant lacking all three small subunits is lethal in early seed development but can be viable in both male and female gametes. Seed and plant viability is restored by any one of the three small subunit genes, including one previously thought to function only in the cytosol of the endosperm. Data herein also show the functionality of a fourth gene encoding the large subunit of this enzyme. Although adenosine diphosphate glucose pyrophosphorylase is shown here to be essential for maize viability, strong evidence for starch synthesis in the endosperm that is independent of this enzyme is also presented. Starch synthesis is distinct in the maize embryo, ovary, leaf and endosperm, and is coordinated among the various tissues.
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Affiliation(s)
- Susan K Boehlein
- Program in Plant Molecular and Cellular Biology, Genetics Institute and the Department of Horticultural Sciences, University of Florida, Gainesville, FL, 32611, USA
| | - Janine R Shaw
- Program in Plant Molecular and Cellular Biology, Genetics Institute and the Department of Horticultural Sciences, University of Florida, Gainesville, FL, 32611, USA
| | - Timothy J Boehlein
- Program in Plant Molecular and Cellular Biology, Genetics Institute and the Department of Horticultural Sciences, University of Florida, Gainesville, FL, 32611, USA
| | - Emily C Boehlein
- Program in Plant Molecular and Cellular Biology, Genetics Institute and the Department of Horticultural Sciences, University of Florida, Gainesville, FL, 32611, USA
| | - L Curtis Hannah
- Program in Plant Molecular and Cellular Biology, Genetics Institute and the Department of Horticultural Sciences, University of Florida, Gainesville, FL, 32611, USA
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Abstract
Promoters regulate gene expression, and are essential biotechnology tools. Since its introduction in the mid-1990s, biotechnology has greatly enhanced maize productivity primarily through the development of insect control and herbicide tolerance traits. Additional biotechnology applications include improving seed nutrient composition, industrial protein production, therapeutic production, disease resistance, abiotic stress resistance, and yield enhancement. Biotechnology has also greatly expanded basic research into important mechanisms that govern plant growth and reproduction. Many novel promoters have been developed to facilitate this work, but only a few are widely used. Transgene optimization includes a variety of strategies some of which effect promoter structure. Recent reviews examine the state of the art with respect to transgene design for biotechnology applications. This chapter examines the use of transgene technology in maize, focusing on the way promoters are selected and used. The impact of new developments in genomic technology on promoter structure is also discussed.
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Saripalli G, Gupta PK. AGPase: its role in crop productivity with emphasis on heat tolerance in cereals. TAG. THEORETICAL AND APPLIED GENETICS. THEORETISCHE UND ANGEWANDTE GENETIK 2015; 128:1893-916. [PMID: 26152573 DOI: 10.1007/s00122-015-2565-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Accepted: 06/16/2015] [Indexed: 05/11/2023]
Abstract
AGPase, a key enzyme of starch biosynthetic pathway, has a significant role in crop productivity. Thermotolerant variants of AGPase in cereals may be used for developing cultivars, which may enhance productivity under heat stress. Improvement of crop productivity has always been the major goal of plant breeders to meet the global demand for food. However, crop productivity itself is influenced in a large measure by a number of abiotic stresses including heat, which causes major losses in crop productivity. In cereals, crop productivity in terms of grain yield mainly depends upon the seed starch content so that starch biosynthesis and the enzymes involved in this process have been a major area of investigation for plant physiologists and plant breeders alike. Considerable work has been done on AGPase and its role in crop productivity, particularly under heat stress, because this enzyme is one of the major enzymes, which catalyses the rate-limiting first committed key enzymatic step of starch biosynthesis. Keeping the above in view, this review focuses on the basic features of AGPase including its structure, regulatory mechanisms involving allosteric regulators, its sub-cellular localization and its genetics. Major emphasis, however, has been laid on the genetics of AGPases and its manipulation for developing high yielding cultivars that will have comparable productivity under heat stress. Some important thermotolerant variants of AGPase, which mainly involve specific amino acid substitutions, have been highlighted, and the prospects of using these thermotolerant variants of AGPase in developing cultivars for heat prone areas have been discussed. The review also includes a brief account on transgenics for AGPase, which have been developed for basic studies and crop improvement.
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Affiliation(s)
- Gautam Saripalli
- Molecular Biology Laboratory, Department of Genetics and Plant Breeding, Ch.Charan Singh University, Meerut, 250004, India
| | - Pushpendra Kumar Gupta
- Molecular Biology Laboratory, Department of Genetics and Plant Breeding, Ch.Charan Singh University, Meerut, 250004, India.
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Saripalli G, Gupta PK. AGPase: its role in crop productivity with emphasis on heat tolerance in cereals. TAG. THEORETICAL AND APPLIED GENETICS. THEORETISCHE UND ANGEWANDTE GENETIK 2015. [PMID: 26152573 DOI: 10.1007/s00122-015-2565-2562] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
AGPase, a key enzyme of starch biosynthetic pathway, has a significant role in crop productivity. Thermotolerant variants of AGPase in cereals may be used for developing cultivars, which may enhance productivity under heat stress. Improvement of crop productivity has always been the major goal of plant breeders to meet the global demand for food. However, crop productivity itself is influenced in a large measure by a number of abiotic stresses including heat, which causes major losses in crop productivity. In cereals, crop productivity in terms of grain yield mainly depends upon the seed starch content so that starch biosynthesis and the enzymes involved in this process have been a major area of investigation for plant physiologists and plant breeders alike. Considerable work has been done on AGPase and its role in crop productivity, particularly under heat stress, because this enzyme is one of the major enzymes, which catalyses the rate-limiting first committed key enzymatic step of starch biosynthesis. Keeping the above in view, this review focuses on the basic features of AGPase including its structure, regulatory mechanisms involving allosteric regulators, its sub-cellular localization and its genetics. Major emphasis, however, has been laid on the genetics of AGPases and its manipulation for developing high yielding cultivars that will have comparable productivity under heat stress. Some important thermotolerant variants of AGPase, which mainly involve specific amino acid substitutions, have been highlighted, and the prospects of using these thermotolerant variants of AGPase in developing cultivars for heat prone areas have been discussed. The review also includes a brief account on transgenics for AGPase, which have been developed for basic studies and crop improvement.
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Affiliation(s)
- Gautam Saripalli
- Molecular Biology Laboratory, Department of Genetics and Plant Breeding, Ch.Charan Singh University, Meerut, 250004, India
| | - Pushpendra Kumar Gupta
- Molecular Biology Laboratory, Department of Genetics and Plant Breeding, Ch.Charan Singh University, Meerut, 250004, India.
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Saripalli G, Gupta PK. AGPase: its role in crop productivity with emphasis on heat tolerance in cereals. TAG. THEORETICAL AND APPLIED GENETICS. THEORETISCHE UND ANGEWANDTE GENETIK 2015; 128:1893-1916. [PMID: 26152573 DOI: 10.1007/s00122-015-25652] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Accepted: 06/16/2015] [Indexed: 05/26/2023]
Abstract
AGPase, a key enzyme of starch biosynthetic pathway, has a significant role in crop productivity. Thermotolerant variants of AGPase in cereals may be used for developing cultivars, which may enhance productivity under heat stress. Improvement of crop productivity has always been the major goal of plant breeders to meet the global demand for food. However, crop productivity itself is influenced in a large measure by a number of abiotic stresses including heat, which causes major losses in crop productivity. In cereals, crop productivity in terms of grain yield mainly depends upon the seed starch content so that starch biosynthesis and the enzymes involved in this process have been a major area of investigation for plant physiologists and plant breeders alike. Considerable work has been done on AGPase and its role in crop productivity, particularly under heat stress, because this enzyme is one of the major enzymes, which catalyses the rate-limiting first committed key enzymatic step of starch biosynthesis. Keeping the above in view, this review focuses on the basic features of AGPase including its structure, regulatory mechanisms involving allosteric regulators, its sub-cellular localization and its genetics. Major emphasis, however, has been laid on the genetics of AGPases and its manipulation for developing high yielding cultivars that will have comparable productivity under heat stress. Some important thermotolerant variants of AGPase, which mainly involve specific amino acid substitutions, have been highlighted, and the prospects of using these thermotolerant variants of AGPase in developing cultivars for heat prone areas have been discussed. The review also includes a brief account on transgenics for AGPase, which have been developed for basic studies and crop improvement.
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Affiliation(s)
- Gautam Saripalli
- Molecular Biology Laboratory, Department of Genetics and Plant Breeding, Ch.Charan Singh University, Meerut, 250004, India
| | - Pushpendra Kumar Gupta
- Molecular Biology Laboratory, Department of Genetics and Plant Breeding, Ch.Charan Singh University, Meerut, 250004, India.
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Huang B, Hennen-Bierwagen TA, Myers AM. Functions of multiple genes encoding ADP-glucose pyrophosphorylase subunits in maize endosperm, embryo, and leaf. PLANT PHYSIOLOGY 2014; 164:596-611. [PMID: 24381067 PMCID: PMC3912092 DOI: 10.1104/pp.113.231605] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
ADP-glucose pyrophosphorylase (AGPase) provides the nucleotide sugar ADP-glucose and thus constitutes the first step in starch biosynthesis. The majority of cereal endosperm AGPase is located in the cytosol with a minor portion in amyloplasts, in contrast to its strictly plastidial location in other species and tissues. To investigate the potential functions of plastidial AGPase in maize (Zea mays) endosperm, six genes encoding AGPase large or small subunits were characterized for gene expression as well as subcellular location and biochemical activity of the encoded proteins. Seven transcripts from these genes accumulate in endosperm, including those from shrunken2 and brittle2 that encode cytosolic AGPase and five candidates that could encode subunits of the plastidial enzyme. The amino termini of these five polypeptides directed the transport of a reporter protein into chloroplasts of leaf protoplasts. All seven proteins exhibited AGPase activity when coexpressed in Escherichia coli with partner subunits. Null mutations were identified in the genes agpsemzm and agpllzm and shown to cause reduced AGPase activity in specific tissues. The functioning of these two genes was necessary for the accumulation of normal starch levels in embryo and leaf, respectively. Remnant starch was observed in both instances, indicating that additional genes encode AGPase large and small subunits in embryo and leaf. Endosperm starch was decreased by approximately 7% in agpsemzm- or agpllzm- mutants, demonstrating that plastidial AGPase activity contributes to starch production in this tissue even when the major cytosolic activity is present.
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Spielbauer G, Li L, Römisch-Margl L, Do PT, Fouquet R, Fernie AR, Eisenreich W, Gierl A, Settles AM. Chloroplast-localized 6-phosphogluconate dehydrogenase is critical for maize endosperm starch accumulation. JOURNAL OF EXPERIMENTAL BOTANY 2013; 64:2231-42. [PMID: 23530131 PMCID: PMC3654415 DOI: 10.1093/jxb/ert082] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Plants have duplicate versions of the oxidative pentose phosphate pathway (oxPPP) enzymes with a subset localized to the chloroplast. The chloroplast oxPPP provides NADPH and pentose sugars for multiple metabolic pathways. This study identified two loss-of-function alleles of the Zea mays (maize) chloroplast-localized oxPPP enzyme 6-phosphogluconate dehydrogenase (6PGDH). These mutations caused a rough endosperm seed phenotype with reduced embryo oil and endosperm starch. Genetic translocation experiments showed that pgd3 has separate, essential roles in both endosperm and embryo development. Endosperm metabolite profiling experiments indicated that pgd3 shifts redox-related metabolites and increases reducing sugars similar to starch-biosynthetis mutants. Heavy isotope-labelling experiments indicates that carbon flux into starch is altered in pgd3 mutants. Labelling experiments with a loss of cytosolic 6PGDH did not affect flux into starch. These results support the known role for plastid-localized oxPPP in oil synthesis and argue that amyloplast-localized oxPPP reactions are integral to endosperm starch accumulation in maize kernels.
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Affiliation(s)
- Gertraud Spielbauer
- Horticultural Sciences Department, University of Florida, Gainesville, FL 32611, USA
| | - Li Li
- Horticultural Sciences Department, University of Florida, Gainesville, FL 32611, USA
| | - Lilla Römisch-Margl
- Lehrstuhl für Genetik, Technische Universität München, 85354 Freising, Germany
| | - Phuc Thi Do
- Max-Planck-Institut für Molekulare Pflanzenphysiologie; Potsdam-Golm, Germany
| | - Romain Fouquet
- Horticultural Sciences Department, University of Florida, Gainesville, FL 32611, USA
| | - Alisdair R. Fernie
- Max-Planck-Institut für Molekulare Pflanzenphysiologie; Potsdam-Golm, Germany
| | - Wolfgang Eisenreich
- Lehrstuhl für Biochemie, Technische Universität München, 85747 Garching, Germany
| | - Alfons Gierl
- Lehrstuhl für Genetik, Technische Universität München, 85354 Freising, Germany
| | - A. Mark Settles
- Horticultural Sciences Department, University of Florida, Gainesville, FL 32611, USA
- * To whom correspondence should be addressed. E-mail:
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Faix B, Radchuk V, Nerlich A, Hümmer C, Radchuk R, Emery RJN, Keller H, Götz KP, Weschke W, Geigenberger P, Weber H. Barley grains, deficient in cytosolic small subunit of ADP-glucose pyrophosphorylase, reveal coordinate adjustment of C:N metabolism mediated by an overlapping metabolic-hormonal control. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2012; 69:1077-1093. [PMID: 22098161 DOI: 10.1111/j.1365-313x.2011.04857.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The barley Risø16 mutation leads to inactivation of cytosolic ADP-Glc pyrophosphorylase, and results in decreased ADP-Glc and endospermal starch levels. Here we show that this mutation is accompanied by a decrease in storage protein accumulation and seed size, which indicates that alteration of a single enzymatic step can change the network of storage metabolism as a whole. We used comprehensive transcript, metabolite and hormonal profiling to compare grain metabolism and development of Risø16 and wild-type endosperm. Despite increased sugar availability in mutant endosperm, glycolytic intermediates downstream of hexose phosphates remained unchanged or decreased, while several glycolytic enzymes were downregulated at the transcriptional level. Metabolite and transcript profiling also indicated an inhibition of the tricarboxylic acid cycle at the level of mitochondrial nicotinamide adenine dinucleotide (NAD)-isocitrate dehydrogenase and an attendant decrease in alpha-ketoglutarate and amino acids levels in Risø16, compared with wild type. Decreased levels of cytokinins in Risø16 endosperm suggested co-regulation between starch synthesis, abscisic acid (ABA) deficiency and cytokinin biosynthesis. Comparative cis-element analysis in promoters of jointly downregulated genes in Risø16 revealed an overlap between metabolic and hormonal regulation, which leds to a coordinated downregulation of endosperm-specific and ABA-inducible gene expression (storage proteins) together with repression by sugars (isocitrate dehydrogenase, amylases). Such co-regulation ensured that decreased carbon fluxes into starch lead to a coordinated inhibition of glycolysis, amino acid and storage proteins biosynthesis, which is useful in the prevention of osmotic imbalances and oxidative stress due to increased accumulation of sugars.
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Affiliation(s)
- Benjamin Faix
- Department Biologie I, Ludwig-Maximilians-Universität München, Grosshaderner Str. 2-4, D-82152 Martinsried, Germany
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Sosso D, Mbelo S, Vernoud V, Gendrot G, Dedieu A, Chambrier P, Dauzat M, Heurtevin L, Guyon V, Takenaka M, Rogowsky PM. PPR2263, a DYW-Subgroup Pentatricopeptide repeat protein, is required for mitochondrial nad5 and cob transcript editing, mitochondrion biogenesis, and maize growth. THE PLANT CELL 2012; 24:676-91. [PMID: 22319053 PMCID: PMC3315240 DOI: 10.1105/tpc.111.091074] [Citation(s) in RCA: 108] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
RNA editing plays an important role in organelle gene expression in various organisms, including flowering plants, changing the nucleotide information at precise sites. Here, we present evidence that the maize (Zea mays) nuclear gene Pentatricopeptide repeat 2263 (PPR2263) encoding a DYW domain-containing PPR protein is required for RNA editing in the mitochondrial NADH dehydrogenase5 (nad5) and cytochrome b (cob) transcripts at the nad5-1550 and cob-908 sites, respectively. Its putative ortholog, MITOCHONDRIAL EDITING FACTOR29, fulfills the same role in Arabidopsis thaliana. Both the maize and the Arabidopsis proteins show preferential localization to mitochondria but are also detected in chloroplasts. In maize, the corresponding ppr2263 mutation causes growth defects in kernels and seedlings. Embryo and endosperm growth are reduced, leading to the production of small but viable kernels. Mutant plants have narrower and shorter leaves, exhibit a strong delay in flowering time, and generally do not reach sexual maturity. Whereas mutant chloroplasts do not have major defects, mutant mitochondria lack complex III and are characterized by a compromised ultrastructure, increased transcript levels, and the induction of alternative oxidase. The results suggest that mitochondrial RNA editing at the cob-908 site is necessary for mitochondrion biogenesis, cell division, and plant growth in maize.
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Affiliation(s)
- Davide Sosso
- University of Lyon, Ecole Normale Supérieure de Lyon, Université Lyon 1, Unité Reproduction et Développement des Plantes, F-69364 Lyon, France
- Institut National de la Recherche Agronomique, Unité Mixte de Recherche 879 Reproduction et Développement des Plantes, F-69364 Lyon, France
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5667 Reproduction et Développement des Plantes, F-69364 Lyon, France
| | - Sylvie Mbelo
- University of Lyon, Ecole Normale Supérieure de Lyon, Université Lyon 1, Unité Reproduction et Développement des Plantes, F-69364 Lyon, France
- Institut National de la Recherche Agronomique, Unité Mixte de Recherche 879 Reproduction et Développement des Plantes, F-69364 Lyon, France
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5667 Reproduction et Développement des Plantes, F-69364 Lyon, France
| | - Vanessa Vernoud
- University of Lyon, Ecole Normale Supérieure de Lyon, Université Lyon 1, Unité Reproduction et Développement des Plantes, F-69364 Lyon, France
- Institut National de la Recherche Agronomique, Unité Mixte de Recherche 879 Reproduction et Développement des Plantes, F-69364 Lyon, France
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5667 Reproduction et Développement des Plantes, F-69364 Lyon, France
| | - Ghislaine Gendrot
- University of Lyon, Ecole Normale Supérieure de Lyon, Université Lyon 1, Unité Reproduction et Développement des Plantes, F-69364 Lyon, France
- Institut National de la Recherche Agronomique, Unité Mixte de Recherche 879 Reproduction et Développement des Plantes, F-69364 Lyon, France
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5667 Reproduction et Développement des Plantes, F-69364 Lyon, France
| | - Annick Dedieu
- University of Lyon, Ecole Normale Supérieure de Lyon, Université Lyon 1, Unité Reproduction et Développement des Plantes, F-69364 Lyon, France
- Institut National de la Recherche Agronomique, Unité Mixte de Recherche 879 Reproduction et Développement des Plantes, F-69364 Lyon, France
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5667 Reproduction et Développement des Plantes, F-69364 Lyon, France
| | - Pierre Chambrier
- University of Lyon, Ecole Normale Supérieure de Lyon, Université Lyon 1, Unité Reproduction et Développement des Plantes, F-69364 Lyon, France
- Institut National de la Recherche Agronomique, Unité Mixte de Recherche 879 Reproduction et Développement des Plantes, F-69364 Lyon, France
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5667 Reproduction et Développement des Plantes, F-69364 Lyon, France
| | - Myriam Dauzat
- Institut National de la Recherche Agronomique, Unité Mixte de Recherche 759 Ecophysiologie des Plantes sous Stress Environnementaux, F-34060 Montpellier, France
| | - Laure Heurtevin
- Institut National de la Recherche Agronomique, Unité Mixte de Recherche 1165 Recherche en Génomique Végétale, F-91057 Evry, France
| | - Virginie Guyon
- Biogemma SAS, Cereals Genetics and Genomics, F-63720 Chappes, France
| | - Mizuki Takenaka
- Department of Molecular Botany, University of Ulm, D-89069 Ulm, Germany
| | - Peter M. Rogowsky
- University of Lyon, Ecole Normale Supérieure de Lyon, Université Lyon 1, Unité Reproduction et Développement des Plantes, F-69364 Lyon, France
- Institut National de la Recherche Agronomique, Unité Mixte de Recherche 879 Reproduction et Développement des Plantes, F-69364 Lyon, France
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5667 Reproduction et Développement des Plantes, F-69364 Lyon, France
- Address correspondence to
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Tamasloukht B, Wong Quai Lam MSJ, Martinez Y, Tozo K, Barbier O, Jourda C, Jauneau A, Borderies G, Balzergue S, Renou JP, Huguet S, Martinant JP, Tatout C, Lapierre C, Barrière Y, Goffner D, Pichon M. Characterization of a cinnamoyl-CoA reductase 1 (CCR1) mutant in maize: effects on lignification, fibre development, and global gene expression. JOURNAL OF EXPERIMENTAL BOTANY 2011; 62:3837-48. [PMID: 21493812 PMCID: PMC3134344 DOI: 10.1093/jxb/err077] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Cinnamoyl-CoA reductase (CCR), which catalyses the first committed step of the lignin-specific branch of monolignol biosynthesis, has been extensively characterized in dicot species, but few data are available in monocots. By screening a Mu insertional mutant collection in maize, a mutant in the CCR1 gene was isolated named Zmccr1(-). In this mutant, CCR1 gene expression is reduced to 31% of the residual wild-type level. Zmccr1(-) exhibited enhanced digestibility without compromising plant growth and development. Lignin analysis revealed a slight decrease in lignin content and significant changes in lignin structure. p-Hydroxyphenyl units were strongly decreased and the syringyl/guaiacyl ratio was slightly increased. At the cellular level, alterations in lignin deposition were mainly observed in the walls of the sclerenchymatic fibre cells surrounding the vascular bundles. These cell walls showed little to no staining with phloroglucinol. These histochemical changes were accompanied by an increase in sclerenchyma surface area and an alteration in cell shape. In keeping with this cell type-specific phenotype, transcriptomics performed at an early stage of plant development revealed the down-regulation of genes specifically associated with fibre wall formation. To the present authors' knowledge, this is the first functional characterization of CCR1 in a grass species.
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Affiliation(s)
- Barek Tamasloukht
- Laboratoire de Recherche en Sciences Végétales, UMR 5546 UPS/CNRS, Pôle de Biotechnologies Végétales,24 chemin de Borde Rouge, B.P. 42617 Auzeville, 31326 Castanet Tolosan, France
| | - Mary Sarah-Jane Wong Quai Lam
- Laboratoire de Recherche en Sciences Végétales, UMR 5546 UPS/CNRS, Pôle de Biotechnologies Végétales,24 chemin de Borde Rouge, B.P. 42617 Auzeville, 31326 Castanet Tolosan, France
| | - Yves Martinez
- Laboratoire de Recherche en Sciences Végétales, UMR 5546 UPS/CNRS, Pôle de Biotechnologies Végétales,24 chemin de Borde Rouge, B.P. 42617 Auzeville, 31326 Castanet Tolosan, France
| | - Koffi Tozo
- Laboratoire de Recherche en Sciences Végétales, UMR 5546 UPS/CNRS, Pôle de Biotechnologies Végétales,24 chemin de Borde Rouge, B.P. 42617 Auzeville, 31326 Castanet Tolosan, France
| | - Odile Barbier
- Laboratoire de Recherche en Sciences Végétales, UMR 5546 UPS/CNRS, Pôle de Biotechnologies Végétales,24 chemin de Borde Rouge, B.P. 42617 Auzeville, 31326 Castanet Tolosan, France
| | - Cyril Jourda
- Laboratoire de Recherche en Sciences Végétales, UMR 5546 UPS/CNRS, Pôle de Biotechnologies Végétales,24 chemin de Borde Rouge, B.P. 42617 Auzeville, 31326 Castanet Tolosan, France
| | - Alain Jauneau
- Laboratoire de Recherche en Sciences Végétales, UMR 5546 UPS/CNRS, Pôle de Biotechnologies Végétales,24 chemin de Borde Rouge, B.P. 42617 Auzeville, 31326 Castanet Tolosan, France
| | - Gisèle Borderies
- Laboratoire de Recherche en Sciences Végétales, UMR 5546 UPS/CNRS, Pôle de Biotechnologies Végétales,24 chemin de Borde Rouge, B.P. 42617 Auzeville, 31326 Castanet Tolosan, France
| | - Sandrine Balzergue
- INRA/CNRS - URGV 2, rue Gaston Crémieux, CP5708, 91057 Evry cedex, France
| | - Jean-Pierre Renou
- INRA/CNRS - URGV 2, rue Gaston Crémieux, CP5708, 91057 Evry cedex, France
| | - Stéphanie Huguet
- INRA/CNRS - URGV 2, rue Gaston Crémieux, CP5708, 91057 Evry cedex, France
| | - Jean Pierre Martinant
- Biogemma, Campus universitaire des Cézeaux, 24 Avenue des Landais, 63170 Aubière, France
| | - Christophe Tatout
- Biogemma, Campus universitaire des Cézeaux, 24 Avenue des Landais, 63170 Aubière, France
| | - Catherine Lapierre
- Institut Jean-Pierre Bourgin, UMR 1318 AgroParisTech/INRA, F-78026 Versailles Cedex, France
| | - Yves Barrière
- INRA, Unité de Génétique et d'Amélioration des Plantes Fourragères, BP6, 86600 Lusignan, France
| | - Deborah Goffner
- Laboratoire de Recherche en Sciences Végétales, UMR 5546 UPS/CNRS, Pôle de Biotechnologies Végétales,24 chemin de Borde Rouge, B.P. 42617 Auzeville, 31326 Castanet Tolosan, France
| | - Magalie Pichon
- Laboratoire de Recherche en Sciences Végétales, UMR 5546 UPS/CNRS, Pôle de Biotechnologies Végétales,24 chemin de Borde Rouge, B.P. 42617 Auzeville, 31326 Castanet Tolosan, France
- To whom correspondence should be addressed. E-mail:
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Corbi J, Debieu M, Rousselet A, Montalent P, Le Guilloux M, Manicacci D, Tenaillon MI. Contrasted patterns of selection since maize domestication on duplicated genes encoding a starch pathway enzyme. TAG. THEORETICAL AND APPLIED GENETICS. THEORETISCHE UND ANGEWANDTE GENETIK 2011; 122:705-22. [PMID: 21060986 DOI: 10.1007/s00122-010-1480-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2010] [Accepted: 10/22/2010] [Indexed: 05/08/2023]
Abstract
Maize domestication from teosinte (Zea mays ssp. parviglumis) was accompanied by an increase of kernel size in landraces. Subsequent breeding has led to a diversification of kernel size and starch content among major groups of inbred lines. We aim at investigating the effect of domestication on duplicated genes encoding a key enzyme of the starch pathway, the ADP-glucose pyrophosphorylase (AGPase). Three pairs of paralogs encode the AGPase small (SSU) and large (LSU) subunits mainly expressed in the endosperm, the embryo and the leaf. We first validated the putative sequence of LSU(leaf) through a comparative expression assay of the six genes. Second, we investigated the patterns of molecular evolution on a 2 kb coding region homologous among the six genes in three panels: teosintes, landraces, and inbred lines. We corrected for demographic effects by relying on empirical distributions built from 580 previously sequenced ESTs. We found contrasted patterns of selection among duplicates: three genes exhibit patterns of directional selection during domestication (SSU(end), LSU(emb)) or breeding (LSU(leaf)), two exhibit patterns consistent with diversifying (SSU(leaf)) and balancing selection (SSU(emb)) accompanying maize breeding. While patterns of linkage disequilibrium did not reveal sign of coevolution between genes expressed in the same organ, we detected an excess of non-synonymous substitutions in the small subunit functional domains highlighting their role in AGPase evolution. Our results offer a different picture on AGPase evolution than the one depicted at the Angiosperm level and reveal how genetic redundancy can provide flexibility in the response to selection.
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Affiliation(s)
- J Corbi
- CNRS, UMR 0320/UMR 8120 Génétique Végétale, Ferme du Moulon, Gif sur Yvette, France
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15
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Genome-wide transcriptional analysis of maize endosperm in response to ae wx double mutations. J Genet Genomics 2010; 37:749-62. [DOI: 10.1016/s1673-8527(09)60092-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2010] [Revised: 08/25/2010] [Accepted: 09/14/2010] [Indexed: 11/20/2022]
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16
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Choulet F, Wicker T, Rustenholz C, Paux E, Salse J, Leroy P, Schlub S, Le Paslier MC, Magdelenat G, Gonthier C, Couloux A, Budak H, Breen J, Pumphrey M, Liu S, Kong X, Jia J, Gut M, Brunel D, Anderson JA, Gill BS, Appels R, Keller B, Feuillet C. Megabase level sequencing reveals contrasted organization and evolution patterns of the wheat gene and transposable element spaces. THE PLANT CELL 2010; 22:1686-701. [PMID: 20581307 PMCID: PMC2910976 DOI: 10.1105/tpc.110.074187] [Citation(s) in RCA: 199] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2010] [Revised: 05/26/2010] [Accepted: 06/08/2010] [Indexed: 05/18/2023]
Abstract
To improve our understanding of the organization and evolution of the wheat (Triticum aestivum) genome, we sequenced and annotated 13-Mb contigs (18.2 Mb) originating from different regions of its largest chromosome, 3B (1 Gb), and produced a 2x chromosome survey by shotgun Illumina/Solexa sequencing. All regions carried genes irrespective of their chromosomal location. However, gene distribution was not random, with 75% of them clustered into small islands containing three genes on average. A twofold increase of gene density was observed toward the telomeres likely due to high tandem and interchromosomal duplication events. A total of 3222 transposable elements were identified, including 800 new families. Most of them are complete but showed a highly nested structure spread over distances as large as 200 kb. A succession of amplification waves involving different transposable element families led to contrasted sequence compositions between the proximal and distal regions. Finally, with an estimate of 50,000 genes per diploid genome, our data suggest that wheat may have a higher gene number than other cereals. Indeed, comparisons with rice (Oryza sativa) and Brachypodium revealed that a high number of additional noncollinear genes are interspersed within a highly conserved ancestral grass gene backbone, supporting the idea of an accelerated evolution in the Triticeae lineages.
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Affiliation(s)
- Frédéric Choulet
- Institut National de la Recherche Agronomique, Université Blaise Pascal, Unité Mixte de Recherche 1095 Genetics Diversity and Ecophysiology of Cereals, F-63100 Clermont-Ferrand, France.
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17
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Affiliation(s)
- Peter L. Keeling
- NSF Engineering Research Center for Biorenewable Chemicals and Iowa State University, Ames, Iowa 50011;
| | - Alan M. Myers
- NSF Engineering Research Center for Biorenewable Chemicals and Iowa State University, Ames, Iowa 50011;
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Weigelt K, Küster H, Rutten T, Fait A, Fernie AR, Miersch O, Wasternack C, Emery RJN, Desel C, Hosein F, Müller M, Saalbach I, Weber H. ADP-glucose pyrophosphorylase-deficient pea embryos reveal specific transcriptional and metabolic changes of carbon-nitrogen metabolism and stress responses. PLANT PHYSIOLOGY 2009; 149:395-411. [PMID: 18987213 PMCID: PMC2613696 DOI: 10.1104/pp.108.129940] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2008] [Accepted: 11/04/2008] [Indexed: 05/19/2023]
Abstract
We present a comprehensive analysis of ADP-glucose pyrophosphorylase (AGP)-repressed pea (Pisum sativum) seeds using transcript and metabolite profiling to monitor the effects that reduced carbon flow into starch has on carbon-nitrogen metabolism and related pathways. Changed patterns of transcripts and metabolites suggest that AGP repression causes sugar accumulation and stimulates carbohydrate oxidation via glycolysis, tricarboxylic acid cycle, and mitochondrial respiration. Enhanced provision of precursors such as acetyl-coenzyme A and organic acids apparently support other pathways and activate amino acid and storage protein biosynthesis as well as pathways fed by cytosolic acetyl-coenzyme A, such as cysteine biosynthesis and fatty acid elongation/metabolism. As a consequence, the resulting higher nitrogen (N) demand depletes transient N storage pools, specifically asparagine and arginine, and leads to N limitation. Moreover, increased sugar accumulation appears to stimulate cytokinin-mediated cell proliferation pathways. In addition, the deregulation of starch biosynthesis resulted in indirect changes, such as increased mitochondrial metabolism and osmotic stress. The combined effect of these changes is an enhanced generation of reactive oxygen species coupled with an up-regulation of energy-dissipating, reactive oxygen species protection, and defense genes. Transcriptional activation of mitogen-activated protein kinase pathways and oxylipin synthesis indicates an additional activation of stress signaling pathways. AGP-repressed embryos contain higher levels of jasmonate derivatives; however, this increase is preferentially in nonactive forms. The results suggest that, although metabolic/osmotic alterations in iAGP pea seeds result in multiple stress responses, pea seeds have effective mechanisms to circumvent stress signaling under conditions in which excessive stress responses and/or cellular damage could prematurely initiate senescence or apoptosis.
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Affiliation(s)
- Kathleen Weigelt
- Leibniz-Institut für Pflanzengenetik und Kulturpflanzenforschung, D-06466 Gatersleben, Germany
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Slewinski TL, Ma Y, Baker RF, Huang M, Meeley R, Braun DM. Determining the role of Tie-dyed1 in starch metabolism: epistasis analysis with a maize ADP-glucose pyrophosphorylase mutant lacking leaf starch. J Hered 2008; 99:661-6. [PMID: 18723774 DOI: 10.1093/jhered/esn062] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In regions of their leaves, tdy1-R mutants hyperaccumulate starch. We propose 2 alternative hypotheses to account for the data, that Tdy1 functions in starch catabolism or that Tdy1 promotes sucrose export from leaves. To determine whether Tdy1 might function in starch breakdown, we exposed plants to extended darkness. We found that the tdy1-R mutant leaves retain large amounts of starch on prolonged dark treatment, consistent with a defect in starch catabolism. To further test this hypothesis, we identified a mutant allele of the leaf expressed small subunit of ADP-glucose pyrophosphorylase (agps-m1), an enzyme required for starch synthesis. We determined that the agps-m1 mutant allele is a molecular null and that plants homozygous for the mutation lack transitory leaf starch. Epistasis analysis of tdy1-R; agps-m1 double mutants demonstrates that Tdy1 function is independent of starch metabolism. These data suggest that Tdy1 may function in sucrose export from leaves.
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Affiliation(s)
- Thomas L Slewinski
- Department of Biology, 208 Mueller Lab, Pennsylvania State University, University Park, PA 16802, USA
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