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Devi V, Bhushan B, Gupta M, Sethi M, Kaur C, Singh A, Singh V, Kumar R, Rakshit S, Chaudhary DP. Genetic and molecular understanding for the development of methionine-rich maize: a holistic approach. FRONTIERS IN PLANT SCIENCE 2023; 14:1249230. [PMID: 37794928 PMCID: PMC10546030 DOI: 10.3389/fpls.2023.1249230] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Accepted: 09/01/2023] [Indexed: 10/06/2023]
Abstract
Maize (Zea mays) is the most important coarse cereal utilized as a major energy source for animal feed and humans. However, maize grains are deficient in methionine, an essential amino acid required for proper growth and development. Synthetic methionine has been used in animal feed, which is costlier and leads to adverse health effects on end-users. Bio-fortification of maize for methionine is, therefore, the most sustainable and environmental friendly approach. The zein proteins are responsible for methionine deposition in the form of δ-zein, which are major seed storage proteins of maize kernel. The present review summarizes various aspects of methionine including its importance and requirement for different subjects, its role in animal growth and performance, regulation of methionine content in maize and its utilization in human food. This review gives insight into improvement strategies including the selection of natural high-methionine mutants, molecular modulation of maize seed storage proteins and target key enzymes for sulphur metabolism and its flux towards the methionine synthesis, expression of synthetic genes, modifying gene codon and promoters employing genetic engineering approaches to enhance its expression. The compiled information on methionine and essential amino acids linked Quantitative Trait Loci in maize and orthologs cereals will give insight into the hotspot-linked genomic regions across the diverse range of maize germplasm through meta-QTL studies. The detailed information about candidate genes will provide the opportunity to target specific regions for gene editing to enhance methionine content in maize. Overall, this review will be helpful for researchers to design appropriate strategies to develop high-methionine maize.
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Affiliation(s)
- Veena Devi
- Division of Biochemistry, Indian Institute of Maize Research, Ludhiana, Punjab, India
| | - Bharat Bhushan
- Division of Biochemistry, Indian Institute of Maize Research, Ludhiana, Punjab, India
| | - Mamta Gupta
- Division of Biotechnology, Indian Institute of Maize Research, Ludhiana, Punjab, India
| | - Mehak Sethi
- Division of Biochemistry, Indian Institute of Maize Research, Ludhiana, Punjab, India
| | - Charanjeet Kaur
- Department of Biochemistry, Punjab Agricultural University, Ludhiana, Punjab, India
| | - Alla Singh
- Division of Biotechnology, Indian Institute of Maize Research, Ludhiana, Punjab, India
| | - Vishal Singh
- Division of Plant Breeding, Indian Institute of Maize Research, Ludhiana, Punjab, India
| | - Ramesh Kumar
- Division of Plant Breeding, Indian Institute of Maize Research, Ludhiana, Punjab, India
| | - Sujay Rakshit
- Division of Plant Breeding, Indian Institute of Maize Research, Ludhiana, Punjab, India
| | - Dharam P. Chaudhary
- Division of Biochemistry, Indian Institute of Maize Research, Ludhiana, Punjab, India
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Xiang X, Hu B, Pu Z, Wang L, Leustek T, Li C. Co-overexpression of AtSAT1 and EcPAPR improves seed nutritional value in maize. FRONTIERS IN PLANT SCIENCE 2022; 13:969763. [PMID: 36186039 PMCID: PMC9520583 DOI: 10.3389/fpls.2022.969763] [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: 06/15/2022] [Accepted: 08/15/2022] [Indexed: 06/16/2023]
Abstract
Maize seeds synthesize insufficient levels of the essential amino acid methionine (Met) to support animal and livestock growth. Serine acetyltransferase1 (SAT1) and 3'-phosphoadenosine-5'-phosphosulfate reductase (PAPR) are key control points for sulfur assimilation into Cys and Met biosynthesis. Two high-MET maize lines pRbcS:AtSAT1 and pRbcS:EcPAPR were obtained through metabolic engineering recently, and their total Met was increased by 1.4- and 1.57-fold, respectively, compared to the wild type. The highest Met maize line, pRbcS:AtSAT1-pRbcS:EcPAPR, was created by stacking the two transgenes, causing total Met to increase 2.24-fold. However, the pRbcS:AtSAT1-pRbcS:EcPAPR plants displayed progressively severe defects in plant growth, including early senescence, stunting, and dwarfing, indicating that excessive sulfur assimilation has an adverse effect on plant development. To explore the mechanism of correlation between Met biosynthesis in maize leaves and storage proteins in developing endosperm, the transcriptomes of the sixth leaf at stage V9 and 18 DAP endosperm of pRbcS:AtSAT1, pRbcS:AtSAT1-pRbcS:EcPAPR, and the null segregants were quantified and analyzed. In pRbcS:AtSAT1-pRbcS:EcPAPR, 3274 genes in leaves (1505 up- and 1769 downregulated) and 679 genes in the endosperm (327 up- and 352 downregulated) were differentially expressed. Gene ontology (GO) and KEGG (Kyoto encyclopedia of genes and genomes) analyses revealed that many genes were associated with Met homeostasis, including transcription factors and genes involved in cysteine and Met metabolism, glutathione metabolism, plant hormone signal transduction, and oxidation-reduction. The data from gene network analysis demonstrated that two genes, serine/threonine-protein kinase (CCR3) and heat shock 70 kDa protein (HSP), were localized in the core of the leaves and endosperm regulation networks, respectively. The results of this study provide insights into the diverse mechanisms that underlie the ideal establishment of enhanced Met levels in maize seeds.
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Affiliation(s)
- Xiaoli Xiang
- Institute of Biotechnology and Nuclear Technology, Sichuan Academy of Agricultural Sciences, Chengdu, China
- The National Engineering Laboratory of Crop Stress Resistance Breeding, Anhui Agricultural University, Hefei, China
| | - Binhua Hu
- Institute of Biotechnology and Nuclear Technology, Sichuan Academy of Agricultural Sciences, Chengdu, China
| | - Zhigang Pu
- Institute of Biotechnology and Nuclear Technology, Sichuan Academy of Agricultural Sciences, Chengdu, China
| | - Lanying Wang
- Institute of Biotechnology and Nuclear Technology, Sichuan Academy of Agricultural Sciences, Chengdu, China
| | - Thomas Leustek
- Department of Plant Biology, Rutgers University, New Brunswick, NJ, United States
| | - Changsheng Li
- The National Engineering Laboratory of Crop Stress Resistance Breeding, Anhui Agricultural University, Hefei, China
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Li C, Song R. The regulation of zein biosynthesis in maize endosperm. TAG. THEORETICAL AND APPLIED GENETICS. THEORETISCHE UND ANGEWANDTE GENETIK 2020; 133:1443-1453. [PMID: 31897513 DOI: 10.1007/s00122-019-03520-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Accepted: 12/18/2019] [Indexed: 05/06/2023]
Abstract
We review the current knowledge regarding the regulation of zein storage proteins biosynthesis and protein body formation, which are crucial processes for the successful accumulation of nutrients in maize kernels. Storage proteins in the seeds of crops in the grass family (Poaceae) are a major source of dietary protein for humans. In maize (Zea mays), proteins are the second largest nutrient component in the kernels, accounting for ~ 10% of the kernel weight. Over half of the storage proteins in maize kernels are zeins, which lack two essential amino acids, lysine and tryptophan. This deficiency limits the use of maize proteins in the food and feed industries. Zeins are encoded by a large super-gene family. During endosperm development, zeins accumulate in protein bodies, which are derived from the rough endoplasmic reticulum. In recent years, our knowledge of the pathways of zein biosynthesis and their deposition within the endosperm has been greatly expanded. In this review, we summarize the current understanding of zeins, including the genes encoding these proteins, their expression patterns and transcriptional regulation, the process of protein body formation, and other biological processes affecting zein accumulation.
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Affiliation(s)
- Chaobin Li
- State Key Laboratory of Plant Physiology and Biochemistry, National Maize Improvement Center, Beijing Key Laboratory of Crop Genetic Improvement, Joint International Research Laboratory of Crop Molecular Breeding, College of Agronomy and Biotechnology, China Agricultural University, Beijing, 100193, China
| | - Rentao Song
- State Key Laboratory of Plant Physiology and Biochemistry, National Maize Improvement Center, Beijing Key Laboratory of Crop Genetic Improvement, Joint International Research Laboratory of Crop Molecular Breeding, College of Agronomy and Biotechnology, China Agricultural University, Beijing, 100193, China.
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Li X, Han Y, Yan Y, Messing J, Xu JH. Genetic diversity and evolution of reduced sulfur storage during domestication of maize. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2018; 94:943-955. [PMID: 29570878 DOI: 10.1111/tpj.13907] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2017] [Revised: 03/01/2018] [Accepted: 03/06/2018] [Indexed: 06/08/2023]
Abstract
The domestication of maize has spanned a period of over 9000 years, during which time its wild relative teosinte underwent natural and artificial selection. We hypothesize that environmental conditions could have played a major role in this process. One factor of environmental variation is soil composition, which includes sulfur availability. Sulfur is reduced during photosynthesis and is used to synthesize cysteine and methionine, which drive the accumulation of δ10 (Zm00001d045937), δ18 (Zm00001d037436), β15 (Zm00001d035760), γ16 (Zm00001d005793), γ27 (Zm00001d020592), and γ50 (Zm00001d020591) zeins, representing the zein2 fraction (z2) of storage proteins in maize seeds. In this study, polymorphisms and haplotypes were detected based on six z2 genes in 60 maize and teosintes lines. Haplotypes were unevenly distributed, and abundant genetic diversity was found in teosintes. Polymorphism was highest in z2δ18, whereas for z2β15 single nucleotide polymorphism (SNP) density and insertion/deletion (indel) abundance were the lowest, indicating differential roles in seed evolution. Indels showed a clustered distribution, and most of these derived from teosintes. The indels not only led to tandem repeat polymorphisms, but also to frameshift mutations, which could also be used as null variants. In addition, neutral evolutionary tests, phylogenetic analyses, and population structures indicated that z2δ10 and z2γ50 had undergone natural selection. Indeed, a natural selection imprint could also be found with z2γ27 and z2γ16, whereas z2δ18 and z2β15 tended to be under neutral evolution. These results suggested that genetic diversity and evolution of a subset of sulfur-rich zeins could be under environmental adaptation during maize domestication.
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Affiliation(s)
- Xinxin Li
- Institute of Crop Science, Zhejiang Key Laboratory of Crop Germplasm, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Yang Han
- Institute of Crop Science, Zhejiang Key Laboratory of Crop Germplasm, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Yan Yan
- Institute of Crop Science, Zhejiang Key Laboratory of Crop Germplasm, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Joachim Messing
- Waksman Institute of Microbiology, Rutgers The State University of New Jersey, Piscataway, NJ, 08854, USA
| | - Jian-Hong Xu
- Institute of Crop Science, Zhejiang Key Laboratory of Crop Germplasm, Zhejiang University, Hangzhou, Zhejiang, 310058, China
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Xiang X, Wu Y, Planta J, Messing J, Leustek T. Overexpression of serine acetyltransferase in maize leaves increases seed-specific methionine-rich zeins. PLANT BIOTECHNOLOGY JOURNAL 2018; 16:1057-1067. [PMID: 29044890 PMCID: PMC5902772 DOI: 10.1111/pbi.12851] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Revised: 09/22/2017] [Accepted: 10/09/2017] [Indexed: 05/19/2023]
Abstract
Maize kernels do not contain enough of the essential sulphur-amino acid methionine (Met) to serve as a complete diet for animals, even though maize has the genetic capacity to store Met in kernels. Prior studies indicated that the availability of the sulphur (S)-amino acids may limit their incorporation into seed storage proteins. Serine acetyltransferase (SAT) is a key control point for S-assimilation leading to Cys and Met biosynthesis, and SAT overexpression is known to enhance S-assimilation without negative impact on plant growth. Therefore, we overexpressed Arabidopsis thaliana AtSAT1 in maize under control of the leaf bundle sheath cell-specific rbcS1 promoter to determine the impact on seed storage protein expression. The transgenic events exhibited up to 12-fold higher SAT activity without negative impact on growth. S-assimilation was increased in the leaves of SAT overexpressing plants, followed by higher levels of storage protein mRNA and storage proteins, particularly the 10-kDa δ-zein, during endosperm development. This zein is known to impact the level of Met stored in kernels. The elite event with the highest expression of AtSAT1 showed 1.40-fold increase in kernel Met. When fed to chickens, transgenic AtSAT1 kernels significantly increased growth rate compared with the parent maize line. The result demonstrates the efficacy of increasing maize nutritional value by SAT overexpression without apparent yield loss. Maternal overexpression of SAT in vegetative tissues was necessary for high-Met zein accumulation. Moreover, SAT overcomes the shortage of S-amino acids that limits the expression and accumulation of high-Met zeins during kernel development.
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Affiliation(s)
- Xiaoli Xiang
- Department of Plant BiologyRutgers UniversityNew BrunswickNJUSA
- Institute of Biotechnology and Nuclear TechnologySichuan Academy of Agricultural SciencesChengduChina
| | - Yongrui Wu
- National Key Laboratory of Plant Molecular GeneticsCAS Center for Excellence in Molecular Plant SciencesInstitute of Plant Physiology & EcologyShanghai Institutes for Biological SciencesChinese Academy of SciencesShanghaiChina
- Waksman Institute of MicrobiologyRutgers UniversityPiscatawayNJUSA
| | - José Planta
- Waksman Institute of MicrobiologyRutgers UniversityPiscatawayNJUSA
| | - Joachim Messing
- Waksman Institute of MicrobiologyRutgers UniversityPiscatawayNJUSA
| | - Thomas Leustek
- Department of Plant BiologyRutgers UniversityNew BrunswickNJUSA
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Planta J, Xiang X, Leustek T, Messing J. Engineering sulfur storage in maize seed proteins without apparent yield loss. Proc Natl Acad Sci U S A 2017; 114:11386-11391. [PMID: 29073061 PMCID: PMC5664557 DOI: 10.1073/pnas.1714805114] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Sulfur assimilation may limit the pool of methionine and cysteine available for incorporation into zeins, the major seed storage proteins in maize. This hypothesis was tested by producing transgenic maize with deregulated sulfate reduction capacity achieved through leaf-specific expression of the Escherichia coli enzyme 3'-phosphoadenosine-5'-phosphosulfate reductase (EcPAPR) that resulted in higher methionine accumulation in seeds. The transgenic kernels have higher expression of the methionine-rich 10-kDa δ-zein and total protein sulfur without reduction of other zeins. This overall increase in the expression of the S-rich zeins describes a facet of regulation of these proteins under enhanced sulfur assimilation. Transgenic line PE5 accumulates 57.6% more kernel methionine than the high-methionine inbred line B101. In feeding trials with chicks, PE5 maize promotes significant weight gain compared with nontransgenic kernels. Therefore, increased source strength can improve the nutritional value of maize without apparent yield loss and may significantly reduce the cost of feed supplementation.
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Affiliation(s)
- Jose Planta
- Waksman Institute of Microbiology, Rutgers University, Piscataway, NJ 08854
| | - Xiaoli Xiang
- Department of Plant Biology, Rutgers University, New Brunswick, NJ 08901
- Institute of Biotechnology and Nuclear Technology, Sichuan Academy of Agricultural Sciences, Chengdu 610061, China
| | - Thomas Leustek
- Department of Plant Biology, Rutgers University, New Brunswick, NJ 08901
| | - Joachim Messing
- Waksman Institute of Microbiology, Rutgers University, Piscataway, NJ 08854;
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Wu Y, Messing J. Proteome balancing of the maize seed for higher nutritional value. FRONTIERS IN PLANT SCIENCE 2014; 5:240. [PMID: 24910639 PMCID: PMC4039071 DOI: 10.3389/fpls.2014.00240] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2014] [Accepted: 05/12/2014] [Indexed: 05/18/2023]
Abstract
Most flowering plant seeds are composed of the embryo and endosperm, which are surrounded by maternal tissue, in particular the seed coat. Whereas the embryo is the dormant progeny, the endosperm is a terminal organ for storage of sugars and amino acids in proteins and carbohydrates, respectively. Produced in maternal leaves during photosynthesis, sugars, and amino acids are transported to developing seeds after flowering, and during germination they nourish early seedlings growth. Maize endosperm usually contains around 10% protein and 70% starch, and their composition ratio is rather stable, because it is strictly regulated through a pre-set genetic program that is woven by networks of many interacting or counteracting genes and pathways. Endosperm protein, however, is of low nutritional value due mainly to the high expression of the α-zein gene family, which encodes lysine-free proteins. Reduced levels of these proteins in the opaque 2 (o2) mutant and α-zein RNAi (RNA interference) transgenic seed is compensated by an increase of non-zein proteins, leading to the rebalancing of the nitrogen sink and producing more or less constant levels of total proteins in the seed. The same rebalancing of zeins and non-zeins has been observed for maize seeds bred for 30% protein. In contrast to the nitrogen sink, storage of sulfur is controlled through the accumulation of specialized sulfur-rich proteins in maize endosperm. Silencing the synthesis of α-zeins through RNAi fails to raise sulfur-rich proteins. Although overexpression of the methionine-rich δ-zein can increase the methionine level in seeds, it occurs at least in part at the expense of the cysteine-rich β- and γ-zeins, demonstrating a balance between cysteine and methionine in sulfur storage. Therefore, we propose that the throttle for the flow of sulfur is placed before the synthesis of sulfur amino acids when sulfur is taken up and reduced during photosynthesis.
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Affiliation(s)
- Yongrui Wu
- Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of SciencesShanghai, China
| | - Joachim Messing
- Waksman Institute of Microbiology, Rutgers UniversityPiscataway, NJ, USA
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Wu Y, Wang W, Messing J. Balancing of sulfur storage in maize seed. BMC PLANT BIOLOGY 2012; 12:77. [PMID: 22646812 PMCID: PMC3420316 DOI: 10.1186/1471-2229-12-77] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2012] [Accepted: 05/30/2012] [Indexed: 05/21/2023]
Abstract
BACKGROUND A balanced composition of amino acids in seed flour is critical because of the demand on essential amino acids for nutrition. However, seed proteins in cereals like maize, the crop with the highest yield, are low in lysine, tryptophan, and methionine. Although supplementation with legumes like soybean can compensate lysine deficiency, both crops are also relatively low in methionine. Therefore, understanding the mechanism of methionine accumulation in the seed could be a basis for breeding cultivars with superior nutritional quality. RESULTS In maize (Zea mays), the 22- and 19-kDa α-zeins are the most prominent storage proteins, nearly devoid of lysine and methionine. Although silencing synthesis of these proteins through RNA interference (RNAi) raises lysine levels in the seed, it fails to do so for methionine. Computational analysis of annotated gene models suggests that about 57% of all proteins exhibit a lysine content of more than 4%, whereas the percentage of proteins with methionine above 4% is only around 8%. To compensate for this low representation, maize seeds produce specialized storage proteins, the 15-kDa β-, 18-kDa and 10-kDa δ-zeins, rich in methionine. However, they are expressed at variant levels in different inbred lines. A654, an inbred with null δ-zein alleles, methionine levels are significantly lower than when the two intact δ-zein alleles are introgressed. Further silencing of β-zein results in dramatic reduction in methionine levels, indicating that β- and δ-zeins are the main sink of methionine in maize seed. Overexpression of the 10-kDa δ-zein can increase the methionine level, but protein analysis by SDS-PAGE shows that the increased methionine levels occur at least in part at the expense of cysteines present in β- and γ-zeins. The reverse is true when β- and γ-zein expression is silenced through RNAi, then 10-kDa δ-zein accumulates to higher levels. CONCLUSIONS Because methionine receives the sulfur moiety from cysteine, it appears that when seed protein synthesis of cysteine-rich proteins is blocked, the synthesis of methionine-rich seed proteins is induced, probably at the translational level. The same is true, when methionine-rich proteins are overexpressed, synthesis of cysteine-rich proteins is reduced, probably also at the translational level. Although we only hypothesize a translational control of protein synthesis at this time, there are well known paradigms of how amino acid concentration can play a role in differential gene expression. The latter we think is largely controlled by the flux of reduced sulfur during plant growth.
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Affiliation(s)
- Yongrui Wu
- Waksman Institute of Microbiology, Rutgers University, 190 Frelinghuysen Road, Piscataway, NJ, 08854, USA
| | - Wenqin Wang
- Waksman Institute of Microbiology, Rutgers University, 190 Frelinghuysen Road, Piscataway, NJ, 08854, USA
| | - Joachim Messing
- Waksman Institute of Microbiology, Rutgers University, 190 Frelinghuysen Road, Piscataway, NJ, 08854, USA
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Wu Y, Goettel W, Messing J. Non-Mendelian regulation and allelic variation of methionine-rich delta-zein genes in maize. TAG. THEORETICAL AND APPLIED GENETICS. THEORETISCHE UND ANGEWANDTE GENETIK 2009; 119:721-31. [PMID: 19504256 DOI: 10.1007/s00122-009-1083-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2009] [Accepted: 05/21/2009] [Indexed: 05/10/2023]
Abstract
Sufficient methionine levels in the seed are critical for the supply of a balanced diet for feed and food. Currently, animal feed is supplemented with chemically synthesized methionine, which could be completely replaced with naturally synthesized methionine. However, insufficient levels of methionine are due to alleles of two genes in the maize genome that are expressed during seed development, which have a high percentage of methionine codons, ranging from 23 to 28%, while free methionine is very low. The two genes, dzs10 and dzs18, belong to the prolamin gene family that arose during the evolution of the grasses and were duplicated during a whole genome duplication event. We have found several dzs10 and dzs18 null alleles caused either by transposon insertion or frame shift mutations. Maize seeds with null mutations of both genes have a normal phenotype in contrast to other prolamin genes, explaining the accumulation of methionine deficiency in normal breeding efforts. Moreover, the trans-regulation of these genes deviates from Mendelian inheritance. One allele of the regulatory locus dzr1 is inherited in a parent-of-origin fashion, while another allele appears to prevent Mendelian segregation of the high-methionine phenotype in backcrosses.
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Affiliation(s)
- Yongrui Wu
- Waksman Institute of Microbiology, Rutgers University, 190 Frelinghuysen Road, Piscataway, NJ 08854, USA
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Lai J, Messing J. Increasing maize seed methionine by mRNA stability. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2002; 30:395-402. [PMID: 12028570 DOI: 10.1046/j.1365-313x.2001.01285.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The amino acid methionine is a common protein building block that is also important in other cellular processes. Plants, unlike animals, synthesize methionine de novo and are thus a dietary source of this nutrient. A new approach for using maize as a source of nutrient methionine is described. Maize seeds, a major component of animal feeds, have variable levels of protein-bound methionine. This variability is a result of post-transcriptional regulation of the Dzs10 gene, which encodes a seed-specific high-methionine storage protein. Here we eliminate methionine variability by identifying and replacing the cis-acting site for Dzs10 regulation using transgenic seeds. Interestingly, two different mechanisms affect mRNA accumulation, one dependent on and the other independent of the untranslated regions (UTRs) of Dzs10 RNA. Accumulation of chimeric Dzs10 mRNA was not reduced in hybrid crosses and was uncoupled from genomic imprinting by Dzr1, a regulator of Dzs10. Uniform high levels of Dzs10 protein were maintained over five backcross generations of the transgene. The increased level of methionine in these transgenic seeds allowed the formulation of a useful animal feed ration without the addition of synthetic methionine.
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Affiliation(s)
- Jinsheng Lai
- Waksman Institute, 190 Frelinghuysen Road, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854-8020, USA
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Affiliation(s)
- J Messing
- Waksman Institute, Rutgers, State University of New Jersey, Piscataway 08854-8020, USA
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Llaca V, Messing J. Amplicons of maize zein genes are conserved within genic but expanded and constricted in intergenic regions. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 1998; 15:211-220. [PMID: 9721679 DOI: 10.1046/j.1365-313x.1998.00200.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The 78,101 base pair long sequence of a cluster of 22-kDa alpha zein genes in the maize inbred BSSS53 was determined. Each zein gene is contained within a repeat unit that varies in length. If such a repeat, or amplicon, is aligned along the entire sequence, a 10.5-fold sequence amplification is delineated. Because of insertions and deletions in intergenic regions, many of the zein genes are spaced over different distances. Only three out of 10 zein-related sequences have an intact open reading frame, indicating an unusual large number of genes unable to contribute to the accumulation of normal-size 22-kDa zein proteins. It is proposed that the seven remaining zein-related sequences be considered gene reserves because of their potential to be restored by gene conversion. Intergenic insertions in the cluster range from 1098 to 14,896 base pairs. Although they are composed of transposable element sequences, they also contain additional open reading frames, two of them showing homology to rice cDNA sequences. The average amplicon is 4423 base pairs long, with the sequence surrounding each zein gene more than 90% conserved. Coincidently, the size of the amplicon is equivalent to the average gene density (one gene within 4640 bp) in the Arabidopsis thaliana genome, one of the smallest in plants. Successive steps of amplification and insertion of DNA might explain to a certain degree how genome size variation has been generated in plants.
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Affiliation(s)
- V Llaca
- Waksman Institute, Rutgers, State University of New Jersey, Piscataway 08855, USA
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Affiliation(s)
- T Ueda
- Waksman Institute, Rutgers University, Piscataway, NJ 08855
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