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Abstract
C4 photosynthesis evolved multiple times independently from ancestral C3 photosynthesis in a broad range of flowering land plant families and in both monocots and dicots. The evolution of C4 photosynthesis entails the recruitment of enzyme activities that are not involved in photosynthetic carbon fixation in C3 plants to photosynthesis. This requires a different regulation of gene expression as well as a different regulation of enzyme activities in comparison to the C3 context. Further, C4 photosynthesis relies on a distinct leaf anatomy that differs from that of C3, requiring a differential regulation of leaf development in C4. We summarize recent progress in the understanding of C4-specific features in evolution and metabolic regulation in the context of C4 photosynthesis.
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Affiliation(s)
- Urte Schlüter
- Institute of Plant Biochemistry, Cluster of Excellence on Plant Sciences (CEPLAS), Heinrich Heine University, 40225 Düsseldorf, Germany; ,
| | - Andreas P M Weber
- Institute of Plant Biochemistry, Cluster of Excellence on Plant Sciences (CEPLAS), Heinrich Heine University, 40225 Düsseldorf, Germany; ,
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Xu J, Bräutigam A, Weber APM, Zhu XG. Systems analysis of cis-regulatory motifs in C4 photosynthesis genes using maize and rice leaf transcriptomic data during a process of de-etiolation. JOURNAL OF EXPERIMENTAL BOTANY 2016; 67:5105-17. [PMID: 27436282 PMCID: PMC5014158 DOI: 10.1093/jxb/erw275] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Identification of potential cis-regulatory motifs controlling the development of C4 photosynthesis is a major focus of current research. In this study, we used time-series RNA-seq data collected from etiolated maize and rice leaf tissues sampled during a de-etiolation process to systematically characterize the expression patterns of C4-related genes and to further identify potential cis elements in five different genomic regions (i.e. promoter, 5'UTR, 3'UTR, intron, and coding sequence) of C4 orthologous genes. The results demonstrate that although most of the C4 genes show similar expression patterns, a number of them, including chloroplast dicarboxylate transporter 1, aspartate aminotransferase, and triose phosphate transporter, show shifted expression patterns compared with their C3 counterparts. A number of conserved short DNA motifs between maize C4 genes and their rice orthologous genes were identified not only in the promoter, 5'UTR, 3'UTR, and coding sequences, but also in the introns of core C4 genes. We also identified cis-regulatory motifs that exist in maize C4 genes and also in genes showing similar expression patterns as maize C4 genes but that do not exist in rice C3 orthologs, suggesting a possible recruitment of pre-existing cis-elements from genes unrelated to C4 photosynthesis into C4 photosynthesis genes during C4 evolution.
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Affiliation(s)
- Jiajia Xu
- CAS Key Laboratory of Computational Biology and State Key Laboratory for Hybrid Rice, CAS-MPG Partner Institute for Computational Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
| | - Andrea Bräutigam
- Institute of Plant Biochemistry, Cluster of Excellence on Plant Sciences (CEPLAS), Heinrich-Heine University, 40225 Düsseldorf, Germany Network Analysis and Modeling, IPK Gatersleben, Correnstrasse 3, D-06466 Stadt Seeland, Germany
| | - Andreas P M Weber
- Institute of Plant Biochemistry, Cluster of Excellence on Plant Sciences (CEPLAS), Heinrich-Heine University, 40225 Düsseldorf, Germany
| | - Xin-Guang Zhu
- CAS Key Laboratory of Computational Biology and State Key Laboratory for Hybrid Rice, CAS-MPG Partner Institute for Computational Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
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Ludwig M. Evolution of the C4 photosynthetic pathway: events at the cellular and molecular levels. PHOTOSYNTHESIS RESEARCH 2013; 117:147-61. [PMID: 23708978 DOI: 10.1007/s11120-013-9853-y] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2013] [Accepted: 05/14/2013] [Indexed: 05/11/2023]
Abstract
The biochemistry and leaf anatomy of plants using C4 photosynthesis promote the concentration of atmospheric CO2 in leaf tissue that leads to improvements in growth and yield of C4 plants over C3 species in hot, dry, high light, and/or saline environments. C4 plants like maize and sugarcane are significant food, fodder, and bioenergy crops. The C4 photosynthetic pathway is an excellent example of convergent evolution, having evolved in multiple independent lineages of land plants from ancestors employing C3 photosynthesis. In addition to C3 and C4 species, some plant lineages contain closely related C3-C4 intermediate species that demonstrate leaf anatomical, biochemical, and physiological characteristics between those of C3 plants and species using C4 photosynthesis. These groups of plants have been extremely useful in dissecting the modifications to leaf anatomy and molecular biology, which led to the evolution of C4 photosynthesis. It is now clear that great variation exists in C4 leaf anatomy, and diverse molecular mechanisms underlie C4 biochemistry and physiology. However, all these different paths have led to the same destination-the expression of a C4 CO2 concentrating mechanism. Further identification of C4 leaf anatomical traits and molecular biological components, and understanding how they are controlled and assembled will not only allow for additional insights into evolutionary convergence, but also contribute to sustainable food and bioenergy production strategies.
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Affiliation(s)
- Martha Ludwig
- School of Chemistry and Biochemistry, The University of Western Australia, 35 Stirling Highway, Crawley, WA, 6009, Australia,
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Williams BP, Aubry S, Hibberd JM. Molecular evolution of genes recruited into C₄ photosynthesis. TRENDS IN PLANT SCIENCE 2012; 17:213-20. [PMID: 22326564 DOI: 10.1016/j.tplants.2012.01.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2011] [Revised: 01/12/2012] [Accepted: 01/16/2012] [Indexed: 05/03/2023]
Abstract
The C₄ pathway is found in 62 lineages of land plants. We assess evidence for parallel versus convergent evolution of C₄ photosynthesis from three approaches: (i) studies of specific genes and cis-elements controlling their expression; (ii) phylogenetic analyses of mRNAs and inferred amino acid sequences; and (iii) analysis of C₃ and C₄ genomes and transcriptomes. Evidence suggests that although convergent evolution is common, parallel evolution can underlie both changes to gene expression and amino acid sequence. cis-elements that direct cell specificity in C₄ leaves are present in C₃ orthologues of genes recruited into C₄, probably facilitating this parallel evolution. From this, and genomic data, we propose that gene duplication followed by neofunctionalisation is not necessarily important in the evolution of C₄ biochemistry.
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Affiliation(s)
- Ben P Williams
- Department of Plant Sciences, Downing Street, University of Cambridge, Cambridge CB2 3EA, UK
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Weissmann S, Brutnell TP. Engineering C4 photosynthetic regulatory networks. Curr Opin Biotechnol 2012; 23:298-304. [PMID: 22261559 DOI: 10.1016/j.copbio.2011.12.018] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2011] [Revised: 12/13/2011] [Accepted: 12/15/2011] [Indexed: 11/25/2022]
Abstract
C4 photosynthesis is a complex metabolic pathway responsible for carbon fixation in major feed, food and bioenergy crops. Although many enzymes driving this pathway have been identified, regulatory mechanisms underlying this system remain elusive. C4 photosynthesis contributes to photosynthetic efficiency in major bioenergy crops such as sugarcane, Miscanthus, switchgrass, maize and sorghum, and international efforts are underway to engineer C4 photosynthesis into C3 crops. A fundamental understanding of the C4 network is thus needed. New experimental and informatics methods can facilitate the accumulation and analysis of high-throughput data to define components of the C4 system. The use of new model plants, closely related to C4 crops, will also contribute to our understanding of the mechanisms that regulate this complex and important pathway.
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Affiliation(s)
- Sarit Weissmann
- Boyce Thompson Institute for Plant Research, Cornell University, Tower Road, Ithaca, NY 14853, United States
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7
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Ludwig M. Carbonic anhydrase and the molecular evolution of C4 photosynthesis. PLANT, CELL & ENVIRONMENT 2012; 35:22-37. [PMID: 21631531 DOI: 10.1111/j.1365-3040.2011.02364.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
C(4) photosynthesis, a biochemical CO(2)-concentrating mechanism (CCM), evolved more than 60 times within the angiosperms from C(3) ancestors. The genus Flaveria, which contains species demonstrating C(3), C(3)-C(4), C(4)-like or C(4) photosynthesis, is a model for examining the molecular evolution of the C(4) pathway. Work with carbonic anhydrase (CA), and C(3) and C(4) Flaveria congeners has added significantly to the understanding of this process. The C(4) form of CA3, a β-CA, which catalyses the first reaction in the C(4) pathway by hydrating atmospheric CO(2) to bicarbonate in the cytosol of mesophyll cells (mcs), evolved from a chloroplastic C(3) ancestor. The molecular modifications to the ancestral CA3 gene included the loss of the sequence encoding the chloroplast transit peptide, and mutations in regulatory regions that resulted in high levels of expression in the C(4) mesophyll. Analyses of the CA3 proteins and regulatory elements from Flaveria photosynthetic intermediates indicated C(4) biochemistry very likely evolved in a specific, stepwise manner in this genus. The details of the mechanisms involved in the molecular evolution of other C(4) plant β-CAs are unknown; however, comparative genetics indicate gene duplication and neofunctionalization played significant roles as they did in Flaveria.
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Affiliation(s)
- Martha Ludwig
- School of Biomedical, Biomolecular and Chemical Sciences [M310], The University of Western Australia, Crawley, Western Australia 6009, Australia.
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Li WJ, Dai LL, Chai ZJ, Yin ZJ, Qu LQ. Evaluation of seed storage protein gene 3′-untranslated regions in enhancing gene expression in transgenic rice seed. Transgenic Res 2011; 21:545-53. [DOI: 10.1007/s11248-011-9552-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2011] [Accepted: 08/30/2011] [Indexed: 11/29/2022]
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Ludwig M. The molecular evolution of β-carbonic anhydrase in Flaveria. JOURNAL OF EXPERIMENTAL BOTANY 2011; 62:3071-3081. [PMID: 21406474 DOI: 10.1093/jxb/err071] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Limited information exists regarding molecular events that occurred during the evolution of C(4) plants from their C(3) ancestors. The enzyme β-carbonic anhydrase (CA; EC 4.2.1.1), which catalyses the reversible hydration of CO(2), is present in multiple forms in C(3) and C(4) plants, and has given insights into the molecular evolution of the C(4) pathway in the genus Flaveria. cDNAs encoding three distinct isoforms of β-CA, CA1-CA3, have been isolated and examined from Flaveria C(3) and C(4) congeners. Sequence data, expression analyses of CA orthologues, and chloroplast import assays with radiolabelled CA precursor proteins from the C(3) species F. pringlei Gandoger and the C(4) species F. bidentis (L.) Kuntze have shown that both contain chloroplastic and cytosolic forms of the enzyme, and the potential roles of these isoforms are discussed. The data also identified CA3 as the cytosolic isoform important in C(4) photosynthesis and indicate that the C(4) CA3 gene evolved as a result of gene duplication and neofunctionalization, which involved mutations in coding and non-coding regions of the ancestral C(3) CA3 gene. Comparisons of the deduced CA3 amino acid sequences from Flaveria C(3), C(4), and photosynthetic intermediate species showed that all the C(3)-C(4) intermediates investigated and F. brownii, a C(4)-like species, have a C(3)-type CA3, while F. vaginata, another C(4)-like species, contains a C(4)-type CA3. These observations correlate with the photosynthetic physiologies of the intermediates, suggesting that the molecular evolution of C(4) photosynthesis in Flaveria may have resulted from a temporally dependent, stepwise modification of protein-encoding genes and their regulatory elements.
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Affiliation(s)
- Martha Ludwig
- School of Biomedical, Biomolecular and Chemical Sciences, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia.
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Abstract
C4 photosynthesis is an adaptation that evolved to alleviate the detrimental effects of photorespiration as a result of the gradual decline in atmospheric carbon dioxide levels. In most C4 plants, two cell types, bundle sheath and mesophyll, cooperate in carbon fixation, and, in so doing, are able to alleviate photorespiratory losses. Although much of the biochemistry is well characterized, little is known about the genetic mechanisms underlying the cell-type specificity driving C4 . However, several studies have shown that regulation acts at multiple levels, including transcriptional, post-transcriptional, post-translational and epigenetic. One example of such a regulatory mechanism is the cell-specific accumulation of major photorespiratory transcripts/proteins in bundle sheath cells, where ribulose-1,5-bisphosphate carboxylase/oxygenase is localized. Although many of the genes are expressed in the bundle sheath, some are expressed in both cell types, implicating post-transcriptional control mechanisms. Recently, ultra-high-throughput sequencing techniques and sophisticated mass spectrometry instrumentation have provided new opportunities to further our understanding of C4 regulation. Computational pipelines are being developed to accommodate the mass of data associated with these techniques. Finally, we discuss a readily transformable C4 grass--Setaria viridis--that has great potential to serve as a model for the genetic dissection of C4 photosynthesis in the grasses.
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Affiliation(s)
- Lin Wang
- Boyce Thompson Institute for Plant Research, Cornell University, Ithaca, NY 14850, USA
| | - Richard B Peterson
- Department of Biochemistry & Genetics, The Connecticut Agricultural Experiment Station, New Haven, CT 06511, USA
| | - Thomas P Brutnell
- Boyce Thompson Institute for Plant Research, Cornell University, Ithaca, NY 14850, USA
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Hibberd JM, Covshoff S. The regulation of gene expression required for C4 photosynthesis. ANNUAL REVIEW OF PLANT BIOLOGY 2010; 61:181-207. [PMID: 20192753 DOI: 10.1146/annurev-arplant-042809-112238] [Citation(s) in RCA: 163] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
C(4) photosynthesis is normally associated with the compartmentation of photosynthesis between mesophyll (M) and bundle sheath (BS) cells. The mechanisms regulating the differential accumulation of photosynthesis proteins in these specialized cells are fundamental to our understanding of how C(4) photosynthesis operates. Cell-specific accumulation of proteins in M or BS can be mediated by posttranscriptional processes and translational efficiency as well as by differences in transcription. Individual genes are likely regulated at multiple levels. Although cis-elements have been associated with cell-specific expression in C(4) leaves, there has been little progress in identifying trans-factors. When C(4) photosynthesis genes from C(4) species are placed in closely related C(3) species, they are often expressed in a manner faithful to the C(4) cycle. Next-generation sequencing and comprehensive analysis of the extent to which genes from C(4) species are expressed in M or BS cells of C(3) plants should provide insight into how the C(4) pathway is regulated and evolved.
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Affiliation(s)
- Julian M Hibberd
- Department of Plant Sciences, University of Cambridge, Cambridge, United Kingdom.
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Brown NJ, Palmer BG, Stanley S, Hajaji H, Janacek SH, Astley HM, Parsley K, Kajala K, Quick WP, Trenkamp S, Fernie AR, Maurino VG, Hibberd JM. C acid decarboxylases required for C photosynthesis are active in the mid-vein of the C species Arabidopsis thaliana, and are important in sugar and amino acid metabolism. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2010; 61:122-33. [PMID: 19807880 DOI: 10.1111/j.1365-313x.2009.04040.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Cells associated with veins of petioles of C(3) tobacco possess high activities of the decarboxylase enzymes required in C(4) photosynthesis. It is not clear whether this is the case in other C(3) species, nor whether these enzymes provide precursors for specific biosynthetic pathways. Here, we investigate the activity of C(4) acid decarboxylases in the mid-vein of Arabidopsis, identify regulatory regions sufficient for this activity, and determine the impact of removing individual isoforms of each protein on mid-vein metabolite profiles. This showed that radiolabelled malate and bicarbonate fed to the xylem stream were incorporated into soluble and insoluble material in the mid-vein of Arabidopsis leaves. Compared with the leaf lamina, mid-veins possessed high activities of NADP-dependent malic enzyme (NADP-ME), NAD-dependent malic enzyme (NAD-ME) and phosphoenolpyruvate carboxykinase (PEPCK). Transcripts derived from both NAD-ME, one PCK and two of the four NADP-ME genes were detectable in these veinal cells. The promoters of each decarboxylase gene were sufficient for expression in mid-veins. Analysis of insertional mutants revealed that cytosolic NADP-ME2 is responsible for 80% of NADP-ME activity in mid-veins. Removing individual decarboxylases affected the abundance of amino acids derived from pyruvate and phosphoenolpyruvate. Reducing cytosolic NADP-ME activity preferentially affected the sugar content, whereas abolishing NAD-ME affected both the amino acid and the glucosamine content of mid-veins.
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Affiliation(s)
- Naomi J Brown
- Department of Plant Sciences, Downing Street, University of Cambridge, Cambridge, CB2 3EA, UK
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Taylor LE, Dai Z, Decker SR, Brunecky R, Adney WS, Ding SY, Himmel ME. Heterologous expression of glycosyl hydrolases in planta: a new departure for biofuels. Trends Biotechnol 2008; 26:413-24. [PMID: 18579242 DOI: 10.1016/j.tibtech.2008.05.002] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2008] [Revised: 05/01/2008] [Accepted: 05/07/2008] [Indexed: 11/18/2022]
Abstract
The concept of expressing non-plant glycosyl hydrolase genes in plant tissue is nearly two decades old, yet relatively little work in this field has been reported. However, resurgent interest in technologies aimed at enabling processes that convert biomass to sugars and fuels has turned attention toward this intuitive solution. There are several challenges facing researchers in this field, including the development of better and more specifically targeted delivery systems for hydrolytic genes, the successful folding and post-translational modification of heterologous proteins and the development of cost-effective process strategies utilizing these transformed plants. The integration of these concepts, from the improvement of biomass production and conversion characteristics to the heterologous production of glycosyl hydrolases in a high yielding bioenergy crop, holds considerable promise for improving the lignocellulosic conversion of biomass to ethanol and subsequently to fuels.
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Affiliation(s)
- Larry E Taylor
- Chemical and Biosciences Center, National Renewable Energy Laboratory, 1617 Cole Blvd, Golden, CO 80401, USA
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Marshall DM, Muhaidat R, Brown NJ, Liu Z, Stanley S, Griffiths H, Sage RF, Hibberd JM. Cleome, a genus closely related to Arabidopsis, contains species spanning a developmental progression from C(3) to C(4) photosynthesis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2007; 51:886-96. [PMID: 17692080 DOI: 10.1111/j.1365-313x.2007.03188.x] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
C(4) photosynthesis involves alterations to leaf development, cell biology and biochemistry. Different lineages of C(4) plants use varying mechanisms to generate the C(4) pathway. Although the biochemistry of C(4) photosynthesis was described around 20 years ago, the phylogenetic distance between Arabidopsis and the traditional C(4) models has not facilitated the transfer of knowledge from Arabidopsis research to understanding C(4) systems. We show that Cleome, a genus closely related to Arabidopsis, contains species spanning a developmental progression from C(3) to C(4) photosynthesis. The majority of species we assessed are C(3) plants but have increased venation in leaves. Three C(3) species have both increased venation and enlarged bundle sheath cells, and there is also a tendency to accumulate proteins and transcripts needed for C(4) photosynthesis. Cleome gynandra shows all the characteristics needed for efficient C(4) photosynthesis, including alterations to leaf biochemistry, cell biology and development, and belongs to the NAD-dependent malic enzyme subtype. Combined with its phylogenetic proximity to Arabidopsis, the developmental progression from C(3) to C(4) photosynthesis within the genus provides a potentially excellent new model to increase our understanding of C(4) photosynthesis, and provide insights into its evolution.
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Affiliation(s)
- Diana M Marshall
- Department of Plant Sciences, Downing Street, University of Cambridge, Cambridge, UK
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Brown NJ, Parsley K, Hibberd JM. The future of C4 research--maize, Flaveria or Cleome? TRENDS IN PLANT SCIENCE 2005; 10:215-21. [PMID: 15882653 DOI: 10.1016/j.tplants.2005.03.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
C4 photosynthesis has evolved multiple times among the angiosperms: the spatial rearrangement of the photosynthetic apparatus, combined with alterations to the leaf structure, allows CO2 to be concentrated around Rubisco. Higher CO2 concentrations at Rubisco decrease the rate of oxygenation and therefore reduce the amount of energy lost through photorespiration. C4 plants are particularly prevalent in tropical and subtropical regions because they can sustain higher rates of net photosynthesis; they also represent some of our most productive crops. To date, most progress in identifying genes crucial for C4 photosynthesis has been made using maize and Flaveria. We propose that Cleome, the most closely related genus containing C4 species to the C3 model Arabidopsis, be used together with Arabidopsis resources to accelerate our progress in elucidating the genetic basis of C4 photosynthesis.
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Affiliation(s)
- Naomi J Brown
- Department of Plant Sciences, Downing Street, University of Cambridge, Cambridge, UK CB2 3EA
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Lai LB, Wang L, Nelson TM. Distinct but conserved functions for two chloroplastic NADP-malic enzyme isoforms in C3 and C4 Flaveria species. PLANT PHYSIOLOGY 2002; 128:125-139. [PMID: 11788758 DOI: 10.1104/pp.010448] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
In the most common C4 pathway for carbon fixation, an NADP-malic enzyme (NADP-ME) decarboxylates malate in the chloroplasts of bundle sheath cells. Isoforms of plastidic NADP-ME are encoded by two genes in all species of Flaveria, including C3, C3-C4 intermediate, and C4 types. However, only one of these genes, ChlMe1, encodes the enzyme that functions in the C4 pathway. We compared the expression patterns of the ChlMe1 and ChlMe2 genes in developing leaves of Flaveria pringlei (C3) and Flaveria trinervia (C4) and in transgenic Flaveria bidentis (C4). ChlMe1 expression in C4 species increases in leaves with high C4 pathway activity. In the C3 species F. pringlei, ChlMe1 expression is transient and limited to early leaf development. In contrast, ChlMe2 is expressed in C3 and C4 species concurrent with stages in chloroplast biogenesis. Because previous studies suggest that NADP-ME activities generally reflect the level of its mRNA abundance, we discuss possible roles of ChlMe1 and ChlMe2 based on these expression patterns.
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Affiliation(s)
- Lien B Lai
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut 06520-8104, USA
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