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Mélida H, García-Angulo P, Alonso-Simón A, Encina A, Alvarez J, Acebes JL. Novel type II cell wall architecture in dichlobenil-habituated maize calluses. PLANTA 2009; 229:617-31. [PMID: 19048286 DOI: 10.1007/s00425-008-0860-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2008] [Accepted: 11/10/2008] [Indexed: 05/15/2023]
Abstract
Growth of maize (Zea mays L.) callus-culture cells was inhibited using dichlobenil (2,6 dichlorobenzonitrile, DCB) concentrations > or =1 microM; I (50) value for the effect on inhibited fresh weight gain was 1.5 microM. By increasing the DCB concentration in the culture medium, DCB-habituated cells became 13 times more tolerant of the inhibitor (I (50): 20 microM). In comparison with non-habituated calluses, DCB-habituated calluses grew slower, were less friable and were formed by irregularly shaped cells surrounded by a thicker cell wall. By using an extensive array of techniques, changes in type II cell wall composition and structure associated with DCB habituation were studied. Walls from DCB-habituated cells showed a reduction of up to 75% in cellulose content, which was compensated for by a net increase in arabinoxylan content. Arabinoxylans also showed a reduction in their extractability and a marked increase in their relative molecular mass. DCB habituation also involved a shift from ferulate to coumarate-rich cells walls, and enrichment in cell wall esterified hydroxycinnamates and dehydroferulates. The content of polymers such as mixed-glucan, xyloglucan, mannans, pectins or proteins did not vary or was reduced. These results prove that the architecture of type II cell walls is able to compensate for deficiencies in cellulose content with a more extensive and phenolic cross-linked network of arabinoxylans, without necessitating beta-glucan or other polymer enhancement. As a consequence of this modified architecture, walls from DCB-habituated cells showed a reduction in their swelling capacity and an increase both in pore size and in resistance to polysaccharide hydrolytic enzymes.
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Affiliation(s)
- Hugo Mélida
- Area de Fisiología Vegetal, Facultad de CC., Biológicas y Ambientales, Universidad de León, 24071, León, Spain
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152
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Gene cloning and heterologous expression of a novel endoglucanase, swollenin, from Trichoderma pseudokoningii S38. Biosci Biotechnol Biochem 2008; 72:2799-805. [PMID: 18997434 DOI: 10.1271/bbb.80124] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The coding sequence of a novel cellulolytic factor, swollenin, was isolated from the cellulolytic fungus Trichoderma pseudokoningii S38. The full-length swo2 gene encodes a protein of 494 amino acids with a calculated molecular mass of 51,393 Da, which includes a putative 22-amino-acid signal peptide. Sequence analysis revealed significant identity between isolated swollenin and that from Trichoderma reesei. The swollenin gene was further expressed and purified in T. reesei QM9414. The expressed swollenin protein was consequently purified by two-step ion exchange chromatography. The purified swollenin had subtle hydrolytic activities on xylan and yeast cell wall glucan, while no apparent activities on carboxymethy cellulose, cotton fiber, filter paper, or cellulose powder CF11 were observed. These results indicate that although swollenin maintains unidentified glycohydrolytic activities, it is inactive against beta-1,4-glycosidic bonds in cellulose. Its exact role in lignocellulose hydrolysis calls for further analysis.
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153
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Pomés A. Allergen structures and biologic functions: the cutting edge of allergy research. Curr Allergy Asthma Rep 2008; 8:425-32. [PMID: 18682111 DOI: 10.1007/s11882-008-0082-y] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Studies of structure and function of allergens using state-of-the-art technologies have led to a better understanding of allergenicity, including aspects related to cross-reactivity, allergen nomenclature, and the identification of antigenic determinants. This information is being applied to the design and production of allergy vaccines, some of which already have proven efficacy and safety in clinical trials.
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Affiliation(s)
- Anna Pomés
- Indoor Biotechnologies, 1216 Harris Street, Charlottesville, VA 22903, USA.
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154
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Crystal structure and activity of Bacillus subtilis YoaJ (EXLX1), a bacterial expansin that promotes root colonization. Proc Natl Acad Sci U S A 2008; 105:16876-81. [PMID: 18971341 DOI: 10.1073/pnas.0809382105] [Citation(s) in RCA: 137] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We solved the crystal structure of a secreted protein, EXLX1, encoded by the yoaJ gene of Bacillus subtilis. Its structure is remarkably similar to that of plant beta-expansins (group 1 grass pollen allergens), consisting of 2 tightly packed domains (D1, D2) with a potential polysaccharide-binding surface spanning the 2 domains. Domain D1 has a double-psi beta-barrel fold with partial conservation of the catalytic site found in family 45 glycosyl hydrolases and in the MltA family of lytic transglycosylases. Domain D2 has an Ig-like fold similar to group 2/3 grass pollen allergens, with structural features similar to a type A carbohydrate-binding domain. EXLX1 bound to plant cell walls, cellulose, and peptidoglycan, but it lacked lytic activity against a variety of plant cell wall polysaccharides and peptidoglycan. EXLX1 promoted plant cell wall extension similar to, but 10 times weaker than, plant beta-expansins, which synergistically enhanced EXLX1 activity. Deletion of the gene encoding EXLX1 did not affect growth or peptidoglycan composition of B. subtilis in liquid medium, but slowed lysis upon osmotic shock and greatly reduced the ability of the bacterium to colonize maize roots. The presence of EXLX1 homologs in a small but diverse set of plant pathogens further supports a role in plant-bacterial interactions. Because plant expansins have proved difficult to express in active form in heterologous systems, the discovery of a bacterial homolog opens the door for detailed structural studies of expansin function.
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155
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Kim ES, Lee HJ, Bang WG, Choi IG, Kim KH. A novel cellulase activity enhancing protein from bacillus subtilis, a functional homolog of a plant expansin. J Biotechnol 2008. [DOI: 10.1016/j.jbiotec.2008.07.986] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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156
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Lee HJ, Kim ES, Lee SY, Ko HJ, Bang WG, Kim KH, Choi IG. Cellulase activity enhancing protein (CAEP) from Hahella chejuensis for pretreatment of lignocellulosic biomass. J Biotechnol 2008. [DOI: 10.1016/j.jbiotec.2008.07.1985] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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157
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Davies JM, Mittag D, Dang TD, Symons K, Voskamp A, Rolland JM, O'Hehir RE. Molecular cloning, expression and immunological characterisation of Pas n 1, the major allergen of Bahia grass Paspalum notatum pollen. Mol Immunol 2008; 46:286-93. [PMID: 18817975 DOI: 10.1016/j.molimm.2008.08.267] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2008] [Revised: 07/30/2008] [Accepted: 08/05/2008] [Indexed: 12/01/2022]
Abstract
Bahia grass, Paspalum notatum, is a clinically important subtropical grass with a prolonged pollination season from spring to autumn. We aimed to clone and characterise the major Bahia grass pollen allergen, Pas n 1. Grass pollen-allergic patients presenting to a tertiary hospital allergy clinic were tested for IgE reactivity with Bahia grass pollen extract by skin prick testing, ImmunoCAP, ELISA and immunoblotting. Using primers deduced from the N-terminal peptide sequence of a group 1 allergen of Bahia grass pollen extract separated by two-dimensional gel electrophoresis, the complete Pas n 1 cDNA was obtained by rapid amplification of cDNA ends and cloned. Biological relevance of recombinant Pas n 1 expressed in Escherichia coli was assessed by serum IgE reactivity and basophil activation. Twenty-nine of 34 (85%) consecutive patients presenting with grass pollen allergy were skin prick test positive to Bahia grass pollen. The Pas n 1 cDNA has sequence homology with the beta-expansin 1 glycoprotein family and is more closely related to the maize pollen group 1 allergen (85% identity) than to ryegrass Lol p 1 or Timothy grass Phl p 1 (64 and 66% identity, respectively). rPas n 1 reacted with serum IgE in 47 of 55 (85%) Bahia grass pollen-allergic patients, activated basophils and inhibited serum IgE reactivity with the 29 kDa band of Bahia grass pollen extract. In conclusion the cDNA for the major group 1 allergen of the subtropical Bahia grass pollen, Pas n 1, was identified and cloned. rPas n 1 is immunologically active and is a valuable reagent for diagnosis and specific immunotherapy of grass pollen allergy.
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Affiliation(s)
- Janet M Davies
- CRC for Asthma and Airways, K25-Medical Foundation Building, University of Sydney, Sydney, NSW 2006, Australia.
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158
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Ghiglione HO, Gonzalez FG, Serrago R, Maldonado SB, Chilcott C, Curá JA, Miralles DJ, Zhu T, Casal JJ. Autophagy regulated by day length determines the number of fertile florets in wheat. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2008; 55:1010-24. [PMID: 18547393 DOI: 10.1111/j.1365-313x.2008.03570.x] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
The wheat spikelet meristem differentiates into up to 12 floret primordia, but many of them fail to reach the fertile floret stage at anthesis. We combined microarray, biochemical and anatomical studies to investigate floret development in wheat plants grown in the field under short or long days (short days extended with low-fluence light) after all the spikelets had already differentiated. Long days accelerated spike and floret development and greening, and the expression of genes involved in photosynthesis, photoprotection and carbohydrate metabolism. These changes started while the spike was in the light-depleted environment created by the surrounding leaf sheaths. Cell division ceased in the tissues of distal florets, which interrupted their normal developmental progression and initiated autophagy, thus decreasing the number of fertile florets at anthesis. A massive decrease in the expression of genes involved in cell proliferation, a decrease in soluble carbohydrate levels, and an increase in the expression of genes involved in programmed cell death accompanied anatomical signs of cell death, and these effects were stronger under long days. We propose a model in which developmentally generated sugar starvation triggers floret autophagy, and long days intensify these processes due to the increased carbohydrate consumption caused by the accelerated plant development.
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Affiliation(s)
- Hernán O Ghiglione
- Bioquímica, Facultad de Agronomía, Universidad de Buenos Aires, Av San Martín 4453, 1417 Buenos Aires, Argentina
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159
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Brotman Y, Briff E, Viterbo A, Chet I. Role of swollenin, an expansin-like protein from Trichoderma, in plant root colonization. PLANT PHYSIOLOGY 2008; 147:779-89. [PMID: 18400936 PMCID: PMC2409044 DOI: 10.1104/pp.108.116293] [Citation(s) in RCA: 130] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Swollenin, a protein first characterized in the saprophytic fungus Trichoderma reesei, contains an N-terminal carbohydrate-binding module family 1 domain (CBD) with cellulose-binding function and a C-terminal expansin-like domain. This protein was identified by liquid chromatography-mass spectrometry among many other cellulolytic proteins secreted in the coculture hydroponics medium of cucumber (Cucumis sativus) seedlings and Trichoderma asperellum, a well-known biocontrol agent and inducer of plant defense responses. The swollenin gene was isolated and its coding region was overexpressed in the same strain under the control of the constitutive pki1 promoter. Trichoderma transformants showed a remarkably increased ability to colonize cucumber roots within 6 h after inoculation. On the other hand, overexpressors of a truncated swollenin sequence bearing a 36-amino acid deletion of the CBD did not differ from the wild type, showing in vivo that this domain is necessary for full protein activity. Root colonization rates were reduced in transformants silenced in swollenin gene expression. A synthetic 36-mer swollenin CBD peptide was shown to be capable of stimulating local defense responses in cucumber roots and leaves and to afford local protection toward Botrytis cinerea and Pseudomonas syringae pv lachrymans infection. This indicates that the CBD domain might be recognized by the plant as a microbe-associated molecular pattern in the Trichoderma-plant interaction.
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Affiliation(s)
- Yariv Brotman
- Department of Plant Pathology and Microbiology, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem, Rehovot 76100, Israel
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160
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Plant genetic engineering for biofuel production: towards affordable cellulosic ethanol. Nat Rev Genet 2008; 9:433-43. [DOI: 10.1038/nrg2336] [Citation(s) in RCA: 396] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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161
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Fudali S, Janakowski S, Sobczak M, Griesser M, Grundler FMW, Golinowski W. Two tomato alpha-expansins show distinct spatial and temporal expression patterns during development of nematode-induced syncytia. PHYSIOLOGIA PLANTARUM 2008; 132:370-83. [PMID: 18275468 DOI: 10.1111/j.1399-3054.2007.01017.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Cyst nematodes induce specific syncytial feeding structures within the root which develop from an initial cell by successive incorporation of neighbouring cells through local cell wall dissolutions followed by hypertrophy of included cells. Expansins are known to induce cell wall relaxation and extension in acidic pH, and they are involved in many processes requiring wall modification from cell expansion to cell wall disassembly. We studied the expression pattern of tomato (Lycopersicon esculentum L., cv. Money Maker) expansins during development of syncytia induced by the potato cyst nematode (Globodera rostochiensis Woll.). Based on semi-quantitative reverse transcription-polymerase chain reaction, two expansin genes, LeEXPA4 and LeEXPA5, were selected for detailed examinations because their expression was either elevated in infected roots (LeEXPA4) or specifically induced in the root upon nematode infection (LeEXPA5). Both genes have distinct spatial and temporal expression patterns that may reflect their different roles in syncytium development. LeEXPA4 transcripts were localized predominantly in parenchymatous vascular cylinder cells surrounding syncytia. This finding suggests that LeEXPA4 might be involved in cell wall disassembly or relaxation, mediating syncytium expansion and/or development of conductive tissues. By contrast, LeEXPA5 transcripts were localized in enlarging syncytial elements. Similarly, in immunogold localization experiments, polyclonal antibodies localized the LeEXPA5 protein in cell walls of syncytial elements. This expression pattern suggests that LeEXPA5 gene is specifically involved in enlargement of cells incorporated into syncytium.
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Affiliation(s)
- Sylwia Fudali
- Department of Botany, Warsaw University of Life Sciences (SGGW), Nowoursynowska 159, Building 37, 02-776 Warsaw, Poland
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162
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Jamet E, Albenne C, Boudart G, Irshad M, Canut H, Pont-Lezica R. Recent advances in plant cell wall proteomics. Proteomics 2008; 8:893-908. [DOI: 10.1002/pmic.200700938] [Citation(s) in RCA: 162] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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163
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Thompson DS. Space and time in the plant cell wall: relationships between cell type, cell wall rheology and cell function. ANNALS OF BOTANY 2008; 101:203-11. [PMID: 17660182 PMCID: PMC2711014 DOI: 10.1093/aob/mcm138] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
BACKGROUND The biomechanical behaviour of plant cells depends upon the material properties of their cell walls and, in many cases, it is necessary that these properties are quite specific. Additionally, physiological regulation may require that target cells responding to hormonal signals or environmental factors are able to modulate these characteristics. ARGUMENT This paper uses a rheological analysis of creep of elongating sunflower (Helianthus annuus) sunflower hypocotyls to demonstrate that the mechanical behaviour of plant cell walls is complex and involves multiple layered processes that can be distinguished from one another by the time-scale over which they lead to a change in tissue dimensions, their sensitivity to pH and temperature, and their responses to changes in spatial arrangement of the cell wall brought about by treatment with high M(r) PEG. Furthermore, it appears possible to regulate individual rheological processes, with limited effect on others, in order to modulate growth without affecting tissue structural integrity. It is proposed that control of the water content of the cell wall and therefore the space between cell wall polymers may be one mechanism by which differential regulation of cell wall biomechanical properties is achieved. This hypothesis is supported by evidence showing that enzyme extracts from growing tissues can cause swelling in cell wall fragments in suspension. IMPLICATIONS The physiological implications of this complexity are then considered for growing tissues, stomatal guard cells and abscission cells. It is noted that, in each circumstance, a different combination of mechanical properties is required and that differential regulation of properties affecting behaviour over different time-scales is often necessary.
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Affiliation(s)
- D S Thompson
- School of Biosciences, University of Westminster, 115 New Cavendish Street, London W1W 6UW, UK.
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164
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Duffort O, Quintana J, Ipsen H, Barber D, Polo F. Antigenic similarity among group 1 allergens from grasses and quantitation ELISA using monoclonal antibodies to Phl p 1. Int Arch Allergy Immunol 2007; 145:283-90. [PMID: 18004069 DOI: 10.1159/000110887] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2007] [Accepted: 08/07/2007] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Group 1 allergens elicit a specific IgE response in about 90% of grass pollen-allergic patients. The aim of this work was to study the antigenic similarity among group 1 allergens from different grasses and to develop a monoclonal antibody (MAb)-based quantitation ELISA. METHODS Twenty specific MAbs were produced from BALB/c mice immunized with natural Phl p 1. These MAbs were tested for specificity with thirteen different grass pollen extracts from the Poaceae family and in cross-inhibition experiments for the binding of Phl p 1. Purified group 1 allergens from Poeae grasses (Dactylis glomerata, Lolium perenne, Festuca pratensis and Poa pratensis) were tested for parallelism in quantitation ELISA. RESULTS Eighteen to nineteen anti-Phl p 1 MAbs recognized the homologous allergen in pollen extracts from grasses of the Poeae tribe. In contrast, only four MAbs recognized group 1 from Cynodon dactylon and Phragmites communis. Four groups of MAbs with different epitope specificity were identified. A grass group 1 quantitation ELISA was developed using a mix of three MAbs on the solid phase and a polyclonal rabbit antibody as the second antibody. The group 1 content could be measured in different batches of Phleum pratense as well as in pollen extracts from Poeae grasses, since they showed parallel dose-response curves. CONCLUSIONS MAbs produced in this work enabled us to show the high antigenic similarity between group 1 allergens from temperate grasses. The results prove the usefulness of the ELISA method developed for standardization of grass allergen products.
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165
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Carey RE, Cosgrove DJ. Portrait of the expansin superfamily in Physcomitrella patens: comparisons with angiosperm expansins. ANNALS OF BOTANY 2007; 99:1131-41. [PMID: 17416912 PMCID: PMC3243571 DOI: 10.1093/aob/mcm044] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
BACKGROUND AND AIMS Expansins are plant cell wall loosening proteins important in a variety of physiological processes. They comprise a large superfamily of genes consisting of four families (EXPA, EXPB, EXLA and EXLB) whose evolutionary relationships have been well characterized in angiosperms, but not in basal land plants. This work attempts to connect the expansin superfamily in bryophytes with the evolutionary history of this superfamily in angiosperms. METHODS The expansin superfamily in Physcomitrella patens has been assembled from the Physcomitrella sequencing project data generated by the Joint Genome Institute and compared with angiosperm expansin superfamilies. Phylogenetic, motif, intron and distance analyses have been used for this purpose. KEY RESULTS A gene superfamily is revealed that contains similar numbers of genes as found in arabidopsis, but lacking EXLA or EXLB genes. This similarity in gene numbers exists even though expansin evolution in Physcomitrella diverged from the angiosperm line approx. 400 million years ago. Phylogenetic analyses suggest that there were a minimum of two EXPA genes and one EXPB gene in the last common ancestor of angiosperms and Physcomitrella. Motif analysis seems to suggest that EXPA protein function is similar in bryophytes and angiosperms, but that EXPB function may be altered. CONCLUSIONS The EXPA genes of Physcomitrella are likely to have maintained the same biochemical function as angiosperm expansins despite their independent evolutionary history. Changes seen at normally conserved residues in the Physcomitrella EXPB family suggest a possible change in function as one mode of evolution in this family.
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Affiliation(s)
- Robert E Carey
- Department of Biology, The Pennsylvania State University, University Park, PA 16802, USA.
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166
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Valdivia ER, Sampedro J, Lamb JC, Chopra S, Cosgrove DJ. Recent proliferation and translocation of pollen group 1 allergen genes in the maize genome. PLANT PHYSIOLOGY 2007; 143:1269-81. [PMID: 17220362 PMCID: PMC1820917 DOI: 10.1104/pp.106.092544] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
The dominant allergenic components of grass pollen are known by immunologists as group 1 allergens. These constitute a set of closely related proteins from the beta-expansin family and have been shown to have cell wall-loosening activity. Group 1 allergens may facilitate the penetration of pollen tubes through the grass stigma and style. In maize (Zea mays), group 1 allergens are divided into two classes, A and B. We have identified 15 genes encoding group 1 allergens in maize, 11 genes in class A and four genes in class B, as well as seven pseudogenes. The genes in class A can be divided by sequence relatedness into two complexes, whereas the genes in class B constitute a single complex. Most of the genes identified are represented in pollen-specific expressed sequence tag libraries and are under purifying selection, despite the presence of multiple copies that are nearly identical. Group 1 allergen genes are clustered in at least six different genomic locations. The single class B location and one of the class A locations show synteny with the rice (Oryza sativa) regions where orthologous genes are found. Both classes are expressed at high levels in mature pollen but at low levels in immature flowers. The set of genes encoding maize group 1 allergens is more complex than originally anticipated. If this situation is common in grasses, it may account for the large number of protein variants, or group 1 isoallergens, identified previously in turf grass pollen by immunologists.
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Affiliation(s)
- Elene R Valdivia
- Department of Biology, Penn State University, University Park, Pennsylvania 16802, USA
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167
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Evered C, Majevadia B, Thompson DS. Cell wall water content has a direct effect on extensibility in growing hypocotyls of sunflower (Helianthus annuus L.). JOURNAL OF EXPERIMENTAL BOTANY 2007; 58:3361-71. [PMID: 17898424 DOI: 10.1093/jxb/erm183] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
It has been proposed that spacing between cellulose microfibrils within plant cell walls may be an important determinant of their mechanical properties. A consequence of this hypothesis is that the water content of cell walls may alter their extensibility and that low water potentials may directly reduce growth rates by reducing cell wall spacing. This paper describes a number of experiments in which the water potential of frozen and thawed growing hypocotyls of sunflower (Helianthus annuus L.) were altered using solutions of high molecular weight polyethylene glycol (PEG) or Dextran while their extension under constant stress was monitored using a creep extensiometer (frozen and thawed tissue was used to avoid confounding effects of turgor or active responses to the treatments). Clear reductions in extensibility were observed using both PEG and Dextran, with effects observed in hypocotyl segments treated with PEG 35 000 solutions with osmotic pressures of > or =0.21 MPa suggesting that the relatively mild stresses required to reduce water potentials of plants in vivo by 0.21 MPa may be sufficient to reduce growth rates via a direct effect on wall extensibility. It is noted, therefore, that the water binding capacity of plant cell walls may be of ecophysiological importance. Measurements of cell walls of sunflower hypocotyls using scanning electron microscopy confirmed that treatment of hypocotyls with PEG solutions reduced wall thickness, supporting the hypothesis that the spatial constraint of movement of cellulose microfibrils affects the mechanical properties of the cell wall.
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Affiliation(s)
- Carol Evered
- School of Biosciences, University of Westminster, 115 New Cavendish Street, London W1W 6UW, UK
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168
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Davis TH. Profile of Daniel J. Cosgrove. Proc Natl Acad Sci U S A 2006; 103:14661-3. [PMID: 17003114 PMCID: PMC1595408 DOI: 10.1073/pnas.0606828103] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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