Solanum lycopersicum as a model system to study pathogenicity mechanisms of Moniliophthora perniciosa, the causal agent of witches' broom disease of Theobroma cacao (click to download PDF)
Marelli, Jean-Philippe, Ph.D., The Pennsylvania State University, 2008, 178 pages; AAT 3336086
Abstract (Summary) Theobroma cacao produces cocoa beans, an essential ingredient for the production of chocolate. This research focuses on enhancing disease resistance in Theobroma cacao via two approaches: The first approach targeted improved understanding of the pathogenicity mechanisms of Moniliophthora perniciosa , the causal agent of witches' broom disease because of its economical impact in South America and the potential threat to unaffected areas in other continents. The second approach involved identifying tomato varieties that differentially interact with M. perniciosa to study mechanisms of pathogenesis and resistance toward the goal of making tomato as a surrogate model for cacao witches' broom. Certain strains of M. perniciosa can infect wild and cultivated solanaceous plants, including Solanum lycopersicum (tomato), which allowed the advantage and convenience of working with an annual plant and make use of the numerous genetic and genomic resources available from tomato plants. The primary goal in this thesis was to elucidate cellular and physiological mechanisms underlying the establishment of fungal biotrophy. The research strongly suggests that during the biotrophic stage, the fungus causes cell multiplication and cell enlargement leading to swelling of stem and petioles. Consistent with these cellular changes, using an auxin reporter system (DR5-GUS) transgenically introduced to a susceptible tomato plant, an overproduction of auxin was found at the sites of infection. To discover new sources of resistance against M. perniciosa in tomato, S. habrochaites , a wild relative of S. lycopersicon , and near isogenic lines (NILs) derived from a cross between them were screened. Solanum habrochaites can block the establishment of biotrophy. One hundred tomato NILs containing different chromosomal sections of the genome of S. habrochaites in a S. lycopersicon background were the source for identifying genome regions of S. habrochaites that contribute to the observed resistance against M. perniciosa . A strong QTL for disease severity (P<0.05), shoot diameter ( P <0.001), and shoot fresh and dry weight ( P <0.0001) was detected on the short arm of chromosome one. This genomic region contains a cluster of genes for resistance against the fungal biotrophic pathogen Cladosporium fulvum . Implications of this thesis for improving cacao breeding strategies will be discussed.
Indexing (document details) School: The Pennsylvania State University School Location: United States -- Pennsylvania Keyword(s): Witches' broom disease, Moniliophthora perniciosa, Theobroma cacao Source: DAI-B 69/11, May 2009 Source type: Dissertation Subjects: Plant sciences Publication Number: AAT 3336086 ISBN: 9780549905981 Document URL: http://ezaccess.libraries.psu.edu/login?url=http://proquest.umi.com/pqdweb?did=1633770651&sid=1&Fmt=2&clientId=9874&RQT=309&VName=PQD ProQuest document ID: 1633770651
Flower development in Theobroma cacao L.: An assessment of morphological and molecular conservation of floral development between Arabidopsis thaliana and Theobroma cacao
Swanson, John-David. Proquest Dissertations And Theses 2005. Section 0176, Part 0309 201 pages; [Ph.D. dissertation].United States -- Pennsylvania: The Pennsylvania State University; 2005. Publication Number: AAT 3173830.
Abstract (Summary)
Comparative anatomical and developmental studies on Theobroma cacao L. flower development were conducted to provide insight into the general mechanisms that control floral development. These studies were also conducted to assess the level of conservation of these systems among plant species, especially with reference to Arabidopsis thaliana. To this end, we underwent a study to compare "normal" flowers of T. cacao to what is already known in model species. To provide complementary approaches to the same set of questions, we examined T. cacao floral development at the morphological, genetic and gene expression levels. Morphological comparisons were made though the analysis of time-lapse photography and light and electron microscopy to create mathematical models of flower development for T. cacao . At the genetic level, we compared EST sequence data from Arabidopsis , poplar, cotton and T. cacao through phylogenetic methods. To precisely localize gene expression patterns during T. cacao flower development, we performed in situ hybridizations using the floral integrator LEAFY as a probe, as well as several ABC genes. Comparison of the T. cacao floral developmental program with that of Arabidopsis revealed that although the final sizes and morphologies of flowers in the two species differ, their developmental programs are strikingly similar both morphologically and genetically. Consistent with this analysis, a cross-species analysis of the current knowledge in this field indicates a high degree of conservation kingdom wide.
Indexing (document details)
Advisor: Guiltinan, Mark, Carlson, John
School: The Pennsylvania State University
School Location: United States -- Pennsylvania
Keyword(s): Theobroma cacao, Flower, Molecular conservation
Source: DAI-B 66/05, p. 2366, Nov 2005
Source type: Dissertation
Subjects: Botany, Statistics, Molecular biology
Publication Number: AAT 3173830
ISBN: 97805421167810
Document URL: http://ezaccess.libraries.psu.edu/login?url=http://proquest.umi.com/pqdweb?did=920930731&Fmt=6&clientId=9874&RQT=309&VName=PQD
ProQuest document ID: 920930731
Genetic engineering of Theobroma cacao and molecular studies on cacao defense responses
Antunez de Mayolo, Gabriela. Proquest Dissertations And Theses 2003. Section 0176, Part 0307 148 pages; [Ph.D. dissertation].United States -- Pennsylvania: The Pennsylvania State University; 2003. Publication Number: AAT 3096927.
Abstract (Summary)
Theobroma cacao , a tropical evergreen tree, holds great economic importance for many small crop farmers in developing countries. Cultivated on over five million hectares worldwide, cocoa production is limited by three major fungal diseases. Disease has resulted in average annual losses estimated at forty percent worldwide. In Brazil alone, production dropped from 400,000 to 100,000 metric tons over the past ten years due to single fungal pathogen.
Research in plant molecular biology has developed an array of new techniques for crop improvement, including tissue culture, quantitative trait loci mapping, marker assisted selection, introduction of novel genes through genetic engineering and the use molecular techniques to investigate basic physiological mechanisms. Through my research I reported use of some of these techniques to improve the efficiency of Agrobacterium mediated transformation of cacao and further used this technique to generate transgenic cacao lines expressing a cacao class I chitinase gene. Furthermore, molecular biology techniques were utilized to initiate studies of defense responses in cacao, and investigate the expression patterns of five cloned cacao ESTs in response to infection and chemical elicitation. These studies will contribute to the development of new disease control strategies with the ultimate goal of providing alternative solutions to cocoa farmers.
Indexing (document details)
Advisor: Guiltinan, Mark J.
School: The Pennsylvania State University
School Location: United States -- Pennsylvania
Keyword(s): Cacao, Defense responses, Theobroma cacao, Crinipellis perniciosa
Source: DAI-B 64/07, p. 3094, Jan 2004
Source type: Dissertation
Subjects: Molecular biology, Plant pathology, Plant propagation
Publication Number: AAT 3096927
Document URL: http://ezaccess.libraries.psu.edu/login?url=http://proquest.umi.com/pqdweb?did=764755071&Fmt=6&clientId=9874&RQT=309&VName=PQD
ProQuest document ID: 764755071
Phosphatase secretion mutants in Arabidopsis thaliana
Tomscha, Jennifer Leigh. Proquest Dissertations And Theses 2001. Section 0176, Part 0817 103 pages; [Ph.D. dissertation].United States -- Pennsylvania: The Pennsylvania State University; 2001. Publication Number: AAT 3036155.
Abstract (Summary)
Phosphatases are important enzymes for understanding plant phosphorus relations. Plant-derived soil phosphatases may help plants during phosphorus deficiency by mobilizing organic phosphorus for plant uptake. In microbes, phosphatases and other responses to phosphorus deficiency are controlled at the transcriptional level by the PHO regulon, and evidence is mounting for the existence of a plant PHO regulon. By isolating Arabidopsis mutants for phosphatase secretion, components of a plant PHO regulon may be identified. Identification and characterization of constitutive phosphatase secretion ( cps ) mutants showed that root-bound phosphatase activity can be increased, and that under low-phosphorus conditions this increased activity can preserve higher root phosphate concentrations, however, there may be a physiological cost in growth associated with this trait. Characterization of the phosphatase under-producing ( pup ) mutants revealed that acid phosphatases can alter whole-plant phosphorus relations, that secreted phosphatases are important for acquiring and/or maintaining phosphate levels when grown in a soil substrate with an organic P component, and that secreted phosphatases are probably under post-transcriptional control. Although the cps and pup mutants are not defective in P deficiency responses, these mutants give us insight into physiologically important components of plant P regulation.
Indexing (document details)
Advisor: Guiltinan, Mark J.
School: The Pennsylvania State University
School Location: United States -- Pennsylvania
Keyword(s): Phosphatase, Arabidopsis thaliana, Root exudates
Source: DAI-B 62/12, p. 5582, Jun 2002
Source type: Dissertation
Subjects: Botany, Plant propagation
Publication Number: AAT 3036155
ISBN: 9780493491042
Document URL: http://ezaccess.libraries.psu.edu/login?url=http://proquest.umi.com/pqdweb?did=726143871&Fmt=6&clientId=9874&RQT=309&VName=PQD
ProQuest document ID: 726143871
Somatic embryogenesis, embryo conversion, micropropagation and factors affecting genetic transformation of Theobroma cacao L
Traore, Abdoulaye. Proquest Dissertations And Theses 2000. Section 0176, Part 0479 135 pages; [Ph.D. dissertation].United States -- Pennsylvania: The Pennsylvania State University; 2000. Publication Number: AAT 9966910.
Abstract (Summary)
The effects of 5 carbon sources (glucose, fructose, maltose, sorbitol, sucrose) and 2 explant types (staminode and petal) on cacao somatic embryogenesis were evaluated. Glucose, fructose and sucrose were found to support cacao somatic embryo production, while no embryos were produced with sorbitol or maltose in the media. Staminode explants were more responsive to somatic embryogenesis than petals, producing up to 99% embryogenic explants and over 20 embryos per responsive explant. In contrast, petal explants produced a maximum of 34% embryogenic explants and a maximum of 8 embryos per responsive explant. Four different media (MS, WP, DKW, and DKW supplemented with potassium nitrate and amino acids) were tested for their ability to support and promote shoot development during embryo conversion. DKW medium supplemented with potassium nitrate and amino acids yielded the highest percentage of normal and total shoot production (59% and 92% respectively). DKW and WPM media supported a higher percentage of conversion (77% each) than did MS medium (59%). The ivory colored type II somatic embryos more frequently produced taproots than did the translucent type I embryos (65% and 35% respectively). In vitro pruning of plantlets with abnormal shoots resulted in axillary meristem growth and conversion into normal plantlets with a rate of 79%. A micropropagation system, including shoot proliferation, was developed for cacao by pruning in vitro somatic embryo derived plantlets. The addition of TDZ to the medium did not affect shoot production from internodal and apical explants. Higher rooting efficiencies of shoot explants were achieved using IBA. Micropropagated and somatic embryo derived plants were acclimated to greenhouse conditions with a success rate averaging 90%. Genetic transformation of cacao staminode tissue was attempted using Agrobacterium or biolistic techniques. Transgenic callus and proembryonic tissue expressing GFP were recovered but no embryo development was obtained. Agrobacterium and the antibiotic cefotaxime at 400mg/L were found to negatively influence staminode explant growth and somatic embryo production.
Indexing (document details)
Advisor: Guiltinan, Mark J.
School: The Pennsylvania State University
School Location: United States -- Pennsylvania
Keyword(s): Somatic embryogenesis, Embryo conversion, Micropropagation, Genetic transformation, Theobroma cacao
Source: DAI-B 61/04, p. 1718, Oct 2000
Source type: Dissertation
Subjects: Plant propagation, Food science, Genetics
Publication Number: AAT 9966910
ISBN: 9780599715608
Document URL: http://ezaccess.libraries.psu.edu/login?url=http://proquest.umi.com/pqdweb?did=731971251&Fmt=6&clientId=9874&RQT=309&VName=PQD
ProQuest document ID: 731971251
Agrobacterium-mediated genetic transformation of apple (Malus domestica Borkh.)
Maximova, Siela Nikolava. Proquest Dissertations And Theses 1997. Section 0176, Part 0479 106 pages; [Ph.D. dissertation].United States -- Pennsylvania: The Pennsylvania State University; 1997. Publication Number: AAT 9802704.
Abstract (Summary)
Apple is an attractive candidate for gene transfer because of its economic importance, ability to easily regenerate from somatic tissue, long juvenile period, and high level of self incompatibility. Unlike sexual breeding, genetic engineering methods allow fast and direct modification of existing cultivars to produce transgenic plants. Transgenic apple plants have already been produced using a bacterial DNA transfer system, however the transformation frequencies reported were low (0.2% to 2.8%).
There are four main components of the Agrobacterium genetic transformation process: initiation (selection of explants), infection, selection of transformed cells and regeneration of transformed plants. This thesis presents research to optimize this process. The first step was to establish an efficient rooting protocol for auxillary shoots from in vitro proliferating cultures. Rooting of individual shoots was induced on a simplified liquid culture medium containing 15 $\mu$M IBA, followed by a root elongation phase on agar solidified medium. Different root induction time periods and temperatures were tested. The best results were recorded after incubation for 2 days at 25$\sp\circ$C with a basipetal V-shaped cut applied. Leaf explants from rooted plants were regenerated on BNZ511 media. Shoot regeneration was strongly enhanced when 3% sorbitol and phytagel were used in the medium. No significant genotype dependent variation in response to the regeneration system was observed amongst the cultivars tested.
'Fuji' leaf explants were cultured with 3 mg/l IBA prior to Agrobacterial infection. The transformation frequency was measured by GUS histochemical assay. Preculture with IBA did not increase transformation efficiency and promoted regeneration of escapes.
Early events of Agrobacterium-mediated transformation of apple were investigated using a synthetic green fluorescent protein reporter gene (SGFP). SGFP expression was first detected 48 hours after infection and very high T-DNA transfer rates were recorded. Transgenic-GFP shoots were regenerated at low frequencies. The detection of SGFP expression confirmed its effectiveness as a new reporter gene for detection of early transformation events and for screening of putative transformants. The results suggested that factors other than Agrobacterium interaction and T-DNA transfer are the rate limiting steps in Agrobacterium-mediated transformation of apple.
Indexing (document details)
Advisor: Guiltinan, Mark
School: The Pennsylvania State University
School Location: United States -- Pennsylvania
Source: DAI-B 58/07, p. 3393, Jan 1998
Source type: Dissertation
Subjects: Plant propagation, Genetics, Molecular biology
Publication Number: AAT 9802704
ISBN: 97805915248410
Document URL: http://ezaccess.libraries.psu.edu/login?url=http://proquest.umi.com/pqdweb?did=736554471&Fmt=6&clientId=9874&RQT=309&VName=PQD
ProQuest document ID: 736554471
Molecular analysis of starch branching enzyme genes in maize (Zea mays L.)
Kim, Kyung-Nam. Proquest Dissertations And Theses 1997. Section 0176, Part 0817 137 pages; [Ph.D. dissertation].United States -- Pennsylvania: The Pennsylvania State University; 1997. Publication Number: AAT 3082065.
Abstract (Summary)
A full-length maize genomic clone was isolated and sequenced which contains the entire coding region of starch branching enzyme I ( Sbe1 ) as well as 5 ' - and 3 ' -flanking sequences. The transcription initiation site of the Sbe1 gene was determined by primer extension analysis to be at an adenine nucleotide located 24 by downstream from the TATA box. Studies using 3 ' -rapid amplification of cDNA ends (3 ' RACE) indicated that polyadenylation occurs 29 by downstream from a putative polyadenylation signal (AATAAA). The transcribed region of the gene consists of 14 exons and 13 introns, distributed over 5.7 kb. Southern blot analysis suggested that two Sbe1 genes with divergent 5 ' -ends of the coding region exist in maize genome. Including the first exon and intron of the Sbe1 gene into a transcriptional chimeric construct of the 5 ' -flanking region (-2190 to +27) fused to luciferase gene dramatically increased gene expression (14 fold) in maize endosperm suspension cells. Transient expression assays of 5 ' deletion and linker-scan constructs identified two positive cis -regulatory elements located in regions, -315 to -295 and -284 to -256, respectively. Northern blot analysis demonstrated that the endogenous Sbe1 mRNA level in cultured maize endosperm suspension cells is modulated by sugar concentrations in the media. Transient expression assays of the 5 ' deletion constructs showed that the promoter sequences between -314 and -145 are necessary for sugar regulation.
A maize genomic DNA fragment containing the entire coding region of starch branching enzyme IIb ( Sbe2b ) as well as 5 ' - and 3 ' -flanking sequences was isolated and sequenced. A consensus TATA-box sequence was found 28 by upstream of the transcription initiation site as determined by primer extension analysis. The transcribed region of the gene is composed of 22 exons and 21 introns distributed over 15,347 bp. Genomic Southern blot analyses suggested that a single Sbe2b gene is present in maize genome. Promoter activity was confirmed with a transcriptional fusion of the Sbe2b 5 ' -flanking region between -2,964 and +100 to luciferase gene, which was subject to transient expression assays in maize endosperm suspension cells. 5 ' deletion analysis revealed that the 122-bp region from -160 to -49 is essential for promoter activity.
Indexing (document details)
Advisor: Guiltinan, Mark J.
School: The Pennsylvania State University
School Location: United States -- Pennsylvania
Keyword(s): Maize, Starch-branching enzyme I
Source: DAI-B 64/02, p. 573, Aug 2003
Source type: Dissertation
Subjects: Botany, Molecular biology
Publication Number: AAT 3082065
Document URL: http://ezaccess.libraries.psu.edu/login?url=http://proquest.umi.com/pqdweb?did=765308041&Fmt=6&clientId=9874&RQT=309&VName=PQD
ProQuest document ID: 765308041
Molecular characterization of starch branching enzyme genes, Sbe1, Sbe2b and Sbe2a in maize (Zea mays L.)
Gao, Ming. Proquest Dissertations And Theses 1996. Section 0176, Part 0817 108 pages; [Ph.D. dissertation].United States -- Pennsylvania: The Pennsylvania State University; 1996. Publication Number: AAT 9702296.
Abstract (Summary)
Expression of the maize starch branching enzyme (SBE) genes Sbe1 and Sbe2b were characterized during kernel development and in vegetative tissues. The onset of Sbe1 and Sbe2b expression during endosperm development was similar to that of other genes involved in starch biosynthesis (Wx, Sh2 and Bt2). However, the expression of She2b peaked earlier than that of Sbe1 in developing endosperm and embryos resulting in a shift in the ratio of Sbe1 to Sbe2b relative message levels during kernel and embryo development. Transcripts hybridizing to the Sbe2b probe were not detectable in leaves or roots which nonetheless have SBEII enzymatic activity, suggesting that there may be another divergent starch branching enzyme II-like gene(s) in maize. A similar expression pattern is shared between the maize genes and related genes in pea, which together with their evolutionary conservation, suggests that the SBE isoforms may play unique roles in starch biosynthesis during plant development.
A putative Sbe2a cDNA (2,795 bp) was isolated. This cDNA is highly conserved in the central region (380 to 2445 bp, 78% similarity), but quite divergent at the 5$\sp\prime$ end (0 to 380 bp, 29% similarity) and the 3$\sp\prime$ UTR region (2445-2763, 38% similarity) with the Sbe2b cDNA counterparts. The amino acid sequences corresponding to the central conserved regions of the Sbe2b and putative Sbe2a cDNAs share 89% sequence similarity. The N-terminal 14 amino acids of ae-B1 endosperm SBEIIa perfectly match those deduced from the putative Sbe2a cDNA. The calculated molecular weight (89.583 kD) from the deduced SBEIIa mature protein closely matches that of experimentally determined endosperm SBEIIa (89 kD). A portion of the putative Sbe2a cDNA was also cloned from ae-B1 endosperm. Northern and RPA analysis with the probe specific to the putative Sbe2a cDNA detected a very low level of transcripts in endosperm and embryo of both ae-B1 and normal W64A kernels, leaves, roots, young stems and tassels of W64A plants. Southern analysis showed that Sbe2a and Sbe2b reside at different genomic loci. These results and data from molecular genetic analysis of ae mutants suggest that this putative Sbe2a cDNA indeed encodes maize SBEIIa.
Indexing (document details)
Advisor: Shannon, Jack, Guiltinan, Mark
School: The Pennsylvania State University
School Location: United States -- Pennsylvania
Source: DAI-B 57/08, p. 4919, Feb 1997
Source type: Dissertation
Subjects: Botany, Molecular biology, Genetics
Publication Number: AAT 9702296
ISBN: 9780591090437
Document URL: http://ezaccess.libraries.psu.edu/login?url=http://proquest.umi.com/pqdweb?did=739371451&Fmt=6&clientId=9874&RQT=309&VName=PQD
ProQuest document ID: 739371451
The following theses are not available online but can be requested for purchase from the Penn State Libarary (www.psu.edu)
DNA binding specificity and interactions with nucleosomal DNA of the plantbZIP protein EmBP-1
Niu, Xiping. Proquest Dissertations And Theses 1995. Section 0176, Part 0307 132 pages; [Ph.D. dissertation].United States -- Pennsylvania: The Pennsylvania State University; 1995. Publication Number: AAT 9612800.
Abstract (Summary)
The wheat basic leucine zipper (bZIP) protein EmBP-1 has been implicated in the mechanisms of abscisic acid mediated gene activation. In order to understand the roles of EmBP-1 in regulating gene transcription, its DNA binding sequence specificity and interactions with nucleosomal DNA were investigated.
The binding specificity of recombinantly expressed EmBP-1 was studied using PCR assisted gel shift selection of DNA from random sequence pools. DNA binding sites were identified both by direct sequencing of a selected pool and by cloning and sequencing individuals from a selected pool. The binding sites were compared by electrophoretic mobility shift assay (EMSA) and DNaseI footprinting, which show that EmBP-1 binds to a family of related sequences with varying degrees of affinity. The highest affinity site bound by EmBP-1 is the palindromic sequence GCCACGTGGC (G-box). EmBP-1 can also bind a number of other sequences with high affinity, however most of these are asymmetric. While nearly all sequences bound by EmBP-1 contain an ACGT core sequence, EmBP-1 can also bind at least two sites with altered cores. These results provide insight into the possible targets which EmBP-1 might bind in vivo.
To investigate the interactions of EmBP-1 with its recognition sites in chromosomal DNA, nucleosome-length DNA segments containing either an abscisic acid responsive element (ABRE) or a high affinity binding site (G-box) were reconstituted into nucleosome cores in vitro. EMSA and DNaseI footprinting demonstrated that nucleosomal templates can be bound by EmBP-1 at reduced affinities relative to naked DNA, which is more dramatic when the binding sites are located near the nucleosomal dyad. Rotational phasing of the G-box sequence revealed up to a 3 fold effect on nucleosome binding by EmBP-1. The results also indicate that nucleosomal inhibition of EmBP-1 binding to ABRE is less than that for G-box even though EmBP-1 has greater affinity for G-box than for ABRE in free DNA. These results are the first demonstration of nucleosome binding by a bZIP protein as well as by any plant transcription factor.
Indexing (document details)
Advisor: Guiltinan, Mark
School: The Pennsylvania State University
School Location: United States -- Pennsylvania
Source: DAI-B 57/01, p. 134, Jul 1996
Source type: Dissertation
Subjects: Molecular biology, Botany
Publication Number: AAT 9612800
Document URL: http://ezaccess.libraries.psu.edu/login?url=http://proquest.umi.com/pqdweb?did=742718231&Fmt=2&clientId=9874&RQT=309&VName=PQD
ProQuest document ID: 742718231
Molecular genetic analysis of multiple isoforms of starch branching enzyme with emphasis on Zea mays L
Fisher, Dane Kinard. Proquest Dissertations And Theses 1995. Section 0176, Part 0369 185 pages; [Ph.D. dissertation].United States -- Pennsylvania: The Pennsylvania State University; 1995. Publication Number: AAT 9600172.
Abstract (Summary)
Plant starch biosynthesis predominantly involves the action of ADPG-pyrophosphorylase, starch synthases, and starch branching enzymes (SBEs). Starch branching enzymes are transglycosylases that split an $\alpha$-1,4-glucosidic linkage in alpha glucans such as amylose or amylopectin 5 to 7 glucose units from a nonreducing end, and transfer the chain to another $\alpha$-1,4-glucan molecule, forming an or $\alpha$-1,6 bond.
Work presented in this thesis involved the cloning and sequence characterization of full length maize endosperm sbe1 and sbe2b cDNAs. The cloned cDNAs were used as sense and antisense constructs to transform tobacco and generate many different independent transgenic lines. It was hoped that this experiment would better explain the activity of each SBE isoform in starch synthesis in vivo. The analysis of starch structure in transgenic lines would define these results. Lines were identified with high levels of mRNA accumulation for sbe1 and sbe2b, but no detectable protein accumulation, or change in starch granule structure by SEM analysis.
The controversy over the number of genes controlling the similar isoforms maize endosperm SBE IIa and IIb was addressed by analysis of 16 alleles of the amylose-extender (ae)locus. The ae locus was previously identified to affect levels of SBE IIb activity alone, and recently was identified as a lesion in the gene for SBE IIb. However, whether SBE IIa is encoded by the same or an independent locus remained unproven. Northern analysis of 16 alleles with the cloned sbe2b gene revealed alleles with altered and absent transcripts. These same alleles retained wild type levels of SBE IIa activity, giving strong evidence for a separate gene for SBE IIa in maize endosperm.
Finally, two cDNAs expressed in Arabidopsis thaliana vegetative and reproductive tissues were cloned and characterized. The two cDNAs belong to a class of plant SBE isoforms including pea sbe1, maize sbe2b, and rice sbe3 (class A). Genomic Southern analysis suggests each cDNA is encoded by a single, distinct locus. This is the first report of the identification and characterization of two distinct class A SBE isoforms expressed in the same plant tissues.
Indexing (document details)
Advisor: Guiltinan, Mark J., Boyer, Charles D.
School: The Pennsylvania State University
School Location: United States -- Pennsylvania
Keyword(s): Arabidopsis thaliana
Source: DAI-B 56/09, p. 4707, Mar 1996
Source type: Dissertation
Subjects: Genetics, Botany, Molecular biology
Publication Number: AAT 9600172
Document URL: http://ezaccess.libraries.psu.edu/login?url=http://proquest.umi.com/pqdweb?did=741318101&Fmt=2&clientId=9874&RQT=309&VName=PQD
ProQuest document ID: 741318101