@article {49674, title = {Evolutionary dynamics of U12-type spliceosomal introns.}, journal = {BMC Evol Biol}, volume = {10}, year = {2010}, month = {2010}, pages = {47}, abstract = {

BACKGROUND: Many multicellular eukaryotes have two types of spliceosomes for the removal of introns from messenger RNA precursors. The major (U2) spliceosome processes the vast majority of introns, referred to as U2-type introns, while the minor (U12) spliceosome removes a small fraction (less than 0.5\%) of introns, referred to as U12-type introns. U12-type introns have distinct sequence elements and usually occur together in genes with U2-type introns. A phylogenetic distribution of U12-type introns shows that the minor splicing pathway appeared very early in eukaryotic evolution and has been lost repeatedly.

RESULTS: We have investigated the evolution of U12-type introns among eighteen metazoan genomes by analyzing orthologous U12-type intron clusters. Examination of gain, loss, and type switching shows that intron type is remarkably conserved among vertebrates. Among 180 intron clusters, only eight show intron loss in any vertebrate species and only five show conversion between the U12 and the U2-type. Although there are only nineteen U12-type introns in Drosophila melanogaster, we found one case of U2 to U12-type conversion, apparently mediated by the activation of cryptic U12 splice sites early in the dipteran lineage. Overall, loss of U12-type introns is more common than conversion to U2-type and the U12 to U2 conversion occurs more frequently among introns of the GT-AG subtype than among introns of the AT-AC subtype. We also found support for natural U12-type introns with non-canonical terminal dinucleotides (CT-AC, GG-AG, and GA-AG) that have not been previously reported.

CONCLUSIONS: Although complete loss of the U12-type spliceosome has occurred repeatedly, U12 introns are extremely stable in some taxa, including eutheria. Loss of U12 introns or the genes containing them is more common than conversion to the U2-type. The degeneracy of U12-type terminal dinucleotides among natural U12-type introns is higher than previously thought.

}, keywords = {Animals, Arabidopsis, Evolution, Molecular, HUMANS, Introns, RNA, Small Nuclear, Spliceosomes}, issn = {1471-2148}, doi = {10.1186/1471-2148-10-47}, author = {Lin, Chiao-Feng and Mount, Stephen M and Jarmo{\l}owski, Artur and Maka{\l}owski, Wojciech} } @article {49675, title = {Two alternatively spliced isoforms of the Arabidopsis SR45 protein have distinct roles during normal plant development.}, journal = {Plant Physiol}, volume = {150}, year = {2009}, month = {2009 Jul}, pages = {1450-8}, abstract = {

The serine-arginine-rich (SR) proteins constitute a conserved family of pre-mRNA splicing factors. In Arabidopsis (Arabidopsis thaliana), they are encoded by 19 genes, most of which are themselves alternatively spliced. In the case of SR45, the use of alternative 3{\textquoteright} splice sites 21 nucleotides apart generates two alternatively spliced isoforms. Isoform 1 (SR45.1) has an insertion relative to isoform 2 (SR45.2) that replaces a single arginine with eight amino acids (TSPQRKTG). The biological implications of SR45 alternative splicing have been unclear. A previously described loss-of-function mutant affecting both isoforms, sr45-1, shows several developmental defects, including defects in petal development and root growth. We found that the SR45 promoter is highly active in regions with actively growing and dividing cells. We also tested the ability of each SR45 isoform to complement the sr45-1 mutant by overexpression of isoform-specific green fluorescent protein (GFP) fusion proteins. As expected, transgenic plants overexpressing either isoform displayed both nuclear speckles and GFP fluorescence throughout the nucleoplasm. We found that SR45.1-GFP complements the flower petal phenotype, but not the root growth phenotype. Conversely, SR45.2-GFP complements root growth but not floral morphology. Mutation of a predicted phosphorylation site within the alternatively spliced segment, SR45.1-S219A-GFP, does not affect complementation. However, a double mutation affecting both serine-219 and the adjacent threonine-218 (SR45.1-T218A + S219A-GFP) behaves like isoform 2, complementing the root but not the floral phenotype. In conclusion, our study provides evidence that the two alternatively spliced isoforms of SR45 have distinct biological functions.

}, keywords = {Alternative Splicing, Amino Acid Sequence, Arabidopsis, Arabidopsis Proteins, Carrier Proteins, Flowers, Molecular Sequence Data, Mutation, Plant Roots, Protein Isoforms, Ribonucleoproteins, RNA-Binding Proteins, sequence alignment}, issn = {0032-0889}, doi = {10.1104/pp.109.138180}, author = {Zhang, Xiao-Ning and Mount, Stephen M} } @article {49676, title = {The draft genome of the transgenic tropical fruit tree papaya (Carica papaya Linnaeus).}, journal = {Nature}, volume = {452}, year = {2008}, month = {2008 Apr 24}, pages = {991-6}, abstract = {

Papaya, a fruit crop cultivated in tropical and subtropical regions, is known for its nutritional benefits and medicinal applications. Here we report a 3x draft genome sequence of {\textquoteright}SunUp{\textquoteright} papaya, the first commercial virus-resistant transgenic fruit tree to be sequenced. The papaya genome is three times the size of the Arabidopsis genome, but contains fewer genes, including significantly fewer disease-resistance gene analogues. Comparison of the five sequenced genomes suggests a minimal angiosperm gene set of 13,311. A lack of recent genome duplication, atypical of other angiosperm genomes sequenced so far, may account for the smaller papaya gene number in most functional groups. Nonetheless, striking amplifications in gene number within particular functional groups suggest roles in the evolution of tree-like habit, deposition and remobilization of starch reserves, attraction of seed dispersal agents, and adaptation to tropical daylengths. Transgenesis at three locations is closely associated with chloroplast insertions into the nuclear genome, and with topoisomerase I recognition sites. Papaya offers numerous advantages as a system for fruit-tree functional genomics, and this draft genome sequence provides the foundation for revealing the basis of Carica{\textquoteright}s distinguishing morpho-physiological, medicinal and nutritional properties.

}, keywords = {Arabidopsis, Carica, Contig Mapping, Databases, Genetic, Genes, Plant, Genome, Plant, Molecular Sequence Data, Plants, Genetically Modified, sequence alignment, Sequence Analysis, DNA, Transcription Factors, Tropical Climate}, issn = {1476-4687}, doi = {10.1038/nature06856}, author = {Ming, Ray and Hou, Shaobin and Feng, Yun and Yu, Qingyi and Dionne-Laporte, Alexandre and Saw, Jimmy H and Senin, Pavel and Wang, Wei and Ly, Benjamin V and Lewis, Kanako L T and Salzberg, Steven L and Feng, Lu and Jones, Meghan R and Skelton, Rachel L and Murray, Jan E and Chen, Cuixia and Qian, Wubin and Shen, Junguo and Du, Peng and Eustice, Moriah and Tong, Eric and Tang, Haibao and Lyons, Eric and Paull, Robert E and Michael, Todd P and Wall, Kerr and Rice, Danny W and Albert, Henrik and Wang, Ming-Li and Zhu, Yun J and Schatz, Michael and Nagarajan, Niranjan and Acob, Ricelle A and Guan, Peizhu and Blas, Andrea and Wai, Ching Man and Ackerman, Christine M and Ren, Yan and Liu, Chao and Wang, Jianmei and Wang, Jianping and Na, Jong-Kuk and Shakirov, Eugene V and Haas, Brian and Thimmapuram, Jyothi and Nelson, David and Wang, Xiyin and Bowers, John E and Gschwend, Andrea R and Delcher, Arthur L and Singh, Ratnesh and Suzuki, Jon Y and Tripathi, Savarni and Neupane, Kabi and Wei, Hairong and Irikura, Beth and Paidi, Maya and Jiang, Ning and Zhang, Wenli and Presting, Gernot and Windsor, Aaron and Navajas-P{\'e}rez, Rafael and Torres, Manuel J and Feltus, F Alex and Porter, Brad and Li, Yingjun and Burroughs, A Max and Luo, Ming-Cheng and Liu, Lei and Christopher, David A and Mount, Stephen M and Moore, Paul H and Sugimura, Tak and Jiang, Jiming and Schuler, Mary A and Friedman, Vikki and Mitchell-Olds, Thomas and Shippen, Dorothy E and dePamphilis, Claude W and Palmer, Jeffrey D and Freeling, Michael and Paterson, Andrew H and Gonsalves, Dennis and Wang, Lei and Alam, Maqsudul} } @article {49680, title = {A computational survey of candidate exonic splicing enhancer motifs in the model plant Arabidopsis thaliana.}, journal = {BMC Bioinformatics}, volume = {8}, year = {2007}, month = {2007}, pages = {159}, abstract = {

BACKGROUND: Algorithmic approaches to splice site prediction have relied mainly on the consensus patterns found at the boundaries between protein coding and non-coding regions. However exonic splicing enhancers have been shown to enhance the utilization of nearby splice sites.

RESULTS: We have developed a new computational technique to identify significantly conserved motifs involved in splice site regulation. First, 84 putative exonic splicing enhancer hexamers are identified in Arabidopsis thaliana. Then a Gibbs sampling program called ELPH was used to locate conserved motifs represented by these hexamers in exonic regions near splice sites in confirmed genes. Oligomers containing 35 of these motifs have been shown experimentally to induce significant inclusion of A. thaliana exons. Second, integration of our regulatory motifs into two different splice site recognition programs significantly improved the ability of the software to correctly predict splice sites in a large database of confirmed genes. We have released GeneSplicerESE, the improved splice site recognition code, as open source software.

CONCLUSION: Our results show that the use of the ESE motifs consistently improves splice site prediction accuracy.

}, keywords = {Alternative Splicing, Arabidopsis, Computational Biology, Enhancer Elements, Genetic, Exons, Genes, Plant, RNA, Plant}, issn = {1471-2105}, doi = {10.1186/1471-2105-8-159}, author = {Pertea, Mihaela and Mount, Stephen M and Salzberg, Steven L} } @article {49682, title = {Comprehensive analysis of alternative splicing in rice and comparative analyses with Arabidopsis.}, journal = {BMC Genomics}, volume = {7}, year = {2006}, month = {2006}, pages = {327}, abstract = {

BACKGROUND: Recently, genomic sequencing efforts were finished for Oryza sativa (cultivated rice) and Arabidopsis thaliana (Arabidopsis). Additionally, these two plant species have extensive cDNA and expressed sequence tag (EST) libraries. We employed the Program to Assemble Spliced Alignments (PASA) to identify and analyze alternatively spliced isoforms in both species.

RESULTS: A comprehensive analysis of alternative splicing was performed in rice that started with >1.1 million publicly available spliced ESTs and over 30,000 full length cDNAs in conjunction with the newly enhanced PASA software. A parallel analysis was performed with Arabidopsis to compare and ascertain potential differences between monocots and dicots. Alternative splicing is a widespread phenomenon (observed in greater than 30\% of the loci with transcript support) and we have described nine alternative splicing variations. While alternative splicing has the potential to create many RNA isoforms from a single locus, the majority of loci generate only two or three isoforms and transcript support indicates that these isoforms are generally not rare events. For the alternate donor (AD) and acceptor (AA) classes, the distance between the splice sites for the majority of events was found to be less than 50 basepairs (bp). In both species, the most frequent distance between AA is 3 bp, consistent with reports in mammalian systems. Conversely, the most frequent distance between AD is 4 bp in both plant species, as previously observed in mouse. Most alternative splicing variations are localized to the protein coding sequence and are predicted to significantly alter the coding sequence.

CONCLUSION: Alternative splicing is widespread in both rice and Arabidopsis and these species share many common features. Interestingly, alternative splicing may play a role beyond creating novel combinations of transcripts that expand the proteome. Many isoforms will presumably have negative consequences for protein structure and function, suggesting that their biological role involves post-transcriptional regulation of gene expression.

}, keywords = {Alternative Splicing, Arabidopsis, DNA, Complementary, Expressed Sequence Tags, Oryza}, issn = {1471-2164}, doi = {10.1186/1471-2164-7-327}, author = {Campbell, Matthew A and Haas, Brian J and Hamilton, John P and Mount, Stephen M and Buell, C Robin} } @article {38168, title = {The complete genome sequence of the Arabidopsis and tomato pathogen Pseudomonas syringae pv. tomato DC3000}, journal = {Proceedings of the National Academy of Sciences of the United States of AmericaProceedings of the National Academy of Sciences of the United States of America}, volume = {100}, year = {2003}, note = {http://www.ncbi.nlm.nih.gov/pubmed/12928499?dopt=Abstract}, type = {10.1073/pnas.1731982100}, abstract = {We report the complete genome sequence of the model bacterial pathogen Pseudomonas syringae pathovar tomato DC3000 (DC3000), which is pathogenic on tomato and Arabidopsis thaliana. The DC3000 genome (6.5 megabases) contains a circular chromosome and two plasmids, which collectively encode 5,763 ORFs. We identified 298 established and putative virulence genes, including several clusters of genes encoding 31 confirmed and 19 predicted type III secretion system effector proteins. Many of the virulence genes were members of paralogous families and also were proximal to mobile elements, which collectively comprise 7\% of the DC3000 genome. The bacterium possesses a large repertoire of transporters for the acquisition of nutrients, particularly sugars, as well as genes implicated in attachment to plant surfaces. Over 12\% of the genes are dedicated to regulation, which may reflect the need for rapid adaptation to the diverse environments encountered during epiphytic growth and pathogenesis. Comparative analyses confirmed a high degree of similarity with two sequenced pseudomonads, Pseudomonas putida and Pseudomonas aeruginosa, yet revealed 1,159 genes unique to DC3000, of which 811 lack a known function.}, keywords = {Arabidopsis, Base Sequence, Biological Transport, Genome, Bacterial, Lycopersicon esculentum, Molecular Sequence Data, Plant Growth Regulators, Plasmids, Pseudomonas, Reactive Oxygen Species, Siderophores, virulence}, author = {Buell, C. Robin and Joardar, Vinita and Lindeberg, Magdalen and J. Selengut and Paulsen, Ian T. and Gwinn, Michelle L. and Dodson, Robert J. and DeBoy, Robert T. and Durkin, A. Scott and Kolonay, James F. and Madupu, Ramana and Daugherty, Sean and Brinkac, Lauren and Beanan, Maureen J. and Haft, Daniel H. and Nelson, William C. and Davidsen, Tanja and Zafar, Nikhat and Zhou, Liwei and Liu, Jia and Yuan, Qiaoping and Khouri, Hoda and Fedorova, Nadia and Tran, Bao and Russell, Daniel and Berry, Kristi and Utterback, Teresa and Aken, Susan E. van and Feldblyum, Tamara V. and D{\textquoteright}Ascenzo, Mark and Deng, Wen-Ling and Ramos, Adela R. and Alfano, James R. and Cartinhour, Samuel and Chatterjee, Arun K. and Delaney, Terrence P. and Lazarowitz, Sondra G. and Martin, Gregory B. and Schneider, David J. and Tang, Xiaoyan and Bender, Carol L. and White, Owen and Fraser, Claire M. and Collmer, Alan} } @article {49685, title = {Improving the Arabidopsis genome annotation using maximal transcript alignment assemblies.}, journal = {Nucleic Acids Res}, volume = {31}, year = {2003}, month = {2003 Oct 1}, pages = {5654-66}, abstract = {

The spliced alignment of expressed sequence data to genomic sequence has proven a key tool in the comprehensive annotation of genes in eukaryotic genomes. A novel algorithm was developed to assemble clusters of overlapping transcript alignments (ESTs and full-length cDNAs) into maximal alignment assemblies, thereby comprehensively incorporating all available transcript data and capturing subtle splicing variations. Complete and partial gene structures identified by this method were used to improve The Institute for Genomic Research Arabidopsis genome annotation (TIGR release v.4.0). The alignment assemblies permitted the automated modeling of several novel genes and >1000 alternative splicing variations as well as updates (including UTR annotations) to nearly half of the approximately 27 000 annotated protein coding genes. The algorithm of the Program to Assemble Spliced Alignments (PASA) tool is described, as well as the results of automated updates to Arabidopsis gene annotations.

}, keywords = {algorithms, Alternative Splicing, Arabidopsis, DNA, Complementary, Expressed Sequence Tags, Genome, Plant, Introns, Plant Proteins, RNA, Plant, sequence alignment, software, Transcription, Genetic, Untranslated Regions}, issn = {1362-4962}, author = {Haas, Brian J and Delcher, Arthur L and Mount, Stephen M and Wortman, Jennifer R and Smith, Roger K and Hannick, Linda I and Maiti, Rama and Ronning, Catherine M and Rusch, Douglas B and Town, Christopher D and Salzberg, Steven L and White, Owen} } @article {49688, title = {Evidence for a plastid origin of plant ethylene receptor genes.}, journal = {Plant Physiol}, volume = {130}, year = {2002}, month = {2002 Sep}, pages = {10-4}, keywords = {Amino Acid Sequence, Anabaena, Arabidopsis, Cyanobacteria, Molecular Sequence Data, Plant Proteins, Plastids, Protein Kinases, Receptors, Cell Surface, Sequence Homology, Amino Acid}, issn = {0032-0889}, doi = {10.1104/pp.005397}, author = {Mount, Stephen M and Chang, Caren} }