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Jarkko Lahdensalo - One of the best experts on this subject based on the ideXlab platform.
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Two phylogenetically highly distinct β-Tubulin genes of the basidiomycete Suillus bovinus
Current Genetics, 2005Co-Authors: Jarmo T. Juuti, Mika T. Tarkka, Sanna Jokela, Lars Paulin, Jarkko LahdensaloAbstract:Genes tubb1 and tubb2 which encode β-Tubulins 1 and 2, respectively, were characterised from the ectomycorrhizal basidiomycete Suillus bovinus . The two β-Tubulins are surprisingly divergent, with the lowest known sequence identity (60%) in any single fungal species. Comparative analysis showed that β-Tubulin 1 and the intron distribution within the tubb1 gene resemble the other β-Tubulins. β-Tubulin 2, in contrast, is the most divergent fully described fungal β-Tubulin and the gene contains at least 21 introns, which is the largest amount known for any β-Tubulin gene. Despite this divergence, both genes are constitutively expressed in the functional compartments of the mycorrhizosphere and in pure cultures. Transcription of tubb1 is about 2.4 times higher than that of tubb2 ; and this difference is also seen at the translation level. Evidence suggested that phosphorylation may be the main post-translational modification of both β-Tubulins. The putative GTP-binding site residues of β-Tubulin 1 match crystallised pig β-Tubulin residues, while five of the nine differences in β-Tubulin 2 match the pig α-Tubulin GTP-site, suggesting the presence of adaptive sequence evolution. In a Bayesian analysis, β-Tubulin 1 joins the other basidiomycete sequences, while β-Tubulin 2 loosely associates with the group of divergent ascomycete sequences without any clear relative among the known full-length fungal β-Tubulin sequences.
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two phylogenetically highly distinct β Tubulin genes of the basidiomycete suillus bovinus
Current Genetics, 2005Co-Authors: Jarmo T. Juuti, Mika T. Tarkka, Sanna Jokela, Lars Paulin, Jarkko LahdensaloAbstract:Genes tubb1 and tubb2 which encode beta-Tubulins 1 and 2, respectively, were characterised from the ectomycorrhizal basidiomycete Suillus bovinus. The two beta-Tubulins are surprisingly divergent, with the lowest known sequence identity (60%) in any single fungal species. Comparative analysis showed that beta-Tubulin 1 and the intron distribution within the tubb1 gene resemble the other beta-Tubulins. beta-Tubulin 2, in contrast, is the most divergent fully described fungal beta-Tubulin and the gene contains at least 21 introns, which is the largest amount known for any beta-Tubulin gene. Despite this divergence, both genes are constitutively expressed in the functional compartments of the mycorrhizosphere and in pure cultures. Transcription of tubb1 is about 2.4 times higher than that of tubb2; and this difference is also seen at the translation level. Evidence suggested that phosphorylation may be the main post-translational modification of both beta-Tubulins. The putative GTP-binding site residues of beta-Tubulin 1 match crystallised pig beta-Tubulin residues, while five of the nine differences in beta-Tubulin 2 match the pig alpha-Tubulin GTP-site, suggesting the presence of adaptive sequence evolution. In a Bayesian analysis, beta-Tubulin 1 joins the other basidiomycete sequences, while beta-Tubulin 2 loosely associates with the group of divergent ascomycete sequences without any clear relative among the known full-length fungal beta-Tubulin sequences.
Mika T. Tarkka - One of the best experts on this subject based on the ideXlab platform.
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Two phylogenetically highly distinct β-Tubulin genes of the basidiomycete Suillus bovinus
Current Genetics, 2005Co-Authors: Jarmo T. Juuti, Mika T. Tarkka, Sanna Jokela, Lars Paulin, Jarkko LahdensaloAbstract:Genes tubb1 and tubb2 which encode β-Tubulins 1 and 2, respectively, were characterised from the ectomycorrhizal basidiomycete Suillus bovinus . The two β-Tubulins are surprisingly divergent, with the lowest known sequence identity (60%) in any single fungal species. Comparative analysis showed that β-Tubulin 1 and the intron distribution within the tubb1 gene resemble the other β-Tubulins. β-Tubulin 2, in contrast, is the most divergent fully described fungal β-Tubulin and the gene contains at least 21 introns, which is the largest amount known for any β-Tubulin gene. Despite this divergence, both genes are constitutively expressed in the functional compartments of the mycorrhizosphere and in pure cultures. Transcription of tubb1 is about 2.4 times higher than that of tubb2 ; and this difference is also seen at the translation level. Evidence suggested that phosphorylation may be the main post-translational modification of both β-Tubulins. The putative GTP-binding site residues of β-Tubulin 1 match crystallised pig β-Tubulin residues, while five of the nine differences in β-Tubulin 2 match the pig α-Tubulin GTP-site, suggesting the presence of adaptive sequence evolution. In a Bayesian analysis, β-Tubulin 1 joins the other basidiomycete sequences, while β-Tubulin 2 loosely associates with the group of divergent ascomycete sequences without any clear relative among the known full-length fungal β-Tubulin sequences.
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two phylogenetically highly distinct β Tubulin genes of the basidiomycete suillus bovinus
Current Genetics, 2005Co-Authors: Jarmo T. Juuti, Mika T. Tarkka, Sanna Jokela, Lars Paulin, Jarkko LahdensaloAbstract:Genes tubb1 and tubb2 which encode beta-Tubulins 1 and 2, respectively, were characterised from the ectomycorrhizal basidiomycete Suillus bovinus. The two beta-Tubulins are surprisingly divergent, with the lowest known sequence identity (60%) in any single fungal species. Comparative analysis showed that beta-Tubulin 1 and the intron distribution within the tubb1 gene resemble the other beta-Tubulins. beta-Tubulin 2, in contrast, is the most divergent fully described fungal beta-Tubulin and the gene contains at least 21 introns, which is the largest amount known for any beta-Tubulin gene. Despite this divergence, both genes are constitutively expressed in the functional compartments of the mycorrhizosphere and in pure cultures. Transcription of tubb1 is about 2.4 times higher than that of tubb2; and this difference is also seen at the translation level. Evidence suggested that phosphorylation may be the main post-translational modification of both beta-Tubulins. The putative GTP-binding site residues of beta-Tubulin 1 match crystallised pig beta-Tubulin residues, while five of the nine differences in beta-Tubulin 2 match the pig alpha-Tubulin GTP-site, suggesting the presence of adaptive sequence evolution. In a Bayesian analysis, beta-Tubulin 1 joins the other basidiomycete sequences, while beta-Tubulin 2 loosely associates with the group of divergent ascomycete sequences without any clear relative among the known full-length fungal beta-Tubulin sequences.
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Tubulin and actin protein patterns in Scots pine (Pinus sylvestris) roots and developing ectomycorrhiza with Suillus bovinus
Physiologia Plantarum, 1996Co-Authors: Sara S. Niini, Mika T. Tarkka, Marjatta RaudaskoskiAbstract:The role of Tubulin and actin in the development of Scots pine (Pinus sylvestris) roots and in the formation of the ectomycorrhiza with the basidiomycete Suillus bovinus was studied by immunoblotting of 2D-gels with anti-Tubulin and anti-actin antibodies. In the short roots the α-Tubulin pattern was different from that in the other root types due to the more acidic pI of the two α-Tubulins. During the formation of the ectomycorrhiza, two new α-Tubulins were detected in the acidic α-Tubulin cluster. No such variation occurred in the plant β-Tubulin patterns. The fungal Tubulins dominated in the ectomycorrhiza, but no changes in Tubulin polypeptide patterns from those in the S. bovinus mycelium were observed. Contrary to the Tubulins, plant actin dominated in the mycorrhiza. The specific α-Tubulin patterns of uninfected and infected short roots indicate that α-Tubulin is involved in the morphogenesis of Pinus sylvestris short roots. The high level of plant actin at early stage of the mycorrhiza formation suggests a significant role of this protein in the interaction between plant cells and fungal hyphae.
Patrick J. Keeling - One of the best experts on this subject based on the ideXlab platform.
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Congruent evidence from α-Tubulin and β-Tubulin gene phylogenies for a zygomycete origin of microsporidia
Fungal genetics and biology : FG & B, 2003Co-Authors: Patrick J. KeelingAbstract:The origin of microsporidia and the evolutionary relationships among the major lineages of fungi have been examined by molecular phylogeny using α-Tubulin and β-Tubulin. Chytrids, basidiomycetes, ascomycetes, and microsporidia were all recovered with high support, and the zygomycetes were consistently paraphyletic. The microsporidia were found to branch within zygomycetes, and showed relationships with members of the Entomophthorales and Zoopagales. This provides support for the microsporidia having evolved from within the fungi, however, the Tubulin genes are difficult to interpret unambiguously since fungal and microsporidian Tubulins are very divergent. Rapid evolutionary rates a characteristic of practically all microsporidian genes studied, so determining their evolutionary history will never be completely free of such difficulties. While the Tubulin phylogenies do not provide a decisive conclusion, they do further narrow the probable origin of microsporidia to a zygomycete-like ancestor.
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The secondary endosymbiont of the cryptomonad Guillardia theta contains alpha-, beta-, and gamma-Tubulin genes.
Molecular biology and evolution, 1999Co-Authors: Patrick J. Keeling, Uwe G. Maier, James A. Deane, Susan Douglas, Clara Hink-schauer, Geoffrey I. McfaddenAbstract:Cryptomonads have acquired photosynthesis through secondary endosymbiosis: they have engulfed and retained a photosynthetic eukaryote. The remnants of this autotrophic symbiont are severely reduced, but a small volume of cytoplasm surrounding the plastid persists, along with a residual nucleus (the nucleomorph) that encodes only a few hundred genes. We characterized Tubulin genes from the cryptomonad Guillardia theta. Despite the apparent absence of microtubules in the endosymbiont, we recovered genes encoding alpha-, beta-, and gamma-Tubulins from the nucleomorph genome of G. theta. The presence of Tubulin genes in the nucleomorph indicates that some component of the cytoskeleton is still present in the cryptomonad symbiont despite the fact that very little cytoplasm remains, no mitosis is known in the nucleomorph, and microtubules have never been observed anywhere in the symbiont. Phylogenetic analyses with nucleomorph alpha- and beta-Tubulins support the origin of the cryptomonad nucleomorph from a red alga. We also characterized alpha and beta-Tubulins from the host nucleus of G. theta and compared these with Tubulins we isolated from two flagellates, Goniomonas truncata and Cyanophora paradoxa, previously proposed to be related to the cryptomonad host. Phylogenetic analyses support a relationship between the cryptomonad host and Goniomonas but do not support any relationship between cryptomonads and Cyanophora.
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The phylogenetic position of alpha- and beta-Tubulins from the Chlorarachnion host and Cercomonas (Cercozoa)
The Journal of eukaryotic microbiology, 1998Co-Authors: Patrick J. Keeling, James A. Deane, Geoffrey I. McfaddenAbstract:Alpha and beta-Tubulin genes from Chlorarachnion and an alpha-Tubulin gene from Cercomonas have been characterised. We found the Cercomonas and Chlorarachnion alpha Tubulins to be closely related to one another, confirming the proposed relationship of these genera. In addition, the Chlorarachnion host and Cercomonas also appear to be more distantly related to Heterolobosea, Euglenozoa, chlorophytes, heterokonts, and alveolates. Chlorarachnion was also found to have two distinctly different types of both alpha- and beta-Tubulin, one type being highly-divergent. Chlorarachnion contains a secondary endosymbiont of green algal origin, raising the possibility that one type of Chlorarachnion Tubulins comes from the host and the other from the endosymbiont. Probing pulsed field-separated chromosomes showed that the highly-divergent genes are encoded by the host genome, and neither alpha- nor beta-Tubulin cDNAs were found to include 5' extensions that might serve as targeting peptides. It appears that Chlorarachnion has distinct and divergent Tubulin paralogues that are all derived from the host lineage. One Chlorarachnion beta-Tubulin was also found to be a pseudogene, which is still expressed but aberrantly processed. Numerous unspliced introns and deletions resulting from mis-splicing are contained in the mRNAs from this gene.
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Alpha-Tubulin from early-diverging eukaryotic lineages and the evolution of the Tubulin family.
Molecular biology and evolution, 1996Co-Authors: Patrick J. KeelingAbstract:The Tubulin gene family, which includes alpha-,beta-, and gamma-Tubulin subfamilies, is composed of highly conserved proteins which are the principle structural and functional components of eukaryotic microtubules. We are interested in (1) establishing when in eukaryotic evolution the duplications leading to paralogous alpha, beta, and gamma subfamilies occurred and (2) the possible utility of Tubulin sequences in reconstructing organismal phylogeny. To broaden the taxonomic representation of alpha-Tubulins so that it roughly equals that of beta-Tubulins, alpha-Tubulin genes from three Microsporidia (Encephalitozoon hellem, Nosema locustae, and Spraguea lophii), two Parabasalia (Monocercomonas sp. and Trichomitus batrachorum), and one Heterolobosean (Acrasis rosea) were sequenced. With these new genes, phylogenetic trees of alpha- and beta-Tubulins were constructed and compared. Trees were congruent with each other, but incongruent with other molecular phylogenies. The agreement between alpha- and beta-Tubulin trees could arise by the co-adaptation of one molecule to variants of the other as a result of their intimate steric association in microtubules. Thus, these trees may not be providing independent support for the phylogenetic results. However, one of these unexpected results, that microsporidia cluster with fungi, is supported by other circumstantial evidence, and may therefore reflect a real relationship despite the basal position usually assigned to microsporidia. Relationships between the three Tubulins were also examined by constructing trees of all three types. These trees were found to be of limited value for determining the position of the root within each subfamily because of the great interfamily distances, but they do confirm the classification of all known genes into three monophyletic subfamilies. Divergent genes from Caenorhabditis elegans and Saccharomyces cerevisiae that have been proposed to represent the novel classes delta- and epsilon-Tubulin were found to be specifically related to gamma-Tubulins from animals and fungi respectively, and therefore are best seen as rapidly evolving orthologues of gamma-Tubulin.
Tim Stearns - One of the best experts on this subject based on the ideXlab platform.
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Centriole triplet microtubules are required for stable centriole formation and inheritance in human cells
eLife, 2017Co-Authors: Jennifer T. Wang, Dong Kong, Jadranka Lončarek, Christian R. Hoerner, Tim StearnsAbstract:Centrioles are composed of long-lived microtubules arranged in nine triplets. However, the contribution of triplet microtubules to mammalian centriole formation and stability is unknown. Little is known of the mechanism of triplet microtubule formation, but experiments in unicellular eukaryotes indicate that delta-Tubulin and epsilon-Tubulin, two less-studied Tubulin family members, are required. Here, we report that centrioles in delta-Tubulin and epsilon-Tubulin null mutant human cells lack triplet microtubules and fail to undergo centriole maturation. These aberrant centrioles are formed de novo each cell cycle, but are unstable and do not persist to the next cell cycle, leading to a futile cycle of centriole formation and disintegration. Disintegration can be suppressed by paclitaxel treatment. Delta-Tubulin and epsilon-Tubulin physically interact, indicating that these Tubulins act together to maintain triplet microtubules and that these are necessary for inheritance of centrioles from one cell cycle to the next.
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Centriole triplet microtubules are required for stable centriole formation and inheritance in human cells
2017Co-Authors: Jennifer T. Wang, Dong Kong, Jadranka Lončarek, Christian R. Hoerner, Tim StearnsAbstract:Centrioles are composed of long-lived microtubules arranged in nine triplets. In unicellular eukaryotes, loss of the noncanonical Tubulins, delta-Tubulin and epsilon-Tubulin, result in loss of the triplet microtubule structure. However, the contribution of triplet microtubules to mammalian centriole formation and stability is unknown. Here, we report the first characterization of delta-Tubulin and epsilon-Tubulin null human cells. Centrioles in cells lacking either delta-Tubulin or epsilon-Tubulin lack triplet microtubules and fail to undergo centriole maturation. These aberrant centrioles are formed de novo each cell cycle, but are unstable and do not persist to the next cell cycle, leading to a futile cycle of centriole formation and disintegration. Disintegration can be suppressed by paclitaxel treatment. Delta-Tubulin and epsilon-Tubulin physically interact, indicating that these Tubulins act together to maintain triplet microtubules and that these are necessary for inheritance of centrioles from one cell cycle to the next.
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insights into microtubule nucleation from the crystal structure of human γ Tubulin
Nature, 2005Co-Authors: Hector Aldaz, Luke M Rice, Tim Stearns, David A AgardAbstract:Tubulin proteins have a central role in the life of eukaryotic cells. αβ-Tubulin polymerizes to form the microtubules required for chromosome segregation and organelle positioning. γ-Tubulin initiates microtubule assembly in vivo and is part of a multimeric complex at the centrosome. The crystal structure of human γ-Tubulin bound to GTPγS is reported this week, the highest resolution (2.7 A) structure of any Tubulin to date. The structure suggests new ways of thinking about the roles of conformational change and nucleotide binding in microtubule assembly. The antitumour drug vinblastine is known to target Tubulin. Its actual binding site and mechanism of action are unknown but now the X-ray structure of vinblastine bound in a Tubulin/protein complex has been determined. Vinblastine introduces a wedge at the junction of two Tubulin molecules, thereby interfering with microtubule production and promoting self-association of Tubulin molecules into spiral aggregates. A hydrophobic groove on the α-Tubulin surface acts both as a binding site for vinblastine and as a point of intermolecular contact in microtubules, so may be an attractive candidate for new microtubule depolymerizing drugs. Microtubules are hollow polymers of αβ-Tubulin that show GTP-dependent assembly dynamics and comprise a critical part of the eukaryotic cytoskeleton. Initiation of new microtubules in vivo requires γ-Tubulin, organized as an oligomer within the 2.2-MDa γ-Tubulin ring complex (γ-TuRC) of higher eukaryotes1,2,3. Structural insight is lacking regarding γ-Tubulin, its oligomerization and how it promotes microtubule assembly. Here we report the 2.7-A crystal structure of human γ-Tubulin bound to GTP-γS (a non-hydrolysable GTP analogue). We observe a ‘curved’ conformation for γ-Tubulin–GTPγS, similar to that seen for GDP-bound, unpolymerized αβ-Tubulin4. Tubulins are thought to represent a distinct class of GTP-binding proteins, and conformational switching in γ-Tubulin might differ from the nucleotide-dependent switching of signalling GTPases. A crystal packing interaction replicates the lateral contacts between α- and β-Tubulins in the microtubule5, and this association probably forms the basis for γ-Tubulin oligomerization within the γ-TuRC. Laterally associated γ-Tubulins in the γ-TuRC might promote microtubule nucleation by providing a template that enhances the intrinsically weak lateral interaction between αβ-Tubulin heterodimers. Because they are dimeric, αβ-Tubulins cannot form microtubule-like lateral associations in the curved conformation5. The lateral array of γ-Tubulins we observe in the crystal reveals a unique functional property of a monomeric Tubulin.
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the mammalian γ Tubulin complex contains homologues of the yeast spindle pole body components spc97p and spc98p
Journal of Cell Biology, 1998Co-Authors: Steven M Murphy, Lenore Urbani, Tim StearnsAbstract:γ-Tubulin is a universal component of microtubule organizing centers where it is believed to play an important role in the nucleation of microtubule polymerization. γ-Tubulin also exists as part of a cytoplasmic complex whose size and complexity varies in different organisms. To investigate the composition of the cytoplasmic γ-Tubulin complex in mammalian cells, cell lines stably expressing epitope-tagged versions of human γ-Tubulin were made. The epitope-tagged γ-Tubulins expressed in these cells localize to the centrosome and are incorporated into the cytoplasmic γ-Tubulin complex. Immunoprecipitation of this complex identifies at least seven proteins, with calculated molecular weights of 48, 71, 76, 100, 101, 128, and 211 kD. We have identified the 100- and 101-kD components of the γ-Tubulin complex as homologues of the yeast spindle pole body proteins Spc97p and Spc98p, and named the corresponding human proteins hGCP2 and hGCP3. Sequence analysis revealed that these proteins are not only related to their respective homologues, but are also related to each other. GCP2 and GCP3 colocalize with γ-Tubulin at the centrosome, cosediment with γ-Tubulin in sucrose gradients, and coimmunoprecipitate with γ-Tubulin, indicating that they are part of the γ-Tubulin complex. The conservation of a complex involving γ-Tubulin, GCP2, and GCP3 from yeast to mammals suggests that structurally diverse microtubule organizing centers such as the yeast spindle pole body and the animal centrosome share a common molecular mechanism for microtubule nucleation.
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γ Tubulin is a highly conserved component of the centrosome
Cell, 1991Co-Authors: Tim Stearns, Louise Evans, Marc W KirschnerAbstract:Abstract We have cloned and characterized γ-Tubulin genes from both X. laevis and S. pombe, and partial genes from maize, diatom, and a budding yeast. The proteins encoded by these genes are very similar to each other and to the original Aspergillus protein, indicating that γ-Tubulins are an ubiquitous and highly conserved subfamily of the Tubulin family. A null mutation of the S. pombe gene is lethal. γ-Tubulin is a minor protein, present at less than 1 % the level of α- and β-Tubulin, and is limited to the centrosome. In particular, γ-Tubulin is associated with the pericentriolar material, the microtubule-nucleating material of the centrosome. γ-Tubulin remains associated with the centrosome when microtubules are depolymerized, suggesting that it is an integral component that might play a role in microtubule organization.
Jarmo T. Juuti - One of the best experts on this subject based on the ideXlab platform.
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Two phylogenetically highly distinct β-Tubulin genes of the basidiomycete Suillus bovinus
Current Genetics, 2005Co-Authors: Jarmo T. Juuti, Mika T. Tarkka, Sanna Jokela, Lars Paulin, Jarkko LahdensaloAbstract:Genes tubb1 and tubb2 which encode β-Tubulins 1 and 2, respectively, were characterised from the ectomycorrhizal basidiomycete Suillus bovinus . The two β-Tubulins are surprisingly divergent, with the lowest known sequence identity (60%) in any single fungal species. Comparative analysis showed that β-Tubulin 1 and the intron distribution within the tubb1 gene resemble the other β-Tubulins. β-Tubulin 2, in contrast, is the most divergent fully described fungal β-Tubulin and the gene contains at least 21 introns, which is the largest amount known for any β-Tubulin gene. Despite this divergence, both genes are constitutively expressed in the functional compartments of the mycorrhizosphere and in pure cultures. Transcription of tubb1 is about 2.4 times higher than that of tubb2 ; and this difference is also seen at the translation level. Evidence suggested that phosphorylation may be the main post-translational modification of both β-Tubulins. The putative GTP-binding site residues of β-Tubulin 1 match crystallised pig β-Tubulin residues, while five of the nine differences in β-Tubulin 2 match the pig α-Tubulin GTP-site, suggesting the presence of adaptive sequence evolution. In a Bayesian analysis, β-Tubulin 1 joins the other basidiomycete sequences, while β-Tubulin 2 loosely associates with the group of divergent ascomycete sequences without any clear relative among the known full-length fungal β-Tubulin sequences.
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two phylogenetically highly distinct β Tubulin genes of the basidiomycete suillus bovinus
Current Genetics, 2005Co-Authors: Jarmo T. Juuti, Mika T. Tarkka, Sanna Jokela, Lars Paulin, Jarkko LahdensaloAbstract:Genes tubb1 and tubb2 which encode beta-Tubulins 1 and 2, respectively, were characterised from the ectomycorrhizal basidiomycete Suillus bovinus. The two beta-Tubulins are surprisingly divergent, with the lowest known sequence identity (60%) in any single fungal species. Comparative analysis showed that beta-Tubulin 1 and the intron distribution within the tubb1 gene resemble the other beta-Tubulins. beta-Tubulin 2, in contrast, is the most divergent fully described fungal beta-Tubulin and the gene contains at least 21 introns, which is the largest amount known for any beta-Tubulin gene. Despite this divergence, both genes are constitutively expressed in the functional compartments of the mycorrhizosphere and in pure cultures. Transcription of tubb1 is about 2.4 times higher than that of tubb2; and this difference is also seen at the translation level. Evidence suggested that phosphorylation may be the main post-translational modification of both beta-Tubulins. The putative GTP-binding site residues of beta-Tubulin 1 match crystallised pig beta-Tubulin residues, while five of the nine differences in beta-Tubulin 2 match the pig alpha-Tubulin GTP-site, suggesting the presence of adaptive sequence evolution. In a Bayesian analysis, beta-Tubulin 1 joins the other basidiomycete sequences, while beta-Tubulin 2 loosely associates with the group of divergent ascomycete sequences without any clear relative among the known full-length fungal beta-Tubulin sequences.
