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PubMed1983

Phylogenetic branching of Trichoptera and Lepidoptera: an ultrastructural analysis on comparative spermatology.

The divergence during the evolution of the sister orders of Trichoptera (caddisflies) and Lepidoptera (moths and butterflies) from their common ancestors is still subject to disagreement. This is partially due to lack of clarity concerning the phylogenetic position of Zeugloptera which is considered to be either a very primitive suborder of Lepidoptera or an order of its own, more archaic than both Trichoptera and Lepidoptera. The ultrastructural analysis on comparative spermatology reported here shows that dichotomous spermatogenesis producing concomitant, normal, anucleate (apyrene) and nucleate (eupyrene) spermatozoa: (1) is generalized in Lepidoptera as it occurs, in addition to higher Lepidoptera, also in the primitive Hepialoidea, (2) is present in Zeugloptera, and (3) is absent from Trichoptera which produce only nucleate spermatozoa. It is concluded that dichotomous spermatogenesis is an evolutionary novelty of Lepidoptera (including Zeugloptera) that was established at the origin of the order, after the divergence of Trichoptera and Lepidoptera.

Animals↗
PubMed2003

Origin of mannose-binding lectin-associated serine protease (MASP)-1 and MASP-3 involved in the lectin complement pathway traced back to the invertebrate, amphioxus.

Mannose-binding lectin-associated serine proteases (MASPs) are involved in complement activation through the lectin pathway. To elucidate the phylogenetic origin of MASP and a primordial complement system, we cloned two MASP cDNAs from amphioxus (Branchiostoma belcheri) of the cephalochordates, considered to be the closest relative of vertebrates. The two sequences, orthologues of mammalian MASP-1 and MASP-3, were produced by alternative processing of RNA from a single gene consisting of a common H chain-encoding region and two L chain-encoding regions, a structure which is similar to that of the human MASP1/3 gene. We also isolated two MASP genes from the ascidian Halocynthia roretzi (urochordates) and found that each of them consists simply of an H chain-encoding region and a single L chain-encoding region. The difference in structure between the ascidian MASP genes and the amphioxus/mammalian MASP genes suggests that a prototype gene was converted to the MASP1/3-type gene possessing two L chain-encoding regions at an early stage of evolution before the divergence of amphioxus. This conclusion is supported by the presence of MASP-1 and MASP-3 homologues in almost all vertebrates, as demonstrated by the cloning of novel cDNA sequences representing lamprey (cyclostomes) MASP-1 and Xenopus MASP-3. The ancient origin of MASP-1 and MASP-3 suggests that they have crucial functions common to all species which emerged after cephalochordates.

Amino Acid Sequence↗
PubMed1991

The evolution of defective and autonomous parvoviruses.

Because of the small size and genetic simplicity of small DNA viruses, parvoviruses would appear to be excellent models for studying viral evolution and adaptation. In an earlier publication we hypothesized the evolution of sequences of cellular "junk" DNA into protective interfering transposons. These transposons would interfere with invading pathogenic viruses by competing with the pathogen DNA for replicative enzymes. We speculated that a small, defective parvovirus, the adeno-associated virus (AAV), which usually requires the presence of a pathogenic helper virus to replicate, may have evolved from such a piece of cellular "junk" DNA. Our theory predicted that AAVs, as a consequence of their defective nature, developed under pressures favoring maintenance of their transposon like qualities. In contrast, disease-causing, autonomous, non-defective parvoviruses such as the B19 agent of humans and the canine parvovirus, even though their origins may have been in cellular DNA, would appear to have developed under totally different evolutionary pressures. In this paper we will present evidence for a common ancestry for the defective and autonomous parvoviruses and discuss the divergent paths this evolution may have taken in establishing the two genera.

Base Sequence↗
PubMed2005

Expression of an additional cathelicidin antimicrobial peptide protects against bacterial skin infection.

Cathelicidin antimicrobial peptides are effectors of innate immune defense in mammals. Humans and mice have only one cathelicidin gene, whereas domesticated mammals such as the pig, cow, and horse have multiple cathelicidin genes. We hypothesized that the evolution of multiple cathelicidin genes provides these animals with enhanced resistance to infection. To test this, we investigated the effects of the addition of cathelicidins by combining synthetic cathelicidin peptides in vitro, by producing human keratinocytes that overexpress cathelicidins in culture, or by producing transgenic mice that constitutively overexpress cathelicidins in vivo. The porcine cathelicidin peptide PR-39 acted additively with human cathelicidin LL-37 to kill group A Streptococcus (GAS). Lentiviral delivery of PR-39 enhanced killing of GAS by human keratinocytes. Finally, transgenic mice expressing PR-39 under the influence of a K14 promoter showed increased resistance to GAS skin infection (50% smaller necrotic ulcers and 60% fewer surviving bacteria). Similarly constructed transgenic mice designed to overexpress their native cathelicidin did not show increased resistance. These findings demonstrate that targeted gene transfer of a xenobiotic cathelicidin confers resistance against infection and suggests the benefit of duplication and divergence in the evolution of antimicrobial peptides.

Animals↗
PubMedDate not supplied

[The similarity of the primary structure and homology of rhodopsin, beta-adrenoreceptor and muscarinic cholinoceptor].

Computer analysis has been made of the primary structure of 6 different types of receptor proteins: rhodopsin, adrenoreceptor, muscarinic acetylcholine receptor, insulin receptor, nicotinic cholinoreceptor, and bacteriorhodopsin. The aim of the present investigation was to elucidate, at least partially, to what extent insignificant similarity in the primary structure of rhodopsin, muscarinic cholinoreceptor and adrenoreceptor is due to divergent, but not convergent, evolution. Nicotinic cholinoreceptor, bacteriorhodopsin and insulin receptor were chosen for comparison with rhodopsin, adrenoreceptor and muscarinic cholinoreceptor since each of these proteins exhibits this or that structural or functional property which is common for rhodopsin, adrenoreceptor or muscarinic cholinoreceptor; on the other hand, nicotinic cholinoreceptor, bacteriorhodopsin and insulin receptor differ from other receptor proteins by their molecular mechanisms. Comparison of the primary structure of rhodopsin, adrenoreceptor and muscarinic cholinoreceptor on the one hand, and insulin receptor, nicotinic cholinoreceptor and bacteriorhodopsin on the other indicates that only the former exhibit similar primary structure, whereas insulin receptor, nicotinic cholinoreceptor and bacteriorhodopsin show no similarity neither in their primary structure, nor in the primary structure of rhodopsin and other receptor proteins which are similar to the latter with respect to their mode of action. The data obtained indicate that similarity in the primary structure between rhodopsin, muscarinic cholinoreceptor and adrenoreceptor is a consequence of divergent, not convergent, evolution; in other words, these receptor proteins are homologous.

Amino Acid Sequence↗
PubMedDate not supplied

Centromere dynamics and chromosome evolution in marsupials.

The eukaryotic centromere poses an interesting evolutionary paradox: it is a chromatin entity indispensable to precise chromosome segregation in all eukaryotes, yet the DNA at the heart of the centromere is remarkably variable. Its important role of spindle attachment to the kinetochore during meiosis and mitosis notwithstanding, recent studies implicate the centromere as an active player in chromosome evolution and the divergence of species. This is exemplified by centromeric involvement in translocations, fusions, inversions, and centric shifts. Often species are defined karyotypically simply by the position of the centromere on certain chromosomes. Little is known about how the centromere, either as a functioning unit of chromatin or as a specific block of repetitive DNA sequences, acts in the creation of these types of chromosome rearrangements in an evolutionary context. Macropodine marsupials (kangaroos and wallabies) offer unique insights into current theories expositing centromere emergence during karyotypic diversification and speciation.

Animals↗
PubMed1999

Monophyly of lampreys and hagfishes supported by nuclear DNA-coded genes.

The phylogenetic position of hagfishes in vertebrate evolution is currently controversial. The 18S and 28S rRNA trees support the monophyly of hagfishes and lampreys. In contrast, the mitochondrial DNAs suggest the close association of lampreys and gnathostomes. To clarify this controversial issue, we have conducted cloning and sequencing of the four nuclear DNA-coded single-copy genes encoding the triose phosphate isomerase, calreticulin, and the largest subunit of RNA polymerase II and III. Based on these proteins, together with the Mn superoxide dismutase for which hagfish and lamprey sequences are available in database, phylogenetic trees have been inferred by the maximum likelihood (ML) method of protein phylogeny. It was shown that all the five proteins prefer the monophyletic tree of cyclostomes, and the total log-likelihood of the five proteins significantly supports the cyclostome monophyly at the level of +/-1 SE. The ML trees of aldolase family comprising three nonallelic isoforms and the complement component group comprising C3, C4, and C5, both of which diverged during vertebrate evolution by gene duplications, also suggest the cyclostome monophyly.

Animals↗
PubMed2001

Heterogeneity of the CYP2D6 gene among Malays in Malaysia.

BACKGROUND: Although Malays shared an origin with Chinese, their evolution saw substantial divergences. Phenotyping studies suggested that they differed in CYP2D6 polymorphism, with higher PM prevalence but lesser right-shift for debrisoquine MRs. OBJECTIVE: To study the genotype distribution of CYP2D6 among the Malays in Malaysia. METHOD: We obtained DNA from 107 Malays and used PCR to determine common CYP2D6 alleles. RESULT: CYP2D6*1 occurred at a frequency of 36.0%, duplicated gene, 0.93%, CYP2D6*4, 2.8%, CYP2D6*5, 5.1%, CYP2D6*9, 3.3%, CYP2D6*10, 49.5% and CYP2D6*17, 0.5%. The findings of CYP2D6*17 and CYP2D6*9 were novel for Asia. The frequency for CYP2D6*10 was lower than in other Asian races. The most frequent genotypes were CYP2D6*1/*10 at 39.3%. Two subjects had genotypes that predicted PM phenotype, 35% showed genotypes that predicted intermediate metabolizers and one subject had a genotype that predicted ultra-rapid metabolism. CONCLUSION: The genetic polymorphism of CYP2D6 in Malays is different from Chinese and Far Eastern races. They may be intermediate between East Asians and Caucasians in CYP2D6 activity. Further study in relation to the evolution of races and disease prevalence may help to identify the contributions of the polymorphism in alleged susceptibility to diseases apart from delineating its contributions to ethnic differences in the pharmacology of CYP2D6 drugs.

Adolescent↗
PubMed2003

Wolbachia and genetic variability in the birdnest blowfly Protocalliphora sialia.

Wolbachia are widespread cytoplasmically inherited bacteria that induce various reproductive alterations in host arthropods, including cytoplasmic incompatibility (CI), an incompatibility between sperm and egg that typically results in embryonic death. CI has been invoked as a possible mechanism for reproductive isolation and speciation in arthropods, by restricting gene flow and promoting maintenance (and evolution) of genetic divergence between populations. Here we investigate patterns of Wolbachia infection and nuclear and mitochondrial differentiation in geographical populations of the birdnest blowfly Protocalliphora sialia. Blowflies in western North America are infected with two A-group Wolbachia, with some individuals singly and others doubly infected. Individuals in eastern North America mostly show single infections with a B-group Wolbachia. Populations in the Midwest are polymorphic for infections and show A- or B-group infection. There is a low level of mitochondrial divergence and perfect concordance of mitochondrial haplotype with infection type, suggesting that two Wolbachia-associated selective sweeps of the mitochondrion have occurred in this species. Amplified fragment length polymorphism analysis of nuclear genetic variation shows genetic differentiation between the eastern-Midwestern and western populations. Both Midwestern and eastern flies infected with A-Wolbachia show eastern nuclear genetic profiles. Current results therefore suggest that Wolbachia has not acted as a major barrier to gene flow between western and eastern-Midwestern populations, although some genetic differentiation between A-Wolbachia infected and B-Wolbachia infected individuals in eastern-Midwestern populations cannot be ruled out.

Animals↗
PubMed2006

Evolutionary rate variation among vertebrate beta globin genes: implications for dating gene family duplication events.

A comprehensive dataset of 62 beta globin gene sequences from various vertebrates was compiled to test the molecular clock and to estimate dates of gene duplications. We found that evolution of the beta globin family of genes is not clock-like, a result that is at odds with the common use of this family as an example of a constant rate of evolution over time. Divergence dates were estimated either with or without assuming the molecular clock, and both analyses produced similar date estimates, which are also in general agreement with estimates reported previously. In addition we report date estimates for seven previously unexamined duplication events within the beta globin family. Despite multiple sources of rate variation, the average rate across the beta globin phylogeny yielded reasonable estimates of divergence dates in most cases. Exceptions were cases of gene conversion, where it appears to have led to underestimates of divergence dates. Our results suggest (i) the major duplications giving rise to the paralogous beta globin genes are associated with significant evolutionary rate variation among gene lineages; and (ii) genes arising from more recent gene duplications (e.g., tandem duplications within lineages) do not appear to differ greatly in rate. We believe this pattern reflects a complex interplay of evolutionary forces where natural selection for diversifying paralogous functions and lineage-specific effects contribute to rate variation on a long-term basis, while gene conversion tends to increase sequence similarity. Gene conversion effects appear to be stronger on recent gene duplicates, as their sequences are highly similar. Lastly, phylogenetic analyses do not support a previous report that avian globins are members of a relic lineage of omega globins.

Animals↗
PubMed2005

Genome rearrangement distances and gene order phylogeny in gamma-Proteobacteria.

Genome rearrangements have been studied in 30 gamma-proteobacterial complete genomes by comparing the order of a reduced set of genes on the chromosome. This set included those genes fulfilling several characteristics, the main ones being that an ortholog was present in every genome and that none of them had been acquired by horizontal gene transfer. Genome rearrangement distances were estimated based on either the number of breakpoints or the minimal number of inversions separating two genomes. Breakpoint and inversion distances were highly correlated, indicating that inversions were the main type of rearrangement event in gamma-Proteobacteria. In general, the progressive increase in sequence-based distances between genome pairs was associated with the increase in their rearrangement-based distances but with several groups of distances not following this pattern. Compared with free-living enteric bacteria, the lineages of Pasteurellaceae were evolving, on average, to relatively higher rates of between 2.02 and 1.64, while the endosymbiotic bacterial lineages of Buchnera aphidicola and Wigglesworthia glossinidia were evolving at moderately higher rates of 1.38 and 1.35, respectively. Because we know that the rearrangement rate in the Bu. aphidicola lineage was close to zero during the last 100-150 Myr of evolution, we deduced that a much higher rate took place in the first period of lineage evolution after the divergence of the Escherichia coli lineage. On the other hand, the lineage of the endosymbiont Blochmannia floridanus did present an almost identical rate to free-living enteric bacteria, indicating that the increase in the genome rearrangement rate is not a general change associated with bacterial endosymbiosis. Phylogenetic reconstruction based on rearrangement distances showed a different topology from the one inferred by sequence information. This topology broke the proposed monophyly of the three endosymbiotic lineages and placed Bl. floridanus as a closer relative to E. coli than Yersinia pestis. These results indicate that the phylogeny of these insect endosymbionts is still an open question that will require the development of specific phylogenetic methods to confirm whether the sisterhood of the three endosymbiotic lineages is real or a consequence of a long-branch attraction phenomenon.

Biological Evolution↗
PubMed2004

Dimorphecolic acid is synthesized by the coordinate activities of two divergent Delta12-oleic acid desaturases.

Dimorphecolic acid (9-OH-18:2Delta(10)(trans)(,12)(trans)) is the major fatty acid of seeds of Dimorphotheca species. This fatty acid contains structural features that are not typically found in plant fatty acids, including a C-9 hydroxyl group, Delta(10),Delta(12)-conjugated double bonds, and trans-Delta(12) unsaturation. Expressed sequence tag analysis was conducted to determine the biosynthetic origin of dimorphecolic acid. cDNAs for two divergent forms of Delta(12)-oleic acid desaturase, designated DsFAD2-1 and Ds-FAD2-2, were identified among expressed sequence tags generated from developing Dimorphotheca sinuata seeds. Expression of DsFAD2-1 in Saccharomyces cerevisiae and soybean somatic embryos resulted in the accumulation of the trans-Delta(12) isomer of linoleic acid (18: 2Delta(9)(cis)(,12)(trans)) rather than the more typical cis-Delta(12) isomer. When co-expressed with DsFAD2-1 in soybean embryos or yeast, DsFAD2-2 converted 18:2Delta(9)(cis)(,12)(trans) into dimorphecolic acid. When DsFAD2-2 was expressed alone in soybean embryos or together with a typical cis-Delta(12)-oleic acid desaturase in yeast, trace amounts of the cis-Delta(12) isomer of dimorphecolic acid (9-OH-18:2Delta(10)(trans,)(12)(cis)) were formed from DsFAD2-2 activity with cis-Delta(12)-linoleic acid [corrected]. These results indicate that DsFAD2-2 catalyzes the conversion of the Delta(9) double bond of linoleic acid into a C-9 hydroxyl group and Delta(10)(trans) double bond and displays a substrate preference for the trans-Delta(12), rather than the cis-Delta(12), isomer of linoleic acid. Overall these data are consistent with a biosynthetic pathway of dimorphecolic acid involving the concerted activities of DsFAD2-1 and DsFAD2-2. The evolution of two divergent Delta(12)-oleic acid desaturases for the biosynthesis of an unusual fatty acid is unprecedented in plants.

Calendula↗
PubMed2005

Extensive chromosomal repatterning and the evolution of sterility barriers in hybrid sunflower species.

New species may arise via hybridization and without a change in ploidy. This process, termed homoploid hybrid speciation, is theoretically difficult because it requires the development of reproductive barriers in sympatry or parapatry. Theory suggests that isolation may arise through rapid karyotypic evolution and/or ecological divergence of hybrid neospecies. Here, we investigate the role of karyotypic change in homoploid hybrid speciation by generating detailed genetic linkage maps for three hybrid sunflower species, Helianthus anomalus, H. deserticola, and H. paradoxus, and comparing these maps to those previously generated for the parental species, H. annuus and H. petiolaris. We also conduct a quantitative trait locus (QTL) analysis of pollen fertility in a BC2 population between the parental species and assess levels of pollen and seed fertility in all cross-combinations of the hybrid and parental species. The three hybrid species are massively divergent from their parental species in karyotype; gene order differences were observed for between 9 and 11 linkage groups (of 17 total), depending on the comparison. About one-third of the karyoypic differences arose through the sorting of chromosomal rearrangements that differentiate the parental species, but the remainder appear to have arisen de novo (six breakages/six fusions in H. anomalus, four breakages/three fusions in H. deserticola, and five breakages/five fusions in H. paradoxus). QTL analyses indicate that the karyotypic differences contribute to reproductive isolation. Nine of 11 pollen viability QTL occur on rearranged chromosomes and all but one map close to a rearrangement breakpoint. Finally, pollen and seed fertility estimates for F1's between the hybrid and parental species fall below 11%, which is sufficient for evolutionary independence of the hybrid neospecies.

Chromosome Mapping↗
PubMed2000

Comparative mapping of human Chromosome 14q11.2-q13 genes with mouse homologous gene regions.

An examination of the synteny blocks between mouse and human chromosomes aids in understanding the evolution of chromosome divergence between these two species. We comparatively mapped the human (HSA) Chromosome (Chr) 14q11.2-q13 cytogenetic region with the intervals of orthologous genes on mouse (MMU) chromosomes. A lack of conserved gene order was identified between the human cytogenetic region and the interval of orthologs on MMU 12. The evolutionary breakpoint junction was defined within 2.5 Mb, where the conserved synteny of genes on HSA 14 changes from MMU 12 to MMU 14. At the evolutionary breakpoint junction, a human EST (GI: 1114654) with identity to the human and mouse BCL2 interacting gene, BNIP3, was mapped to mouse Chr 3. New gene homologs of LAMB1, MEOX2, NRCAM, and NZTF1 were identified on HSA 7 and on the proximal cytogenetic region of HSA 14 by mapping mouse genes recently reported to be genetically linked within the relevant MMU 12 interval. This study contributes to the identification of homology relationships between the genes of HSA 14q11.2-q13 and mouse Chr 3, 12, and 14.

Animals↗
PubMed2003

Characterization of hey bHLH genes in teleost fish.

Hairy-related basic helix-loop-helix (bHLH) transcription factors are targets of Delta-Notch signaling and represent essential components for a number of cell fate decisions during vertebrate embryogenesis. Hey genes encode a subfamily of hairy-related proteins that have been implicated in processes like somitogenesis, blood vessel and heart development. We have identified and characterized hey genes in three teleost fish lineages using degenerate PCR and database searches. Phylogenetic analysis of Hey proteins suggests a complex pattern of evolution with high divergence of hey2 in Takifugu rubripes (Fugu, Japanese pufferfish) and possibly loss in the related Tetraodon nigroviridis (the freshwater pufferfish). In addition, duplication of hey1 in both pufferfishes, Fugu and Tetraodon, was observed. Conversely, zebrafish (Danio rerio) has the same complement of three hey genes as known from mammals. All three hey genes show much more restricted gene expression profiles in zebrafish when compared to mouse. Importantly, while all three murine Hey genes are expressed in overlapping patterns in the presomitic mesoderm (PSM) and somites, in zebrafish only hey1 shows PSM and somite expression in a highly dynamic fashion. Therefore, while overlapping expression might account for redundancy of hey function in higher vertebrates, this is unlikely to be the case in zebrafish. In deltaD (dlD) deficient after-eight zebrafish mutants, the dynamic expression of hey1 in the PSM is impaired and completely lost in newly formed somitomeres. Overexpression of dlD on the other hand results in the ectopic expression of hey1 in the axial mesoderm. Hence, hey1 represents a target of Delta-Notch signaling dynamically expressed during somite formation in zebrafish.

Amino Acid Sequence↗
PubMed2004

Tracking repeats using significance and transitivity.

MOTIVATION: Internal repeats in coding sequences correspond to structural and functional units of proteins. Moreover, duplication of fragments of coding sequences is known to be a mechanism to facilitate evolution. Identification of repeats is crucial to shed light on the function and structure of proteins, and explain their evolutionary past. The task is difficult because during the course of evolution many repeats diverged beyond recognition. RESULTS: We introduce a new method TRUST, for ab initio determination of internal repeats in proteins. It provides an improvement in prediction quality as compared to alternative state-of-the-art methods. The increased sensitivity and accuracy of the method is achieved by exploiting the concept of transitivity of alignments. Starting from significant local suboptimal alignments, the application of transitivity allows us to (1) identify distant repeat homologues for which no alignments were found; (2) gain confidence about consistently well-aligned regions; and (3) recognize and reduce the contribution of non-homologous repeats. This re-assessment step enables us to derive a virtually noise-free profile representing a generalized repeat with high fidelity. We also obtained superior specificity by employing rigid statistical testing for self-sequence and profile-sequence alignments. Assessment was done using a database of repeat annotations based on structural superpositioning. The results show that TRUST is a useful and reliable tool for mining tandem and non-tandem repeats in protein sequence databases, capable of predicting multiple repeat types with varying intervening segments within a single sequence. AVAILABILITY: The TRUST server (together with the source code) is available at http://ibivu.cs.vu.nl/programs/trustwww

Algorithms↗
PubMed1999

Stat protein transactivation domains recruit p300/CBP through widely divergent sequences.

The signal transduction and activator of transcription (Stat) gene family has been highly conserved throughout evolution. Gene duplication and divergence has produced 7 mammalian Stat genes, each of which mediates a distinct process. While some Stat proteins are activated by multiple cytokines, Stat2 is highly specific for responses to type I interferon. We have cloned mouse Stat2 and found that while its sequence was more divergent from its human homologue than any other mouse-human Stat pairs, it was fully functional even in human cells. Overall sequence identity was only 69%, compared with 85-99% similarity for other Stat genes, and several individual domains that still served similar or identical functions in both species were even less well conserved. The coiled-coil domain responsible for interaction with IRF9 was only 65% identical and yet mouse Stat2 interacted with either human or mouse IRF9; the carboxyl terminus was only 30% identical and yet both regions functioned as equal transactivation domains. Both mouse and human transactivation domains recruited the p300/CBP coactivator and were equally sensitive to inhibition by adenovirus E1A protein. Interestingly, the Stat3 carboxyl terminus also functioned as a transactivator capable of recruiting p300/CBP, as does the Stat1 protein, although with widely differing potencies. Yet these proteins share no sequence similarity with Stat2. These data demonstrate that highly diverged primary sequences can serve similar or identical functions, and that the minimal regions of similarity between human and mouse Stat2 may define the critical determinants for function.

Amino Acid Sequence↗
PubMed1996

Plant cell enlargement and the action of expansins.

Plant cells are caged within a distended polymeric network (the cell wall), which enlarges by a process of stress relaxation and slippage (creep) of the polysaccharides that make up the load-bearing network of the wall. Protein mediators of wall creep have recently been isolated and characterized. These proteins, called expansins, appear to disrupt the noncovalent adhesion of matrix polysaccharides to cellulose microfibrils, thereby permitting turgor-driven wall enlargement. Expansin activity is specifically expressed in the growing tissues of dicotyledons and monocotyledons. Sequence analysis of cDNAs indicates that expansins are novel proteins, without previously known functional motifs. Comparison of expansin cDNAs from cucumber, pea, Arabidopsis and rice shows that the proteins are highly conserved in size and amino acid sequence. Phylogenetic analysis of expansin sequences suggests that this multigene family diverged before the evolution of angiosperms. Speculation is presented about the role of this gene family in plant development and evolution.

Amino Acid Sequence↗