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At least 19 recordsLinked to original sources
PubMed2003

Allozymic differentiation of the Antirrhinum graniticum and the Antirrhinum meonanthum species groups.

Forty populations from eight taxa belonging to six species of Antirrhinum were studied for electrophoretic differentiation at 14 allozyme loci. All the studied species show that marker alleles and genetic distances between conspecific populations are lower than for other species of the genus. Results permit the recognition of A. onubensis and A. boissieri at specific rank. The low level of genetic distance together with morphological characters and sympatric range, support the recognition of A. ambiguum as a new subspecies of A. graniticum, as A. graniticum ssp. ambiguum Mateu & Segarra stat. nov. The results of the study support separation of the studied taxa into two groups coinciding with subsections Streptosepalum and Antirrhinum, but disagreeing with the arrangement of species into them. According to the results of the study these groups consist of A. meonanthum and A. braun-blanquetii (Streptosepalum) and A. graniticum s.l., A. onubensis and A. boissieri (Antirrhinum). The status of A. meonanthum var. rothmaleri requires further clarification.

Antirrhinum↗
PubMed2001

Low diversity and divergence in the fil1 gene family of Antirrhinum (Scrophulariaceae).

Detailed nucleotide diversity studies revealed that the fil1 gene of Antirrhinum, which has been reported to be single copy, is a member of a gene family composed of at least five genes. In four Antirrhinum majus populations with different mating systems and one A. graniticum population, diversity within populations is very low. Divergence among Antirrhinum species and between Antirrhinum and Digitalis is also low. For three of these genes we also obtained sequences from a more divergent member of the Scrophulariaceae, Verbascum nigrum. Compared with Antirrhinum, little divergence is again observed. These results, together with similar data obtained previously for five cycloidea genes, suggest either that these gene families (or the Antirrhinum genome) are unusually constrained or that there is a low rate of substitution in these lineages. Using a sample of 52 genes, based on two measures of codon usage (ENC and GC3 content), we show that cyc and fil1 are among the least biased Antirrhinum genes, so that their low diversity is not due to extreme codon bias.

Arabidopsis Proteins↗
PubMed2004

Molecular cytogenetic characterization of the Antirrhinum majus genome.

As a model system in classical plant genetics, the genus Antirrhinum has been well studied, especially in gametophytic self-incompatibility, flower development biology, and transposon-induced mutation. In contrast to the advances in genetic and molecular studies, little is known about Antirrhinum cytogenetics. In this study, we isolated two tandem repetitive sequences, CentA1 and CentA2, from the centromeric regions of Antirrhinum chromosomes. A standard karyotype has been established by anchoring these centromeric repeats on meiotic pachytene chromosome using FISH. An ideogram based on the DAPI-staining pattern of pachytene chromosomes was developed to depict the distribution of heterochromatin in the Antirrhinum majus genome. To integrate the genetic and chromosomal maps, we selected one or two molecular markers from each linkage group to screen an Antirrhinum transformation-competent artificial chromosome (TAC) library. These genetically anchored TAC clones were labeled as FISH probes to hybridize to pachytene chromosomes of A. majus. As a result, the relationship between chromosomes and the linkage groups (LGs) in Antirrhinum has been established.

Antirrhinum↗
PubMed2001

Epidermal control of floral organ identity by class B homeotic genes in Antirrhinum and Arabidopsis.

To assess the contribution of the epidermis to the control of petal and stamen organ identity, we have used transgenic Antirrhinum and Arabidopsis plants that expressed the Antirrhinum class B homeotic transcription factors DEFICIENS (DEF) and GLOBOSA (GLO) in the epidermis. Transgene expression was controlled by the ANTIRRHINUM FIDDLEHEAD (AFI) promoter, which directs gene expression to the L1 meristematic layer and, later, to the epidermis of differentiating organs. Transgenic epidermal DEF and GLO chimeras display similar phenotypes, suggesting similar epidermal contributions by the two class B genes in ANTIRRHINUM: Epidermal B function autonomously controls the differentiation of Antirrhinum petal epidermal cell types, but cannot fully control the pattern of cell divisions and the specification of sub-epidermal petal cell-identity by epidermal signalling. This non-autonomous control is enhanced if the endogenous class B genes can be activated from the epidermis. The developmental influence of epidermal B function in Antirrhinum stamen development is very limited. In contrast, epidermal B function in Arabidopsis can control most if not all epidermal and sub-epidermal differentiation events in petals and stamens, without any contribution from the endogenous class B genes. Possible reasons for differences in the efficacy of B-function-mediated cell communication between the two species are discussed. Interestingly, our experiments uncovered partial incompatibility between class B functional homologues. Although the DEFICIENS/PISTILLATA heterodimer is functional in transgenic Arabidopsis plants, the APETALA3/GLOBOSA heterodimer is not.

Arabidopsis↗
PubMed2005

Functional conservation and maintenance of expression pattern of FIDDLEHEAD-like genes in Arabidopsis and Antirrhinum.

In Arabidopsis, loss of function of the epidermis-specific FDH gene coding for a putative beta-ketoacyl-CoA synthase results in ectopic organ fusions in mutants. Corresponding mutants are not available for Antirrhinum majus, however, organ fusions can be induced in both species by chloroacetamide inhibitors of beta-ketoacyl-CoA synthases using a chemical genetics approach. We isolated the ortholog of FDH from Antirrhinum majus, the ANTIRRHINUM FIDDLEHEAD (AFI ) gene, and showed that AFI complements fdh when expressed in the epidermis under control of the FDH promoter. Like FDH, the AFI gene exhibits protodermis- and epidermis-specific expression, and its promoter directs the expression of reporter genes to the epidermis in transgenic Antirrhinum and Arabidopsis. We demonstrate down-regulation of the FDH promoter in the epidermis of the ovary septum, thereby supporting the assumption that FDH-like genes may directly facilitate the cell-cell interactions that need to occur during carpel fusion and pollen tube growth. Up-regulation of FDH in the stomium, on the other hand, provides evidence for its possible involvement in cell separation during anther dehiscence. Down-regulation of the FDH and AFI promoters in the septum is observed in transgenic Arabidopsis but not in Antirrhinum plants. This probably reflects differences in the ontogeny of the ovary septum between the two species. We also show that epidermis-specific FDH-like genes may not be able to efficiently elongate fatty acid chains when misexpressed in seeds.

3-Oxoacyl-(Acyl-Carrier-Protein) Synthase↗
PubMedDate not supplied

Polymorphic microsatellites in Antirrhinum (Scrophulariaceae), a genus with low levels of nuclear sequence variability.

In Antirrhinum, reproductive systems range from self-compatible to self-incompatible, but the actual outcrossing rates of self-compatible populations are not known. Thus the extent to which levels of variability and inbreeding differ among Antirrhinum populations is not known. In order to address this issue we isolated nine Antirrhinum nuclear microsatellite loci. In contrast to several nuclear genes that show low levels of sequence variation, six of the microsatellite loci indicate high levels of variability within and between Antirrhinum species. The highly self-compatible Antirrhinum majus ssp. cirrhigerum population has high levels of variability and no significant deviation from Hardy-Weinberg equilibrium, suggesting substantial rates of outcrossing.

Antirrhinum↗
PubMed2002

AhSL28, a senescence- and phosphate starvation-induced S-like RNase gene in Antirrhinum.

Several species of higher plants have been found to contain S-like ribonucleases (RNases), which are homologous to S-RNases controlling self-incompatibility. No S-like RNase genes have been isolated from self-incompatible Antirrhinum. To investigate the relationship between S- and S-like RNases, we cloned a gene named AhSL28 encoding an S-like RNase in Antirrhinum. Amino acid sequence, genomic structure and phylogenetic analyses indicated that AhSL28 is most similar to RNS2, an S-like RNase from Arabidopsis thaliana and formed a distinct subclass together with several other S-like RNases within the S-RNase superfamily. Unlike S-RNase genes in Antirrhinum, AhSL28 is not only expressed in pistils but also in leaves, petals, sepals and anthers, in particular, showing a strong expression in vascular tissues and transmitting track. Moreover, its RNA transcripts were induced during leaf senescence and phosphate (Pi) starvation but not by wounding, indicating that AhSL28 plays a role in remobilizing Pi and other nutrients, particularly when cells senesce and are under limited Pi conditions in Antirrhinum. Possible evolutionary relations of S- and S-like RNases as well as signal transduction pathways related to S-like RNase action are discussed.

Amino Acid Sequence↗
PubMed2003

An everlasting pioneer: the story of Antirrhinum research.

Despite the tremendous success of Arabidopsis thaliana, no single model can represent the vast range of form that is seen in the approximately 250,000 existing species of flowering plants (angiosperms). Here, we consider the history and future of an alternative angiosperm model--the snapdragon Antirrhinum majus. We ask what made Antirrhinum attractive to the earliest students of variation and inheritance, and how its use led to landmark advances in plant genetics and to our present understanding of plant development. Finally, we show how the wide diversity of Antirrhinum species, combined with classical and molecular genetics--the two traditional strengths of Antirrhinum--provide an opportunity for developmental, evolutionary and ecological approaches. These factors make A. majus an ideal comparative angiosperm.

Antirrhinum↗
PubMed2006

DNA degradation and nuclear degeneration during programmed cell death in petals of Antirrhinum, Argyranthemum, and Petunia.

Programmed cell death (PCD) was studied in the petals of Antirrhinum majus, Argyranthemum frutescens, and Petunia hybrida, using DNA degradation and changes in nuclear morphology as parameters. The petals exhibit loss of turgor (wilting) as a visible symptom of PCD. DNA degradation, as shown on agarose gels, occurred in all species studied, prior to visible wilting. The number of DNA masses in all the petals of a flower, determined by flow cytometry, markedly increased in Argyranthemum and Petunia, but decreased in Antirrhinum. Many small DNA masses were observed in Argyranthemum and Petunia. The surface of each small DNA mass stained with the lipophilic fluorochrome 3,3'-dihexyloxacarbocyanine iodide (DiOC6), indicating that these masses were surrounded by a membrane. In Antirrhinum, in contrast, the chromatin fragmented into several small spherical clumps that remained inside a large membranous structure. Nuclear fragmentation, therefore, did not occur in Antirrhinum, whereas nuclear fragmentation possibly was a cause of the small DNA masses in Argyranthemum and Petunia. It is concluded that at least two contrasting nuclear morphologies exist during PCD. In the first, the chromatin fragments inside the nucleus, not accompanied--or followed--by nuclear fragmentation. In the second, a large number of DNA masses were observed each enveloped by a membrane. The second type was probably due, at least partially, to nuclear fragmentation.

Antirrhinum↗
PubMed2003

Rapid molecular evolution of CYCLOIDEA-like genes in Antirrhinum and its relatives.

The CYCLOIDEA (CYC) and DICHOTOMA (DICH) genes encode related TCP transcription factors that control floral asymmetry in Antirrhinum majus. Analysis of sequences from relatives of Antirrhinum suggested that CYC and DICH arose from a gene duplication in an ancestor of the tribe Antirrhineae and have subsequently evolved at similar rates. Coding regions outside the conserved functional TCP and R domains differed by numerous indels, suggesting rapid evolution and low constraint on amino acid sequence. An analysis of variability within the genus Antirrhinum revealed very similar CYC alleles in 17 representative species, consistent with most of the species having diverged within the last 1 myr. Whereas substitution mutations appear to have accumulated constantly, one Antirrhinum CYC allele provided evidence for sporadic and rapid accumulation of insertion mutations.

Antirrhinum↗
PubMed2004

The F-box protein AhSLF-S2 physically interacts with S-RNases that may be inhibited by the ubiquitin/26S proteasome pathway of protein degradation during compatible pollination in Antirrhinum.

Self-incompatibility S-locus-encoded F-box (SLF) proteins have been identified in Antirrhinum and several Prunus species. Although they appear to play an important role in self-incompatible reaction, functional evidence is lacking. Here, we provide several lines of evidence directly implicating a role of AhSLF-S(2) in self-incompatibility in Antirrhinum. First, a nonallelic physical interaction between AhSLF-S(2) and S-RNases was demonstrated by both coimmunoprecipitation and yeast two-hybrid assays. Second, AhSLF-S(2) interacts with ASK1- and CULLIN1-like proteins in Antirrhinum, and together, they likely form an Skp1/Cullin or CDC53/F-box (SCF) complex. Third, compatible pollination was specifically blocked after the treatment of the proteasomal inhibitors MG115 and MG132, but they had little effect on incompatible pollination both in vitro and in vivo, indicating that the ubiquitin/26S proteasome activity is involved in compatible pollination. Fourth, the ubiquitination level of style proteins was increased substantially after compatible pollination compared with incompatible pollination, and coimmunoprecipitation revealed that S-RNases were ubiquitinated after incubating pollen proteins with compatible but not with incompatible style proteins, suggesting that non-self S-RNases are possibly degraded by the ubiquitin/26S proteasome pathway. Fifth, the S-RNase level appeared to be reduced after 36 h of compatible pollination. Taken together, these results show that AhSLF-S(2) interacts with S-RNases likely through a proposed SCF(AhSLF-S2) complex that targets S-RNase destruction during compatible rather than incompatible pollination, thus providing a biochemical basis for the inhibition of pollen tube growth as observed in self-incompatible response in Antirrhinum.

Antirrhinum↗
PubMed2001

The MADS-box gene DEFH28 from Antirrhinum is involved in the regulation of floral meristem identity and fruit development.

DEFH28 is a novel MADS-box gene from Antirrhinum majus. Phylogenetic reconstruction indicates that it belongs to the SQUA-subfamily of MADS-box genes. Based on its expression pattern and the phenotype of transgenic plants it is predicted that DEFH28 exerts a dual function during flower development, namely control of meristem identity and fruit development. Firstly, DEFH28 is expressed in the inflorescence apical meristem and might control, together with SQUAMOSA (SQUA), floral meristem identity in Antirrhinum. Also, DEFH28 is sufficient to switch inflorescence shoot meristem to a floral fate in transgenic Arabidopsis thaliana plants. Secondly, DEFH28 is expressed in carpel walls, where it may regulate carpel wall differentiation and fruit maturation. Support for this later role comes from overexpression of DEFH28 throughout the silique in transgenic Arabidopsis plants where it altered the identity of the replum and valve margin cells so that they adopted a valve cell identity. This late aspect of the DEFH28 function is identical to the FRUITFULL (FUL) function of Arabidopsis as demonstrated in gain-of-function plants. FUL, like DEFH28, belongs to the SQUA-subfamily of MADS-box genes. DEFH28 most likely represents the ortholog of FUL. Promoter analysis shows that the control mechanism conferring a carpel wall specific expression has been conserved between Antirrhinum and Arabidopsis during evolution. Although the overall flower development between Antirrhinum and Arabidopsis is very similar, their carpels mature into different types of fruits: capsules and siliques, respectively. Therefore, it is suggested that the role of DEFH28 in control of carpel wall differentiation reflects a conserved molecular mechanism integrated into two very different carpel developmental pathways.

Amino Acid Sequence↗
PubMed2001

Low rates of silent substitution in nuclear genes of two distantly related Scrophulariaceae (Antirrhinum and Verbascum).

Low levels of genetic diversity and divergence at nuclear loci have previously been observed for cycloidea and fil1-like genes within and between several Antirrhinum species, and divergence at these loci is also low between species in genera at different levels of relatedness in the former family Scrophulariaceae (Digitalis and Verbascum). The low divergence values are surprising, because (based on the sequences of chloroplast loci) the Scrophulariaceae are thought to be polyphyletic, with two anciently diverged clades, and the species we compared belonged to the two different clades. Here, we extend our studies of sequence divergence to more nuclear genes: fil2, far, globosa, and ADH: Detailed studies revealed that in Antirrhinum these genes belong to gene families. Low levels of divergence between Antirrhinum and Verbascum were observed for four of the loci studied, fil2-1, fil2-2, far-L, and globosa, similar to our previous observations. We discuss hypotheses to explain these low synonymous divergence values. For Adh, no cases of very similar sequences were found, but, rather, our sequences from the three different genera (Antirrhinum, Digitalis, and Verbascum) were all very diverged. Repeated gene duplication and loss of elements in the Adh gene family is likely in these lineages, making it impossible to determine orthology of the Adh genes.

Cell Nucleus↗
PubMed2005

The pollen-specific DEFH125 promoter from Antirrhinum is bound in vivo by the MADS-box proteins DEFICIENS and GLOBOSA.

The Antirrhinum DEFH125 MADS-box protein is expressed in maturing pollen and thus likely participates in the regulation of pollen development. Here, we describe the characterization of a 2.5 kbp promoter fragment conferring pollen-specific GUS expression in Antirrhinum, as well as in the distantly related species Arabidopsis. Taking advantage of the higher sensitivity of the diphtheria toxin A-chain (DTA) reporter gene assay, onset of DEFH125 promoter activity could be defined to start at the late unicellular microspore stage. Stamen development in Antirrhinum is governed by the class B MADS-box genes DEFICIENS (DEF) and GLOBOSA (GLO). The respective proteins form a heterodimer and are expressed throughout stamens, except for microspores. Complementary expression patterns of DEFH125 and DEF/GLO during later stamen development tempted us to investigate whether the DEF/GLO heterodimer might bind the DEFH125 promoter and could thus be involved in repressing the DEFH125 expression. The ChIP technique was applied to investigate protein/DNA interactions occurring in vivo. We report the identification of a 200 bp DEFH125 promoter fragment that is in vivo bound by DEF and GLO proteins. This fragment contains a CArG-box motif, known to mediate DNA binding of MADS-box proteins. Implications for a likely function of DEF and GLO in the transcriptional control of DEFH125 are discussed.

Antirrhinum↗
PubMed2003

A linkage map of an F2 hybrid population of Antirrhinum majus and A. molle.

To increase the utility of Antirrhinum for genetic and evolutionary studies, we constructed a molecular linkage map for an interspecific hybrid A. majus x A. molle. An F(2) population (n = 92) was genotyped at a minimum of 243 individual loci. Although distorted transmission ratios were observed at marker loci throughout the genome, a mapping strategy based on a fixed framework of codominant markers allowed the loci to be placed into eight robust linkage groups consistent with the haploid chromosome number of Antirrhinum. The mapped loci included 164 protein-coding genes and a similar number of unknown sequences mapped as AFLP, RFLP, ISTR, and ISSR markers. Inclusion of sequences from mutant loci allowed provisional alignment of classical and molecular linkage groups. The total map length was 613 cM with an average interval of 2.5 cM, but most of the loci were aggregated into clusters reducing the effective distance between markers. Potential causes of transmission ratio distortion and its effects on map construction were investigated. This first molecular linkage map for Antirrhinum should facilitate further mapping of mutations, major QTL, and other coding sequences in this model genus.

Antirrhinum↗
PubMed2005

Light quality and temperature effects on antirrhinum growth and development.

An experiment was carried out to examine the effects of light quality on the growth and development of antirrhinum under three different temperatures 19 degrees C, 24 degrees C and 27 degrees C in glasshouses. Five different colour filters (i.e. 'Red absorbing', 'Blue absorbing', 'Blue and Red absorbing' and two 'partially Blue absorbing' materials) were tested, with one clear polythene as a control. Plant height, internode length and leaf area were significantly affected by the spectral filters as well as the temperature. Analysis of color filter's effect on presumed photoreceptors to exist indicated that antirrhinum plant height was regulated by the action of a blue acting photoreceptor (BAP) and not the phytochrome. There was no evidence for an effect of phytochrome or BAP on time to flowering, however, increasing temperature levels effectively decreased the time to flowering. To predict the effects of different spectral qualities and temperature, simple models were created from data on plant height, internode length and time to flowering. These models were then applied to simulate the potential benefits of spectral filters and temperature in manipulation of growth control and flowering in antirrhinum.

Antirrhinum↗
PubMed2002

Molecular variation at the self-incompatibility locus in natural populations of the genera Antirrhinum and Misopates.

The self-incompatibility system of flowering plants is a classic example of extreme allelic polymorphism maintained by frequency-dependent selection. We used primers designed from three published Antirrhinum hispanicum S-allele sequences in PCR reactions with genomic DNA of plants sampled from natural populations of Antirrhinum and Misopates species. Not surprisingly, given the polymorphism of S-alleles, only a minority of individuals yielded PCR products of the expected size. These yielded 35 genomic sequences, of nine different sequence types of which eight are highly similar to the A. hispanicum S-allele sequences, and one to a very similar unpublished Antirrhinum S-like RNase sequence. The sequence types are well separated from the S-RNase sequences from Solanaceae and Rosaceae, and also from most known "S-like" RNase sequences (which encode proteins not involved in self-incompatibility). An association with incompatibility types has so far been established for only one of the putative S-alleles, but we describe evidence that the other sequences are also S-alleles. Variability in these sequences follows the pattern of conserved and hypervariable regions seen in other S-RNases, but no regions have higher replacement than silent diversity, unlike the results in some other species.

Alleles↗
PubMed1996

Alteration of tobacco floral organ identity by expression of combinations of Antirrhinum MADS-box genes.

Floral organ identity is largely controlled by the spatially restricted expression of several MADS-box genes. In Antirrhinum majus these organ identity genes include DEF, GLO and PLE. Single and double mutant analyses indicated that the type of organ found in a particular whorl is dependent on which combination of these genes is expressed there. This paper reports the ectopic expression of Antirrhinum organ identity genes, alone and in combinations, in transgenic tobacco. Although the phenotypes are broadly in agreement with the genetic predictions, several unexpected features are observed which provide information concerning the action of the organ identity genes. The presumed tobacco homologue of DEF, NTDEF, has been isolated and used to investigate the influence of ectopic expression of the Antirrhinum organ identity genes on the endogenous tobacco genes. Analysis of the spatial and temporal expression patterns of NTDEF and NTGLO reveals that the boundaries are not coincident and that differences exist in the regulatory mechanisms of the two genes concerning both induction and maintenance of gene expression. Evidence is provided which indicates that organ development is sensitive to the relative levels of organ identity gene expression. Expression of the organ identity genes outside the flower or inflorescence produced no effects, suggesting that additional factors are required to mediate their activity. These results demonstrate that heterologous genes can be used to predictably influence floral organ identity but also reveal the existence of unsuspected control mechanisms.

Amino Acid Sequence↗