Genetic mapping of the novel <Emphasis Type="Italic">Turnip mosaic virus</Emphasis> resistance gene <Emphasis Type="Italic">TuRB03</Emphasis> in <Emphasis Type="Italic">Brassica napus</Emphasis>

A new source of resistance to the pathotype 4 isolate of Turnip mosaic virus (TuMV) CDN 1 has been identified in Brassica napus (oilseed rape). Analysis of segregation of resistance to TuMV isolate CDN 1 in a backcross generation following a cross between a resistant and a susceptible B. napus line showed that the resistance was dominant and monogenic. Molecular markers linked to this dominant resistance were identified using amplified fragment length polymorphism (AFLP) and microsatellite bulk segregant analysis. Bulks consisted of individuals from a BC₁ population with the resistant or the susceptible phenotype following challenge with CDN 1. One AFLP and six microsatellite markers were associated with the resistance locus, named TuRB03, and these mapped to the same region on chromosome N6 as a previously mapped TuMV resistance gene TuRB01. Further testing of TuRB03 with other TuMV isolates showed that it was not effective against all pathotype 4 isolates. It was effective against some, but not all pathotype 3 isolates tested. It provided further resolution of TuMV pathotypes by sub-dividing pathotypes 3 and 4. TuRB03 also provides a new source of resistance for combining with other resistances in our attempts to generate durable resistance to this virus.     

Transgenic resistance to <Emphasis Type="Italic">Cymbidium mosaic virus</Emphasis> in <Emphasis Type="Italic">Dendrobium</Emphasis> expressing the viral capsid protein gene

A Taiwan isolate of Cymbidium mosaic virus (CymMV-CS) was isolated from infected Cymbidium sinesis Willd. The cDNA of the capsid protein (CP) gene was synthesized and sequenced. Alignment of this CP gene with other reported CPs revealed homologies of 92–98% at the nucleotide level and 98–99% at the amino acid level. To generate virus-resistant varieties, the CymMV-CS CP gene was transformed into Dendrobium protocorms through particle bombardment. Transformants were selected on medium supplemented with 20 mg/L hygromycin and the presence of the transgene was confirmed by polymerase chain reaction, Southern, Northern and Western blot analyses. Transgenic Dendrobium harboring the CymMV CP gene expressed a very low level of virus accumulation four months post-inoculation with CymMV, as detected by ELISA. The transgenic plants exhibited much milder symptoms than the non-transgenic plants upon challenge with CymMV virionsSequence data reported from this article have been deposited at the GenBank Data Libraries under Accession No. AY429021.     

Fine mapping of <Emphasis Type="Italic">RYMV3</Emphasis>: a new resistance gene to <Emphasis Type="Italic">Rice yellow mottle virus</Emphasis> from <Emphasis Type="Italic">Oryza glaberrima</Emphasis>

Key message

A new resistance gene against Rice yellow mottle virus was identified and mapped in a 15-kb interval. The best candidate is a CC-NBS-LRR gene.

Abstract

Rice yellow mottle virus (RYMV) disease is a serious constraint to the cultivation of rice in Africa and selection for resistance is considered to be the most effective management strategy. The aim of this study was to characterize the resistance of Tog5307, a highly resistant accession belonging to the African cultivated rice species (Oryza glaberrima), that has none of the previously identified resistance genes to RYMV. The specificity of Tog5307 resistance was analyzed using 18 RYMV isolates. While three of them were able to infect Tog5307 very rapidly, resistance against the others was effective despite infection events attributed to resistance-breakdown or incomplete penetrance of the resistance. Segregation of resistance in an interspecific backcross population derived from a cross between Tog5307 and the susceptible Oryza sativa variety IR64 showed that resistance is dominant and is controlled by a single gene, named RYMV3. RYMV3 was mapped in an approximately 15-kb interval in which two candidate genes, coding for a putative transmembrane protein and a CC-NBS-LRR domain-containing protein, were annotated. Sequencing revealed non-synonymous polymorphisms between Tog5307 and the O. glaberrima susceptible accession CG14 in both candidate genes. An additional resistant O. glaberrima accession, Tog5672, was found to have the Tog5307 genotype for the CC-NBS-LRR gene but not for the putative transmembrane protein gene. Analysis of the cosegregation of Tog5672 resistance with the RYMV3 locus suggests that RYMV3 is also involved in Tog5672 resistance, thereby supporting the CC-NBS-LRR gene as the best candidate for RYMV3.

     

Evaluation of genes from <Emphasis Type="Italic">eIF4E</Emphasis> and <Emphasis Type="Italic">eIF4G</Emphasis> multigenic families as potential candidates for partial resistance QTLs to <Emphasis Type="Italic">Rice yellow mottle virus</Emphasis> in rice

QTLs for partial resistance to Rice yellow mottle virus (RYMV) in rice were mapped in two populations of doubled-haploid lines (DHLs) and recombinant inbred lines (RILs) derived from the same cross but evaluated for different resistance criteria (virus content and symptom severity). An integrative map was used to compare the two genetic maps and a global analysis of both populations was performed. Most of the QTLs previously identified in DHL population were confirmed with increased significance and precision. As many recent studies evidenced the role of eukaryotic translation initiation factors (eIF) of 4E and 4G families in plant susceptibility to RNA viruses, we checked if these genes co-locate with QTLs of resistance to RYMV. Their systematic in silico identification was carried out on the rice genome and their physical locations were compared to QTL positions on the integrative map. In order to confirm or not the co-locations observed, the analysis was completed by evaluation of near-isogenic lines, QTL fine mapping and sequencing of candidate genes. Three members from eIF4G family could be retained as reliable candidates whereas eIF4E genes, commonly found to govern resistances in other plant/virus interactions, were discarded. Together with the recent identification of an eIF(iso)4G as a major resistance gene, data suggests an important role of genes from eIF4G family in rice resistance to RYMV but does not exclude the contribution of factors different from the translation initiation complex. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

The symptom difference induced by <Emphasis Type="Italic">Tobacco mosaic virus</Emphasis> and <Emphasis Type="Italic">Tomato mosaic virus</Emphasis> in tobacco plants containing the <Emphasis Type="Italic">N</Emphasis> gene is determined by movement protein gene

Tobacco mosaic virus (TMV) and Tomato mosaic virus (ToMV) are two closely related viruses in the genus Tobamovirus, but they induce obviously different sizes of necrotic lesions in tobacco plants containing the N gene. Comparison of the symptoms produced by TMV, ToMV and a chimaeric virus (T/OMP), in which the TMV movement protein (MP) gene was replaced by the ToMV MP gene, showed T/OMP caused necrotic lesions that were similar in size to those of ToMV in tobacco plants containing the N gene. The coat protein and MP of the three viruses accumulated in planta with similar levels, and the replication level of TMV and T/OMP in protoplasts also had no difference. Comparison of the activities of defense-related enzymes (PAL, POD and PPO) induced by the three viruses also showed that the variability of enzyme activity induced by T/OMP was similar to that induced by TMV, but different from that induced by ToMV. The results indicate that the size difference of necrotic lesions induced by TMV and ToMV in tobacco plants containing the N gene results from the functional difference of their MP genes.     

Changes in leaf tissue of <Emphasis Type="Italic">Carica papaya</Emphasis> during single and mixed infections with <Emphasis Type="Italic">Papaya ringspot virus</Emphasis> and <Emphasis Type="Italic">Papaya mosaic virus</Emphasis>

Papaya (Carica papaya L.) is susceptible to viral diseases caused by Papaya mosaic virus (PapMV) and Papaya ringspot virus (PRSV), which limit fruit production and affect economic yield. The symptoms produced by both the viruses are similar in early stages of infection and include vein and leaf chlorosis, which develop into mosaic at later stages of infection when leaf lamina can get reduced in size and distorted with a shoe-string aspect. Digital image analyses, such as fractal dimension (FD) and lacunarity (λ) were used here to examine papaya tissue after single and mixed infections of PRSV and PapMV. Morphological changes, such as hypoplasia, hyperplasia, and neoplasia are described in tissues with viral infections. Furthermore, we quantified these changes and suggest three ranges of tissue damage according to their λ values in rank 1 (0.01 to 0.39), rank 2 (0.4 to 0.79), and rank 3 (0.8 to 1). Our analyses suggest that in synergism and antagonism there is a competition of both viruses to occupy the same mesophyll cells, as indicated by their intermediate values of lacunarity.     

Fine-mapping and identification of a novel locus <Emphasis Type="Italic">Rsc15</Emphasis> underlying soybean resistance to <Emphasis Type="Italic">Soybean mosaic virus</Emphasis>

Key message

Rsc15, a novel locus underlying soybean resistance to SMV, was fine mapped to a 95-kb region on chromosome 6. The Rsc15- mediated resistance is likely attributed to the gene GmPEX14 , the relative expression of which was highly correlated with the accumulation of H ₂ O ₂ along with the activities of POD and CAT during the early stages of SMV infection in RN-9.

Abstract

Soybean mosaic virus (SMV) causes severe yield losses and seed quality deterioration in soybean [Glycine max (L.) Merr.] worldwide. A series of single dominant SMV resistance genes have been identified on respective soybean chromosomes 2, 13 and 14, while one novel locus, Rsc15, underlying resistance to the virulent SMV strain SC15 from soybean cultivar RN-9 has been recently mapped to a 14.6-cM region on chromosome 6. However, candidate gene has not yet been identified within this region. In the present study, we aimed to fine map the Rsc15 region and identify candidate gene(s) for this invaluable locus. High-resolution fine-mapping revealed that the Rsc15 gene was located in a 95-kb genomic region which was flanked by the two simple sequence repeat (SSR) markers SSR_06_17 and BARCSOYSSR_06_0835. Allelic sequence comparison and expression profile analysis of candidate genes inferred that the gene Glyma.06g182600 (designated as GmPEX14) was the best candidate gene attributing for the resistance of Rsc15, and that genes encoding receptor-like kinase (RLK) (i.e., Glyma.06g175100 and Glyma.06g184400) and serine/threonine kinase (STK) (i.e., Glyma.06g182900 and Glyma.06g183500) were also potential candidates. High correlations were established between the relative expression level of GmPEX14 and the hydrogen peroxide (H₂O₂) concentration and activities of catalase (CAT) and peroxidase (POD) during the early stages of SMV-SC15 infection in RN-9. The results of the present study will be useful in marker-assisted breeding for SMV resistance and will lead to further understanding of the molecular mechanisms of host resistance against SMV.

     

Genetic analysis and fine mapping of <Emphasis Type="Italic">Watermelon mosaic virus</Emphasis> resistance gene in cucumber

Watermelon mosaic virus (WMV) is an important disease of cucumber (Cucumis sativus L.) that is difficult to control in the field. Some resistant lines are available, and understanding the inheritance of the disease and mapping the gene or genes that confer resistance will facilitate the development of further resistant varieties. In this study, the inheritance and gene mapping for resistance to WMV in cucumber were conducted using populations derived from the cross between susceptible ‘65G’ and resistant ‘02245’ inbred lines. Genetic analysis showed that resistance to WMV in ‘02245’ is controlled by a single recessive gene designated as wmv ⁰²²⁴⁵ mapped to chromosome 6 (Chr.6). The region was flanked by the molecular markers SSRWMV60-23 and CAPS-W1 with genetic distances of 0.34 and 1.19 cM from the wmv ⁰²²⁴⁵ locus, respectively. The 134.7 kb physical distance of this region includes 21 candidate genes. Comparison of the genotypic and phenotypic results showed that the accuracy rate of the most closely linked marker SSRWMV60-23 was 94.0 %. This marker will be used for molecular marker-assisted selection to select resistant lines, and future research will be directed at identifying and cloning the resistance gene.     

<Emphasis Type="Italic">ABCB1</Emphasis> single nucleotide polymorphisms in the Brazilian population

The ABCB1/MDR-1 gene, which encodes P-glycoprotein, is highly polymorphic. We analyzed 278 healthy Brazilian individuals through PCR–RFLP to identify ABCB1 variants and determine the genotypic and allelic frequencies. Genotypic frequencies for C1236T (rs1128503) were 0.31 for CC, 0.60 for CT and 0.09 for TT and allelic frequencies were 0.61 and 0.39 for C and T, respectively. Genotypic frequencies for C3435T (rs1045642) were 0.24 for CC, 0.61 for CT and 0.15 for TT, and allelic frequencies were 0.55 and 0.45 for C and T, respectively. Both variants showed significant differences in genotypic frequencies for both studied regions. Gender comparisons did not show significant differences between genotypes at both sites. Significant differences were observed between C1236C and C3435T and also C1236C and C3435C. Comparisons between ABCB1 polymorphisms in Brazilians and other populations show significant differences. The understanding of the effects of several drugs associated to these variants may help an individualized treatment in clinical practice.     

Rapid identification of QTLs underlying resistance to <Emphasis Type="Italic">Cucumber mosaic virus</Emphasis> in pepper (<Emphasis Type="Italic">Capsicum frutescens</Emphasis>)

Key message

Next-generation sequencing enabled a fast discovery of QTLs controlling CMV resistant in pepper. The gene CA02g19570 as a possible candidate gene of qCmr2.1 was identified for resistance to CMV in pepper.

Abstract

Cucumber mosaic virus (CMV) is one of the most important viruses infecting pepper, but the genetic basis of CMV resistance in pepper is elusive. In this study, we identified a candidate gene for CMV resistance QTL, qCmr2.1 through SLAF-seq. Segregation analysis in F₂, BC₁ and F_2:3 populations derived from a cross between two inbred lines ‘PBC688’ (CMV-resistant) and ‘G29’ (CMV-susceptible) suggested quantitative inheritance of resistance to CMV in pepper. Genome-wide comparison of SNP profiles between the CMV-resistant and CMV-susceptible bulks constructed from an F₂ population identified two QTLs, designated as qCmr2.1 on chromosome 2 and qCmr11.1 on chromosome 11 for resistance to CMV in PBC688, which were confirmed by InDel marker-based classical QTL mapping in the F₂ population. As a major QTL, joint SLAF-seq and traditional QTL analysis delimited qCmr2.1 to a 330 kb genomic region. Two pepper genes, CA02g19570 and CA02g19600, were identified in this region, which are homologous with the genes LOC104113703, LOC104248995, LOC102603934 and LOC101248357, which were predicted to encode N-like protein associated with TMV-resistant in Solanum crops. Quantitative RT-PCR revealed higher expression levels of CA02g19570 in CMV resistance genotypes. The CA02g19600 did not exhibit obvious regularity in expression patterns. Higher relative expression levels of CA02g19570 in PBC688 and F₁ were compared with those in G29 during days after inoculation. These results provide support for CA02g19570 as a possible candidate gene of qCmr2.1 for resistance to CMV in pepper.

     

Resequencing of the <Emphasis Type="Italic">Col1A1</Emphasis> gene of <Emphasis Type="Italic">Oryctolagus cuniculus</Emphasis> identifies splicing errors and single nucleotide polymorphisms

Next generation sequencing technologies have accelerated the rate at which whole genome sequencing (WGS) data is acquired. The sheer volume of data generated by WGS requires computational annotation to define potential coding regions and chromosomal features. The accuracy of genomic annotation is thus limited by the power of the computational algorithm and the sequence coverage provided by the raw data. Sequencing of the New Zealand White (NZW) rabbit has been performed to a 7× depth of coverage, leaving large gaps in coverage and potential errors within the draft assembly. In the present study, we have resequenced the collagen type I, alpha 1 (Col1A1) gene of Oryctolagus cuniculus (n?=?8). We have characterized the full length cDNA, identified splicing errors within the reference sequence, and identified single nucleotide polymorphisms within the gene. These data underscore the need for a higher resolution assembly of the rabbit genome to advance research in this important large animal model.     

Expression of an extracellular ribonuclease gene increases resistance to <Emphasis Type="Italic">Cucumber mosaic virus</Emphasis> in tobacco

Background

The apoplast plays an important role in plant defense against pathogens. Some extracellular PR-4 proteins possess ribonuclease activity and may directly inhibit the growth of pathogenic fungi. It is likely that extracellular RNases can also protect plants against some viruses with RNA genomes. However, many plant RNases are multifunctional and the direct link between their ribonucleolytic activity and antiviral defense still needs to be clarified. In this study, we evaluated the resistance of Nicotiana tabacum plants expressing a non-plant single-strand-specific extracellular RNase against Cucumber mosaic virus.

Results

Severe mosaic symptoms and shrinkage were observed in the control non-transgenic plants 10 days after inoculation with Cucumber mosaic virus (CMV), whereas such disease symptoms were suppressed in the transgenic plants expressing the RNase gene. In a Western blot analysis, viral proliferation was observed in the uninoculated upper leaves of control plants, whereas virus levels were very low in those of transgenic plants. These results suggest that resistance against CMV was increased by the expression of the heterologous RNase gene.

Conclusion

We have previously shown that tobacco plants expressing heterologous RNases are characterized by high resistance to Tobacco mosaic virus. In this study, we demonstrated that elevated levels of extracellular RNase activity resulted in increased resistance to a virus with a different genome organization and life cycle. Thus, we conclude that the pathogen-induced expression of plant apoplastic RNases may increase non-specific resistance against viruses with RNA genomes.

     

Novel single nucleotide polymorphisms and haplotypes within the bovine<Emphasis Type="Italic"> CXCR2</Emphasis> gene

The objectives of this study were to identify single nucleotide polymorphisms (SNPs) and resulting haplotypes in the bovine CXCR2 gene. A 311-bp segment of the bovine CXCR2 gene was amplified and sequenced. Five SNPs at positions 612, 684, 777, 858, and 861 were expressed in both Holstein and Jersey dairy cattle. Four SNPs resulted in synonymous substitutions, while a non-synonymous switch at position 777 (GC) resulted in a glutamine to histidine substitution at amino acid residue 245. Strong linkage disequilibrium was exhibited for both breeds among all five loci (P<0.001). Both allele and genotype frequencies differed significantly with respect to breed at four of the five loci (P<0.001). The five polymorphisms generated ten distinct haplotypes. Six haplotypes were common between the two breeds, while Holsteins and Jerseys each uniquely expressed two haplotypes. Of the six common haplotypes, two represented 83% of the Jersey population; whereas four of these haplotypes represented 95% of the Holstein population.     

<Emphasis Type="Italic">Agrobacterium tumefaciens</Emphasis>-mediated transformation of poinsettia, <Emphasis Type="Italic">Euphorbia pulcherrima</Emphasis>, with virus-derived hairpin RNA constructs confers resistance to <Emphasis Type="Italic">Poinsettia mosaic virus</Emphasis>

Agrobacterium-mediated transformation for poinsettia (Euphorbia pulcherrima Willd. Ex Klotzsch) is reported here for the first time. Internode stem explants of poinsettia cv. Millenium were transformed by Agrobacterium tumefaciens, strain LBA 4404, harbouring virus-derived hairpin (hp) RNA gene constructs to induce RNA silencing-mediated resistance to Poinsettia mosaic virus (PnMV). Prior to transformation, an efficient somatic embryogenesis system was developed for poinsettia cv. Millenium in which about 75% of the explants produced somatic embryos. In 5 experiments utilizing 868 explants, 18 independent transgenic lines were generated. An average transformation frequency of 2.1% (range 1.2-3.5%) was revealed. Stable integration of transgenes into the poinsettia nuclear genome was confirmed by PCR and Southern blot analysis. Both single- and multiple-copy transgene integration into the poinsettia genome were found among transformants. Transgenic poinsettia plants showing resistance to mechanical inoculation of PnMV were detected by double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA). Northern blot analysis of low molecular weight RNA revealed that transgene-derived small interfering (si) RNA molecules were detected among the poinsettia transformants prior to inoculation. The Agrobacterium-mediated transformation methodology developed in the current study should facilitate improvement of this ornamental plant with enhanced disease resistance, quality improvement and desirable colour alteration. Because poinsettia is a non-food, non-feed plant and is not propagated through sexual reproduction, this is likely to be more acceptable even in areas where genetically modified crops are currently not cultivated.     

<Emphasis Type="Italic">Galleria</Emphasis><Emphasis Type="Italic">mellonella</Emphasis> are Resistant to <Emphasis Type="Italic">Pneumocystis</Emphasis><Emphasis Type="Italic">murina</Emphasis> Infection

Studying Pneumocystis has proven to be a challenge from the perspective of propagating a significant amount of the pathogen in a facile manner. The study of several fungal pathogens has been aided by the use of invertebrate model hosts. Our efforts to infect the invertebrate larvae Galleria mellonella with Pneumocystis proved futile since P. murina neither caused disease nor was able to proliferate within G. mellonella. It did, however, show that the pathogen could be rapidly cleared from the host.     

<Emphasis Type="Italic">EPSTI1</Emphasis> polymorphisms are associated with systemic lupus erythematosus

Epithelial stromal interaction 1 (EPSTI1) is an interferon (IFN) response gene, which was originally identified as a stromal fibroblast-induced gene in breast cancer. Our previous study using a customized SNP chip found evidence of an association between EPSTI1 and susceptibility to the chronic inflammatory disease, systematic lupus erythematosus (SLE). This study aimed to validate whether polymorphisms in EPSTI1 are associated with susceptibility to SLE. We analyzed genotype and allele frequencies of SNPs at EPSTI1 using genomic DNA from 119 patients with SLE and 512 healthy controls. We found that the genotype frequencies of rs1044856 and rs1359184 in patients with SLE were significantly different from those found in the control group (P?=?0.03 and P?=?0.01, respectively). In addition, we found that genotype and allele frequencies of rs1359184 in female patients with SLE were significantly different from those found in female controls (P?=?0.02 and P?=?0.04, respectively). We identified two major haplotypes in EPSTI1 that were significantly different between patients with SLE and healthy controls (P?=?0.01 and P?=?0.05, respectively). Furthermore, we found that rs1359184 and rs1044856 in EPSTI1 were associated with antinuclear antibody (ANA) and erythrocyte sedimentation rate (ESR) levels in patients with SLE (P?=?0.0035 and P?=?0.021, respectively). Our findings indicate that polymorphisms in EPSTI1 are associated with susceptibility to SLE and that haplotypes at EPSTI1 may be useful genetic markers for SLE.     

<Emphasis Type="Italic">Pm37</Emphasis>, a new broadly effective powdery mildew resistance gene from <Emphasis Type="Italic">Triticum </Emphasis><Emphasis Type="Italic">timopheevii</Emphasis>

Powdery mildew is an important foliar disease in wheat, especially in areas with a cool or maritime climate. A dominant powdery mildew resistance gene transferred to the hexaploid germplasm line NC99BGTAG11 from T. timopheevii subsp. armeniacum was mapped distally on the long arm of chromosome 7A. Differential reactions were observed between the resistance gene in NC99BGTAG11 and the alleles of the Pm1 locus that is also located on chromosome arm 7AL. Observed segregation in F_2:3 lines from the cross NC99BGTAG11 × Axminster (Pm1a) demonstrate that germplasm line NC99BGTAG11 carries a novel powdery mildew resistance gene, which is now designated as Pm37. This new gene is highly effective against all powdery mildew isolates tested so far. Analyses of the population with molecular markers indicate that Pm37 is located 16 cM proximal to the Pm1 complex. Simple sequence repeat (SSR) markers Xgwm332 and Xwmc790 were located 0.5 cM proximal and distal, respectively, to Pm37. In order to identify new markers in the region, wheat expressed sequence tags (ESTs) located in the distal 10% of 7AL that were orthologous to sequences from chromosome 6 of rice were targeted. The two new EST-derived STS markers were located distal to Pm37 and one marker was closely linked to the Pm1a region. These new markers can be used in marker-assisted selection schemes to develop wheat cultivars with pyramids of powdery mildew resistance genes, including combinations of Pm37 in coupling linkage with alleles of the Pm1 locus.     

<Emphasis Type="Italic">Ty</Emphasis>1<Emphasis Type="Italic">/copia</Emphasis>- and <Emphasis Type="Italic">Ty</Emphasis>3<Emphasis Type="Italic">/gypsy</Emphasis>-like DNA sequences in <Emphasis Type="Italic">Helianthus </Emphasis>species

Two repeated DNA sequences isolated from a partial genomic DNA library of Helianthus annuus, p HaS13 and p HaS211, were shown to represent portions of the int gene of a Ty3 /gypsy retroelement and of the RNase-Hgene of a Ty1 /copia retroelement, respectively. Southern blotting patterns obtained by hybridizing the two probes to BglII- or DraI-digested genomic DNA from different Helianthus species showed p HaS13 and p HaS211 were parts of dispersed repeats at least 8 and 7 kb in length, respectively, that were conserved in all species studied. Comparable hybridization patterns were obtained in all species with p HaS13. By contrast, the patterns obtained by hybridizing p HaS211 clearly differentiated annual species from perennials. The frequencies of p HaS13- and p HaS211-related sequences in different species were 4.3x10(4)-1.3x10(5) copies and 9.9x10(2)-8.1x10(3) copies per picogram of DNA, respectively. The frequency of p HaS13-related sequences varied widely within annual species, while no significant difference was observed among perennial species. Conversely, the frequency variation of p HaS211-related sequences was as large within annual species as within perennials. Sequences of both families were found to be dispersed along the length of all chromosomes in all species studied. However, Ty3 /gypsy-like sequences were localized preferentially at the centromeric regions, whereas Ty1/ copia-like sequences were less represented or absent around the centromeres and plentiful at the chromosome ends. These findings suggest that the two sequence families played a role in Helianthusgenome evolution and species divergence, evolved independently in the same genomic backgrounds and in annual or perennial species, and acquired different possible functions in the host genomes.