Chromosome inversion polymorphisms in Drosophila melanogaster II. Geographic clines and climatic associations in Australasia,North America and Asia

The four paracentric autosomal chromosome inversions In(2L)t, In(2R)NS, In(3L)P and In(3R)R are commonly polymorphic in natural populations of D. melanogaster in Australasia, North America and Asia, with latitudinal clines in the frequencies of each inversion in each region. In each region inversion frequency decreases with increasing distance from the equator, although the precise relationship between frequency and latitude varies between inversions and, for In(2L)t and In(2R)NS, among regions. Each inversion also shows a longitudinal cline in at least one region but none show such a cline in all three. Although no inversion's frequency is associated with the same climatic variable in all three regions, inversion frequencies are generally positively related to annual maximum temperature and, more particularly, minimum temperature and minimum rainfall. The directions of the latitudinal clines and the climatic associations are consonant with evidence from D. melanogaster that inversion frequencies decline in winter. They are also consonant with evidence from some other Drosophila species that inversion heterozygosities are lower at the geographic margins than at the centre of the species' ranges.     

MATING PREFERENCE AND ITS RELEVANCE TO ADAPTATION IN DROSOPHILA MELANOGASTER: INVERSION POLYMORPHISM AND DDT RESISTANCE

The importance of adult mating success as a component of fitness influencing inversion polymorphism in two DDT-resistant populations of Drosophila melanogaster was investigated. The polymorphism involved In(3R)P and the Standard (St) gene arrangement. In population 731R the St/St females showed greater mating propensity than In/In females, while in population J2 the In/In females showed a significant positive association between mating propensity and the percentage of St/St males present. Mating preference data showed that St/St males were selectively favored over In/In males in both populations. No differences were observed between St/St and St/In karyotypes in either population. Frequency-dependent mating in the form of a rare male mating disadvantage for the In/In males tested against the St/St males in 731R was observed; the St/St males in this case showed a marginally significant rare male mating advantage. Thus, mating success as well as previously measured fecundity and fertility all indicate a selective advantage of the St chromosome over the In chromosome in both populations. This fitness relationship does not predict the equilibrium condition of 70–80% St/In, 20–30% In/In, and 0–10% St/St found in the DDT environment, whereas previously collected larval viability data and estimated adult survivorship do. In at least one population (731R), the adult mating success data do predict the dynamics of the polymorphism in the absence of DDT, whereas viability does not. These results, although limited to two populations under two environments (presence or absence of DDT), suggest that the relationship between adaptation to the environment under study and various components of fitness needs to be investigated fully before assessing which fitness components are most important in determining the effects of natural selection in specific populations.     

Speciation and chromosomal evolution of the Baikalian endemic chironomids of the genus Sergentia Kief. (Diptera, Chironomidae): Karyotype divergence and chromosomal polymorphism in the populations of eurybathic species Sergentia flavodentata Tshern. and littoral species Sergentia baicalensis Tshern

Specific karyotype structure and chromosomal polymorphism was investigated in the populations of the Baikalian endemic chironomid species, eurybathic Sergentia flavodentata Tshernovskij, 1949 and littoral Sergentia baicalensis Tshernovskij, 1949. In addition to two fluctuating homozygous inversions in arms A and E, both species were characterized by species-specific karyotype features, namely, nucleolar organizer in the region 1 of chromosome IV in S. flavodentata, and inversion in arm F in S. baicalensis. Moreover, S. baicalensis demonstrated the presence of intraspecific population polymorphism. The populations differing in the presence of secondary overlapping inversion in arm A were found. The highest number of chromosomal rearrangements (7) was detected in S. flavodentata. Most of these rearrangements (six) were found in the population from the underwater thermal spring at a depth of 420 to 430 m (Northern Baikal, Frolikha Bay). In the populations from Middle and Southern Baikal, a rare pericentric inversion in chromosome I was described. In S. baicalensis, in addition to two common heterozygous inversions in arms C and F, disturbance of homologous pairing in different regions of the remaining arms were often detected. Stable chromosomal polymorphism preserved during 13 years in the population of S. flavodentata from the region of hydrothermal venting, serves as an evidence of high genetic plasticity of the species, which favors successful colonization of different Baikal depths and biotopes. Original Russian Text ? V.I. Proviz, 2008, published in Genetika, 2008, Vol. 44, No. 9, pp. 1191–1202.     

Speciation and chromosomal evolution of the palaearctic species of chironomids of the genus Sergentia Kieffer (Diptera, Chironomidae): Chromosome polymorphism in the populations of S. baueri Wülker et al., 1999, S. prima Proviz et al., 1997, and S. electa Proviz et al., 1999 from the Irkutsk reservoir

Chromosome polymorphism was studied in populations of three Palaearctic species of chironomids of the genus Sergentia Kieffer (Diptera, Chironomidae) from the Irkutsk reservoir: S. baueri Wülker et al., 1999, S. prima Proviz et al., 1997, and S. electa Proviz et al., 1999. It was found that in S. baueri heterozygous individuals constitute 72% of the population with 0.8 of inversion per individual. In total, three inversion sequences were detected. The most widespread was the inversion in regions 7–12 of the arm IIIR with the borders similar to those of the inversion in the Far East S. baueri populations and in populations of other species of the genus. In S. prima, heterozygotes constituted 60%, with the number of inversions per individual was 1.3. Seven inversion sequences were revealed, of which three were found in chromosome IV. In the S. electa population, only one inversion sequence was observed in chromosome III in 36% of larvae (0.4 of inversion per individual). The level of chromosome polymorphism in the populations of the Palaearctic species is comparable with that in the populations of endemic Sergentia from the Baikal Lake. Ten rearrangements were revealed in each of the two groups, but similar borders of chromosome regions were established only for two inversions. In the studied Sergentia species, chromosome IV has the most variable structure.     

Achiasmate Segregation of a B Chromosome from the X Chromosome in Two Species of Psyllids (Psylloidea, Homoptera)

The segregation of a B chromosome from the X chromosome was studied in male meiosis in two psyllid species, Rhinocola aceris (L.) and Psylla foersteri (Flor.) (Psylloidea, Homoptera). The frequency of segregation was determined from cells at metaphase II. In R. aceris, the B chromosome was mitotically stable and segregated quite regularly from the X chromosome in four geographically distant populations, while it showed less regular, but preferential segregation in one population. This was attributed to the presence of B chromosome variants that differ in their ability to interact with the X chromosome in segregation. In P. foersteri, the B chromosome was mitotically unstable and segregated preferentially from the X chromosome in spermatocyte cysts, which displayed one B chromosome in every cell. Behaviour of the B chromosome and X chromosome univalents during meiotic prophase and at metaphase I in R. aceris, and during anaphase I in P. foersteri suggested that the regular segregation resulted from the incorporation of B chromosomes in achiasmate segregation mechanisms with the X chromosome in the place occupied by the Y chromosome in species with XY system. The regular segregation of a B chromosome from the X chromosome may obscure the distinction of a B chromosome and an achiasmate Y chromosome in some cases. This revised version was published online in August 2006 with corrections to the Cover Date.     

The association between inversion In(3R)Payne and clinally varying traits in Drosophila melanogaster

In Drosophila melanogaster, inversion In(3R)Payne increases in frequency towards low latitudes and has been putatively associated with variation in size and thermal resistance, traits that also vary clinally. To assess the association between size and inversion, we obtained isofemale lines of inverted and standard karyotype of In(3R)Payne from the ends of the Australian D. melanogaster east coast cline. In the northern population, there was a significant association between In(3R)Payne and body size, with standard lines from this population being relatively larger than inverted lines. In contrast, the inversion had no influence on development time or cold resistance. We strengthened our findings further in a separate study with flies from populations from the middle of the cline as well as from the cline ends. These flies were scored for wing size and the presence of In(3R)Payne using a molecular marker. In females, the inversion accounted for around 30% of the size difference between cline ends, while in males the equivalent figure was 60%. Adaptive shifts in size but not in the other traits are therefore likely to have involved genes closely associated with In(3R)Payne. Because the size difference between karyotypes was similar in different populations, there was no evidence for coadaptation within populations.     

R factor variants with enhanced sex factor activity in Pseudomonas aeruginosa

Summary The R factor R68 readily promotes chromosome transfer in Pseudomonas aeruginosa strain PAT, but shows little such sex factor activity in strain PAO. A variant of this plasmid, R68.45, has been isolated which produces recombinants in PAO plate matings at frequencies of 10^-3–10^-5 per donor cell for markers in the 0–60 min region of the chromosome. Little or no chromosome transfer was shown in liquid media. The kinetics of chromosome transfer were studied by interrupting matings on solid media with nalidixic acid. Five chromosomal markers, mapping in widely spaced regions of the chromosome all entered 3–5 min after initiation of mating. These results, combined with linkage studies, indicate that R68.45, unlike the Pseudomonas sex factors FP2 and FP39, promotes chromosome transfer from a range of origin sites and can thus be used for mapping the region of the P. aeruginosa chromosome later than 40 min.R68.45 and other similar variants were isolated from rare chromosomal recombinants appearing in crosses between PAO(R68) donors and PAO recipients in which selection for argB ⁺ was made. Selection for other chromosomal markers did not result in such variants suggesting that plasmids of the R68.45 type arise by recombination of genetic material between the R68 plasmid and certain regions of the bacterial chromosome.     

Characterization of a major QTL for adult plant resistance to stripe rust in US soft red winter wheat

Stripe rust, caused by Puccinia striiformis f. sp. tritici, is an important disease of soft red winter wheat in the eastern region of the USA. Pioneer 26R61 has provided effective resistance to stripe rust for 10 years. To elucidate the genetic basis of the resistance, a mapping population of 178 recombinant inbred lines (RILs) was developed using single-seed descent from a cross between Pioneer 26R61 and the susceptible cultivar AGS 2000. A genetic map with 895 markers covering all 21 chromosomes was used for QTL analysis. One major QTL was detected, explaining up to 56.0% of the mean phenotypic variation, flanked by markers Xbarc124 and Xgwm359, and assigned to the distal 22% of the short arm of wheat chromosome 2A. Evidence showed that it was different from Yr17 derived from Ae. ventricosa, the only formally named Yr gene in 2AS, and the QTL was temporarily designated as YrR61. In addition, a minor QTL, QYr.uga-6AS, probably conditioned high-temperature adult plant resistance. The QTL explained 6–7% of the trait variation. Preliminary test of the flanking markers for YrR61, in two cultivars and two promising breeding lines with Pioneer 26R61 in their pedigree, indicated that YrR61 was present in these cultivars and lines, and these markers could therefore be used in marker-assisted selection.     

Further studies on the interchromosomal effect on crossing over in Drosophila melanogaster affecting the preconditions of exchange

The second chromosome inversion In (2L+2R) Cy in a heterozygous condition was studied for its effect on frequency and interference of crossing over in three different regions of the X chromosome of Drosophila melanogaster. A significant increase in crossing over frequency was observed in the proximal and distal regioins of the X chromosome while in the middle of the chromosome crossing over frequency remained unaltered. The effect on interference remained unaltered at both ends of the X chromosome while a significant decrease was observed in the middle of the chromosome. These results suggest that the interchromosomal effect on crossing over affects the preconditions of exchange differently in different regions of the X chromosome, and possibly the duration of chromosome pairing.     

Molecular Variation of Adh and P6 Genes in an African Population of Drosophila Melanogaster and Its Relation to Chromosomal Inversions

Four-cutter molecular polymorphism of Adh and P6, and chromosome inversion polymorphism of chromosome II were investigated in 95 isogenic lines of an Ivory Coast population of Drosophila melanogaster, a species assumed to have recently spread throughout the world from a West African origin. The P6 gene showed little linkage disequilibrium with the In(2L)t inversion, although it is located within this inversion. This suggests that the inversion and the P6 locus have extensively exchanged genetic information through either double crossover or gene conversion. Allozymic variation in ADH was in linkage disequilibrium with In(2L)t and In(2R)NS inversions. Evidence suggests either that inversion linkage with the Fast allele is selectively maintained, or that this allele only recently appeared. Molecular polymorphism at the Adh locus in the Ivory Coast is not higher than in North American populations. New haplotypes specific to the African population were found, some of them connect the ``Wa(s)-like' haplotypes found at high frequencies in the United States to the other slow haplotypes. Their relation with In(2L)t supports the hypothesis that Wa(s) recently recombined away from an In(2L)t chromosome which may be the cause of its divergence from the other haplotypes.     

Fine mapping,physical mapping and development of diagnostic markers for the <Emphasis Type="Italic">Rrs2</Emphasis> scald resistance gene in barley

The Rrs2 gene confers resistance to the fungal pathogen Rhynchosporium secalis which causes leaf scald, a major barley disease. The Rrs2 gene was fine mapped to an interval of 0.08 cM between markers 693M6_6 and P1D23R on the distal end of barley chromosome 7HS using an Atlas (resistant) × Steffi (susceptible) mapping population of 9,179 F₂-plants. The establishment of a physical map of the Rrs2 locus led to the discovery that Rrs2 is located in an area of suppressed recombination within this mapping population. The analysis of 58 barley genotypes revealed a large linkage block at the Rrs2 locus extending over several hundred kb which is present only in Rrs2 carrying cultivars. Due to the lack of recombination in the mapping population and the presence of a Rrs2-specific linkage block, we assume a local chromosomal rearrangement (alien introgression or inversion) in Rrs2 carrying varieties. The variety analysis led to the discovery of eight SNPs which were diagnostic for the Rrs2 phenotype. Based on these SNPs diagnostic molecular markers (CAPS and pyrosequencing markers) were developed which are highly useful for marker-assisted selection in resistance gene pyramiding programmes for Rhynchosporium secalis resistance in barley.     

Impact of functionalized coligands on the pharmacokinetics of 99mTcIII '4+1' mixed-ligand complexes conjugated to bombesin

Bombesins (BN) containing ^99mTc ‘4 + 1’ complexes may be useful to detect tumors expressing the gastrin-releasing peptide receptor (GRPR). Derivatives of the formula [^99mTc(NS₃R)(L2-BN_st)] were synthesized, in which Tc(III) is coordinated by an isocyanide L2-BN_st bearing the peptide (BN_st = βAla-βAla-Gln-Trp-Ala-Val-Gly-His-Cha-Nle-NH₂) and a tetradentate chelator NS₃R. NS₃R consists of 2,2′,2″-nitrilotriethanethiol (NS₃) bearing a crown ether (NS₃crown), an aliphatic amine (NS₃en) and a tricarboxylic acid (NS₃(COOH)₃). Non-radioactive Re compounds were prepared and analysed by electrospray ionization mass spectrometry. The structural similarity to the ^99mTc conjugates was demonstrated by their identical HPLC elution profiles. The lipophilicity of [^99mTc(NS₃R)(L2-BN_st)] decreased depending on the coligands NS₃crown (log D_O/W, pH = 7.4, 0.98 ± 0.11), NS₃en (− 0.49 ± 0.07) and NS₃(COOH)₃ (− 2.01 ± 0.09). Biodistribution in normal rats was characterized by an increasing kidney uptake and a decreasing uptake into the liver corresponding to the reduced lipophilicity of the conjugates. The pancreatic uptake expressed by the organ/blood ratio of standardized uptake values at 60 min p.i. in rats was 8.6 ± 1.2 for [^99mTc(NS₃en)(L2-BN_st)] and higher compared to the other conjugates. The pancreas/liver ratio of the SUV at 60 min p.i. in rats was highest for [^99mTc(NS₃(COOH)₃)(L2-BN_st)] at 8.4 ± 1.3. [^99mTc(NS₃en)(L2-BN_st)] was further studied in tumor-bearing mice and its pancreas/blood and pancreas/liver ratios were lower, however the pancreas/kidney ratios were higher in mice compared to rats. The activity uptake of [^99mTc(NS₃en)(L2-BN_st)] into the PC-3 tumor xenografts was low (%ID/g: 0.83 ± 0.18 at 60 min; SUV: 0.21 ± 0.05 at 60 min) but specific.     

Heterochromatin variation in chromosome X in a natural population of Anopheles willmori (Diptera: Culicidae) of Thailand

Among the eight families of Anopheles willmori derived from individual wild-caught females collected from Chiangmai Province (northern Thailand) and examined, four isofemale lines showed variation in the X chromosome, including the normal X₁ and three aberrant types (X₃, X₄ and X_L). It is postulated that these different types of X chromosomes could have arisen as a result of spontaneous chromosomal rearrangements involving tandem translocation and paracentric inversion followed by acquisition of constitutive heterochromatin. Such rare events of chromosomal changes have become established in the natural population of An. willmori in northern Thailand.     

Speciation and chromosomal evolution of the Baikalian endemic chironomids of the genus Sergentia Kief. (Diptera, Chironomidae): Karyotype divergence and chromosomal polymorphism in the populations of deep-water species Sergentia nebulosa Linevitsh et al. and Sergentia assimilis Proviz V. et Proviz L.

Specific karyotype structure and chromosomal polymorphism was investigated in the populations of Sergentia nebulosa Linevitsh et al., 1984 and Sergentia assimilis Proviz V. et Proviz L., 1999, the deep-water endemic chironomid species (Diptera, Chironomidae) from the Baikal Lake. The distinguishing feature of the karyotypes of these species, compared to the other Baikalian Sergentia, is well-developed nucleolus in region 6 of arm C. Both species display the presence of interspecific population polymorphism, determined by the structure of this arm. In some populations, chromosome regions from 4 to 6 contain a homozygous inversion, which is absent in the other populations. The distinguishing karyotype feature of S. assimilis, which shares fluctuating homozygous inversions with the other species, is the presence of two species-specific homozygous inversions. These are the secondary overlapping inversion in arm A, regions 2 to 7, and the inversion in regions 4 to 10 of arm G. Both species of interest contain nucleolus organizer in region 10 of arm G. In populations of S. nebulosa, six heterozygous inversions localized in arms A, B, C, F, and G were discovered. The highest number of heterozygotes for inversions (71%) was observed in the population from Southern Baikal. In arm B of S. assimilis, one heterozygous inversion and heterozygosity for nucleolus organizer in the chromosome region 16 was detected. Chromosomal evolution of Baikalian Sergentia, and the role of inversion polymorphism in the population adaptation is discussed. Original Russian Text ? V.I. Proviz, 2008, published in Genetika, 2008, Vol. 44, No. 12, pp. 1627–1637.     

Karyotypic polymorphism of the zebra finch Z chromosome

We describe a karyotypic polymorphism on the zebra finch Z chromosome. This polymorphism was discovered because of a difference in the position of the centromere and because it occurs at varying frequencies in domesticated colonies in the USA and Germany and among two zebra finch subspecies. Using DNA fluorescent in situ hybridization to map specific Z genes and measurements of DNA replication, we show that this polymorphism is the result of a large pericentric inversion involving the majority of the chromosome. We sequenced a likely breakpoint for the inversion and found many repetitive sequences. Around the breakpoint, there are numerous repetitive sequences and several copies of PAK3 (p21-activated kinase 3)-related sequences (PAK3Z) which showed testes-specific expression by RT-PCR. Our findings further suggest that the sequenced genome of the zebra finch may be derived from a male heterozygote for the Z chromosome polymorphism. This finding, in combination with regional differences in the frequency of the polymorphism, has important consequences for future studies using zebra finches.     

Genomic evidence for role of inversion 3RP of Drosophila melanogaster in facilitating climate change adaptation

Chromosomal inversion polymorphisms are common in animals and plants, and recent models suggest that alternative arrangements spread by capturing different combinations of alleles acting additively or epistatically to favour local adaptation. It is also thought that inversions typically maintain favoured combinations for a long time by suppressing recombination between alternative chromosomal arrangements. Here, we consider patterns of linkage disequilibrium and genetic divergence in an old inversion polymorphism in Drosophila melanogaster (In(3R)Payne) known to be associated with climate change adaptation and a recent invasion event into Australia. We extracted, karyotyped and sequenced whole chromosomes from two Australian populations, so that changes in the arrangement of the alleles between geographically separated tropical and temperate areas could be compared. Chromosome‐wide linkage disequilibrium (LD) analysis revealed strong LD within the region spanned by In(3R)Payne. This genomic region also showed strong differentiation between the tropical and the temperate populations, but no differentiation between different karyotypes from the same population, after controlling for chromosomal arrangement. Patterns of differentiation across the chromosome arm and in gene ontologies were enhanced by the presence of the inversion. These data support the notion that inversions are strongly selected by bringing together combinations of genes, but it is still not clear if such combinations act additively or epistatically. Our data suggest that climatic adaptation through inversions can be dynamic, reflecting changes in the relative abundance of different forms of an inversion and ongoing evolution of allelic content within an inversion.     

Evidence for an association between markers on chromosome 19q and non-syndromic cleft lip with or without cleft palate in two groups of multiplex families

It has been reported that BCL3 on chromosome 19q, or a nearby gene, may play a role in the etiology of non-syndromic cleft lip with or without cleft palate (NSCL/P) in some families. We tested 30 USA and 11 Mexican multiplex NSCL/P families for four markers on chromosome 19q: D19S178, APOC2/AC1, APOC2/007, and BCL3. While likelihood-based linkage analysis failed to show significant evidence of linkage, the transmission disequilibrium test indicated highly significant deviation from independent assortment of allele 3 at the BCL3 marker in both data sets (USA:P = 0.001; Mexican: P = 0.018; both combined: P < 0.001) and for allele 13 of the D19S178 marker in the Mexican data set (P = 0.004). These results support an association, possibly due to linkage disequilibrium, between chromosome 19 markers and a putative NSCL/P locus. Received: 10 May 1996 / Revised: 31 July 1996     

Trans-inactivation: Repression in a wrong place

Trans-inactivation is the repression of genes on a normal chromosome under the influence of a rearranged homologous chromosome demonstrating the position effect variegation (PEV). This phenomenon was studied in detail on the example of brown^Dominant allele causing the repression of wild-type brown gene on the opposite chromosome. We have investigated another trans-inactivation-inducing chromosome rearrangement, In(2)A4 inversion. In both cases, brown^Dominant and In(2)A4, the repression seems to be the result of dragging of the euchromatic region of the normal chromosome into the heterochromatic environment. It was found that cis-inactivation (classical PEV) and trans-inactivation show different patterns of distribution along the chromosome and respond differently to PEV modifying genes. It appears that the causative mechanism of trans-inactivation is de novo heterochromatin assembly on euchromatic sequences dragged into the heterochromatic nuclear compartment. Trans-inactivation turns out to be the result of a combination of heterochromatin-induced position effect and the somatic interphase chromosome pairing that is widespread in Diptera.     

CYTOGENETIC STUDIES IN CLARKIA,SECTION PRIMIGENIA. II. A CYTOLOGICAL SURVEY OF CLARKIA ARCUATA AND CLARKIA LASSENENSIS

Clarkia arcuata and C. lassenensis are the 2 members of the subsection Flexicaules. Although closely related morphologically, they show very different patterns of chromosomal variability in nature. About 25% of the plants grown from wild seed of C. arcuata, a predominantly cross-pollinating species, were heterozygous for 1 or 2 translocations; such heterozygotes were found in 5 of the 9 populations sampled. An analysis of the chromosome pairing in intraspecific crosses indicated that at least 5 different translocations giving a ring of 4 with the “standard” strain, 2 giving a ring of 6, and 2 giving a ring of 8 are present in nature. No arrangement was found with widespread distribution, and it is impossible to say at present what might be the primitive arrangement of this species. One population was found to contain an inversion, a rearrangement which is very rare in Clarkia at the intraspecific level. In C. lassenensis, a predominantly self-pollinating species, only 6% (3 plants) of a sample of 53 were translocation heterozygotes, and these heterozygotes were found in only 2 of 13 populations. Intraspecific crosses indicated that one chromosome arrangement, the “standard,” was present throughout the species range.     

Chromosome inversions in Indian Drosophila melanogaster

Ten laboratory stocks of Drosophila melanogaster initiated from females collected in different localities in India were analysed for chromosome inversions. Six inversions were found to be present, three in 2L, one in 2R, one in 3L and one in 3R. Out of these six inversions, three are new and are being reported for the first time. Furthermore, this is the first report of inversion polymorphism in Indian D. melanogaster. The persistence of inversion polymorphism in our laboratory stocks of D. melanogaster which were maintained for more than one year under laboratory conditions, suggests some heterotic advantage of inversion heterozygotes.