scholarly journals Landscape and taxon age are associated with differing patterns of hybridization in two Eucalyptus (Myrtaceae) subgenera

2020 ◽  
Vol 127 (1) ◽  
pp. 49-62
Author(s):  
T P Robins ◽  
R M Binks ◽  
M Byrne ◽  
S D Hopper
Keyword(s):  
Evolutionary Process ◽  
F1 Hybrids ◽  
Divergence Times ◽  
Eucalyptus Species ◽  
Reproductive Barriers ◽  
Nucleotide Polymorphism ◽  
Plant Populations ◽  
Single Nucleotide ◽  
Clonal Spread

Abstract Background and Aims Hybridization is an important evolutionary process that can have a significant impact on natural plant populations. Eucalyptus species are well known for weak reproductive barriers and extensive hybridization within subgenera, but there is little knowledge of whether patterns of hybridization differ among subgenera. Here, we examine eucalypts of Western Australia’s Stirling Range to investigate how patterns of hybridization are associated with landscape and taxon age between the two largest Eucalyptus subgenera: Eucalyptus and Symphyomyrtus. In doing so, we tested a hypothesis of OCBIL (old, climatically buffered, infertile landscape) theory that predicts reduced hybridization on older landscapes. Methods Single nucleotide polymorphism markers were applied to confirm the hybrid status, parentage and genetic structure of five suspected hybrid combinations for subg. Eucalyptus and three combinations for subg. Symphyomyrtus. Key Results Evidence of hybridization was found in all combinations, and parental taxa were identified for most combinations. The older parental taxa assessed within subg. Eucalyptus, which are widespread on old landscapes, were identified as well-defined genetic entities and all hybrids were exclusively F1 hybrids. In addition, many combinations showed evidence of clonality, suggesting that the large number of hybrids recorded from some combinations is the result of long-term clonal spread following a few hybridization events rather than frequent hybridization. In contrast, the species in subg. Symphyomyrtus, which typically occur on younger landscapes and are more recently evolved, showed less distinction among parental taxa, and where hybridization was detected, there were high levels of introgression. Conclusions Reduced hybridization in subg. Eucalyptus relative to extensive hybridization in subg. Symphyomyrtus affirmed the hypothesis of reduced hybridization on OCBILs and demonstrate that clade divergence times, landscape age and clonality are important drivers of differing patterns of speciation and hybridization in Eucalyptus.

scholarly journals Polymorphism of the complement 5 gene is associated with large artery atherosclerosis stroke in Chinese patients

2016 ◽  
Vol 74 (11) ◽  
pp. 881-886 ◽  
Author(s):  
Hui Wu ◽  
Yingfeng Weng ◽  
Lan Zheng ◽  
Huanyin Li ◽  
Qi Gong ◽  
...  
Keyword(s):  
Ischemic Stroke ◽  
Chinese Patients ◽  
Large Artery ◽  
Nucleotide Polymorphism ◽  
Term Outcome ◽  
Single Nucleotide ◽  
Long Term Outcome ◽  
Risk Predictors ◽  
The Complement System

ABSTRACT The complement system has been confirmed to play an increasingly important role in ischemic stroke (IS). This study aimed to determine whether the single-nucleotide polymorphism of the complement 5 (C5) gene independently influences the occurrence, severity, and long-term outcome of IS in Chinese patients. Methods C5 rs17611 genetic variants were investigated in 494 IS patients and 330 control individuals .Ischemic stroke was classified into subtypes and patients were assessed 90 days post-stroke with the modified Rankin Scale to determine stroke outcome. Results The presence of C5 polymorphism was associated with the incidence of large artery atherosclerosis (LAA)-subtype IS (n =2 00; p = 0.031), which even persisted after adjustment for covariates (OR = 1.518; 95%CI = 1.093–2.018; p = 0.013). However, no association was found between genotypes and the severity and outcome of stroke (p = 0.978; p = 0.296). Conclusions The C5 polymorphism might contribute to the risk of LAA-subtype IS independently of other known risk predictors.

scholarly journals Evidence for the Contribution of Point Mutations tovlsE Variation and for Apparent Constraints on the Net Accumulation of Sequence Changes in vlsE during Infection with Lyme Disease Spirochetes

2001 ◽  
Vol 183 (20) ◽  
pp. 5855-5861 ◽  
Author(s):  
Shian-Ying Sung ◽  
John V. McDowell ◽  
Richard T. Marconi
Keyword(s):  
Lyme Disease ◽  
Gene Conversion ◽  
Sequence Variation ◽  
Frameshift Mutation ◽  
Point Mutations ◽  
Gene Families ◽  
Nucleotide Polymorphism ◽  
Single Nucleotide ◽  
Variable Regions

ABSTRACT In the Lyme disease spirochetes, both the ospE andvlsE gene families have been demonstrated to undergo sequence variation during infection. To further investigate the mechanisms associated with the generation of vls variation, single-nucleotide polymorphism and subsequent DNA sequence analyses were performed on the vlsE gene and its paralog, BBJ51, a related gene with a frameshift mutation. These analyses focused on a series of postinfection clonal populations obtained from mice infected with Borrelia burgdorferi B31MIpc or its clonal derivative, B31MIc53. vlsE, but not BBJ51, was found to undergo sequence changes during infection. Consistent with that reported previously (J.-R. Zhang et al., Cell 89:275–285, 1997) many of the sequence changes appear to have arisen through gene conversion events and to be localized to the variable regions of vlsE. However, analysis of the vlsE nucleotide sequences revealed that some sequence changes were the result of point mutations, as these changes did not have potential contributing sources in thevls cassettes. To determine if sequence changes accumulate in vlsE over long-term infection, thevlsE genes of clonal populations recovered after 7 months of infection in mice were analyzed. While new sequence changes developed, a significant number of these changes resulted in the restoration of the vlsE sequence of the original infecting clone. In addition, we noted that some positions within the variable regions (VR) are stable even though the cassettes possess residues that could contribute to sequence variation through gene conversion. These analyses suggest that the total number of amino acid sequence changes that can be maintained by VlsE levels off during infection. In summary, in this report we demonstrate that the development of point mutations serves as a second mechanism by which vlsE sequence variation can be generated and that the capacity for vlsEvariation, while still significant, is less than previously postulated.

scholarly journals The effect of a single nucleotide polymorphism on human α2-antiplasmin activity

Blood ◽  
2007 ◽  
Vol 109 (12) ◽  
pp. 5286-5292 ◽  
Author(s):  
Victoria J. Christiansen ◽  
Kenneth W. Jackson ◽  
Kyung N. Lee ◽  
Patrick A. McKee
Keyword(s):  
Single Nucleotide Polymorphism ◽  
Amino Acid ◽  
Amino Terminus ◽  
Healthy Population ◽  
Plasma Samples ◽  
Nucleotide Polymorphism ◽  
Single Nucleotide ◽  
Genotype Frequencies ◽  
Polymorphic Forms

Abstract The primary inhibitor of plasmin, α2-antiplasmin (α2AP), is secreted by the liver into plasma with Met as the amino-terminus. During circulation, Met-α2AP is cleaved by antiplasmin-cleaving enzyme (APCE), yielding Asn-α2AP, which is crosslinked into fibrin approximately 13 times faster than Met-α2AP. The Met-α2AP gene codes for either Arg or Trp as the sixth amino acid, with both polymorphic forms found in human plasma samples. We determined the Arg6Trp genotype frequency in a healthy population and its effects on Met-α2AP cleavage and fibrinolysis. Genotype frequencies were RR 62.5%, RW 34.0%, and WW 3.5%. The polymorphism related to the percentage of Met-α2AP in plasma was WW (56.4%), RW (40.6%), and RR (23.6%). WW plasma tended to have shorter lysis times than RR and RW plasmas. APCE cleaved purified Met-α2AP(Arg6) approximately 8-fold faster than Met-α2AP(Trp6), which is reflected in Asn-α2AP/Met-α2AP ratios with time in RR, RW, and WW plasmas. Removal of APCE from plasma abrogated cleavage of Met-α2AP. We conclude that the Arg6Trp polymorphism is functionally significant, as it clearly affects conversion of Met-α2AP to Asn-α2AP, and thereby, the rate of α2AP incorporation into fibrin. Therefore, the Arg6Trp polymorphism may play a significant role in governing the long-term deposition/removal of intravascular fibrin.

scholarly journals Gene flow between introduced and native Eucalyptus species: exotic hybrids are establishing in the wild

2003 ◽  
Vol 51 (4) ◽  
pp. 429 ◽  
Author(s):  
R. C. Barbour ◽  
B. M. Potts ◽  
R. E. Vaillancourt
Keyword(s):  
Gene Flow ◽  
Native Species ◽  
Parental Species ◽  
F1 Hybrids ◽  
Eucalyptus Species ◽  
Eucalyptus Nitens ◽  
Natural Hybrids ◽  
In The Wild ◽  
Long Term Impact

F1 hybrids between exotic Eucalyptus nitens plantations and native E. ovata have previously been reported among seedlings grown from open-pollinated seed collected from E. ovata, on the island of Tasmania. Such exotic hybrid seedlings have now been found in the wild adjacent to plantations at three locations. The proportion of exotic hybrids in open-pollinated seed collected from nearby mature E. ovata was 5.5%. This level compares with only 0.4% for natural hybrids between native species at these sites (E. ovata, E. viminalis and E.�rodwayi). Detection of hybrids was initially based on their deviant morphology, which was generally intermediate between parental species. This subjective classification was then successfully verified by morphometric and allozyme analyses. Pure E. nitens seedlings (wildlings) were restricted to within 30 m of these plantations, whereas established hybrids were found up to 310 m from the plantations. This pattern of establishment reflects dispersal of exotic seed and pollen respectively. It is likely that the recent expansion of the eucalypt plantation estate in Australia will cause an increase in the frequency of exotic hybrids. However, the long-term impact of such hybridisation is yet to be assessed.

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