Allozyme polymorphism of Mdh and α-Gpdh in Ixodes ricinus populations: comparison of borreliae-infected and uninfected ticks

Abstract

Ixodes ricinus Linnaeus (Acari: Ixodidae) ticks are vectors of numerous infectious diseases in humans and animals. The allozyme variability of MDH and alpha-Gpdh was detected by native polyacrylamide gel electrophoresis in I. ricinus natural populations in three localities in Serbia. Four alleles of Mdh locus (MDH 1, MDH 2, MDH 3 and MDH X) and four alleles of alpha-Gpdh locus (VS, S, F and VF) were detected. Interpopulation differences in Mdh and alpha-Gpdh allele frequencies were statistically insignificant. Significant difference in alpha-Gpdh allele frequencies between males and females was recorded in the largest sample only. Differences in allele frequencies, detected between borreliae-infected and uninfected I. ricinus ticks, were close to the level of statistical significance, especially for alpha-Gpdh locus. Clear significant difference appeared in females when sexes were tested separatelly (P = 0.037). It is interesting that genotypes containing rarer alleles (MDH 1 and S) were infected in higher proportion in comparison to other genotypes. Our results point towards a possible role of Mdh and alpha-Gpdh loci in I. ricinus ticks in the determination of energy requirements for host seeking. Sex differences in alpha-Gpdh allele frequencies suggest that selective pressure, concerning efficiency of reserve materials utilisation, points to alpha-Gpdh rather than to Mdh locus.

Seasonal and Spatial Occurrence of Glycerol-3-Phosphate Dehydrogenase Variability inIxodes ricinus(Acari: Ixodidae) Populations

“…2; Table 2). The similarity between frequencies of GPDH 441 haplotypes and previously reported frequencies of related Gpdh alleles (Radulović 2005, Radulović et al 2006, detected in I. ricinus samples from the same localities in Serbia, goes in favor of this assumption. Haplotypes GPDH 441 1 and GPDH 441 2 were detected in all investigated samples, while GPDH 441 3 haplotype was present in samples from Makiš and Košutnjak localities only.…”

“…This assumption was based on a demonstrated adaptive role of GPDH variability in populations of some Drosophila and Collias species (Johnson 1976, Alahiotis et al 1977, as well as on Þndings concerning differential mobility of I. ricinus ticks with different Gpdh (gene encoding GPDH) genotype at low temperatures (Healy 1979). Four alleles of Gpdh were detected in I. ricinus populations from different parts of Europe by allozyme electrophoresis (Healy 1979, Delaye et al 1997, Radulović et al 2006, supporting the hypothesis of Healy et al (2004).…”

“…The results obtained so far indicate that the polymorphism of Gpdh gene represent an adaptation of I. ricinus to environmental temperature ßuctuations (Healy et al 2004, Radulović 2005, Radulović et al 2006. Four alleles of the Gpdh locus (very fast, VF; fast, F; slow, S; and very slow, VS) identiÞed enzyme polymorphism in I. ricinus populations across Europe (Healy 1979, Delaye et al 1997, Radulović et al 2006).…”

“…Haplotypes GPDH 441 1 and GPDH 441 2 were detected in all investigated samples, while GPDH 441 3 haplotype was present in samples from Makiš and Košutnjak localities only. It is interesting that Radulović et al (2006) reported presence of rare VS and VF alleles of the Gpdh gene in I. ricinus ticks from one locality of the Belgrade area, while those alleles were not present in samples from other Serbian localities. In addition, the rare Gpdh alleles (Radulović et al 2006), as well as GPDH 441 3 haplotype in the current study, were detected only in female ticks.…”

“…Four alleles of the Gpdh locus (very fast, VF; fast, F; slow, S; and very slow, VS) identiÞed enzyme polymorphism in I. ricinus populations across Europe (Healy 1979, Delaye et al 1997, Radulović et al 2006). Radulović (2010) and Radulović et al (2010) performed comparative analysis of Gpdh gene sequences and GPDH allozymes in individual I. ricinus ticks.…”