An AFLP-based genetic linkage map of Plasmodium chabaudi chabaudi

Abstract

Background: Plasmodium chabaudi chabaudi can be considered as a rodent model of human malaria parasites in the genetic analysis of important characters such as drug resistance and immunity. Despite the availability of some genome sequence data, an extensive genetic linkage map is needed for mapping the genes involved in certain traits.

Methods: The inheritance of 672 Amplified Fragment Length Polymorphism (AFLP) markers from two parental clones (AS and AJ) of P. c. chabaudi was determined in 28 independent recombinant progeny clones. These, AFLP markers and 42 previously mapped Restriction Fragment Length Polymorphism (RFLP) markers (used as chromosomal anchors) were organized into linkage groups using Map Manager software.

Results: 614 AFLP markers formed linkage groups assigned to 10 of 14 chromosomes, and 12 other linkage groups not assigned to known chromosomes. The genetic length of the genome was estimated to be about 1676 centiMorgans (cM). The mean map unit size was estimated to be 13.7 kb/cM. This was slightly less then previous estimates for the human malaria parasite, Plasmodium falciparum

Conclusion: The P. c. chabaudi genetic linkage map presented here is the most extensive and highly resolved so far available for this species. It can be used in conjunction with the genome databases of P. c chabaudi, P. falciparum and Plasmodium yoelii to identify genes underlying important phenotypes such as drug resistance and strain-specific immunity.

Figure 1

Linkage map for chromosomes 1, 5, 6 and 7 of the P. c. chabaudi genome. The AFLP and RFLP markers assigned to chromosomes are displayed with genetic distances (in cM). AFLP markers were named as follows: the first two letters identify the clone to which a marker is specific, the next two letters indicate the EcoRI primer selective bases, the numbers identify the marker for that clone and primer combination in order of its molecular size, and the last two letters identify the MseI selective bases. RFLP markers were based on genes previously identified [1].

Figure 2

Linkage map for chromosomes 8–11 of the P. c. chabaudi genome. The AFLP and RFLP markers assigned to chromosomes are displayed with genetic distances (in cM).

Figure 3

Linkage map for chromosomes 12 and 13 of the P. c. chabaudi genome. The AFLP and RFLP markers assigned to chromosomes are displayed with genetic distances (in cM).

Figure 4

Unassigned linkage groups containing more than 8 markers. The AFLP markers assigned to unassigned linkage groups are displayed with genetic distances (in cM)

Figure 5

Relationship between genetic size and physical size of each chromosome. The relationship between the estimated genetic sizes and physical sizes of chromosomes 1, 5–13 (Table 1) is shown. The correlation between these two variables is 0.794.