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6. DO ANY SPECIES BOUNDARIES...
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The region A is located on the distal side of the heme group and corresponds to the N-
termini of bacterial catalase-peroxidase, while the regions B and C are located on proximal
side of heme and correspond to the C-termini of bacterial enzyme. Furthermore, the
CLUSTALX alignment of protein sequences of 60 plant peroxidases proved that the greatest
sequence similarity (76%) is achieved on the distal side with the so called the catalytic
triad (Arg92, Trp95, His96). Differences in the level of polymorphism revealed by different
pairs of primers in Calamagrostis arundinacea and correlation between katG polymorphism
and peroxidase zymotypes have provided the first evidences that at least some of katG
primers can amplify sequences of plant peroxidases (Krzakowa et al. 2007). In general,
the pairs of katG primers that reveal low polymorphism amplify the conservative region encoding
the distal side of heme peroxidase while the relatively high polymorphism is generated
by katG primers complementary to the sequence encoding the C-termini of KatG gene.
The tight linkage between four katG markers and Per3 locus on LG6 of L. multiflorum and
L. perenne as well as between katG2-15 and Per1 on LG4 are among first and the strongest
arguments that primers derived from M. tuberculosis KatG gene amplify sequences of plant
peroxidases. This observation may have further applications in using katG markers as a road
map for studying peroxidases in plants. Somehow surprising is that some katG markers are
also linked with loci encoding the other enzymes such as Gtdh1, Mdh2, Hk2 and Acoh. This
can suggest that those enzymes are of bacterial origin as well.
The Mendelian inheritance and linkage with enzymatic loci together with earlier results
from phylogenetic analyses (Zielinski and Polok 2005) strongly support the utility of katG
markers derived from bacterial sequences in genetic studies in plants. The same is true for
IS6110 based markers and we believe that for several other markers derived from bacterial
sequences e.g., hot fragment of rpo and pol genes that have been also tested. Therefore we
propose to assign this system as Bacteria Specific Amplification Polymorphism (B-SAP).
The main feature of all bacteria derived sequences is their relatively high conservatism within
a species exhibited as low polymorphism and dramatic differences between even closely
related species.
To summarize, the outcome of genetic mapping studies in L. multiflorum and L. perenne
demonstrated clearly that no species boundaries exist between them. Eventually some diversification
can be observed on transposon level but this is far away from the birth of reproduction
barriers. Therefore the classification of both taxa as a single “species complex”,
with subspecies, as already suggested in the preceding chapters, seems more appropriate
to their biological status. The genetic map-based appraisals provide support for postulated
early divergence of L. multiflorum and L. perenne and thus confirm the utility of genetic maps
in evolutionary studies. In the light of the present data, it is obvious that a refined understanding
of evolutionary processes is possible if the precise loci, sequences or chromosome
regions underlying differences between species can be identified. Techniques for generating
large numbers of genetic markers and the availability of markers from different model species
are likely to make genetic mapping more common for wild species. Genetic maps also enable
to map QTLs including those responsible for early evolution as well as to compare closely
related species. Up to the present genetic maps have been by-products of breeding activities
and searches for genes responsible for important characters as well as markers for marker
assisted selection. Therefore first interspecific comparisons were done for crops. The goal of