Submitted to: Fungal Genetics Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: March 25, 2000
Publication Date: N/A
Technical Abstract: DNA fingerprinting has been used extensively to characterize populations of the septoria tritici blotch pathogen, Mycosphaerella graminicola. Although it was assumed that the highly polymorphic DNA fingerprints of M. graminicola might reflect the action of transposable elements, there was no direct evidence to support that conclusion. To test the transposable element hypothesis, the DNA fingerprint probe pSTL70 was sequenced, along with other clones that hybridized with pSTL70. Analysis of these sequences identified a long direct repeat adjacent to the end of a reverse transcriptase gene. These are characteristic of transposable elements identified in other fungi. Southern analysis with only the reverse transcriptase sequence as a probe duplicated the original DNA fingerprint pattern. Analysis of 60 progeny from a cross between two Dutch isolates of M. graminicola identified many new bands that were not present in the parents. Thus, the transposable element is active during meiosis. To tes for movement during asexual reproduction, ten single-spore isolates were obtained from each of the two parents of the mating population. Each single-spore isolate was then carried for nine additional single-spore generations to yield 20 lines, each the result of ten generations of asexual reproduction. The ten lines derived from isolate IPO 323 were identical for DNA fingerprint. However, four of the ten lines from isolate 94269 showed a gain or loss of one or more DNA fingerprint bands. Thus, the transposable element was capable of movement during 100 generations of asexual reproduction of isolate 94269. These results indicate that the DNA fingerprint probe pSTL70 identifies a transposable element in M. graminicola that is active during both sexual and asexual reproduction.