Submitted to: Septoria International Workshop Proceedings
Publication Type: Proceedings
Publication Acceptance Date: September 21, 1999
Publication Date: N/A
Interpretive Summary: Septoria tritici leaf blotch, caused by the fungus Mycosphaerella graminicola, is one of the most serious diseases of wheat worldwide. A better understanding of the population biology of this fungus could guide the development of improved disease management strategies. Much of what is known about the population genetics of this organism has come from analyses using the DNA fingerprint probe pSTL70. Although this probe has been used for many years, little is known about the nature of the probe or why it gives a DNA fingerprint. The most likely hypothesis is that it codes for some sort of movable genetic element or transposon. To test the transposable element hypothesis, several additional clones of DNA that are related to pSTL70 were identified from M. graminicola. Comparison of the DNA sequences of three clones plus that of the original pSTL70 probe revealed that part of the pSTL70 clone codes for a gene that in Saccharomyces (bread yeast) is involved in sensing and responding to changes in the concentration of solutes outside a cell. The function of this gene in M. graminicola remains unknown. The remaining portion of the pSTL70 clone contains a long DNA sequence that is repeated 3.5 times, and a partial coding sequence for an enzyme that causes DNA to move These are characteristics of transposons which strongly supports the transposable element hypothesis. This information will be extremely useful to scientists to understand and explain the DNA fingerprint pattern produced by pSTL70. It may also make it possible to identify specific DNA fingerprint loci, which could be used by plant pathologists for a quick, easy method for analysis of the population genetics of this important plant pathogen.
Technical Abstract: Clones hybridizing to the Mycosphaerella graminicola DNA fingerprint probe pSTL70 were identified from subgenomic libraries and sequenced. Analyses of the DNA sequences of these clones plus the original pSTL70 clone revealed that pSTL70 contains part of the open reading frame for a probable homologue of an osmosensing histidine kinase gene from yeast. The remaining portion of the clone contained a partial reverse transcriptase gene sequence and a 29 base pair direct repeat, which could mean that the clone is a transposable element. Methods for converting transposable elements into improved DNA fingerprinting techniques are discussed.