GRASSHOPPER, A LONG TERMINAL REPEAT (LTR) RETROELEMENT IN THE PHYTOPATHOGENIC FUNGUS MAGNAPORTHE-GRISEA

The fungal phytopathogen Magnaporthe grisea parasitizes a wide variety of gramineous hosts. In the course of investigating the genetic relat ionship between pathogen genotype and host specificity we identified a retroelement that is present in some strains of M. grisea that infect finger millet and goosegrass (members of the plant genus Eleusine). T he element, designated grasshopper (grh), is present in multiple copie s and dispersed throughout the genome. DNA sequence analysis showed th at grasshopper contains 198 base pair direct, long terminal repeats (L TRs) with features characteristic of retroviral and retrotransposon LT Rs. Within the element we identified an open reading frame with sequen ces homologous to the reverse transcriptase, RNaseH, and integrase dom ains of retroelement pol genes. Comparison of the open reading frame w ith sequences from other retroelements showed that grh is related to t he gypsy family of retrotransposons. Comparisons of the distribution o f the grasshopper element with other dispersed repeated D N A sequence s in M. grisea indicated that grasshopper was present in a broadly dis persed subgroup of Eleusine pathogens, suggesting that the element was acquired subsequent to the evolution of this host-specific form. We p resent arguments that the amplification of different retroelements wit hin populations of M. grisea is a consequence of the clonal organizati on of the fungal populations.