CHARACTERIZATION OF THE TRANSCRIPT OF A NEW CLASS OF RETROPOSON-TYPE REPETITIVE ELEMENT CLONED FROM THE POWDERY MILDEW FUNGUS, ERYSIPHE-GRAMINIS

The putative master transcript of a novel class of repetitive element has been cloned from the fungus Erysiphe graminis f.sp. hordei. Sequen ce analysis of the cDNA revealed that the element, designated Eg-R1, i s a member of the retroposon superfamily with properties in common wit h SINEs and LINEs (short or long interspersed elements). SINE-like pro perties include the transcript size (approximately 700 bp), and the la ck of major open reading frames. In contrast, the fact that the transc ript is polyadenylated and is most probably transcribed by RNA polymer ase II, suggests a functional relationship to LINEs. Except for a shor t, but striking, sequence identity to a published SINE from the same f ungus, no similar sequence was found in database searches. A constitut ively high transcript level is found throughout the asexual life cycle of the fungus. Small differences in band patterns on Southern blots w ere observed between two isolates of E, graminis f.sp. hordei, while t he band patterns in an isolate of the very close relative E. graminis f.sp. tritici in general appear dissimilar, This may imply that the el ement is currently active. Recent dispersal is confirmed by the observ ation that an approximately 550 bp internal HinfI fragment is conserve d in the majority of the copies in all three isolates. Approximately 5 0 copies are present in E. graminis f.sp. hordei.