Evolution and Organization of a Highly Dynamic, Subtelomeric Helicase Gene Family in the Rice Blast Fungus Magnaporthe grisea

Evolution and Organization of a Highly Dynamic, Subtelomeric Helicase Gene Family in the Rice Blast Fungus Magnaporthe grisea

Weimin Gao^a, Chang Hyun Khang^a, Sook-Young Park^b, Yong-Hwan Lee^b, and Seogchan Kang^a
^a Department of Plant Pathology, The Pennsylvania State University, University Park, Pennsylvania 16802
^b School of Agricultural Biotechnology, Seoul National University, 103 Seodoon-Dong, Suwan 441-744, Korea

Corresponding author: Seogchan Kang, The Pennsylvania State University, 311 Buckhout Laboratory, University Park, PA 16802., sxk55{at}psu.edu (E-mail)

Communicating editor: J. J. LOROS

Sequence analysis of a 13-kb telomeric region in O-137, a ricepathogenic isolate of Magnaporthe grisea, uncovered a novelgene, designated TLH1 (telomere-linked helicase 1). The TLH1gene is a member of a gene family, and the sequences flankingthis gene family have also been amplified. Genetic mapping showedthat most members of the TLH gene family are tightly linkedto the telomeres. A physical mapping technique, termed RecA-mediatedAchilles' heel cleavage, and cloning and sequencing of two additionaltelomeres of O-137 associated with the TLH gene family confirmedthat most members of the TLH gene family are located within10 kb from the telomeric repeat. A survey of M. grisea strainsfrom diverse hosts revealed that the gene family is ubiquitouslypresent among rice pathogens, but is absent from almost allisolates of hosts other than rice. The gene family appears tobe highly dynamic, undergoing frequent deletion/amplificationevents. Given the presence of similar helicase gene familiesin chromosome ends of Saccharomyces cerevisiae and Ustilagomaydis, the initial association of helicase genes with fungaltelomeres might date back to very early stages of the fungalevolution.

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