TITLE	The kalilo family of fungal plasmids
AUTHOR	Anthony J. F. Griffiths Department of Botany, University of British Columbia, Vancouver, Canada V6T 1Z4
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ABSTRACT	A. J. F. Griffiths (1997). The prototypic kalilo plasmid is approximately 9 kb long and has the structure of an invertron. There are 5'-bound terminal proteins, a long terminal inverted repeat (TIR) and two ORFs corresponding to viral RNA and DNA polymerases. Kalilo plasmids have been found in several different heterothallic and one pseudohomothallic species of Neurospora from around the world. No examples have been found in true homothallic species. The prototypic plasmid was found in N. intermedia on the Hawaiian island of Kauai. It causes death by integration into the mtDNA, creating an inserted form flanked by long symmetrical repeats of the mtDNA flanking one side of the insertion point. The plasmid can be transmitted horizontally through heterokaryosis or sexually via the maternal parent. Spread is potentially explosive and can be prevented by cell incompatibility or by suppressor mutations. The related plasmid LA-kalilo has been found in N. tetrasperma from Louisiana, USA. This is essentially the same as kalilo but shows a short deletion in the middle of each TIR. This plasmid has been found not to insert into mtDNA. In a related genus Gelasinospora, also from Louisiana, a relative called Gel-kalilo has been found. This plasmid shows many differences from kalilo, but is still obviously homologous over large regions. This plasmid also does not integrate into the mtDNA. Lack of integration can be due to structural differences or to host genome suppression. The plasmids have arrived in their present hosts by a combination of vertical descent from a common ancestor and horizontal asexual transmission.
KEYWORD	Mitochondria; mtDNA; Neurospora; Plasmid, Senescence;
ARTICLE INFO	Botanical Bulletin of Academia Sinica, Volume 39 Number 3 July 1998, page 147-152, 6 pages
PUBLISHER	Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan, Republic of China