排序方式: 共有3条查询结果,搜索用时 78 毫秒
1
1.
Kalilo is a linear 9-kb plasmid, isolated originally from Hawaiian strains of the heterothallic fungus Neurospora intermedia. Its properties include terminal inverted repeats, two ORFs coding for a presumptive DNA and an RNA polymerase, and the ability
to cause senescence in its original host and in the closely related species Neurospora crassa. We have examined natural isolates alleged to contain plasmids homologous to kalilo. Most of these isolates do in fact contain
plasmids with so close an identity to kalilo as to be certain relatives. We found a new case of kalilo in Neurospora tetrasperma from Moorea-Tahiti, and a new case of LA-kalilo (previously found only in N. tetrasperma) in N. crassa from Haiti. A previously unreported, substantially shorter, kalilo variant has been found in three geographically separate
isolates of the heterothallic species Neurospora discreta. Therefore, if the previously reported kalilo variant from the genus Gelasinospora is included, in all there are four members of the kalilo plasmid family. The main differences between these plasmids are
in the terminal inverted repeats (TIRs). The phylogeny of the TIR sequences is largely congruent with that of nuclear DNA
in the species in which they are found, suggesting that the plasmids are related by vertical descent throughout the evolution
of these species. However, there are two cases of a plasmid found in a heterothallic and a pseudohomothallic species in the
same global area; these cases might have arisen from more recent horizontal transmission or introgression.
Received: 14 July / 17 September 1999 相似文献
2.
Monica Marcinko-Kuehn Xiao Yang Fons Debets David J. Jacobson Anthony J. F. Griffiths 《Current genetics》1994,26(4):336-343
Two Louisiana strains of Neurospora tetrasperma contain a linear plasmid (LA-kalDNA) with a restriction map identical to the Hawaiian Neurospora intermedia senescence plasmid, kalDNA, but with termini 100 nucleotide pairs shorter. One of these strains also bore a circular plasmid similar to the Hawaiian circular plasmid Hanalei-2. One species probably acquired both plasmids from the other by horizontal transfer, at a time sufficiently distant for sequence divergence to take place. Many LA-kalDNA-bearing derivative strains senesced, but this plasmid does not guarantee senescence. Furthermore, LA-kalDNA does not insert into mtDNA. One senescent strain showed no LA-kalDNA. The plasmids are effectively transmitted via the pseudohomothallic sexual cycle. Single mating-type derivatives transmit plasmids maternally. 相似文献
3.
There are four different variants of the kalilo “family” of linear mitochondrial plasmids. This family is found in several
heterothallic species and one pseudohomothallic species of Neurospora, as well as in one homothallic species of Gelasinospora. The mode of dispersal of these plasmids is not known. Horizontal transmission has proved difficult to demonstrate. Another
possibility is transfer by introgression, and this is modelled in the present paper. We have used introgression and subsequent
heterokaryosis to successfully transfer the LA-kalilo plasmid from a Haitian strain of Neurospora crassa to the standard Oak Ridge N. crassa background, the LA-kalilo plasmid from the pseudohomothallic Neurospora tetrasperma to N. crassa, and the kalilo plasmid from N. crassa to N. tetrasperma. Thus, introgression is shown to be a possible avenue of dispersal between species. The recipient strains were all senescent
but the mechanism of this senescence is not known. It could be caused by the plasmids, but if so the mechanism is novel since
plasmid/mtDNA junction fragments of the type found in the standard mode of mtDNA insertion could not be detected. However,
mtDNA changes were observed in the senescent recipients.
Received: 15 February / 24 June 1999 相似文献
1