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The recent transfer of a homing endonuclease gene.

ABSTRACT: The myxomycete Didymium iridis (isolate Panama 2) contains a mobile group I intron named Dir.S956-1 after position 956 in the nuclear small subunit (SSU) rRNA gene. The intron is efficiently spread through homing by the intron-encoded homing endonuclease I-DirI. Homing endonuclease genes (HEGs) usually spread with their associated introns as a unit, but infrequently also spread independent of introns (or inteins). Clear examples of HEG mobility are however sparse. Here, we provide evidence for the transfer of a HEG into a group I intron named Dir.S956-2 that is inserted into the SSU rDNA of the Costa Rica 8 isolate of D.iridis. Similarities between intron sequences that flank the HEG and rDNA sequences that flank the intron (the homing endonuclease recognition sequence) suggest that the HEG invaded the intron during the recent evolution in a homing-like event. Dir.S956-2 is inserted into the same SSU site as Dir.S956-1. Remarkably, the two group I introns encode distantly related splicing ribozymes with phylogenetically related HEGs inserted on the opposite strands of different peripheral loop regions. The HEGs are both interrupted by small spliceosomal introns that must be removed during RNA maturation.

SUBMITTER: Haugen P

PROVIDER: S-EPMC1110740 | biostudies-literature | 2005

REPOSITORIES: biostudies-literature

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The recent transfer of a homing endonuclease gene.

Haugen Peik P Wikmark Odd-Gunnar OG Vader Anna A Coucheron Dag H DH Sjøttem Eva E Johansen Steinar D SD

Nucleic acids research 20050512 8

The myxomycete Didymium iridis (isolate Panama 2) contains a mobile group I intron named Dir.S956-1 after position 956 in the nuclear small subunit (SSU) rRNA gene. The intron is efficiently spread through homing by the intron-encoded homing endonuclease I-DirI. Homing endonuclease genes (HEGs) usually spread with their associated introns as a unit, but infrequently also spread independent of introns (or inteins). Clear examples of HEG mobility are however sparse. Here, we provide evidence for t ...[more]

PMID: 15891115

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Project description:SummaryHoming endonuclease genes (HEGs) exist naturally in many single-celled organisms and can show extremely strong genetic drive allowing them to spread through populations into which they are introduced. They are being investigated as tools to manipulate the populations of important vectors of human disease, in particular the mosquitoes that transmit malaria. Before HEGs can be deployed, it is important to study their spatial spread in order to design efficient release strategies.A spatially explicit model is developed to study the spread of a HEG through a landscape whose structure is defined by the distribution of mosquito breeding and feeding sites. The model is motivated by the biology of the major vectors of malaria in Africa. The conditions for spread, fixation and loss of two major types of HEG are explored in different landscapes.In landscapes where mosquito resources are abundant, the conditions for spread are well approximated by a mean-field model. Where a HEG imposes a genetic load, it can cause population extinction, though spatial models more often predict population suppression.In certain types of landscapes where mosquito resources are rare, an introduced HEG may be prevented from moving between local mosquito populations and so a simple release strategy is unlikely to be effective, yet if the HEG succeeds in spreading population extinction is a feasible outcome. Increasing the number of release sites at the expense of releasing fewer mosquitoes per site reduces the probability that a HEG will fail.Synthesis and applications. The model presented asks for the first time how the spatial structure of mosquito populations will influence the effectiveness of a technology that is being rapidly developed for vector control. If homing endonuclease genes (HEGs) are to be used in this way, we have qualified the importance of accounting for landscape characteristics in both the execution and the expectation of their application. The next stage is to use the model to study the spread of HEGs through real landscapes where releases may take place, something that will be facilitated by the results of the present study.

Dataset Information

The recent transfer of a homing endonuclease gene.

Publications

The recent transfer of a homing endonuclease gene.

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