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Selection for replicases in protocells.

Bianconi G, Zhao K, Chen IA, Nowak MA - PLoS Comput. Biol. (2013)

Bottom Line: In a well-mixed medium, natural selection would not favor such replicases because their presence equally benefits sequences with or without replicase activity.Here we show that protocells can select for replicases.We calculate the error threshold that is compatible with selecting for replicases.

View Article: PubMed Central - PubMed

Affiliation: School of Mathematical Sciences, Queen Mary University of London, London, United Kingdom.

ABSTRACT
We consider a world of nucleotide sequences and protocells. The sequences have the property of spontaneous self-replication. Some sequences - so-called replicases - have enzymatic activity in the sense of enhancing the replication rate of all (or almost all) sequences. In a well-mixed medium, natural selection would not favor such replicases because their presence equally benefits sequences with or without replicase activity. Here we show that protocells can select for replicases. We assume that sequences replicate within protocells and that protocells undergo spontaneous division. This leads to particular population structures which can augment the abundance of replicases. We explore various assumptions regarding replicase activity and protocell division. We calculate the error threshold that is compatible with selecting for replicases.

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Error threshold for the four replicases under study.In the left panels the protocells of maximal size  divide into two daughter cells. In the right panels the protocells of maximal size  divide into many () daughter cells. Curves were generated by numerical simulation as described in the text.
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pcbi-1003051-g004: Error threshold for the four replicases under study.In the left panels the protocells of maximal size divide into two daughter cells. In the right panels the protocells of maximal size divide into many () daughter cells. Curves were generated by numerical simulation as described in the text.

Mentions: For replicase it is harder to select for sequences. The reason is that an sequence can only help other sequences to reproduce but not itself. Again we find an error threshold, but this time we do not obtain a simple closed form expression. We derive a numerical solution, which is shown in Figure 4. We observe that division into two daughter cells leads to less restrictive conditions (for given ) than division into many. In this case if protocells divide into many daughter cells, then each sequence starts off alone within a cell; here single sequences have no advantage over single sequences. On the other hand, if protocells divide into two, then for larger it is typically the case that each sequences is together with other sequences after cell division and immediately benefits from the enzymatic activity.


Selection for replicases in protocells.

Bianconi G, Zhao K, Chen IA, Nowak MA - PLoS Comput. Biol. (2013)

Error threshold for the four replicases under study.In the left panels the protocells of maximal size  divide into two daughter cells. In the right panels the protocells of maximal size  divide into many () daughter cells. Curves were generated by numerical simulation as described in the text.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3649988&req=5

pcbi-1003051-g004: Error threshold for the four replicases under study.In the left panels the protocells of maximal size divide into two daughter cells. In the right panels the protocells of maximal size divide into many () daughter cells. Curves were generated by numerical simulation as described in the text.
Mentions: For replicase it is harder to select for sequences. The reason is that an sequence can only help other sequences to reproduce but not itself. Again we find an error threshold, but this time we do not obtain a simple closed form expression. We derive a numerical solution, which is shown in Figure 4. We observe that division into two daughter cells leads to less restrictive conditions (for given ) than division into many. In this case if protocells divide into many daughter cells, then each sequence starts off alone within a cell; here single sequences have no advantage over single sequences. On the other hand, if protocells divide into two, then for larger it is typically the case that each sequences is together with other sequences after cell division and immediately benefits from the enzymatic activity.

Bottom Line: In a well-mixed medium, natural selection would not favor such replicases because their presence equally benefits sequences with or without replicase activity.Here we show that protocells can select for replicases.We calculate the error threshold that is compatible with selecting for replicases.

View Article: PubMed Central - PubMed

Affiliation: School of Mathematical Sciences, Queen Mary University of London, London, United Kingdom.

ABSTRACT
We consider a world of nucleotide sequences and protocells. The sequences have the property of spontaneous self-replication. Some sequences - so-called replicases - have enzymatic activity in the sense of enhancing the replication rate of all (or almost all) sequences. In a well-mixed medium, natural selection would not favor such replicases because their presence equally benefits sequences with or without replicase activity. Here we show that protocells can select for replicases. We assume that sequences replicate within protocells and that protocells undergo spontaneous division. This leads to particular population structures which can augment the abundance of replicases. We explore various assumptions regarding replicase activity and protocell division. We calculate the error threshold that is compatible with selecting for replicases.

Show MeSH