Home » Uncategorized » Evolutionary dynamics of transposable elements in a small RNA world

Evolutionary dynamics of transposable elements in a small RNA world





Figure 2. Evolutionary games in the germline. (a) In D. melanogaster, fifteen nurse cells contribute maternal resources to the developing egg, but are fated for apoptosis. (b) In A. thaliana, multiple haploid nuclei contribute to the female gametophyte, but only the egg cell passes genetic material to the next generation. In both plants and animals, flanking somatic tissues also promote gametogenesis but are excluded from subsequent generations. In D.melanogaster (a) piRNAs are derived from somatic cells and in nurse cells within a structure called the nuage. An ancestral gene duplication has yielded specialization of the piRNA machinery within the developing egg chamber. piRNAs produced by Aubergine function solely within the germline where as piRNAs produced by Piwi function in somatic follicle cells as well. These somatic piRNAs are specialized to defend against retrovirus-like TEs that proliferate in the soma and spread into the germline. In flowering plants (b)multiple companion nuclei including somatic nuclei, nuclei fated to the endosperm and nuclei within the pollen tube also contribute TE-derived siRNAs. Red arrows indicate the potential paths of TE evolutionary escape from tissues that will not enter the next generation toward those tissues that do. AC, antipodal cells; NC, nurse cells; PN, polar nuclei; PTN, pollen tube nucleus; SC, synergid cells; SN, somatic nucleus; Sperm.E, sperm fertilizing the central cell, thus establishing the endoderm. 


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