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BMC Evolutionary Biology

, 12:101

First Online: 26 June 2012Received: 07 September 2011Accepted: 06 June 2012DOI: 10.1186-1471-2148-12-101

Cite this article as: Alvarez-Venegas, R. & Avramova, Z. BMC Evol Biol 2012 12: 101. doi:10.1186-1471-2148-12-101

Abstract

BackgroundConserved domains are recognized as the building blocks of eukaryotic proteins. Domains showing a tendency to occur in diverse combinations ‘promiscuous’ domains are involved in versatile architectures in proteins with different functions. Current models, based on global-level analyses of domain combinations in multiple genomes, have suggested that the propensity of some domains to associate with other domains in high-level architectures increases with organismal complexity. Alternative models using domain-based phylogenetic trees propose that domains have become promiscuous independently in different lineages through convergent evolution and are, thus, random with no functional or structural preferences. Here we test whether complex protein architectures have occurred by accretion from simpler systems and whether the appearance of multidomain combinations parallels organismal complexity. As a model, we analyze the modular evolution of the PWWP domain and ask whether its appearance in combinations with other domains into multidomain architectures is linked with the occurrence of more complex life-forms. Whether high-level combinations of domains are conserved and transmitted as stable units cassettes through evolution is examined in the genomes of plant or metazoan species selected for their established position in the evolution of the respective lineages.

ResultsUsing the domain-tree approach, we analyze the evolutionary origins and distribution patterns of the promiscuous PWWP domain to understand the principles of its modular evolution and its existence in combination with other domains in higher-level protein architectures. We found that as a single module the PWWP domain occurs only in proteins with a limited, mainly, species-specific distribution. Earlier, it was suggested that domain promiscuity is a fast-changing volatile feature shaped by natural selection and that only a few domains retain their promiscuity status throughout evolution. In contrast, our data show that most of the multidomain PWWP combinations in extant multicellular organisms humans or land plants are present in their unicellular ancestral relatives suggesting they have been transmitted through evolution as conserved linear arrangements ‘cassettes’. Among the most interesting biologically relevant results is the finding that the genes of the two plant Trithorax family subgroups ATX1-2 and ATX3-4-5 have different phylogenetic origins. The two subgroups occur together in the earliest land plants Physcomitrella patens and Selaginella moellendorffii.

ConclusionGain-loss of a single PWWP domain is observed throughout evolution reflecting dynamic lineage- or species-specific events. In contrast, higher-level protein architectures involving the PWWP domain have survived as stable arrangements driven by evolutionary descent. The association of PWWP domains with the DNA methyltransferases in O. tauri and in the metazoan lineage seems to have occurred independently consistent with convergent evolution. Our results do not support models wherein more complex protein architectures involving the PWWP domain occur with the appearance of more evolutionarily advanced life forms.

Electronic supplementary materialThe online version of this article doi:10.1186-1471-2148-12-101 contains supplementary material, which is available to authorized users.

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Autor: Raúl Alvarez-Venegas - Zoya Avramova

Fuente: https://link.springer.com/







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