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RISS 인기검색어
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- 저자 : Turkewitz, Aaron P. (검색결과 1 건)
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Bright, Lydia J.,Kambesis, Nichole,Nelson, Scott Brent,Jeong, Byeongmoon,Turkewitz, Aaron P. Public Library of Science 2010 PLoS genetics Vol.6 No.10
<▼1><P>Cellular sophistication is not exclusive to multicellular organisms, and unicellular eukaryotes can resemble differentiated animal cells in their complex network of membrane-bound structures. These comparisons can be illuminated by genome-wide surveys of key gene families. We report a systematic analysis of Rabs in a complex unicellular Ciliate, including gene prediction and phylogenetic clustering, expression profiling based on public data, and Green Fluorescent Protein (GFP) tagging. Rabs are monomeric GTPases that regulate membrane traffic. Because Rabs act as compartment-specific determinants, the number of Rabs in an organism reflects intracellular complexity. The <I>Tetrahymena</I> Rab family is similar in size to that in humans and includes both expansions in conserved Rab clades as well as many divergent Rabs. Importantly, more than 90% of Rabs are expressed concurrently in growing cells, while only a small subset appears specialized for other conditions. By localizing most Rabs in living cells, we could assign the majority to specific compartments. These results validated most phylogenetic assignments, but also indicated that some sequence-conserved Rabs were co-opted for novel functions. Our survey uncovered a rare example of a nuclear Rab and substantiated the existence of a previously unrecognized core Rab clade in eukaryotes. Strikingly, several functionally conserved pathways or structures were found to be associated entirely with divergent Rabs. These pathways may have permitted rapid evolution of the associated Rabs or may have arisen independently in diverse lineages and then converged. Thus, characterizing entire gene families can provide insight into the evolutionary flexibility of fundamental cellular pathways.</P></▼1><▼2><P><B>Author Summary</B></P><P>Single-celled organisms appear simple compared to multicellular organisms, but this may not be true at the level of the individual cell. In fact, microscopic observations suggest that protists can possess networks of organelles just as elaborate as those in animal cells. Consistent with this idea, recent analysis has identified large families of genes in protists that are predicted to act as determinants for complex membrane networks. To test these predictions and to probe relationships between cellular structures across a wide swath of evolution, we focused on one gene family in the single-celled organism <I>Tetrahymena</I>. These genes control the traffic between organelles, with each gene controlling a single step in this traffic. We asked three questions about each of 56 genes in the family. First, what is the gene related to in humans? Second, under what conditions is the gene being used in <I>Tetrahymena</I>? Third, what is the role of each gene? The results provide insights into both the dynamics and evolution of membrane traffic, including the finding that some pathways appearing both structurally and functionally similar in protists and animals are likely to have arisen independently in the two lineages.</P></▼2>
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