types of phylogenetic tissue
Answers
Abstract
Our understanding of tissue expression evolution in multi-cellular model organisms has been considerably advanced with the help of high-throughput technologies from EST, microarray to RNA-seq. Yet, many controversies remained unsolved, ranging from the evolutionary patterns of tissue expressions to expression phylogenetic analysis. Moreover, despite numerous reports published, it is desirable to have a general framework for study of tissue expression evolution. In this article, we first provide an up-to-date and concise review for the study of tissue expression evolution in multi-cellular organisms
Answer:
Our understanding of tissue expression evolution in multi-cellular model organisms has been considerably advanced with the help of high-throughput technologies from EST, microarray to RNA-seq. Yet, many controversies remained unsolved, ranging from the evolutionary patterns of tissue expressions to expression phylogenetic analysis. Moreover, despite numerous reports published, it is desirable to have a general framework for study of tissue expression evolution. In this article, we first provide an up-to-date and concise review for the study of tissue expression evolution in multi-cellular organisms. While the expression phylogeny of the same tissues sampled from closely or intermediately related species largely reflects the species phylogeny, we demonstrate that phylogenetic network approach may shed some lights for our understanding of the developmental similarity and evolutionary relatedness during the multi-tissue evolution.
Explanation:
As one of pioneer studies, Enard et al . [ 8 ] compared the transcriptome in blood leukocytes, liver and brain of humans, chimpanzees, orangutans and macaques using microarrays. Using a number of distance measures for the expression difference of the same tissue between organisms, they identified species-specific gene expression patterns, indicating a good correspondence between the expression distance and the relatedness of the species. Indeed, using the neighbor-joining method, the expression distances of the same tissue can largely reconstruct the known primate species phylogeny. Later, Khaitovich et al . [ 9 ] compared humans and chimpanzees with respect to differences in expression levels and protein-coding sequences for genes that are actively expressed in brain, heart, liver, kidney and testis, and found that the phylogenetic patterns of differences in gene expression and gene sequences are virtually similar.
Rifkin et al . [ 10 ] studied the variations in genome-wide gene expression among closely related species Drosophila simulans , Drosophila yakuba and four strains of Drosophila melanogaster during a major developmental transition at the start of metamorphosis. Based on microarray, they statistically predicted differentially expressed genes between species, and found that these differences in gene expression were consistent with the phylogenetic relationship based on biogeography and sequence data. For 27% of all of the genes in these genomes that differ in their developmental expression between at least two species, they investigated the evolutionary forces that may shape this variation. Overall, expression changes of transcription factor genes were relatively stable, whereas those of their downstream targets were more likely to have evolved.