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The article offers information on the description of Sirenians and Cetaceans genome. Topics discussed Sirenians and cetaceans are unique among mammals for exhibiting a purely aquatic lifestyle, resulting in dramatic morphological, physiological, and behavioral changes; mentions that Cetacea contains 88 extant species, that divided into the 70 toothed whales, Odontoceti and the 18 baleen whales and highlights the Genome size to correlate with various cellular, morphological, developmental.

A promising recent development in molecular biology involves viewing the genome as a mini-ecosystem, where genetic elements are compared to organisms and the surrounding cellular and genomic structures are regarded as the local environment. Here, we critically evaluate the prospects of ecological neutral theory ( ENT), a popular model in ecology, as it applies at the genomic level. This assessment requires an overview of the controversy surrounding neutral models in community ecology. In particular, we discuss the limitations of using ENT both as an explanation of community dynamics and as a null hypothesis. We then analyse a case study in which ENT has been applied to genomic data. Our central finding is that genetic elements do not conform to the requirements of ENT once its assumptions and limitations are made explicit. We further compare this genome-level application of ENT to two other, more familiar approaches in genomics that rely on neutral mechanisms: Kimura's molecular neutral theory and Lynch's mutational-hazard model. Interestingly, this comparison reveals that there are two distinct concepts of neutrality associated with these models, which we dub 'fitness neutrality' and 'competitive neutrality'. This distinction helps to clarify the various roles for neutral models in genomics, for example in explaining the evolution of genome size. [ABSTRACT FROM AUTHOR]

Crustaceans are enormously diverse both phylogenetically and ecologically, but they remain substantially underrepresented in the existing genome size database. An expansion of this dataset could be facilitated if it were possible to obtain genome size estimates from ethanol-preserved specimens. In this study, two tests were performed in order to assess the reliability of genome size data generated using preserved material. First, the results of estimates based on flash-frozen versus ethanol-preserved material were compared across 37 species of crustaceans that differ widely in genome size. Second, a comparison was made of specimens from a single species that had been stored in ethanol for 1-14 years. In both cases, the use of gill tissue in Feulgen image analysis densitometry proved to be a very viable approach. This finding is of direct relevance to both new studies of field-collected crustaceans as well as potential studies based on existing collections. © 2014 International Society for Advancement of Cytometry [ABSTRACT FROM AUTHOR]

Experimental infections of Arabidopsis thaliana ( Arabidopsis) with genomically characterized plant pathogens such as Pseudomonas syringae have facilitated the dissection of canonical eukaryotic defence pathways and parasite virulence factors. Plants are also attacked by herbivorous insects, and the development of an ecologically relevant genetic model herbivore that feeds on Arabidopsis will enable the parallel dissection of host defence and reciprocal resistance pathways such as those involved in xenobiotic metabolism. An ideal candidate is Scaptomyza flava, a drosophilid fly whose leafmining larvae are true herbivores that can be found in nature feeding on Arabidopsis and other crucifers. Here, we describe the life cycle of S. flava on Arabidopsis and use multiple approaches to characterize the response of Arabidopsis to S. flava attack. Oviposition choice tests and growth performance assays on different Arabidopsis ecotypes, defence-related mutants, and hormone and chitin-treated plants revealed significant differences in host preference and variation in larval performance across Arabidopsis accessions. The jasmonate and glucosinolate pathways in Arabidopsis are important in mediating quantitative resistance against S. flava, and priming with jasmonate or chitin resulted in increased resistance. Expression of xenobiotic detoxification genes was reduced in S. flava larvae reared on Arabidopsis jasmonate signalling mutants and increased in plants pretreated with chitin. These results and future research directions are discussed in the context of developing a genetic model system to analyse insect-plant interactions. [ABSTRACT FROM AUTHOR]

Abstract It has long been known that polyploid organisms are more prevalent in arctic than in temperate environments. Past explanations for this geographical trend have focused on the role of glacial cycles in generating polyploids and the influence of abiotic factors in favouring polyploidy in the north. In combination, these mechanisms probably suffice to explain the observed geographical cline in ploidy levels in members of the Daphnia pulex complex in the Holarctic. While only diploid members of the D. pulex complex are found in the temperate regions of North America and Europe, allozyme and DNA quantification analyses indicate that the southern Argentine pulex -complex fauna is dominated by polyploids. Indeed, the present study is the first to document the presence of polyploid members of the D. pulex complex in any temperate climate. The results of phylogeographic analyses suggest that this difference in polyploid distribution between the northern and southern hemispheres is based more on ecological and historical contingencies than direct selection for polyploidy. Specifically, competition with diploid relatives probably limits the lower latitudinal range of polyploids in the north, but appears not to have occurred in Argentina. Because of these differences, the present study provides important insights into the diverse factors that determine the distributions and evolutionary fates of polyploid organisms. [ABSTRACT FROM AUTHOR]

Examines the debate surrounding the C-value enigma in the genome size diversity of organisms. Analysis of the theories for solving the C-value enigma; Discussion on the evidence in favor of a causal connection between DNA content and cell size; Discussion on the evolutionary implications of genome size diversity.

Experimental infections of Arabidopsis thaliana (Arabidopsis) with genomically characterized plant pathogens such as Pseudomonas syringae have facilitated the dissection of canonical eukaryotic defence pathways and parasite virulence factors. Plants are also attacked by herbivorous insects, and the development of an ecologically relevant genetic model herbivore that feeds on Arabidopsis will enable the parallel dissection of host defence and reciprocal resistance pathways such as those involved in xenobiotic metabolism. An ideal candidate is Scaptomyza flava, a drosophilid fly whose leafmining larvae are true herbivores that can be found in nature feeding on Arabidopsis and other crucifers. Here, we describe the life cycle of S. flava on Arabidopsis and use multiple approaches to characterize the response of Arabidopsis to S. flava attack. Oviposition choice tests and growth performance assays on different Arabidopsis ecotypes, defence-related mutants, and hormone and chitin-treated plants revealed significant differences in host preference and variation in larval performance across Arabidopsis accessions. The jasmonate and glucosinolate pathways in Arabidopsis are important in mediating quantitative resistance against S. flava, and priming with jasmonate or chitin resulted in increased resistance. Expression of xenobiotic detoxification genes was reduced in S. flava larvae reared on Arabidopsis jasmonate signalling mutants and increased in plants pretreated with chitin. These results and future research directions are discussed in the context of developing a genetic model system to analyse insect–plant interactions., Organismic and Evolutionary Biology