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991.
992.
Aleksandr Gavrin Brent N. Kaiser Dietmar Geiger Stephen D. Tyerman Zhengyu Wen Ton Bisseling Elena E. Fedorova 《The Plant cell》2014,26(9):3809-3822
In legume–rhizobia symbioses, the bacteria in infected cells are enclosed in a plant membrane, forming organelle-like compartments called symbiosomes. Symbiosomes remain as individual units and avoid fusion with lytic vacuoles of host cells. We observed changes in the vacuole volume of infected cells and thus hypothesized that microsymbionts may cause modifications in vacuole formation or function. To examine this, we quantified the volumes and surface areas of plant cells, vacuoles, and symbiosomes in root nodules of Medicago truncatula and analyzed the expression and localization of VPS11 and VPS39, members of the HOPS vacuole-tethering complex. During the maturation of symbiosomes to become N2-fixing organelles, a developmental switch occurs and changes in vacuole features are induced. For example, we found that expression of VPS11 and VPS39 in infected cells is suppressed and host cell vacuoles contract, permitting the expansion of symbiosomes. Trafficking of tonoplast-targeted proteins in infected symbiotic cells is also altered, as shown by retargeting of the aquaporin TIP1g from the tonoplast membrane to the symbiosome membrane. This retargeting appears to be essential for the maturation of symbiosomes. We propose that these alterations in the function of the vacuole are key events in the adaptation of the plant cell to host intracellular symbiotic bacteria. 相似文献
993.
Joelle C. Y. Lai Brent P. Thoma Paul F. Clark Darryl L. Felder Peter K. L. Ng 《Zoologica scripta》2014,43(1):52-64
The evolutionary relationships of the brachyuran crab superfamily Eriphioidea, commonly known as stone or rubble crabs, are examined. Analysis of three mitochondrial (12S, 16S and COI) and two nuclear loci (18S and Histone 3) was carried out for 51 taxa representing the Carpilioidea, Dairoidea, Eriphioidea, Goneplacoidea, Parthenopoidea, Pilumnoidea, Portunoidea, Pseudozioidea and Xanthoidea. Phylogenetic analyses of molecular data used three methods of inference that recovered similar topologies with minor differences. Maximum parsimony analysis of 20 morphological characters taken from first zoeas of 11 species yielded two equally parsimonious trees and generally supported the molecular analyses. None of the analyses recovered Eriphioidea as monophyletic, and each of the eriphioid families represented by two or more taxa was shown to be polyphyletic in both molecular and larval analyses. This study indicates that the present classification based on adult morphology is incongruent with phylogenetic relationships and that the diagnostic characters the result of convergence (particularly in feeding morphology) rather than shared ancestry. 相似文献
994.
Ian R. Bradbury Sophie Hubert Brent Higgins Tudor Borza Sharen Bowman Ian G. Paterson Paul V. R. Snelgrove Corey J. Morris Robert S. Gregory David C. Hardie Jeffrey A. Hutchings Daniel E. Ruzzante Chris T. Taggart Paul Bentzen 《Proceedings. Biological sciences / The Royal Society》2010,277(1701):3725-3734
Despite the enormous economic and ecological importance of marine organisms, the spatial scales of adaptation and biocomplexity remain largely unknown. Yet, the preservation of local stocks that possess adaptive diversity is critical to the long-term maintenance of productive stable fisheries and ecosystems. Here, we document genomic evidence of range-wide adaptive differentiation in a broadcast spawning marine fish, Atlantic cod (Gadus morhua), using a genome survey of single nucleotide polymorphisms. Of 1641 gene-associated polymorphisms examined, 70 (4.2%) tested positive for signatures of selection using a Bayesian approach. We identify a subset of these loci (n = 40) for which allele frequencies show parallel temperature-associated clines (p < 0.001, r2 = 0.89) in the eastern and western north Atlantic. Temperature associations were robust to the statistical removal of geographic distance or latitude effects, and contrasted ‘neutral’ loci, which displayed no temperature association. Allele frequencies at temperature-associated loci were significantly correlated, spanned three linkage groups and several were successfully annotated supporting the involvement of multiple independent genes. Our results are consistent with the evolution and/or selective sweep of multiple genes in response to ocean temperature, and support the possibility of a new conservation paradigm for non-model marine organisms based on genomic approaches to resolving functional and adaptive diversity. 相似文献
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Walter R. Hoeh Donald T. Stewart Brent W. Sutherland Eleftherios Zouros 《Evolution; international journal of organic evolution》1996,50(6):2276-2286
Previous studies have shown that marine mussels (genus Mytilus) and a freshwater mussel (Pyganodon grandis) contain two distinct gender-associated mitotypes, which is a characteristic feature of the phenomenon of doubly uniparental inheritance (DUI) of mitochondrial DNA (mtDNA). Here we present evidence for the presence of distinct male (M) and female (F) mitotypes in three other bivalve species, the mytilid Geukensia demissa, and the unionid species P. fragilis and Fusconaia flava. Nucleotide sequences of a segment of the COI gene from the M and F mitotypes from each of the three mytilid species (M. edulis, M. trossulus, G. demissa) and three unionid species (P. grandis, P. fragilis, F. flava) were used for phylogenetic analysis. The analysis suggests three independent origins of M and F mitotypes for the six species examined; one for the three unionid species, one for the two Mytilus species, and one for Geukensia. The first of these F/M divergence events, while of uncertain age, predates the divergence of the two unionid genera and is likely older than either of the two F/M divergence events in the mytilid taxa. The most parsimonious explanation of multiple F/M divergence events is that they represent independent origins of DUI. Another possibility is that, in a given taxon, an F or M mitotype assumes the role of the opposite mitotype (by virtue of a mechanism that remains to be clarified) and subsequently was fixed within its new gender. The fixation of a mtDNA lineage derived from a mitotype of switched function would reset the divergence of the gender-associated lineages to zero, thereby mimicking a de novo split of F and M lineages from a preexisting mtDNA genome that was not gender specific. Further broad-scale taxonomic studies of the occurrence of distinct M and F mitotypes may allow for the evaluation of the latter hypothesis. 相似文献
1000.
John C. Docherty Bettie Sue Siler Masters Gay D. Firneisz Brent A. Schacter 《Biochemical and biophysical research communications》1982,105(3):1005-1013
The isomeric composition of biliverdin formed by the degradation of heme by purified NADPH-cytochrome reductase has been determined by high performance liquid chromatography. Methemalbumin heme yields a mixture of the four biliverdin IX isomers while myoglobin yields only the IX-α isomer of biliverdin. In both cases biliverdin is a minor product of the reaction. Addition of purified heme oxygenase to the methemalbumin NADPH-cytochrome reductase system confers α-selectivity on the reaction and allows stoichiometric conversion of heme to biliverdin. Thus the role of heme oxygenase in enzymatic heme degradation appears to be to provide a suitable environment for quantitative conversion of heme to biliverdin in addition to conferring α-selectivity on the reaction. 相似文献