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101.
Variation in rates of molecular evolution now appears to be widespread. The
demonstration that body size is correlated with rates of molecular
evolution suggests that physiological and ecological factors may be
involved in molecular rate variation, but large-scale comparative studies
are still lacking. Here, we use complete cytochrome b sequences from 85
species of tube-nosed seabirds (order Procellariiformes) and 5 outgroup
species of penguins (order Sphenisciformes) to test for an association
between body mass and rates of molecular evolution within the former avian
order. Cladistic analysis of the 90 sequences estimates a phylogeny largely
consistent with the traditional taxonomy of the Procellariiformes. The
Diomedeidae, Procellariidae, and Pelecanoididae are monophyletic, while the
Hydrobatidae are basal and paraphyletic. However, the two subfamilies
within the Hydrobatidae (Hydrobatinae and Oceanitinae) are monophyletic. A
likelihood ratio test detects significant deviation from clocklike
evolution in our data. Using a sign test for an association between body
mass and branch length in the seabird phylogeny, we find that larger taxa
tend to have shorter terminal branch lengths than smaller taxa. This
observation suggests that rates of mitochondrial DNA evolution are slower
for larger taxa. Rate calibrations based on the fossil record reveal
concordant body size effects. We interpret these results as evidence for a
metabolic rate effect, as the species in this order exhibit large
differences in metabolic rates, which are known to be highly correlated
with body mass in this group. Our results support previous findings of body
size effects and show that this effect can be significant even within a
single avian order. This suggests that even lineage-specific molecular
clocks may not be tenable if calibrations involve taxa with different
metabolic rates.
相似文献
102.
103.
Molecular evolution of chloroplast DNA sequences 总被引:13,自引:1,他引:12
Comparative data on the evolution of chloroplast genes are reviewed. The
chloroplast genome has maintained a similar structural organization over
most plant taxa so far examined. Comparisons of nucleotide sequence
divergence among chloroplast genes reveals marked similarity across the
plant kingdom and beyond to the cyanobacteria (blue-green algae). Estimates
of rates of nucleotide substitution indicate a synonymous rate of 1.1 x
10(-9) substitutions per site per year. Noncoding regions also appear to be
constrained in their evolution, although addition/deletion events are
common. There have also been evolutionary changes in the distribution of
introns in chloroplast encoded genes. Relative to mammalian mitochondrial
DNA, the chloroplast genome evolves at a conservative rate.
相似文献
104.
Improvement of high‐resolution fluorescence in situ hybridisation mapping on chromosomes of Brassica oleracea var. capitata
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K. Yang Y. Zhang R. Converse J. Lv M. Shi H. Zhang L. Zhu 《Plant biology (Stuttgart, Germany)》2016,18(2):325-331
The low resolution of chromosome‐based Fluorescence in situ hybridisation (FISH) mapping is primarily due to the structure of the plant cell wall and cytoplasm and the compactness of regular chromosomes, which represent a significant obstacle to FISH. In order to improve spatial resolution and signal detection sensitivity, we provide a reproducible method to generate high‐quality extended chromosomes that are ~13 times as long as their pachytene counterparts. We demonstrate that proteinase K used in this procedure is crucial for stretching pachytene chromosomes of Brassica oleracea in the context of a modified Carnoy's II fixative (6:1:3, ethanol:chloroform:acetic acid). The quality of super‐stretched chromosomes was assessed in several FISH experiments. FISH signals from both repetitive 5S rDNA and single‐copy ARC1 on super‐stretched chromosomes are brighter than those on other different types of chromosome due to enhanced accessibility to targets on stretched pachytene chromosomes. In conclusion, the resulting extended chromosomes are suitable for FISH mapping for repetitive DNA sequences and the localisation of a single‐copy locus, and FISH performed on super‐stretched chromosomes can achieve significantly higher sensitivity and spatial resolution than other chromosome‐based FISH mapping techniques. 相似文献
105.
People can eat a food without having a strong preference for it, and people can prefer a food without eating it. Given this seeming disconnect between attitude and behavior, which type of measure or segment can best be used to profile or identify loyal consumer segments of a food, such as soy? This research compares a usage‐based method (heavy‐light‐nonusers) with a new attitude‐based method (seeker‐neutral‐avoider), and finds that the attitude‐based method differentiates purchase‐related intentions better than the usage‐based method. Implications for profiling consumer taste patterns and consumer segments are provided. 相似文献
106.
A. Laperche Y. Aigu M. Jubault M. Ollier S. Guichard P. Glory SE. Strelkov A. Gravot MJ. Manzanares-Dauleux 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2017,130(4):669-684
Key message
Nitrogen levels can modulate the effectiveness of clubroot resistance in an isolate- and host-specific manner. While the same QTL were detected under high and low nitrogen, their effects were altered.Abstract
Clubroot, caused by Plasmodiophora brassicae, is one of the most damaging diseases of oilseed rape and is known to be affected by nitrogen fertilization. However, the genetic factors involved in clubroot resistance have not been characterized under nitrogen-limiting conditions. This study aimed to assess the variability of clubroot resistance under different nitrogen levels and to characterize the impact of nitrogen supply on genetic resistance factors. Linkage analyses and a genome-wide association study were conducted to detect QTL for clubroot resistance and evaluate their sensitivity to nitrogen. The clubroot response of a set of 92 diverse oilseed rape accessions and 108 lines derived from a cross between ‘Darmor-bzh’ (resistant) and ‘Yudal’ (susceptible) was studied in the greenhouse under high- and low-nitrogen conditions, following inoculation with the P. brassicae isolates eH and K92-16. Resistance to each isolate was controlled by a major QTL and a few small-effects QTL. While the same QTL were detected under both high and low nitrogen, their effects were altered. Clubroot resistance to isolate eH, but not K92-16, was greater under a low-N supply versus a high-N supply. New sources of resistance were found among the oilseed rape accessions under both low and high-N conditions. The results are discussed relative to the literature and from a crop improvement perspective.107.
The one-on-one bioassay was developed using Steinernema carpocapsae (All) nematodes against the wax moth larva, Galleria mellonella. The assay was used to develop and compare virulence profiles of both in vitro- and in vivo-produced nematodes and to provide a quality assessment 'standard' for in vitro-produced nematodes. The bioassay was subsequently used to develop virulence profiles for Steinernema carpocapsae (UK), S. feltiae (UK), S. feltiae (R1.5), S. feltiae (SN), S. glaseri (NJ-43), and S. riobrave (RGV). These profiles are unique for each species and isolate and are used as a standard of virulence in routine quality assessment of nematodes produced in liquid fermentation. 相似文献
108.
Simulation of a cross-flow shrinking-bed reactor for the hydrolysis of lignocellulosics. 总被引:1,自引:0,他引:1
A O Converse 《Bioresource technology》2002,81(2):109-116
An idealized model is developed for the case in which biomass slurry is conveyed through an annulus, with water or steam entering through an inner porous wall and liquid product leaving through an outer porous wall. It is assumed that the ratio of occluded liquid to solid in the slurry is a constant, Rws, and that non-occluded water is immediately removed from the reactor. The goal of > 90% sugar yield with > 10% sugar in the product is almost reached (88% glucose yield, 91% xylose yield, 47 g/l glucose and 45 g/l xylose) at 240 degrees C, 1% acid. Rws = 1 and a radial wash water flow of three times the initial mass flow of solids to the reactor per meter of reactor length per g/l of sugar concentration in the occluded water. If Rws is limited to 3, the yield falls to 85% and the total sugar concentration to 61 g/l. Even without cross-flow wash, the yields can be increased by about 16 percentage points, compared to plug flow, by extracting excess liquid through the outer wall as it is formed. At 200 degrees C, where one might prefer to operate for ease of control and concern about the possibility of making fermentation inhibitors at higher temperatures, the maximum glucose yield in a plug-flow reactor is low (12-13%) whereas in a cross-flow reactor, at a high cross-flow wash rate, it can still be quite high (60-83%) but at a very low concentration (0.57-1.47%). In these simulations it is assumed that one-half of the inerts is solubilized. The formation of oligomers is neglected. 相似文献
109.
MARIA-MARCELA POVEDA MARIE-CLAUDE SOUQUAL MARIE-THÉRÈSE FAUVEL JACQUES GAMISANS THIERRY GAUQUELIN 《Botanical journal of the Linnean Society. Linnean Society of London》2002,140(2):165-168
The cuticular wax composition of leaves has been analysed in three western European populations (Corsica, central Pyrenees, northern Alps) of Juniperus communis var. saxatilis Pall. (= J. nana Willd., nom illeg.) and in one population of J. communis L. var. depressa Pursh. from North America (Sierra Nevada). Gas chromatography shows the presence of 13 alkanes in all samples ranging from C23 to C35 with important intraspecific polymorphism in alkane content. The dominant alkanes range from C33 to C35 . Alkanes C21 and C22 were found only in Corsica and Sierra Nevada populations. Canonical discriminant analysis separated the J. communis L. var. depressa Pursh. of the population of Sierra Nevada from other populations of J. communis var. saxatilis Pall. on the basis of their higher C31 content and the constant presence of C21 and C22 alkanes. J. communis var. saxatilis Pall. populations from the Pyrenees are close to northern Alps populations characterized by high concentrations of C33 , C34 and C35 alkanes. This paper confirms the existence of Juniperus var. saxatilis Pall. in the Pyrenees (France). © The Linnean Society of London, Botanical Journal of the Linnean Society , 2002, 140 , 165–168. 相似文献
110.
Fourteen native strains of Trichoderma spp. from wildand agricultural pathosystems in the state of Yucatan, Mexico, with growth-promoting ability of Capsicum chinense Jacq. seedlings were evaluated and antagonistic effect of their filtrate against second-stage juveniles (J2) of Meloidogyne incognita. The strains Th05-02 and Th27-08 showed the best significant effects on plant hight variable increments 55.57 and 47.62%, theTh07-04 with 29.48% more root length, theTh02-01 and Th07-04 isolates increased from 48.71 to 84.61% in volume radical and 53.40% of total dry biomass. Statistical analysis (p≤0.001) of Th43 and Th43-13-14 filtrates caused 100% mortality at 24 and 48h. In the test of reversibility to 24 h after replacing the filtrates Th43-13, Th43-14, TH09-06 and TH20-07 by sterile distilled water, the J2 did not recover their viability, so they were considered as the best potential strains of Trichoderma spp. with antagonistic capacity in J2 of M.incognita. 相似文献