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951.
Contribution of Mutation and RNA Recombination to the Evolution of a Plant Pathogenic RNA 总被引:10,自引:0,他引:10
Miguel A. Aranda Aurora Fraile Joaquín Dopazo José M. Malpica Fernando García-Arenal 《Journal of molecular evolution》1997,44(1):81-88
The nucleotide sequence of 17 variants of the satellite RNA of cucumber mosaic virus (CMV-satRNA) isolated from field-infected
tomato plants in the springs of 1989, 1990, and 1991 was determined. The sequence of each of the 17 satRNAs was unique and
was between 334 and 340 nucleotides in length; 57 positions were polymorphic. There was much genetic divergence, ranging from
0.006 to 0.141 nucleotide substitutions per site for pairwise comparisons, and averaging 0.074 for any pair. When the polymorphic
positions were analyzed relative to a secondary structure model proposed for CMV-satRNAs, it was found that there were significantly
different numbers of changes in base-paired and non–base-paired positions, and that mutations that did not disrupt base pairing
were preferred at the putatively paired sites. This supports the concept that the need to maintain a functional structure
may limit genetic divergence of CMV-satRNA. Phylogenetic analyses showed that the 17 CMV-satRNA variants clustered into two
subgroups, I and II, and evolutionary lines proceeding by the sequential accumulation of mutations were apparent. Three satRNA
variants were outliers for these two phylogenetic groups. They were shown to be recombinants of subgroup I and II satRNAs
by calculating phylogenies for different molecular regions and by using Sawyer's test for gene conversion. At least two recombination
events were required to produce these three recombinant satRNAs. Thus, recombinants were found to be frequent (∼17%) in natural
populations of CMV-satRNA, and recombination may make an important contribution to the generation of new variants. To our
knowledge this is the first report of data allowing the frequency of recombinant isolates in natural populations of an RNA
replicon to be estimated.
Received: 14 May 1996 / Accepted: 17 July 1996 相似文献
952.
Maria Manuela M. Caniça Chang Y. Lu Rajagopal Krishnamoorthy Gérard C. Paul 《Journal of molecular evolution》1997,44(1):57-65
The molecular diversity of inhibitor-resistant TEM (IRT) enzymes was explored using a strategy which involved DNA amplification
by polymerase chain reaction (PCR), analysis of restriction fragment length polymorphism (RFLP), and direct nucleotide sequencing.
The study of plasmid-borne genes from 27 strains, resistant to amoxicillin and β-lactamase-inhibitor combinations, identified
mutations resulting in amino acid change at positions 69, 244, 275, and 276 known to be associated with the IRT phenotype
and a mutation at nucleotide position 162 in the promoter region. These mutations were found to lie on two different gene
sequences, described here as ``TEM-1B like' and ``TEM-2 like' restriction linkage groups. Further analysis, of nucleotide
sequences of promoter and coding regions of the β-lactamases, confirmed that a given mutation causing IRT phenotype could
be associated with two different gene sequence frameworks and two different causal mutations could lie on identical gene sequence
framework. These data argue in favor of convergent phenotypic evolution of IRT enzymes under the selective pressure imposed
by the intensive clinical use of β-lactam–β-lactamase inhibitor combinations.
Received: 18 March 1996 / Accepted: 15 July 1996 相似文献
953.
Juan Cabezas-Herrera María Teresa Moral-Naranjo F. Javier Campoy Cecilio J. Vidal 《Journal of neurochemistry》1997,69(5):1964-1974
Abstract: The distribution and glycosylation of acetylcholinesterase (AChE) forms in vesicles derived from sarcoplasmic reticulum of normal muscle (NMV) were investigated and compared with those from dystrophic muscle vesicles (DMV). AChE activity was similar in NMV and DMV. Most of the AChE in NMV and half in DMV were released with Triton X-100. Asymmetric (A12 ) and globular hydrophilic and amphiphilic (GH 4 , GA 4 , GA 2 , and GA 1 ) AChE species occurred in NMV and DMV, the lighter forms being predominant. The percentage of GH 4 and GA 4 decreased in DMV. A fraction of the AChE that could not be extracted with detergent was detached with collagenase. Most of the detergent-released A12 AChE from NMV and nearly half in DMV failed to bind to Ricinus communis agglutinin (RCA-I). Conversely, the collagenase-detached isoforms bound to RCA, revealing that asymmetric AChE associated with internal membranes or basal lamina differed in glycosylation. Moreover, nearly half of GA 4 AChE in DMV and a few in NMV bound to RCA. Most of the RCA-unreactive GA 4 forms in NMV come from sarcolemma. The results indicate that dystrophy induces minor changes in the distribution and glycosylation of AChE forms in internal membranes of muscle. 相似文献
954.
955.
956.
Consuelo Díaz de la Guardia Roberto Alonso Francisca Alba Francisco Valle 《Aerobiologia》1995,11(1):47-50
We have carried out a study on the annual and daily pollen concentrations from Gramineae over four consecutive years in the atmosphere of Granada (Spain). Samples of pollen grains were collected by the volumetric method with the aid of a Burkard sporetrap. Gramineae, according both to their high sensitizing capacity and to data from allergologists, are responsible for many pollinoses diagnosed in this area. In this work, daily pollen levels from April to July are monitored and the variations identified are interpreted in relation to meteorological conditions. Results indicated that the highest airborne concentrations of Gramineae pollen were found in May and June, although the beginning and intensity of pollination have been variable during these 4 years. 相似文献
957.
Summary A protocol for obtaining regenerated fertile plants from mesophyll protoplasts of three lines of Matthiola incana is described. Protoplasts were isolated from leaves of 21–28 days old Matthiola plants grown in controlled environment. Sustained divisions were achieved when protoplasts were embedded in sodium alginate. Up to 2.0 % of the protoplasts developed into colonies which could be transferred to shoot regeneration media. More than 25 % of the obtained calluses regenerated shoots. About 4 % of these shoots could be rooted and after transfer to soil phenotypically normal plants have been obtained.Abbreviations 2,4-D
2,4-dichlorphenoxyacetic acid
- NAA
naphthalene acetic acid
- IAA
indole-3-acetic acid
- BAP
6-banzylaminopurine
- IPA
isopentenyladenine
- IPAR
isopentenyladenosine
- MES
(2-[N-morpholino]) ethanesulfonic acid 相似文献
958.
Maira Oropeza Palmira Guevara Eva de García José Luis Ramírez 《Plant Molecular Biology Reporter》1995,13(2):182-191
Somaclonal variants resistant to sugarcane mosaic virus (SCMV) were obtained from susceptible sugarcane cv PR62258 through
somatic embryogenesis by increasing the number of subcultures of the embryogenic callus tissue in MS medium with 3 mg/L 2,4-dichlorophenoxyacetic
acid. Transfers were made at 30-day intervals for 1, 2 or 3 subcultures. Two somaclones, namely AT626 and BT627, were selected
by their resistance to SCMV. These subclones have maintained the resistance trait over seven years of testing in the field.
In this report we identified the somaclonal SCMV resistant variants from the maternal line and the nonresistant somaclones,
using the RAPD technique. 相似文献
959.
The distribution of noradrenaline and adrenaline in the brain of the urodele amphibian Pleurodeles waltlii has been studied with antibodies raised against noradrenaline and the enzymes dopamine--hydroxylase and phenylethanolamine-N-methyltransferase. Noradrenaline-containing cell bodies were found in the anterior preoptic area, the hypothalamic nucleus of the periventricular organ, the locus coeruleus and in the solitary tract/area postrema complex at the level of the obex. Noradrenergic fibers are widely distributed throughout the brain innervating particularly the ventrolateral forebrain, the medial amygdala, the lateral part of the posterior tubercle, the parabrachial region and the ventrolateral rhombencephalic tegmentum. Putative adrenergic cell bodies were found immediately rostral to the obex, ventral to the solitary tract. Whereas the cell bodies and their dendrites were Golgi-like stained, axons were more difficult to trace. Nevertheless, some weakly immunoreactive fibers could be traced to the basal forebrain. A comparison of these results with data previously obtained in anurans reveals not only several general features, but also some remarkable species differences.Abbreviations
Acc
Nucleus accumbens
-
AP
area postrema
-
Apl
amygdala, pars lateralis
-
Apm
amygdala, pars medialis
-
ca
commissura anterior
-
Cb
cerebellum
-
cc
central canal
-
Dp
dorsal pallium
-
epl
external plexiform layer
-
gl
glomerular layer of the olfactory bulb
-
H
ganglion habenulae
-
igl
internal granular layer
-
Ip
nucleus interpeduncularis
-
Lc
locus coeruleus
-
Ll
lateral line lobe
-
Lp
lateral pallium
-
Ls
lateral septum
-
ml
mitral cell layer
-
Mp
medial pallium
-
Ms
medial septum
-
nPT
nucleus pretectalis
-
NPv
nucleus of the periventricular organ
-
nV
nervus trigeminus
-
oc
optic chiasm
-
Poa
preoptic area
-
Ri
nucleus reticularis inferior
-
SC
nucleus suprachiasmaticus
-
sol
solitary tract
-
Str
striatum
- thd
thalamus dorsalis
-
thv
thalamus ventralis
-
To
tectum opticum
-
TP
tuberculum posterius
-
V
ventricle
-
VH
ventral hypothalamic nucleus
-
III
nucleus nervi oculomotorii
-
IXm
nucleus motorius nervi glossopharyngei
-
Xm
nucleus motorius nervi vagi 相似文献
960.
G. Ramírez-Zarzosa F. Gil R. Latorre A. Ortega A. García-Alcaráz E. Abellán J. M. Vázquez O. López-Albors A. Arencibia F. Moreno 《Cell and tissue research》1995,280(2):217-224
Fibre-type differentiation of the lateral musculature has been studied in Sparus aurata (L.) and Dicentrarchus labrax (L.) during larval development. Histochemical and ultrastructural techniques show two presumptive muscle layers and two germinative zones of presumptive myoblasts. At hatching, myotomal muscle consists of a monolayer of thin undifferentiated cells near the skin (first germinative zone) overlying another mono-layer of small diameter fibres extending hypaxially and epaxially away from the transverse septum. Below this, there is a much thicker, deep layer of fibres, generally large in diameter and polygonal in shape. The presumptive myoblasts are located between these two layers of fibres in the second germinative zone. Initially, the superficial and deep muscle fibres show high and low myosin ATPase activity, respectively. Both layers grow by generating new fibres from the two mentioned germinative zones. At the end of larval life, the superficial layer changes its histochemical profile from high to low myosin ATPase activity and, at the same time, intermediate or pink muscle fibres can be observed by oxidative activity (the NADH-TR reaction). Morphometric analysis shows a significant increase in mean fibre diameter during successive ages, as shown by the Student's t-test (hypertrophic growth). Skewness and kurtosis values of fibre diameters point to the generation of a new fibre population from the germinative zones (hyperplastic growth). 相似文献