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991.
Lanfermeijer FC Dijkhuis J Sturre MJ de Haan P Hille J 《Plant molecular biology》2003,52(5):1039-1051
In tomato, infections by tomato mosaic virus are controlled by durable Tm-22 resistance. In order to gain insight into the processes underlying disease resistance and its durability, we cloned and analysed the Tm-22 resistance gene and the susceptible allele, tm-2. The Tm-22 gene was isolated by transposon tagging using a screen in which plants with a destroyed Tm-22 gene survive. The Tm-22 locus consists of a single gene that encodes an 861 amino acid polypeptide, which belongs to the CC-NBS-LRR class of resistance proteins. The putative tm-2 allele was cloned from susceptible tomato lines via PCR with primers based on the Tm-22 sequence. Interestingly, the tm-2 gene has an open reading frame that is comparable to the Tm-22 allele. Between the tm-2 and the Tm-22 polypeptide 38 amino acid differences are present of which 26 are located in the second half of the LRR-domain. Susceptible tomato plants, which were transformed with the Tm-22 gene, displayed resistance against ToMV infection. In addition, virus specificity, displayed by the Tm-22 resistance was conserved in these transgenic lines. To explain the durability of this resistance, it is proposed that the Tm-22-encoded resistance is aimed at the Achilles' heel of the virus. 相似文献
992.
Background
Insertions and deletions of DNA segments (indels) are together with substitutions the major mutational processes that generate genetic variation. Here we focus on recent DNA insertions and deletions in protein coding regions of the human genome to investigate selective constraints on indels in protein evolution. 相似文献993.
Liu J Rumsey JW Das M Molnar P Gregory C Riedel L Hickman JJ 《In vitro cellular & developmental biology. Animal》2008,44(5-6):162-168
We are attempting to recreate a stretch reflex circuit on a patterned Bio-MEMS (bio-microelectromechanical systems) chip with deflecting micro-cantilevers. The first steps to recreate this system is to be able to grow individual components of the circuit (sensory neuron, motoneuron, skeletal muscle, and muscle spindle) on a patternable, synthetic substrate coating the MEMS device. Sensory neurons represent the afferent portion of the stretch reflex arc and also play a significant role in transmitting the signal from the muscle spindle to the spinal cord motoneurons. We have utilized a synthetic silane substrate N-1[3-(trimethoxysilyl) propyl) diethylenetriamine (DETA) on which to grow and pattern the cells. DETA forms a self-assembled monolayer on a variety of silicon substrates, including glass, and can be patterned using photolithography. In this paper, we have evaluated the growth of sensory neurons on this synthetic silane substrate. We have investigated the immunocytochemical and electrophysiological properties of the sensory neurons on DETA and compared the resultant properties with a biological control substrate (ornithine/laminin). Immunocytochemical studies revealed the survival and growth of all three subtypes of sensory neurons: trkA, trkB, and trkC on both surfaces. Furthermore, whole-cell patch clamp recordings were used to study the electrophysiological properties of the sensory neurons on the two surfaces. There were no significant differences in the electrical properties of the neurons grown on either surface. This is the first study analyzing the immunocytochemical and electrophysiological properties of sensory neurons grown long-term in a completely defined environment and on a nonbiological substrate. 相似文献
994.
Olendzenski L Liu L Zhaxybayeva O Murphey R Shin DG Gogarten JP 《Journal of molecular evolution》2000,51(6):587-599
Members of the Deinococcaceae (e.g., Thermus, Meiothermus, Deinococcus) contain A/V-ATPases typically found in Archaea or Eukaryotes which were probably acquired by horizontal gene transfer. Two methods were used to quantify the extent to which archaeal or eukaryotic genes have been acquired by this lineage. Screening of a Meiothermus ruber library with probes made against Thermoplasma acidophilum DNA yielded a number of clones which hybridized more strongly than background. One of these contained the prolyl tRNA synthetase (RS) gene. Phylogenetic analysis shows the M. ruber and D. radiodurans prolyl RS to be more closely related to archaeal and eukaryal forms of this gene than to the typical bacterial type. Using a bioinformatics approach, putative open reading frames (ORFs) from the prerelease version of the D. radiodurans genome were screened for genes more closely related to archaeal or eukaryotic genes. Putative ORFs were searched against representative genomes from each of the three domains using automated BLAST. ORFs showing the highest matches against archaeal and eukaryotic genes were collected and ranked. Among the top-ranked hits were the A/V-ATPase catalytic and noncatalytic subunits and the prolyl RS genes. Using phylogenetic methods, ORFs were analyzed and trees assessed for evidence of horizontal gene transfer. Of the 45 genes examined, 20 showed topologies in which D. radiodurans homologues clearly group with eukaryotic or archaeal homologues, and 17 additional trees were found to show probable evidence of horizontal gene transfer. Compared to the total number of ORFs in the genome, those that can be identified as having been acquired from Archaea or Eukaryotes are relatively few (approximately 1%), suggesting that interdomain transfer is rare. 相似文献
995.
Mona N. Högberg Róbert Blaško Lisbet Holm Bach Niles J. Hasselquist Gustaf Egnell Torgny Näsholm Peter Högberg 《Plant and Soil》2014,381(1-2):45-60
Background and aims
To find out how N-saturated forests can return to an N-limited state, we examined the recovery of biotic N sinks under decreasing N supply.Methods
. We studied a 40-year-old experiment in Pinus sylvestris forest, with control plots, N0, three N treatments, N1-N3, of which N3 was stopped after 20 years, allowing observation of recovery.Results
In N3, the N concentration in foliage was still slightly elevated, but the N uptake capacity of ectomycorrhizal (ECM) roots in N3 was no longer lower than in N0. Per area the amount of a biomarker for fungi, here mainly attributed ECM, was higher in N3 and N0 than in N1 and N2. Retention of labeled 15NH4 + by the soil was greater in the control (99 %) and N3 (86 %), than in N1 (45 %) and N2 (29 %); we ascribe these differences to biotic retention because cation exchange capacity did not vary. Gross N mineralisation and retention of N correlated, negatively and positively, respectively, with abundance of ECM fungal biomarker.Conclusions
. The results suggest a key role for ECM fungi in regulating the N cycle. We propose, in accordance with plant C allocation theory, that recovery is driven by increased tree below-ground C allocation to ECM roots and fungi. 相似文献996.
Karen Molyneux Barbra J. Starman Peter H. Byers Raymond Dalgleish 《Human genetics》1993,90(6):621-628
RNase A protection analysis was used in the search for the cause of a non-lethal osteogenesis imperfecta (OI) phenotype (Sillence type III). Cleavage of the hybrid formed between a normal 2(I) sequence and RNA isolated from the patient indicated the presence of a mismatch. The position of the mismatch was determined and the corresponding area of COL1A2 was amplified using the polymerase chain reaction. Sequencing of cloned amplified DNA revealed the deletion, which was not present in either parent, of the final three bases of exon 19 in one of the patient's two COL1A2 alleles. The deletion results in the loss of amino acid 255 (a valine encoded by the last codon of exon 19) of the triple helical region of half of the 2(I) collagen chains but does not disrupt the splicing of the heterogeneous nuclear RNA (hnRNA). This provides further evidence that OI type III may result from autosomal dominant mutations rather than only from autosomal recessive mutations as had previously been believed. 相似文献
997.
998.
Host load prediction using linear models 总被引:11,自引:0,他引:11
This paper evaluates linear models for predicting the Digital Unix fivesecond host load average from 1 to 30 seconds into the future. A detailed statistical study of a large number of long, fine grain load traces from a variety of real machines leads to consideration of the Box–Jenkins models (AR, MA, ARMA, ARIMA), and the ARFIMA models (due to selfsimilarity.) We also consider a simple windowedmean model. The computational requirements of these models span a wide range, making some more practical than others for incorporation into an online prediction system. We rigorously evaluate the predictive power of the models by running a large number of randomized testcases on the load traces and then datamining their results. The main conclusions are that load is consistently predictable to a very useful degree, and that the simple, practical models such as AR are sufficient for host load prediction. We recommend AR(16) models or better for host load prediction. We implement an online host load prediction system around the AR(16) model and evaluate its overhead, finding that it uses miniscule amounts of CPU time and network bandwidth. 相似文献
999.
Bencharit S Edwards CC Morton CL Howard-Williams EL Kuhn P Potter PM Redinbo MR 《Journal of molecular biology》2006,363(1):201-214
Human carboxylesterase 1 (hCE1) is a drug and endobiotic-processing serine hydrolase that exhibits relatively broad substrate specificity. It has been implicated in a variety of endogenous cholesterol metabolism pathways including the following apparently disparate reactions: cholesterol ester hydrolysis (CEH), fatty acyl Coenzyme A hydrolysis (FACoAH), acyl-Coenzyme A:cholesterol acyltransfer (ACAT), and fatty acyl ethyl ester synthesis (FAEES). The structural basis for the ability of hCE1 to perform these catalytic actions involving large substrates and products has remained unclear. Here we present four crystal structures of the hCE1 glycoprotein in complexes with the following endogenous substrates or substrate analogues: Coenzyme A, the fatty acid palmitate, and the bile acids cholate and taurocholate. While the active site of hCE1 was known to be promiscuous and capable of interacting with a variety of chemically distinct ligands, these structures reveal that the enzyme contains two additional ligand-binding sites and that each site also exhibits relatively non-specific ligand-binding properties. Using this multisite promiscuity, hCE1 appears structurally capable of assembling several catalytic events depending, apparently, on the physiological state of the cellular environment. These results expand our understanding of enzyme promiscuity and indicate that, in the case of hCE1, multiple non-specific sites are employed to perform distinct catalytic actions. 相似文献
1000.