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实时观测根瘤及根系形态对于豆科植物研究具有重要意义,但目前还缺乏一个便于观测根系、高效结瘤、适宜生长且经济实用的豆科植物培养体系。以蒺藜苜蓿(Medicago truncatula)为植物材料,建立了一种可实时观测根瘤及根系形态的纸袋水培法,并与其它常用方法进行对比。结果表明,依赖于石英砂等固体介质栽培蒺藜苜蓿对根瘤和根系形态的实时观测造成障碍,而水培和喷雾培养等方法的根瘤菌接种效率不高,且不便观测侧根发育情况。采用纸袋水培法探讨了褪黑素对蒺藜苜蓿根系发育的影响,发现褪黑素具有降低根瘤形成效率、抑制侧根伸长、增加侧根数目以及增大侧根与主根之间夹角等作用。因此,纸袋水培法能够高效接种根瘤菌且为实时无损伤观测根瘤及根系形态提供了可能,是一种适用于豆科植物简单有效的培养方法。  相似文献   
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Scorpion toxin Ctri9577, as a potent Kv1.3 channel blocker, is a new member of the α-KTx15 subfamily which are a group of blockers for Kv4.x potassium channels. However, the pharmacological function of Ctri9577 for Kv4.x channels remains unknown. Scorpion toxin Ctri9577 was found to effectively inhibit Kv4.3 channel currents with IC50 value of 1.34 ± 0.03 μM. Different from the mechanism of scorpion toxins as the blocker recognizing channel extracellular pore entryways, Ctri9577 was a novel gating modifier affecting voltage dependence of activation, steady-state inactivation, and the recovery process from the inactivation of Kv4.3 channel. However, Ctri9755, as a potent Kv1.3 channel blocker, was found not to affect voltage dependence of activation of Kv1.3 channel. Interestingly, pharmacological experiments indicated that 1 μM Ctri9755 showed less inhibition on Kv4.1 and Kv4.2 channel currents. Similar to the classical gating modifier of spider toxins, Ctri9577 was shown to interact with the linker between the transmembrane S3 and S4 helical domains through the mutagenesis experiments. To the best of our knowledge, Ctri9577 was the first gating modifier of potassium channels among scorpion toxin family, and the first scorpion toxin as both gating modifier and blocker for different potassium channels. These findings further highlighted the structural and functional diversity of scorpion toxins specific for the potassium channels.  相似文献   
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【目的】通过基因缺失和噬菌体溶原转换研究大肠杆菌运动相关基因flhDC、fliA、fliD和fliE对Stx2噬菌体ΦMin27溶原菌的影响。【方法】本实验利用Red重组酶系统,构建了大肠杆菌MG1655的缺失株MG1655△flhDC、MG1655△fliA、MG1655△fliD及MG1655△fliE,并将flhDC片段、fliA片段、fliD片段和fliE片段连接pUC18后分别转化相应的突变株,得到相应的互补菌株。通过Stx2噬菌体ΦMin27的感染获得各缺失株的溶原株MG1655△flhDCФMin27、MG1655△fliAФMin27、MG1655△fliDФMin27及MG1655△fliEФMin27。随后测定了野生株、缺失株、互补株和溶原株的运动能力,并通过荧光定量PCR分析了flhDC缺失前后野生株和溶原株其他运动相关基因表达量的变化。【结果】Stx2噬菌体ФMin27溶原感染可促进MG1655的fliA和fliD基因的表达,增强宿主菌MG1655的运动特性;MG1655在flhDC基因缺失的状态下,fliA和fliD基因的表达同步出现上调,但运动性未发生变化,而MG1655△flhDC溶原菌丧失了运动特性,基因转录水平检测发现MG1655△flhDCФMin27与MG1655△flhDC相比,fliA和fliD基因的表达同步出现显著下调,而对fliE基因的表达几乎没有影响。fliA、fliD和fliE单个基因的缺失对大肠杆菌MG1655和Stx2噬菌体ΦMin27溶原菌的运动性几乎没有影响。【结论】提示fliA和fliD基因共同参与了鞭毛运动的调控,flhDC基因可影响噬菌体溶原菌株的运动性,为进一步研究噬菌体溶原与宿主基因之间的相互调节作用提供理论依据。  相似文献   
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R E Lewis  L Cao  D Perregaux  M P Czech 《Biochemistry》1990,29(7):1807-1813
The ability of tumor-promoting phorbol diesters to inhibit both insulin receptor tyrosine kinase activity and its intracellular signaling correlates with the phosphorylation of the insulin receptor beta subunit on serine and threonine residues. In the present studies, mouse 3T3 fibroblasts transfected with a human insulin receptor cDNA and expressing greater than one million of these receptors per cell were labeled with [32P]phosphate and treated with or without 100 nM 4 beta-phorbol 12 beta-myristate 13 alpha-acetate (PMA). Phosphorylated insulin receptors were immunoprecipitated and digested with trypsin. Alternatively, insulin receptors affinity purified from human term placenta were phosphorylated by protein kinase C prior to trypsin digestion of the 32P-labeled beta subunit. Analysis of the tryptic phosphopeptides from both the in vivo and in vitro labeled receptors by reversed-phase HPLC and two-dimensional thin-layer separation revealed that PMA and protein kinase C enhanced the phosphorylation of a peptide with identical chromatographic properties. Partial hydrolysis and radiosequence analysis of the phosphopeptide derived from insulin receptor phosphorylated by protein kinase C indicated that the phosphorylation of this tryptic peptide occurred specifically on a threonine, three amino acids from the amino terminus of the tryptic fragment. Comparison of these data with the known, deduced receptor sequence suggested that the receptor-derived tryptic phosphopeptide might be Ile-Leu-Thr(P)-Leu-Pro-Arg. Comigration of a phosphorylated synthetic peptide containing this sequence with the receptor-derived phosphopeptide confirmed the identity of the tryptic fragment. The phosphorylation site corresponds to threonine 1336 in the human insulin receptor beta subunit.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
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Key message

Rice breeding programs based on pedigree schemes can use a genomic model trained with data from their working collection to predict performances of progenies produced through rapid generation advancement.

Abstract

So far, most potential applications of genomic prediction in plant improvement have been explored using cross validation approaches. This is the first empirical study to evaluate the accuracy of genomic prediction of the performances of progenies in a typical rice breeding program. Using a cross validation approach, we first analyzed the effects of marker selection and statistical methods on the accuracy of prediction of three different heritability traits in a reference population (RP) of 284 inbred accessions. Next, we investigated the size and the degree of relatedness with the progeny population (PP) of sub-sets of the RP that maximize the accuracy of prediction of phenotype across generations, i.e., for 97 F5–F7 lines derived from biparental crosses between 31 accessions of the RP. The extent of linkage disequilibrium was high (r 2 = 0.2 at 0.80 Mb in RP and at 1.1 Mb in PP). Consequently, average marker density above one per 22 kb did not improve the accuracy of predictions in the RP. The accuracy of progeny prediction varied greatly depending on the composition of the training set, the trait, LD and minor allele frequency. The highest accuracy achieved for each trait exceeded 0.50 and was only slightly below the accuracy achieved by cross validation in the RP. Our results thus show that relatively high accuracy (0.41–0.54) can be achieved using only a rather small share of the RP, most related to the PP, as the training set. The practical implications of these results for rice breeding programs are discussed.
  相似文献   
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