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101.
Multifaceted plant responses to circumvent Phe hyperaccumulation by downregulation of flux through the shikimate pathway and by vacuolar Phe sequestration
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Joseph H. Lynch Irina Orlova Chengsong Zhao Longyun Guo Rohit Jaini Hiroshi Maeda Tariq Akhtar Junellie Cruz‐Lebron David Rhodes John Morgan Guillaume Pilot Eran Pichersky Natalia Dudareva 《The Plant journal : for cell and molecular biology》2017,92(5):939-950
Detrimental effects of hyperaccumulation of the aromatic amino acid phenylalanine (Phe) in animals, known as phenylketonuria, are mitigated by excretion of Phe derivatives; however, how plants endure Phe accumulating conditions in the absence of an excretion system is currently unknown. To achieve Phe hyperaccumulation in a plant system, we simultaneously decreased in petunia flowers expression of all three Phe ammonia lyase (PAL) isoforms that catalyze the non‐oxidative deamination of Phe to trans‐cinnamic acid, the committed step for the major pathway of Phe metabolism. A total decrease in PAL activity by 81–94% led to an 18‐fold expansion of the internal Phe pool. Phe accumulation had multifaceted intercompartmental effects on aromatic amino acid metabolism. It resulted in a decrease in the overall flux through the shikimate pathway, and a redirection of carbon flux toward the shikimate‐derived aromatic amino acids tyrosine and tryptophan. Accumulation of Phe did not lead to an increase in flux toward phenylacetaldehyde, for which Phe is a direct precursor. Metabolic flux analysis revealed this to be due to the presence of a distinct metabolically inactive pool of Phe, likely localized in the vacuole. We have identified a vacuolar cationic amino acid transporter (PhCAT2) that contributes to sequestering excess of Phe in the vacuole. In vitro assays confirmed PhCAT2 can transport Phe, and decreased PhCAT2 expression in PAL‐RNAi transgenic plants resulted in 1.6‐fold increase in phenylacetaldehyde emission. These results demonstrate mechanisms by which plants maintain intercompartmental aromatic amino acid homeostasis, and provide critical insight for future phenylpropanoid metabolic engineering strategies. 相似文献
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Martina Trokter Catarina Felisberto‐Rodrigues Adam Cryar Konstantinos Thalassinos Richard D Hayward Elena V Orlova Gabriel Waksman 《The EMBO journal》2017,36(20):3080-3095
Type IV secretion (T4S) systems are versatile bacterial secretion systems mediating transport of protein and/or DNA. T4S systems are generally composed of 11 VirB proteins and 1 VirD protein (VirD4). The VirB1‐11 proteins assemble to form a secretion machinery and a pilus while the VirD4 protein is responsible for substrate recruitment. The structure of VirD4 in isolation is known; however, its structure bound to the VirB1‐11 apparatus has not been determined. Here, we purify a T4S system with VirD4 bound, define the biochemical requirements for complex formation and describe the protein–protein interaction network in which VirD4 is involved. We also solve the structure of this complex by negative stain electron microscopy, demonstrating that two copies of VirD4 dimers locate on both sides of the apparatus, in between the VirB4 ATPases. Given the central role of VirD4 in type IV secretion, our study provides mechanistic insights on a process that mediates the dangerous spread of antibiotic resistance genes among bacterial populations. 相似文献
104.
Kostiuk SV Zamulaeva IA Agapova RK Ermakov AV Saenko AS Orlova NV Smirnova SG Veĭko NN Spitkovskiĭ DM 《Radiatsionnaia biologiia, radioecologiia / Rossi?skaia akademiia nauk》2008,48(1):5-13
Some properties of the cell-free DNA (cfDNA) of peripheral blood plasma were assessed in 153 employees of atomic industry enterprises. The contents of ribosomal repeat (rDNA) and its concentration in plasma increased in cfDNA of the group of persons in comparison with non-irradiated individuals. The contents of satellite III in cfDNA of donors and of irradiated persons do not differ and less than in DNA nucleus. The correlation between cumulative dose of radiation, contents of rDNA in cfDNA and the frequency of lymphocytes bearing mutations at T-cell receptor (TCR) locus was obtained. The definition of three indications in irradiated persons: the contents of ribosomal genes in cfDNA, TCR-mutant cell frequency and concentration of ribosomal genes in blood plasma--may be useful for revealing individuals in organism of which an intensive cell apoptosis takes place and there is an increased probability of carcinogenesis and of progress of disease of immune system. 相似文献
105.
A new species of the genus Telangiopsis, T. nonnae O. Orlova et Zavialova, was described on the basis of a microsporangiate organ from the Lower Carboniferous deposits of the
Novgorod Region. The morphology of branching fertile axes, synangia, and sporangia was thoroughly studied. The three-dimensional
system of fertile axes branches monopodially; ultimate axes bear numerous connivent bunches of synangia, which consist of
three to six basally fused elongated ovate sporangia. The morphology and ultrastructure of prepollen grains were studied,
which were extracted from the rock matrix surrounding the sporangia. The two-layered exine includes a well-developed endexine
and an alveolate ectexine, with one-three rows of large thin-walled alveolae. The new species was compared with other Early
Carboniferous microsporangiate organs. 相似文献
106.
Takao Koeduka Irina Orlova Thomas J. Baiga Joseph P. Noel Natalia Dudareva Eran Pichersky 《The Plant journal : for cell and molecular biology》2009,58(6):961-969
Floral scent has been extensively investigated in plants of the South American genus Petunia. Flowers of Petunia integrifolia emit mostly benzaldehyde, while flowers of Petunia axillaris subsp. axillaris emit a mixture of volatile benzenoid and phenylpropanoid compounds that include isoeugenol and eugenol. Flowers of the artificial hybrid Petunia hybrida, a cross between P. integrifolia and P. axillaris, emit a similar spectrum of volatiles as P. axillaris subsp. axillaris. However, the flowers of P. axillaris subsp. parodii emit neither isoeugenol nor eugenol but contain high levels of dihydroconiferyl acetate in the petals, the main scent‐synthesizing and scent‐emitting organs. We recently showed that both isoeugenol and eugenol in P. hybrida are biosynthesized from coniferyl acetate in reactions catalyzed by isoeugenol synthase (PhIGS1) and eugenol synthase (PhEGS1), respectively, via a quinone methide‐like intermediate. Here we show that P. axillaris subsp. parodii has a functional EGS gene that is expressed in flowers, but its IGS gene contains a frame‐shift mutation that renders it inactive. Despite the presence of active EGS enzyme in P. axillaris subsp. parodii, in the absence of IGS activity the coniferyl acetate substrate is converted by an as yet unknown enzyme to dihydroconiferyl acetate. By contrast, suppressing the expression of PhIGS1 in P. hybrida by RNA interference also leads to a decrease in isoeugenol biosynthesis, but instead of the accumulation of dihydroconiferyl acetate, the flowers synthesize higher levels of eugenol. 相似文献
107.
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109.
Multiple distinct assemblies reveal conformational flexibility in the small heat shock protein Hsp26
White HE Orlova EV Chen S Wang L Ignatiou A Gowen B Stromer T Franzmann TM Haslbeck M Buchner J Saibil HR 《Structure (London, England : 1993)》2006,14(7):1197-1204
Small heat shock proteins are a superfamily of molecular chaperones that suppress protein aggregation and provide protection from cell stress. A key issue for understanding their action is to define the interactions of subunit domains in these oligomeric assemblies. Cryo-electron microscopy of yeast Hsp26 reveals two distinct forms, each comprising 24 subunits arranged in a porous shell with tetrahedral symmetry. The subunits form elongated, asymmetric dimers that assemble via trimeric contacts. Modifications of both termini cause rearrangements that yield a further four assemblies. Each subunit contains an N-terminal region, a globular middle domain, the alpha-crystallin domain, and a C-terminal tail. Twelve of the C termini form 3-fold assembly contacts which are inserted into the interior of the shell, while the other 12 C termini form contacts on the surface. Hinge points between the domains allow a variety of assembly contacts, providing the flexibility required for formation of supercomplexes with non-native proteins. 相似文献
110.
Clare DK Orlova EV Finbow MA Harrison MA Findlay JB Saibil HR 《Structure (London, England : 1993)》2006,14(7):1149-1156
The vacuolar ATPase integral membrane c-ring from Nephrops norvegicus occurs in paired complexes in a double membrane. Using cryo-electron microscopy and single particle image processing of 2D crystals, we have obtained a projection structure of the c-ring of N. norvegicus. The c-ring was found to be very flexible, most likely as a result of an expanded conformation of the c subunits. This structure may support a role for the vacuolar ATPase c-rings in membrane fusion. 相似文献