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1

Electronic Resource

Sulphate and micronutrients can modulate the expression levels of myrosinases in Sinapis alba plants (1998)

Visvalingam, Seetha ; Hønsi, Torunn G. ; Bones, Atle M.

Copenhagen : Munksgaard International Publishers

Physiologia plantarum 104 (1998), S. 0

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ISSN: 1399-3054

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: The myrosinase-glucosinolate system is considered to be a major component of the preformed defence system of Brassicaceae species. This hypothesis has influenced the belief that the components of the myrosinase-glucosinolate system are present at fixed levels which are independent of environmental factors. In the present study we show that external availability of nutrients can modulate the expression levels of myrosinase enzymes (EC 3.2.3.1). Nutrients such as sulphate, iron, copper, zinc and manganese were tested for their modulation effect on myrosinase expression levels and activity in roots, stems, cotyledons and buds of Sinapis alba seedlings at four different developmental stages. The most sensitive organ was the bud where iron deficiency approximately doubled the myrosinase activity. Removal of sulphate and all four micronutrients reduced the myrosinase activity to approximately half of the activity in plants supplemented with all these nutrients. The myrosinase polypeptides can be divided into classes based on molecular mass after reduction. The nutritional status influenced mainly the 68-kDa class of myrosinases as revealed by western blot and laser scan densitometry of the immunolabelled blots.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1034/j.1399-3054.1998.1040105.x

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2

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Horizontal gene transfer from transgenic plants to terrestrial bacteria – a rare event? (1998)

Nielsen, Kaare M ; Bones, Atle M ; Smalla, Kornelia ; [et al.]

Oxford, UK : Blackwell Publishing Ltd

FEMS microbiology reviews 22 (1998), S. 0

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ISSN: 1574-6976

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: Today, 12 years after the first field release of a genetically modified plant (GMP), over 15 000 field trials at different locations have been performed. As new and unique characteristics are frequently introduced into GMPs, risk assessment has to be performed to assess their ecological impact. The possibilities of horizontal gene transfer (HGT; no parent-to-offspring transfer of genes) from plants to microorganisms are frequently evaluated in such risk assessments of GMPs before release into the field. In this review we indicate why putative HGT from plants to terrestrial (soil and plant associated) bacteria has raised concern in biosafety evaluations. Further, we discuss possible pathways of HGT from plants to bacteria, outline the barriers to HGT in bacteria, describe the strategies used to investigate HGT from plants to bacteria and summarize the results obtained. Only a few cases of HGT from eukaryotes such as plants to bacteria have been reported to date. These cases have been ascertained after comparison of DNA sequences between plants and bacteria. Although experimental approaches in both field and laboratory studies have not been able to confirm the occurrence of such HGT to naturally occurring bacteria, recently two studies have shown transfer of marker genes from plants to bacteria based on homologous recombination. The few examples of HGT indicated by DNA sequence comparisons suggest that the frequencies of evolutionarily successful HGT from plants to bacteria may be extremely low. However, this inference is based on a small number of experimental studies and indications found in the literature. Transfer frequencies should not be confounded with the likelihood of environmental implications, since the frequency of HGT is probably only marginally important compared with the selective force acting on the outcome. Attention should therefore be focused on enhancing the understanding of selection processes in natural environments. Only an accurate understanding of these selective events will allow the prediction of possible consequences of novel genes following their introduction into open environments.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1574-6976.1998.tb00362.x

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3

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The myrosinase-glucosinolate system, its organisation and biochemistry (1996)

Bones, Atle M. ; Rossiter, John T.

Oxford, UK : Blackwell Publishing Ltd

Physiologia plantarum 97 (1996), S. 0

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ISSN: 1399-3054

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: The myrosinase-glucosinolate system is involved in a range of biological activities affecting herbivorous insects, plants and fungi. The system characteristic of the order Capparales includes sulphur-containing substrates, the degradative enzymes myrosinases, and cofactors. The enzyme-catalyzed hydrolysis of glucosinolates initially involves cleavage of the thioglucoside linkage, yielding D-glucose and an unstable thiohydroximate-O-sulphonate that spontaneously rearranges, resulting in the production of sulphate and one of a wide range of possible reaction products. The products are generally a thiocyanate, isothiocyanate or nitrile, depending on factors such as substrate, pH or availability of ferrous ions. Glucosinolates in crucifers exemplify components that are often present in food and feed plants and are a major problem in the utilization of products from the plants. Toxic degradation products restrict the use of cultivated plants, e.g. those belonging to the Brassicaceae. The myrosinase-glucosinolate system may, however, have several functions in the plant. The glucosinolate degradation products are involved in defence against insects and phytopathogens. and potentially in sulphur and nitrogen metabolism and growth regulation. The compartmentalization of the components of the myrosinase-glucosinolate system and the cell-specific expression of the myrosinase represents a unique plant defence system. In this review, we summarize earlier results and discuss the organisation and biochemistry of the myrosinase-glucosinolate system.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1399-3054.1996.tb00497.x

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4

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Expression and occurrence of uracil-DNA glycosylase in higher plants (1993)

Bones, Atle M.

Oxford, UK : Blackwell Publishing Ltd

Physiologia plantarum 88 (1993), S. 0

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ISSN: 1399-3054

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: Uracil-DNA glycosylase (UDG) is the first enzyme in the base excision repair pathway for removal of uracil in DNA. DNA repair capacity is likely to be a critical factor in mutagenesis and thereby in the capacity to prevent genetic damage and unwanted variation. We have studied expression of UDG in 9 higher plant species. The highest expression of UDG was measured in Solanum tuberosum. A comparison of 6 Solanum tuberosum cultivars showed that the specific activity ranged from 30 pmol mg1 protein min−1 in the cultivar Laila to 80 pmol mg−1 protein min−1 in the cultivar Ostara. Measurement of UDG in Begonia X cheimantha gave no indications of enzyme activity. The possible effects of no or low UDG activity is discussed.In vitro cultures of Solanum tuberosum and Thymus vulgaris were used to examine the effect of auxin and cytokinin on the UDG activity. Axillary shoots of Solanum tuberosum were cultured on medium including 20 variations in hormone concentration. Auxin (1-naphtaleneacetic acid) increased the expression of UDG. Plants cultured on medium supplemented with 3 mg 1−1 1-naphtaleneacetic acid showed a specific UDG activity which was approximately 3-fold higher than the activity in controls. The cytokinin benzyladenine reduced the specific UDG activity at concentrations in the range 0.25–10 mg 1−1.In vitro cultured Saintpaulia ionantha was used to examine UDG activity during initiation, conditioning and multiplication cycles. In general, highest expression of UDG was measured in the conditioning cycle on hormone free medium. Measurement of UDG expression during single subculture periods, clearly showed that UDG expression may vary over one culture period. Expression of UDG was in general highest three weeks after transfer to fresh medium.Of different seedling organs from 0- to 15-day-old Brassica napus L., roots and hypocotyls showed the highest UDG activities. In cotyledons a very low and nearly constant specific activity was observed. In 12-day-old seedlings the activity in roots was approximately 20 times higher than the activity in cotyledons.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1399-3054.1993.tb01389.x

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5

Electronic Resource

Cloning and characterization of rac-like cDNAs from Arabidopsis thaliana (1997)

Winge, Per ; Brembu, Tore ; Bones*, Atle M.

Springer

Plant molecular biology 35 (1997), S. 483-495

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ISSN: 1573-5028

Keywords: actin cytoskeleton ; GTP-binding proteins ; plant defence ; polymerase chain reaction (PCR) ; Rac proteins ; signal transduction

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract The Rho family of GTPases are in higher eukaryotes divided into 3 major subfamilies; the Rho, Rac and Cdc42 proteins. In plants, however, the Rho family is restricted to one large family of Rac-like proteins. From work with mammalian phagocytes the Rac proteins are known to activate a multicomponent NADPH-dependent oxidase which results in accumulation of H2O2, a process termed oxidative burst. In plants a similar oxidative burst is observed and plays an important role in its defence against pathogen infections, suggesting a similar role for the plant Rac-like proteins. The Rho family of GTPases proteins are also involved in control of cell morphology, and are also thought to mediate signals from cell membrane receptors. In a broad search for members of the Ras superfamily in plants, several new small GTP-binding proteins were found. We report here the identification and molecular cloning of 5 rac-like cDNAs from Arabidopsis thaliana, Arac1–5. The Rac-like proteins deduced from the cDNA sequences all share 80–95% homology, but show considerably more diversity on the nucleotide level, indicating that this is an ancient gene family. Four of the rac genes were found to be expressed in all tissues examined, but one gene, Arac2, was expressed exclusively in the root, hypocotyl and stem. Our results show that the rac gene family in A. thaliana consists of at least 10 different genes.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1005804508902

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The Seminavis robusta genome provides insights into the evolutionary adaptations of benthic diatoms (2020)

Osuna-Cruz, Cristina Maria ; Bilcke, Gust ; Vancaester, Emmelien ; [et al.]

Springer Nature

In: Nature Communications. 2020; 11(1): 3320. Published 2020 Jul 03. doi: 10.1038/s41467-020-17191-8.

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Publication Date: 2020-07-03

Description: Benthic diatoms are the main primary producers in shallow freshwater and coastal environments, fulfilling important ecological functions such as nutrient cycling and sediment stabilization. However, little is known about their evolutionary adaptations to these highly structured but heterogeneous environments. Here, we report a reference genome for the marine biofilm-forming diatom Seminavis robusta, showing that gene family expansions are responsible for a quarter of all 36,254 protein-coding genes. Tandem duplications play a key role in extending the repertoire of specific gene functions, including light and oxygen sensing, which are probably central for its adaptation to benthic habitats. Genes differentially expressed during interactions with bacteria are strongly conserved in other benthic diatoms while many species-specific genes are strongly upregulated during sexual reproduction. Combined with re-sequencing data from 48 strains, our results offer insights into the genetic diversity and gene functions in benthic diatoms.

Electronic ISSN: 2041-1723

Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General , Physics

Published by Springer Nature

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bHLH-PAS protein RITMO1 regulates diel biological rhythms in the marine diatomPhaeodactylum tricornutum (2019)

Annunziata, Rossella ; Ritter, Andrés ; Fortunato, Antonio Emidio ; [et al.]

National Academy of Sciences

In: PNAS - Proceedings of the National Academy of Sciences of the United States of America. 2019; 116(26): 13137-13142. Published 2019 Jun 06. doi: 10.1073/pnas.1819660116.

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Publication Date: 2019-06-06

Description: Periodic light–dark cycles govern the timing of basic biological processes in organisms inhabiting land as well as the sea, where life evolved. Although prominent marine phytoplanktonic organisms such as diatoms show robust diel rhythms, the mechanisms regulating these processes are still obscure. By characterizing aPhaeodactylum tricornutumbHLH-PAS nuclear protein, hereby named RITMO1, we shed light on the regulation of the daily life of diatoms. Alteration of RITMO1 expression levels and timing by ectopic overexpression results in lines with deregulated diurnal gene expression profiles compared with the wild-type cells. Reduced gene expression oscillations are also observed in these lines in continuous darkness, showing that the regulation of rhythmicity by RITMO1 is not directly dependent on light inputs. We also describe strong diurnal rhythms of cellular fluorescence in wild-type cells, which persist in continuous light conditions, indicating the existence of an endogenous circadian clock in diatoms. The altered rhythmicity observed in RITMO1 overexpression lines in continuous light supports the involvement of this protein in circadian rhythm regulation. Phylogenetic analysis reveals a wide distribution of RITMO1-like proteins in the genomes of diatoms as well as in other marine algae, which may indicate a common function in these phototrophs. This study adds elements to our understanding of diatom biology and offers perspectives to elucidate timekeeping mechanisms in marine organisms belonging to a major, but under-investigated, branch of the tree of life.

Print ISSN: 0027-8424

Electronic ISSN: 1091-6490

Topics: Biology , Medicine , Natural Sciences in General