| 43671. |
- Johansson, Oskar N., 1984, et al.
(författare)
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A quick and robust method for quantification of the hypersensitive response in plants
- 2015
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Ingår i: Peerj. - : PeerJ. - 2167-8359. ; 3
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Tidskriftsartikel (refereegranskat)abstract
- One of the most studied defense reactions of plants against microbial pathogens is the hypersensitive response (HR). The HR is a complex multicellular process that involves programmed cell death at the site of infection. A standard method to quantify plant defense and the HR is to measure the release of cellular electrolytes into water after infiltration with pathogenic bacteria. In this type of experiment, the bacteria are typically delivered into the plant tissue through syringe infiltration. Here we report the development of a vacuum infiltration protocol that allows multiple plant lines to be infiltrated simultaneously and assayed for defense responses. Vacuum infiltration did not induce more wounding response in Arabidopsis leaf tissue than syringe inoculation, whereas throughput and reproducibility were improved. The method was used to study HR-induced electrolyte loss after treatment with the bacterium Pseudomonas syringae pv. tomato DC3000 harboring the effector AvrRpm1, AvrRpt2 or AvrRps4. Specifically, the influence of bacterial titer on AvrRpm1-induced HR was investigated. Not only the amplitude, but also the timing of the maximum rate of the HR reaction was found to be dose-dependent. Finally, using vacuum infiltration, we were able quantify induction of phospholipase D activity after AvrRpm1 recognition in leaves labeled with (PO4)-P-33.
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| 43672. |
- Johansson, Oskar N., 1984, et al.
(författare)
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Friends With Benefits: Exploring the Phycosphere of the Marine Diatom Skeletonema marinoi
- 2019
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Ingår i: Frontiers in Microbiology. - : Frontiers Media SA. - 1664-302X. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Marine diatoms are the dominant phytoplankton in the temperate oceans and coastal regions, contributing to global photosynthesis, biogeochemical cycling of key nutrients and minerals and aquatic food chains. Integral to the success of marine diatoms is a diverse array of bacterial species that closely interact within the diffusive boundary layer, or phycosphere, surrounding the diatom partner. Recently, we isolated seven distinct bacterial species from cultures of Skeletonema marinoi, a chain-forming, centric diatom that dominates the coastal regions of the temperate oceans. Genomes of all seven bacteria were sequenced revealing many unusual characteristics such as the existence of numerous plasmids of widely varying sizes. Here we have investigated the characteristics of the bacterial interactions with S. marinoi, demonstrating that several strains (Arenibacter algicola strain SMS7, Marinobacter salarius strain SMRS, Sphingorhabdus flavimaris strain SMR4y, Sulfitobacter pseudonitzschiae strain SMR1, Yoonia vestfoldensis strain SMR4r and Roseovarius mucosus strain SMR3) stimulate growth of the diatom partner. Testing of many different environmental factors including low iron concentration, high and low temperatures, and chemical signals showed variable effects on this growth enhancement by each bacterial species, with the most significant being light quality in which green and blue but not red light enhanced the stimulatory effect on S. marinoi growth by all bacteria. Several of the bacteria also inhibited growth of one or more of the other bacterial strains to different extents when mixed together. This study highlights the complex interactions between diatoms and their associated bacteria within the phycosphere, and that further studies are needed to resolve the underlying mechanisms for these relationships and how they might influence the global success of marine diatoms.
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| 43673. |
- Johansson, Oskar N., 1984, et al.
(författare)
-
Phenomics reveals a novel putative chloroplast fatty acid transporter in the marine diatom Skeletonema marinoi involved in temperature acclimation
- 2019
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 9
-
Tidskriftsartikel (refereegranskat)abstract
- Diatoms are the dominant phytoplankton in temperate oceans and coastal regions and yet little is known about the genetic basis underpinning their global success. Here, we address this challenge by developing the first phenomic approach for a diatom, screening a collection of randomly mutagenized but identifiably tagged transformants. Based upon their tolerance to temperature extremes, several compromised mutants were identified revealing genes either stress related or encoding hypothetical proteins of unknown function. We reveal one of these hypothetical proteins is a novel putative chloroplast fatty acid transporter whose loss affects several fatty acids including the two omega-3, long-chain polyunsaturated fatty acids - eicosapentaenoic and docosahexaenoic acid, both of which have medical importance as dietary supplements and industrial significance in aquaculture and biofuels. This mutant phenotype not only provides new insights into the fatty acid biosynthetic pathways in diatoms but also highlights the future value of phenomics for revealing specific gene functions in these ecologically important phytoplankton.
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| 43674. |
- Johansson, Oskar N., 1984, et al.
(författare)
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Redundancy among phospholipase D isoforrns in resistance triggered by recognition of the Pseudomonas syringae effector AyrRpm1 in Arabidopsis thaliana
- 2014
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Ingår i: Frontiers in Plant Science. - : Frontiers Media SA. - 1664-462X. ; 5
-
Tidskriftsartikel (refereegranskat)abstract
- Plants possess a highly sophisticated system for defense against microorganisms. So called MAMP (microbe-associated molecular patterns) triggered immunity (MTI) prevents the majority of non-adapted pathogens from causing disease. Adapted plant pathogens use secreted effector proteins to interfere with such signaling. Recognition of microbial effectors or their activity by plant resistance (R)-proteins triggers a second line of defense resulting in effector triggered immunity (ETI). The latter usually comprises the hypersensitive response (HR) which includes programmed cell death at the site of infection. Phospholipase D (PLD) mediated production of phosphatidic acid (PA) has been linked to both MTI and ETI in plants. Inhibition of PLD activity has been shown to attenuate MTI as well as ETI. In this study, we systematically tested single and double knockouts in all 12 genes encoding PLDs in Arabidopsis thaliana for effects on ETI and MTI. No single PLD could be linked to ETI triggered by recognition of effectors secreted by the bacterium Pseudomonas syringae. However, repression of PLD dependent PA production by n-butanol strongly inhibited the HR following Pseudomonas syringae effector recognition. In addition some p/d mutants were more sensitive to n-butanol than wild type. Thus, the effect of mutations of PLDs could become detectable, and the corresponding genes can be proposed to be involved in the HR. Only knockout of PLEA caused a loss of MTI-induced cell wall based defense against the non-host powdery mildew Erysiphe pisi. This is thus in stark contrast to the involvement of a multitude of PLD isoforms in the HR triggered by AvrRpm1 recognition.
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| 43675. |
- Johansson, Oskar N., 1984, et al.
(författare)
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Skeletonema marinoi as a new genetic model for marine chain-forming diatoms
- 2019
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 9
-
Tidskriftsartikel (refereegranskat)abstract
- Diatoms are ubiquitous primary producers in marine ecosystems and freshwater habitats. Due to their complex evolutionary history, much remains unknown about the specific gene functions in diatoms that underlie their broad ecological success. In this study, we have genetically transformed the centric diatom Skeletonema marinoi, a dominant phytoplankton species in temperate coastal regions. Transformation of S. marinoi is the first for a true chain-forming diatom, with the random genomic integration via non homologous recombination of a linear DNA construct expressing the resistance gene to the antibiotic zeocin. A set of molecular tools were developed for reliably identifying the genomic insertion site within each transformant, many of which disrupt recognizable genes and constitute null or knock-down mutations. We now propose S. marinoi as a new genetic model for marine diatoms, representing true chain-forming species that play a central role in global photosynthetic carbon sequestration and the biogeochemical cycling of silicates and various nutrients, as well as having potential biotechnological applications.
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| 43676. |
- Johansson, Oskar, et al.
(författare)
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Role of the penetration-resistance genes PEN1, PEN2 and PEN3 in the hypersensitive response and race-specific resistance in Arabidopsis thaliana
- 2014
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Ingår i: Plant Journal. - : Wiley. - 0960-7412. ; 79:3, s. 466-476
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Tidskriftsartikel (refereegranskat)abstract
- Plants are highly capable of recognizing and defending themselves against invading microbes. Adapted plant pathogens secrete effector molecules to suppress the host's immune system. These molecules may be recognized by host-encoded resistance proteins, which then trigger defense in the form of the hypersensitive response (HR) leading to programmed cell death of the host tissue at the infection site. The three proteins PEN1, PEN2 and PEN3 have been found to act as central components in cell wall-based defense against the non-adapted powdery mildew Blumeria graminis fsp. hordei (Bgh). We found that loss of function mutations in any of the three PEN genes cause decreased hypersensitive cell death triggered by recognition of effectors from oomycete and bacterial pathogens in Arabidopsis. There were considerable additive effects of the mutations. The HR induced by recognition of AvrRpm1 was almost completely abolished in the pen2 pen3 and pen1 pen3 double mutants and the loss of cell death could be linked to indole glucosinolate breakdown products. However, the loss of the HR in pen double mutants did not affect the plants' ability to restrict bacterial growth, whereas resistance to avirulent isolates of the oomycete Hyaloperonospora arabidopsidis was strongly compromised. In contrast, the double and triple mutants demonstrated varying degrees of run-away cell death in response to Bgh. Taken together, our results indicate that the three genes PEN1, PEN2 and PEN3 extend in functionality beyond their previously recognized functions in cell wall-based defense against non-host pathogens.
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| 43677. |
- Johansson, Petter, et al.
(författare)
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A Ronkin type function for coamoebas
- 2017
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Ingår i: Journal of Geometric Analysis. - : Springer Science and Business Media LLC. - 1050-6926 .- 1559-002X. ; 27:1, s. 643-670
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Tidskriftsartikel (refereegranskat)abstract
- The Ronkin function plays a fundamental role in the theory of amoebas. We introduce an analogue of the Ronkin function in the setting of coamoebas. It turns out to be closely related to a certain toric arrangement known as the shell of the coamoeba and we use our Ronkin type function to obtain some properties of it.
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| 43678. |
- Johansson, Patrik, et al.
(författare)
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Accelerometry combined with heart rate telemetry in the assessment of total energy expenditure
- 2006
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Ingår i: Br J Nutr. ; 95:3, s. 631-9
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the present study was: (1) to develop a new method for total energy expenditure (TEE) assessment, using accelerometry (ACC) and heart rate (HR) telemetry in combination; (2) to validate the new method against the criterion measure (DLW) and to compare with two of the most common methods, FLEX-HR and ACC alone. In the first part of the study VO(2), HR and ACC counts were measured in twenty-seven subjects during walking and running on a treadmill. Considering the advantages and disadvantages of the HR and ACC methods an analysis model was developed, using ACC at intensities of low and medium levels and HR at higher intensities. During periods of inactivity, RMR is used. A formula for determining TEE from ACC, HR and RMR was developed: TEE = 1.1x(EQ(HR) x TT(HR) + EQ(ACC1) x TT(ACC1) + EQ(ACC2) x TTACC2 + RMR x TT(RMR)). In the validation part of the study a sub-sample of eight subjects wore an accelerometer, HR was logged and TEE was measured for 14 d with the DLW method. Analysis of the Bland-Altman plots with 95 % CI indicates that there are no significant differences in TEE estimated with HR-ACC and ACC alone compared with TEE measured with DLW. It is concluded that the HR-ACC combination as well as ACC alone has potential as a method for assessment of TEE during free-living activities as compared with DLW.
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| 43679. |
- Johansson, P, et al.
(författare)
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Anabolic androgenic steroids affects alcohol intake, defensive behaviors and brain opioid peptides in the rat.
- 2000
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Ingår i: Pharmacology, biochemistry, and behavior. - 0091-3057. ; 67:2, s. 271-9
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Tidskriftsartikel (refereegranskat)abstract
- The present study investigated whether a relationship exists between nandrolone decanoate and voluntary ethanol intake in laboratory rats. Animals were subjected to daily subcutaneous injections with nandrolone decanoate (15 mg/kg) during 2 weeks. One group of animals was tested for voluntary alcohol intake 1 week after the end of the 2-week treatment period and another group received alcohol 3 weeks after the treatment. In addition, assessment of defensive behaviors and immunoreactivity (ir) levels of the brain opioid peptides dynorphin B and Met-enkephalin-Arg-Phe (MEAP) were performed. The nandrolone decanoate-treated animals were significantly more aggressive and showed lower fleeing and freeezing reaction than the oil-treated controls. Treatment with nandrolone decanoate enhanced voluntary alcohol intake, regardless if it was presented 1 or 3 weeks after end of the treatment period. These animals had a decreased activity of dynorphin B-ir in the nucleus accumbens, decreased levels of MEAP-ir in the periaqueductal gray (PAG) and higher levels of MEAP-ir in the hypothalamus compared to controls. In line with previous studies, this suggests that the altered dynorphin B-ir activity may promote the rewarding effects of ethanol and thereby increasing alcohol intake, whereas MEAP-ir may be associated with the ability to control the aggressive reaction. Abuse of nandrolone decanoate may thus constitute a risk factor for increased alcohol consumption and defensive aggression. In human, this constellation of behavioral symptoms is closely related to acts of crimes and violence and is often observed among those abusing anabolic androgenic steroids.
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| 43680. |
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