Aromatic Cytokinin Arabinosides Promote PAMP-like Responses and Positively Regulate Leaf Longevity.

Cytokinins are plant hormones with biological functions ranging from coordination of plant growth to the regulation of biotic and abiotic stress-related responses and senescence. The components of the plant immune system can learn from past elicitations by microbial pathogens and herbivores and adapt to new threats. It is known that plants can enter the primed state of enhanced defense induced by either natural or synthetic compounds. While the involvement of cytokinins in defense priming has been documented, no comprehensive model of their action has been provided to date. Here, we report the functional characterization of two aromatic cytokinin derivatives, 6-benzylaminopurine-9-arabinosides (BAPAs), 3-methoxy-BAPA and 3-hydroxy-BAPA, that proved to be effective in delaying senescence in detached leaves while having low interactions with the cytokinin pathway. An RNA-seq profiling study on Arabidopsis leaves treated with 3-methoxy-BAPA revealed that short and extended treatments with this compound shifted the transcriptional response markedly toward defense. Both treatments revealed upregulation of genes involved in processes associated with plant innate immunity such as cell wall remodeling and upregulation of specific MAP kinases, most importantly MPK11, which is a MAPK module involved in stress-related signaling during the pathogen-associated molecular patterns (PAMPs) response. In addition, elevated levels of JA and its metabolites, jasmonate/ethylene-driven upregulation of PLANT DEFENSIN 1.2 (PDF1.2) and other defensins, and also temporarily elevated levels of reactive oxygen species marked the plant response to 3-methoxy-BAPA treatment. Synergistic interactions were observed when plants were cotreated with 3-hydroxy-BAPA and the flagellin-derived bacterial PAMP peptide (flg22), leading to the enhanced expression of the PAMP-triggered immunity (PTI) marker gene FRK1. Our data collectively show that some BAPAs can sensitively prime the PTI responses in a low micromolar range of concentrations while having no observable negative effects on the overall fitness of the plant.

Brominated flame retardants and perfluoroalkyl substances in sediments from the Czech aquatic ecosystem.

This study reports results of analysis of various groups of halogenated chemicals, including brominated flame retardants (BFRs), such as polybrominated diphenyl ethers (PBDEs), hexabromocyclododecanes (HBCDs), tetrabromobisphenol A (TBBPA) and perfluoroalkyl substances (PFASs) in 31 sediment samples collected in different localities of the Czech Republic. In this survey, identification of potential sources of these compounds was also performed; therefore several sampling sites located in highly industrialized areas were involved. Concentrations of target groups of analytes determined in sediments from several Czech rivers examined within this study decreased in the following order: decabromodiphenyl ether (BDE 209) >>> TBBPA~HBCDs~linear perfluorooctane sulfonate (L-PFOS)>other PBDEs~perfluorinated carboxylic acids (PFCAs)~perfluorooctane sulfonamide (FOSA). When compared the contamination by two monitored groups of halogenated compounds, the total content of ∑BFRs was significantly higher, i.e. in the range from the method quantification limit (MQL) to 528 µg/kg dry weight (dw) (median value 5.68 µg/kg dw), than the total concentration of ∑PFASs, that was in the range from MQL to 25.5 µg/kg dw (median value 1.48 µg/kg dw). The extremely highest content of BFR group (265-528 µg/kg dw) was found in sediments collected in sampling sites on the Labe and Luzická Nisa Rivers, which are located in highly chemical industrialized areas and also in the sample from the locality Lampertice obtained from the sedimentation tank close to the factory processing and storing waste. These concentrations were a little bit higher or comparable to those found in similar highly industrialized areas worldwide.

Occurrence of perfluoroalkyl substances (PFASs) in various food items of animal origin collected in four European countries.

This study summarises the results of the levels of 21 perfluoroalkyl substances (PFASs) in 50 selected pooled samples representing 15 food commodities with the special focus on those of animal origin, as meat, seafood, fish, milk, dairy products and hen eggs, which are commonly consumed in various European markets, e.g. Czech, Italian, Belgian and Norwegian. A new, rapid sample preparation approach based on the QuEChERS extraction procedure was applied. Ultra-performance liquid chromatography (UHPLC) coupled to tandem mass spectrometry (MS/MS) employing electrospray ionisation (ESI) in negative mode was used for the quantification of target analytes. Method quantification limits (MQLs) were in the range of 1-10 ng kg(-1) (ng l(-1)) for fish, meat, hen eggs, cheese and milk, and in the range of 2.5-125 ng kg(-1) for butter. Only 16 of the group of 21 PFASs were found in at least one analysed sample. From 16 PFASs, perfluorooctane sulfonate (PFOS) was the most frequently detected analyte present in approximately 50% of samples (in the range of 0.98-2600 ng kg(-1)). PFCAs with C8-C14 carbon chain were presented in approximately 20% of samples. The concentration ranges of individual compounds in the respective groups of PFASs were: 2.33-76.3 ng kg(-1) for PFSAs (without PFOS), 4.99-961 ng kg(-1) for PFCAs, 10.6-95.4 ng kg(-1) for PFPAs, and 1.61-519 ng kg(-1) for FOSA. The contamination level in the analysed food commodities decreased in the following order: seafood > pig/bovine liver >> freshwater/marine fish > hen egg > meat >> butter. When comparing the total contamination and profiles of PFASs in food commodities that originated from various sampling countries, differences were identified, and the contents decreased as follows: Belgium >> Norway, Italy > Czech Republic.

Occurrence of brominated flame retardants and perfluoroalkyl substances in fish from the Czech aquatic ecosystem.

This study reports results of analysis of various groups of halogenated compounds, including brominated flame retardants (BFRs), such as polybrominated diphenylethers (PBDEs), hexabromocyclododecane (HBCD), tetrabromobisphenol A (TBBPA) and perfluoroalkyl substances (PFASs) in 48 fish samples collected in eight localities from the Czech Republic. In this survey, identification of potential sources of these chemicals was also performed; therefore several sampling sites located in highly industrialized areas were also selected. Perfluorooctanesulfonate (PFOS) was dominating in all tested fish samples. Generally, the content of ∑BFRs was significantly lower, i.e. in the range of 0.21-19.9 µg/kg wet weight, ww (median value 2.37 µg/kg ww) compared to the concentration of ∑PFASs that was in the range of 0.15-877 µg/kg ww (median value 8.5 µg/kg ww). The extremely high content of PFOS (842 µg/kg ww) was found in fish muscle tissue from the locality situated on the Bílina River, where chemical industry is located. This concentration was comparable to those found in similar highly industrialized areas worldwide.

Occurrence of halogenated contaminants in fish from selected river localities and ponds in the Czech Republic.

The occurrence of organohalogenated compounds including major persistent chlorinated pollutants, such as polychlorinated biphenyls (PCBs) and DDT and its metabolites, brominated flame retardants (BFRs), represented by polybrominated diphenylethers (PBDEs) and hexabromocyclododecane (HBCD), together with currently widely discussed perfluorinated compounds (PFCs), mainly perfluorooctane sulfonic acid was monitored in several fish species collected from Czech rivers. Eleven sampling locations in highly industrialized areas were chosen. In addition, wild species of 14 farmed fish (grown in dedicated ponds) were also analysed. With respect to the contamination in different areas, chlorinated chemicals were dominant. PCBs and DDTs ranged from 4.8 to 211 and 2 to 791 µg/kg wet weight, respectively. Concentrations of BFRs and PFCs were significantly lower and ranged from 0.6 to 10.2 and 0.9 to 62 µg/kg wet weight, respectively. The highest levels of target analyte groups were found in fish muscle tissue in localities situated on the lower part of the Elbe River: Levels of DDT, HCB, PBDEs, and perfluorooctane sulfonic acid (PFOS) were as high as 791, 77.6, 14.4 and 193 µg/kg wet weight, respectively, in Usti nad Labem and in the sample originated from the confluence of Elbe with Bilina River; a sum of PCBs at a level of 211 µg/kg was detected.