Browsing by Subject "ethylene"

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  • Vuorinen, Katariina; Zamora, Olena; Vaahtera, Lauri; Overmyer, Kirk; Brosché, Mikael (2021)
    Plants require interaction between signaling pathways to differentiate and integrate stress responses and deploy appropriate defenses. The hormones ethylene, salicylic acid (SA), and jasmonic acid (JA) are important regulators of plant defenses. Numerous interactions between these signaling pathways are the cornerstone of robust plant immunity. Additionally, during the early response to pathogens, reactive oxygen species (ROS) act as signaling molecules. Here, we examined the extent of signal interaction in the early stages of Botrytis cinerea infection. To enable a comparison between B. cinerea infection with ROS signaling, we subjected plants to ozone treatment, which stimulates an apoplastic ROS burst. We used a collection of single, double, and triple signaling mutants defective in hormone signaling and biosynthesis and subjected them to B. cinerea infection and ozone treatment at different timepoints. We examined lesion size, cell death, and gene expression (both quantitatively and spatially). The two treatments shared many similarities, especially in JA-insensitive mutants, which were sensitive to both treatments. Unexpectedly, a B. cinerea- susceptible JA-insensitive mutant (coil), became tolerant when both SA biosynthesis and signaling was impaired (coil npr1 sid2), demonstrating that JA responses may be under the control of SA. Extensive marker gene analysis indicated JA as the main regulator of both B. cinerea and ozone defenses. In addition, we identified the transcription factor SRI_ as a crucial regulator of PLANT DEFENSIN expression and cell-death regulation, which contributes to resistance to B. cinerea. Overall, our work further defines the context of ROS in plant defense signaling.
  • Nykänen, Heli (Helsingfors universitet, 2009)
    Greenhouse cucumber (Cucumis sativus) is one of the most important vegetables in Finland with annual consumption of about 30 million kilogrammes. The cucumber itself generates ethylene at a low level, but excessive ethylene concentrations (>0.5 ppm) in ambient air causes quality losses, like yellowing and softening. The problem is that cucumbers often share the same airspace with ethylene generating fruits and vegetables during transport, storage and sale. The literature review deals with ethylene synthesis and its effects in vegetables. Also, ethylene measurements and detection, as well as ethylene exhaustion, and inhibition are discussed. The aim of the experimental study was to find the best available packaging material for greenhouse cucumbers. From 13 different packaging alternatives, studied in a preliminary test, the most promising were selected for storage experiments. Cucumbers were cultivated in greenhouses in SouthWest Finland. Packed cucumbers were stored at 12 ºC and in airflow with 1 ppm ethylene for 14 or 7 days for the first and second trial, respectively. Analyses were performed once a week. They consisted of O2and CO2concentrations of packages and sensory quality of whole and sliced cucumbers. Cucumbers were also photographed. Results showed that cucumbers packed in low oxygen transmission film deteriorated fast, whereas too many holes in a package resulted in high weight losses. Cucumbers packed in shrinkwrapped PEpackages with micro holes had lighter green colour than other cucumbers after 13 days. Cucumbers packed in biodegradable film had nearly 25 % weight loss after 27 days compared to other packages causing weight loss of 3 %. After 13 and 21 days’ storage time the freshness of taste was better if the PPpouch with an ethylene scavenger was used. The currentlyused shrinkwrapped PEpackage with micro holes proved to be a good choice for cucumbers if there is no risk of ethylene in food chain. If ethylene is present, it is better to use a PPpouch with micro holes. In that case, additional benefit of improved freshness of taste can be achieved by using ethylene scavengers.
  • El-Khaledl, Yusuf C.; Roth, Florian; Rädecker, Nils; Kharbatia, Najeh; Jones, Burton H.; Voolstra, Christian R.; Wild, Christian (2020)
    Nitrogen (N) cycling in coral reefs is of key importance for these oligotrophic ecosystems, but knowledge about its pathways is limited. While dinitrogen (N-2) fixation is comparably well studied, the counteracting denitrification pathway is under-investigated, mainly because of expensive and relatively complex experimental techniques currently available. Here, we combined two established acetylene-based assays to one single setup to determine N-2-fixation and denitrification performed by microbes associated with coral reef substrates/organisms simultaneously. Accumulating target gases (ethylene for N-2-fixation, nitrous oxide for denitrification) were measured in gaseous headspace samples via gas chromatography. We measured N-2-fixation and denitrification rates of two Red Sea coral reef substrates (filamentous turf algae, coral rubble), and demonstrated, for the first time, the co-occurrence of both N-cycling processes in both substrates. N-2-fixation rates were up to eight times higher during the light compared to the dark, whereas denitrification rates during dark incubations were stimulated for turf algae and suppressed for coral rubble compared to light incubations. Our results highlight the importance of both substrates in fixing N, but their role in relieving N is potentially divergent. Absolute N-2-fixation rates of the present study correspond with rates reported previously, even though likely underestimated due to an initial lag phase. Denitrification is also presumably underestimated due to incomplete nitrous oxide inhibition and/or substrate limitation. Besides these inherent limitations, we show that a relative comparison of N-2-fixation and denitrification activity between functional groups is possible. Thus, our approach facilitates cost-efficient sample processing in studies interested in comparing relative rates of N-2-fixation and denitrification.