Calcium signalling mediated by Calmodulin (CaM) and calmodulin-like (CML) proteins is critical to plant immunity. CaM and CML regulate a wide range of target proteins and cellular responses. While ...many CaM-binding proteins have been identified, few have been characterized for their specific role in plant immunity. Here, we report new data on the biological function of a CML-interacting partner, PRR2 (PSEUDO-RESPONSE REGULATOR 2), a plant specific transcription factor. Until now, the physiological relevance of PRR2 remained largely unknown. Using a reverse genetic strategy in A. thaliana, we identified PRR2 as a positive regulator of plant immunity. We propose that PRR2 contributes to salicylic acid (SA)-dependent responses when challenged with the phytopathogenic bacterium Pseudomonas syringae. PRR2 is transcriptionally upregulated by SA and P. syringae, enhances SA biosynthesis and SA signalling responses; e.g. in response to P. syringae, PRR2 induces the production of SA and the accumulation of the defence-related protein PR1. Moreover, PRR2 overexpressing lines exhibit an enhanced production of camalexin, a phytoalexin that confers enhanced resistance against pathogens. Together, these data reveal the importance of PRR2 in plant immune responses against P. syringae and suggest a novel function for this particular plant specific transcription factor in plant physiology.
•PRR2 interacts with TCPs from class I and II.•TCP19 and 20 control PPR2 protein stability.•These TCP mobilize the complex in particular nuclear subdomains.
Plants possess a large set of ...transcription factors both involved in the control of plant development or in plant stress responses coordination. We previously identified PRR2, a Pseudo-Response Regulator, as a plant-specific CML-interacting partner. We reported that PRR2 acts as a positive actor of plant defense by regulating the production of antimicrobial compounds. Here, we report new data on the interaction between PRR2 and transcription factors belonging to the Teosinte branched Cycloidea and PCF (TCP) family. TCPs have been described to be involved in plant development and immunity. We evaluated the ability of PRR2 to interact with seven TCPs representative of the different subclades of the family. PRR2 is able to interact with TCP13, TCP15, TCP19 and TCP20 in yeast two-hybrid system and in planta interactions were validated for TCP19 and TCP20. Transient expression in tobacco highlighted that PRR2 protein is more easily detected when co-expressed with TCP19 or TC20. This stabilization is associated with a specific sub-nuclear localization of the complex in Cajal bodies or in nuclear speckles according to the interaction of PRR2 with TCP19 or TCP20 respectively. The interaction between PRR2 and TCP19 or TCP20 would contribute to the biological function in specific nuclear compartments.
ABSTRACT
The physiological and photosynthetic responses of Littorella uniflora (L.) Ascherson, an amphibious macrophyte of isoetid life form, to rapid and prolonged emersion onto dry land, was ...studied at a reservoir. Water relations were little affected in the short term, but declining water potential and turgor pressure indicated water stress after flowering. High leaf lacunal CO2 concentrations suggested continued CO2 uptake from sediments. In contrast, a switch from Crassulacean acid metabolism (CAM) to C3 photosynthesis was indicated by much lower levels of ΔH+ (down minus dusk titratable acidity) and phosphoenolpyruvate carboxylase (PEPC) activity in new terrestrial leaves, 7–8‐fold higher activity of ribulose bisphosphate carboxylase oxygenase (Rubisco), and increased chlorophyll and soluble protein contents. Accumulated nitrate and amino acid pools were depleted, whereas storage of carbohydrates as soluble sugars, fructan and starch increased. Plant carbon and nitrogen isotope ratios (δ13C and δ15N) declined, perhaps reflecting changes in C fixation processes, N metabolism, and source C and N. In leaves of plants grown half‐emersed for an extended period, contrasting activities of PEPC and Rubisco were found in submersed and emersed portions. Overall, L. uniflora showed considerable phenotypic plasticity, yet seemed to remain poised for re‐submersion; these characteristics could be adaptive in the unpredictable water margin habitat.
The photosynthetic physiology of Crassulacean acid metabolism was investigated in two Kalanchoë species with differing leaf succulence. The magnitude of CAM was higher for the more succulent leaves ...of K. daigremontiana, compared to the less succulent leaves of K. pinnata. High succulence was related to low mesophyll conductance: K. pinnata was able to maximize diurnal carbon gain by the C₃ pathway, whereas increased succulence is associated with a higher commitment to the CAM cycle in K. daigremontiana. The Rubisco specificity factor, τ, determining selectivity for CO₂ over O₂, was similar for both species (~88), and lower than that of Spinacea (~95), but in contrast to C₄ plants, the Rubisco KmCO₂ (determined independently) was also lower in Kalanchoë spp. than in spinach. Differences in light use were related to the nature of the sink strength in each Phase of CAM, with PEPC activity resulting in low electron transport rates. Decarboxylation was marked by high, non-saturated rates of electron transport, with Rubisco activity and activation state increasing in both species during the course of the light period. The degree of succulence, and extent of CAM activity, was associated with a progressive inhibition of PSII photochemistry and potential Rubisco activity during the night in both species. Rubisco could be 'woken up' more rapidly in K. pinnata, whereas 45 min light acclimation was required for full recovery of electron transport and Rubisco activity in K. daigremontiana. Leaf morphology therefore seems to alter the expression of and dependence on CAM, but also the extent of co-regulation of carboxylase networks and light use capacity.
Littorella uniflora (L.) Ascherson is a small, perennial,
amphibious rhizophyte of rosette life-form which is
common along the margins of lakes, tarns and reservoirs
where water-level fluctuations ...are often rapid and
unpredictable. The majority of plants are continuously
submersed and reproduce vegetatively, but a small
proportion become completely emersed for variable lengths
of time, when flowering and seed set occur. To find
out how L. uniflora adjusts to sudden emersion we studied
the plants at a reservoir where water level falls each
spring and remains low throughout the summer; L. uniflora
adjusted very quickly showing a degree of phenotypic
plasticity not expected in a ‘stress tolerator’, including
the production of a new set of terrestrial leaves with
reduced lacunal volume and increased stomatal density, a
rapid increase in leaf growth rate, and flowering within
3–4 wk. Comparison of terrestrial L. uniflora with aquatic
plants growing permanently submersed in lake and tarn
habitats showed that three to fourfold more carbon (C) and
nitrogen (N) was incorporated into above-ground
biomass by emersed plants. However, ramet production in the
aquatic environment appeared to be more costly,
in terms of C and N invested, than terrestrial flower and
seed production. The combination of continuous,
submersed vegetative spread with the capacity for a high
degree of phenotypic plasticity allowing some flower and
seed production to occur during brief periods of emersion
seems to account for the success of this plant in the amphibious niche.
The recent severe and frequent PM2.5 (i.e., fine particles smaller than 2.5 μm) pollution in China has aroused unprecedented public concern. The first two years of PM2.5 measurements in China are ...reported and compared with those of Europe and the United States. The average PM2.5 concentration in China is approximately 5 times that over Europe and America. The contribution of atmospheric dispersion to such air quality is evaluated in this study. Air stagnation or its absence is a good indicator of the atmosphere’s capability to disperse its pollutants, but the NOAA definition of an air stagnation event is found to not be applicable to China since it depends on vertical mixing that is weakened in China by the effects of terrain. To address this deficiency, a new threshold for air stagnation events is proposed that depends on the 10-m wind speed, boundary layer height, and occurrence of precipitation. This newly defined air stagnation closely tracks the day-to-day variation of PM2.5 concentrations. Such events are more frequent over China than over Europe and the United States during autumn and winter, especially over the Sichuan basin and Jing-Jin-Ji region of China. If China had the same frequency of air stagnation as the United States or Europe, 67% and 82% of its stations would improve their current air quality during autumn and winter (e.g., an average of 12% decrease in PM2.5 concentrations for the Jing-Jin-Ji region in wintertime). Its severe pollution and frequent air stagnation conditions make controls on emission less effective in China than elsewhere.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
This project is designed to simulate a transfer of oil liquids from an oil tanker. This practical project presents an easy method of realizing such a system with the observance of the safety ...conditions. The software that underlies the operation of the Arduino Mega development board used in the project is exposed.
The development of natural competence by bacteria in situ is considered one of the main factors limiting transformation-mediated gene exchanges in the environment. Ralstonia solanacearum is a plant ...pathogen that is also a naturally transformable bacterium that can develop the competence state during infection of its host. We have attempted to determine whether this bacterium could become the recipient of plant genes. We initially demonstrated that plant DNA was released close to the infecting bacteria. We constructed and tested various combinations of transgenic plants and recipient bacteria to show that the effectiveness of such transfers was directly related to the ratio of the complexity of the plant genome to the number of copies of the transgene.
Repair and maintenance (R&M) work of a ship involves all activities carried out, on board the ship or in the shipyard, in order to prevent and correct potential failures. In general, the terms of ...repair and maintenance of the ship are used together and involve the docking action of the ship for carrying out a standard maintenance routine, according to the requirements of the classification societies under whose supervision vessels are operated, at specified periods. Docking refers to the complex process of repair and maintenance of ships (on time and within the limits of the estimated budget based on the technical specifications of works) while stationed in the shipyard. The certification of the works is carried out, through concerted actions, both by the shipyard, as a contractor, as well as the owner / technical manager of the vessel, as beneficiary. The paper aims to emphasize some aspects of this process with a high degree of complexity, by schematizing, originally, the processes carried out.
Alignment means the determination of displacements and breaks between two shafts and their elimination so that the geometric axes of the shafts become approximately collinear, and the deviations are ...within the permissible limits. This paper presents the methodological steps of the shaft line alignment (as a case study for a bulk carrier vessel of 180 000 tdw) through two classic approaches: with the help of a ruler and feeler gauge (templet) respectively with the help of dial gauge. Comparative analysis of the performances of the two methods, can provide essential information to an engineer in choosing the optimal option for alignment of the shaft lines both in the case of vessels in service and, mainly, in the case of new building's. The originality of the work consists in carrying out the detailed calculations for displacements and breaks, with the graphical highlighting of the calculated values in the limit allowed intervals. Also, for each method are presented and commented the advantages and disadvantages.
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