Light effect on the hormonal and transcriptional status of winter and spring wheat plants during cold hardening
ABSTRACT: The effect of light during the development of freezing tolerance was studied in winter wheat (Triticum aestivum L. var. Mv Emese) and spring wheat variety Nadro. Ten-day-old plants were cold hardened at 5°C for 12 days either under normal (250 mmol m-2 s-1) or low light (20 mmol m-2 s-1) conditions. Samples of Emese (E) and Nadro (N) plants grown at 18°C under normal (NL) and low (LL) light fluences were compared to each other in a simple loop design and E-NL vs. E-LL; N-NL vs. N-LL; E-NL vs. NLL and E-LL vs. N-LL comparisons were made.
Project description:Plant thylakoid membranes contain hundreds of proteins closely interplaying to cope with ever-changing environmental conditions. We investigated how P. sativum (pea) grown at different irradiances optimizes light-use efficiency through the differential accumulation of thylakoid proteins. Thylakoid membranes from plants grown under limiting (LL), normal (NL) and high (HL) light intensity were characterized by combining chlorophyll fluorescence measurements with quantitative proteomic analysis. Protein sequences retrieved from available transcriptomic data considerably improved the protein profiling. We found that increasing growth irradiance affects the electron transport kinetics but not Photosystem (PS) I and II relative abundance. Two acclimation strategies were evident comparing plants acclimated to LL with higher irradiances: 1) in NL, plants turn on photoprotective responses mostly regulating the PSII light-harvesting capacity either accumulating Lhcb4.3 or favouring the xanthophyll cycle; 2) in HL, plants reduce the LHCII pool and enhance the PSII repair cycle. At increasing growth irradiance, plants increase the accumulation of ATP synthase and boost the electron transport to finely tune the ΔpH across the membrane and adjust the thylakoid architecture to optimize protein trafficking. Our results provide a quantitative snapshot on how plants coordinate light-harvesting, electron transport and protein synthesis adjusting the thylakoid membrane proteome in a light-dependent manner
Project description:Calcium (Ca2+) and redox signaling play important roles in acclimation processes from archaea to eukaryotic organisms. Herein we characterized a unique protein from Chlamydomonas reinhardtii that has the competence to integrate Ca2+- and redox-related signaling. This protein, designated as calredoxin (CRX), combines four Ca2+-binding EF-hands and a thioredoxin (TRX) domain. A crystal structure of CRX, at 1.6 Å resolution, revealed an unusual calmodulin-fold of the Ca2+-binding EF-hands, which is functionally linked via an inter-domain communication path with the enzymatically active TRX domain. CRX is chloroplast-localized and interacted with a chloroplast 2-Cys-peroxiredoxin (PRX1). Ca2+-binding to CRX is critical for its TRX activity and for efficient binding and reduction of PRX1. Thereby, CRX represents a new class of Ca2+-dependent "sensor-responder" proteins. Genetically engineered Chlamydomonas strains with strongly diminished amounts of CRX revealed altered photosynthetic electron transfer and were affected in oxidative stress response underpinning a function of CRX in stress acclimation.
Project description:Arabidopsis (Arabidopsis thaliana) leaf was exposed to excess light for 30 min and 2 hours or to 24 µM DBMIB for 30 min and 2 hours. Expression levels relative to low light (LL) were determined
Project description:Aspergillus fumigatus contributes to invasive and allergic pulmonary disease in immunocompromised individuals. The pulmonary mucus of cystic fibrosis (CF) patients displays elevated levels of the pleiotropic cathelicidin antimicrobial peptide LL-37 and the aim of this work was to assess the effect of LL-37 on the growth A. fumigatus. Exposure of A. fumigatus conidia to high concentrations of intact LL-37 (100 μg/ml) for 24 hours had a positive effect on growth (277.45 ± 22.59% (p < 0.01)) whereas scrambled LL-37 (76.45 ± 7.46%) did not. Exposure of 24 hour pre-formed mycelium to 5 μg/ml LL-37 for 48 hours increased hyphal wet weight significantly (4.37 ± 0.23 g, p < 0.001) compared to the control (2.67 ± 0.05 g). Amino acid leakage from mycelium was observed in the presence of LL-37 and gliotoxin secretion was increased at 24 hours from LL-37 exposed hyphae (169.1 ± 6.36 ng/mg hyphae, p < 0.05) compared to the control (102 ± 18.81 ng/mg hyphae). Quantitative proteomic analysis of 24 hour LL-37 treated hyphae revealed an increase in the abundance of proteins associated with growth (eIF-5A (16.3 fold increased), tissue degradation (aspartic endopeptidase (4.7 fold increased)) and allergic reactions (Asp F13 (10 fold increased)). By 48 hours there was an increase in proteins indicative of cellular stress (glutathione peroxidase (9 fold increased)), growth (eIF-5A (6 fold increased), and virulence (ribonuclease mitogillin (3.7 fold increased). These results indicate that LL-37 stimulates A. fumigatus growth and this may result in increased fungal growth and secretion of toxins in the lungs of CF patients.
Project description:To identify the respective roles of light and ROS in the photoinhibition process and detect a possible light-driven tolerance to oxidative stress, we compared the transcriptomic responses of Synechococcus sp. WH7803 acclimated to low (LL) or high light (HL) to oxidative stress, induced by hydrogen peroxide (H202) or methylviologen (MV). Cultures were acclimated during many generations to continuous low light (LL, 18 ?mol photons m-2 s-1, hereafter LL cells) and high light (HL, 250 ?mol photons m-2 s-1, hereafter HL cells) provided by Sylvania Daylight 58W/154 fluorescent bulbs. For all stress experiments performed in this study, exponentially growing cultures (1 to 3 x 107 cells mL-1), were split into subcultures and submitted to oxidative stress by addition of H2O2 or MV and harvested when PSII quantum yield fell to half of the initial value. For H2O2 experiments, this level of PSII photoinactivation was reached 2 h after submitting LL and HL cultures to 750 µM and 25 µM respectively. Because of the large divergence in dose and kinetics responses to MV between LL- and HL cells, it was not possible to find MV concentrations leading to 50 % decrease of quantum yield at the same time for both light acclimations. Thus, array analyses for MV were performed on HL and LL cultures incubated at the same MV concentration (50 µM) but harvested once PSII quantum yield was halved, i.e. after 1 and 3.5 h of stress respectively. All hybridizations were performed on 4 independent biological replicates and using as reference sample a pool of RNA from all samples investigated in this study. Pairwise comparison were performed to analyze the stress induced by either H2O2 or MV on both LL- and HL cultures (i.e. LL-Ct vs. LL+MV, LL-Ct vs. LL+H2O2, HL-Ct vs. HL+MV, HL-Ct vs. HL+H2O2) as well as to compare the steady state acclimation to different light conditions (i.e. LL-Ct vs. HL-Ct).
Project description:Poplar (Populus trichocarpa, clone Nisqually-1) plants were grown in a Conviron PGR 15 growth chamber using precise control of temperature, light, and humidity. Diurnal (driven) conditions included 12L:12D light cycles and 25C/12C thermocycles in three different combinations. These were: photocycles (LDHH), 12 hrs. light (L)/12 hrs. dark (D) at a constant temperature (25C; HH); photo/thermocycles (LDHC): 12 hrs. light (L) /12 hrs. dark (D) with a high day temperature (25C) and a low night temperature (12C); and thermocycles (LLHC): continuous light (LL) with 12 hrs. high/12 hrs. low temperature (25C, day; 12C, night). Light intensity and relative humidity were 700 micromol m-2s-2 and 50%, respectively. Three-month-old poplar plants were entrained for at least one week under the respective condition prior to initiation of each experiment. Leaves and stems from individual poplar plants were collected every four hours for 48 hrs in driven (diurnal) conditions followed by a two day freerun spacer under continuous light/temperature followed by two additional days of sampling under the same continuous free run condition.
Project description:A mapping population of Brassica rapa (BraIRRI, IMB211xR500) was grown under four external calcium and magnesium concentrations in controlled conditions. RNA was extracted and hybridised to the Affymetrix Brassica Exon 1.0 ST array. The aim of the experiment was to identify cis- and trans- expression quantitative trait loci. In total 279 samples were analysed. The parents of the mapping population were grown at all four treatment levels (LL, HL, LH, HH) with three biological replicates per treatment, plus 12 technical replicates (n=36). A 2x2 combination of external calcium and magnesium concentrations were imposed to give four treatments (LL, HL, LH, HH) as follows: the high (H) concentrations were 3.5 g L-1 (24 mM) CaCl2 and 3.04 g L-1 (15 mM) MgCl2 and the low (L) concentrations were 0.44 g L-1 (3 mM) CaCl2 and 0.2 g L-1 (1 mM) MgCl2 For the mapping population (total = 85 lines), 85 lines were analysed for the LL treatment, 81 lines were analysed for the LH treatment and 65 lines were analysed for the HL treatment. Twelve technical replicates were also analysed.
Project description:Rice (Oryza sativa, spp. Indica, cv. 93-11) plants were grown in a Conviron PGR 15 growth chamber using precise control of temperature, light, and humidity.<br>Diurnal (driven) conditions included 12L:12D light cycles and 31C/20C thermocycles in three different combinations. These were: photocycles (LDHH), 12 hrs. light (L)/12 hrs. dark (D) at a constant temperature (31C; HH); photo/thermocycles (LDHC): 12 hrs. light (L) /12 hrs. dark (D) with a high day temperature (31C) and a low night temperature (20C); and thermocycles (LLHC): continuous light (LL) with 12 hrs. high/12 hrs. low temperature (31C, day; 20C, night). Light intensity and relative humidity were 1000 micromol m-2s-2 and 60%, respectively.<br>Three-month-old rice plants were entrained for at least one week under the respective condition prior to initiation of each experiment. Leaves and stems from individual rice plants were collected every four hours for 48 hrs in driven (diurnal) conditions followed by a two day freerun spacer under continuous light/temperature followed by two additional days of sampling under the same continuous free run condition.