The protein secondary structure and pigments' microenvironment in photosystem 1 (PS1) complexes were studied in the temperature range of 25-80 °C using Fourier transform infrared (FT-IR) and circular dichroism (CD) spectroscopy, respectively. Quantitative analysis of the component bands of the amide I band (1 700-1 600 cm-1) showed no significant change below 50 °C. However, apparent conformational changes occurred at 60 °C and further continued at 70 and 80 °C accompanied with transitions of secondary structure mainly from α-helix to the β-sheet structures. CD analysis demonstrated that the regular arrangement, viz. protein microenvironment of pigments of PS1 complexes, was destroyed by heat treatment which might come from the changes of protein secondary structure of PS1. The CD signals at 645 nm contributed by chlorophyll (Chl) b of light-harvesting complex 1 (LHC1) were easily destroyed at the beginning of heat treatment (25-60 °C). When temperature reached 70 and 80 °C, the CD signals at 478 nm contributed mainly by Chl b of LHC1 and 498 nm contributed by carotenoids decreased most rapidly, indicating that LHC1 was more sensitive to high temperature than core complexes. In addition, the oxygen uptake rate decreased by 90.81 % at 70 °C and was lost completely at 80 °C showing that heat treatment damaged the regular function of PS1 complexes. This may be attributed to heat-induced changes of pigment microenvironment and protein secondary structure, especially transmembrane α-helix located in PsaA/B of PS1. and Z.-H. Hu ... [et al.].
The effect of sulphur deprivation and irradiance (180 and 750 µmol m-2 s-1) on plant growth and enzyme activities of carbon, nitrogen, and sulphur metabolism were studied in maize (Zea mays L. Pioneer cv. Latina) plants over a 15-d-period of growth. Increase in irradiance resulted in an enhancement of several enzyme activities and generally accelerated the development of S deficiency. ATP sulphurylase (ATPs; EC 2.7.7.4) and o-acetylserine sulphydrylase (OASs; EC 4.2.99.8) showed a particular and different pattern as both enzymes exhibited maximum activity after 10 d from the beginning of deprivation period. Hence in maize leaves the enzymes of C, N, and S metabolism were differently regulated during the leaf development by irradiance and sulphur starvation. and S. Astolfi, M. G. de Biasi, C. Passera.
The contents of chlorophyll (Chl), leaf biomass, and soluble proteins were markedly decreased in phytoplasma infected apple leaves. Similar results were also observed for ribulose-1,5-bisphosphate carboxylase, 14CO2 fixation, and nitrate reductase activity. In contrast, the contents of sugars, starch, amino acids, and total saccharides were significantly increased in phytoplasma infected leaves. In isolated chloroplasts, phytoplasma infection caused marked inhibition of whole photosynthetic electron chain and photosystem 2 (PS2) activity. The artificial exogenous electron donor, diphenyl carbazide, significantly restored the loss of PS2 activity in infected leaves. Similar results were obtained when Fv/Fm was evaluated by in vivo Chl a fluorescence kinetic measurements. and M. Bertamini ... [et al.].
Energy transfer of aromatic amino acids in photosystem 2 (PS2) core antenna complexes CP43 and CP47 was studied using absorption spectroscopy, fluorescence spectroscopy, and the 0.35 nm crystal structure of PS2 core complex. The energy of tyrosines (Tyrs) was not effectively transferred to tryptophans (Trps) in CP43 and CP47. The fluorescence emission spectrum of CP43 and CP47 by excitation at 280 nm should be a superposition of the Tyr and Trp fluorescence emission spectra. The aromatic amino acids in CP43 and CP47 could transfer their energy to chlorophyll (Chl) a molecules by the Dexter mechanism and the Föster mechanism, and the energy transfer efficiency in CP47 was much higher than that in CP43. In CP47 the Föster mechanism must be the dominant energy transfer mechanism between aromatic amino acids and Chl a molecules, whereas in CP43 the Dexter mechanism must be the dominant one. Hence solar ultraviolet radiation brings not only damages but also benefits to plants. and Y. G. Qu .... [et al.].
Photoinhibition of photosynthesis was studied in young and mature detached sun needles of cypress under high irradiance (HI) of about 1 900 μmol m-2 s-1. The degree of photoinhibition was determined by means of the ratio of variable to maximum chlorophyll (Chl) fluorescence (Fv/Fm) and electron transport measurements. Compared with the mature needles, the young needles, containing about half the amount of Chl a+b per unit area, exhibited a higher proportion of total carotenoids (Car) as xanthophyll cycle pigments and had an increased ratio of Car/Chl a+b. The potential efficiency of photosystem (PS) 2, Fv/Fm, markedly declined in HI-treated young needles without significant increase of F0 level. In contrast, the Fv/Fm ratio declined with significant increase of F0 level in mature needles. In isolated thylakoids, the rate of whole chain and PS2 activity markedly decreased in young HI-needles in comparison with mature needles. A smaller inhibition of PS1 activity was observed in both needles. In the subsequent dark incubation, fast recovery was found in both needle Types that reached maximum PS2 efficiencies similar to those observed in non-photoinhibited needles. The artificial exogenous electron donors DPC, NH2OH, and Mn2+ failed to restore the HI-induced loss of PS2 activity in mature needles, while DPC and NH2OH significantly restored it in young needles. Hence, HI-inactivation was on the donor side of PS2 in young needles and on the acceptor side of PS2 in mature needles. Quantification of the PS2 reaction centre proteins D1 and 33 kDa protein of water splitting complex following HI-exposure of needles showed pronounced differences between young and mature needles. The large loss of PS2 activity in HI-needles was due to the marked loss of D1 protein of the PS2 reaction centre in mature needles and of the 33 kDa protein in young needles. and N. La Porta ... [et al.]
The appearance of variations in the protein profile of Ostertagia ostertagi (Stiles, 1892) infective larvae (L3), which were induced by hypobiosis triggering factors, was evaluated by means of SDS-PAGE and densitometric analysts. Area integration analyses of their protein profiles was carried out between 66 and 77 kDa. Important quantitative variations were identified in the protein levels of the induced larvae, where a 5.25 fold increase compared to the control was observed. Two 75.4 and 70 kDa protein bands were found which exceeded the control profile by 4.5 and 44 fold, respectively. This fact suggests that the changes brought about in the process of hypobiosis induction are restricted. This work demonstrates changes at a molecular level corresponding with biological changes induced by conditions causing O. ostertagi hypobiosis.
Autophagy is the basic catabolic mechanism that involves degradation of dysfunctional cellular components through the action of lysosome as well as supplying energy and compounds for the synthesis of essential biomacromolecules. This process enables cells to survive stress from the external environment like nutrient deprivation. Autophagy is important in the breakdown of proteins, carbohydrates and lipids as well. Furthermore, recent studies have shown that autophagy is critical in wide range of normal human physiological processes, and defective autophagy is associated with diverse diseases, including lysosomal storage disease, myopathies, neurodegeneration and various metabolic disorders. This review summarizes the most up-to-date findings on what role autophagy plays in metabolism., Z. Papáčková, M. Cahová., and Obsahuje bibliografii
The influence of a cytokinin, 6-benzylaminopurine (BAP), on chloroplast structure was studied using biochemical methods and electron microscopy. The average degree of thylakoid stacking was determined by digitonin fractionation and differential centrifugation of chloroplasts from tobacco plantlets after treatment with different concentrations of BAP in agar medium during cultivation in viíro. An elevated concentration of BAP in the medium induced an increase in grana stacking. This was in accordance with the lowering of the chlorophyll a/b ratio in these chloroplasts. The relative amoímt of proteins and carotenoids increased in both stromal and (to a lesser extent) granal chloroplast thylakoid fractions with the BAP concentration. The electron microscopic studies revealed nearly the same volume density of thylakoid membranes within chloroplasts of BAP treated plantlets and control ones. In the BAP treated plantlets the chloroplasts were smaller and had a profound accumulation of starch inclusions and a more flattened shape than the chloroplasts of control plantlets. The volume density of plastoglobuli in chloroplasts did not decrease under the influence of BAP,
Prosopis juliflora is a hardy plant tolerant to drought, salinity, extremes of soil pH, and heavy metal stress. We isolated and characterized a photosystem 2 (PS2) gene PsbR (Pj PsbR) and its promoter. Northern analysis for Pj PsbR in P. juliflora leaves under 25 % polyethylene glycol stress showed steady decrease in transcript level at 12, 24, and 48 h after stress application. Under 90 mM H2O2 stress, transcript level dropped drastically at 12 h, but increased again compared to the control at 24 h. A 1.7 kb fragment upstream the 5' UTR of this gene (putative promoter) was isolated and analyzed in silico. Several putative cis-acting DNA elements were identified in this sequence. and G. Suja, A. Parida.
Three-year-old plants of Parthenium argentatum Gray cv. 11591 grown under natural photoperiod were exposed for 60 d to low night temperature (LNT) of 15 °C (daily from 18:00 to 06:00). Effects of the treatment on net photosynthetic rates (PN), rubber accumulation, and associated biochemical traits were examined. LNT initially reduced PN with a parallel decline in the activities of ribulose-1,5-bisphosphate carboxylase, fructose bisphosphatase, and sucrose phosphate synthase for 20-30 d. Later, LNT enhanced PN and the activities of photosynthetic enzymes. Associated with high PN in LNT-treated guayule plants was a two-fold increase in rubber content and rubber transferase activity per unit of protein. The initial decrease in PN in LNT-treated guayule was associated with low content of chlorophyll (a+b), large starch accumulation, and higher ratio of glucose-6-phosphate/fructose-6-phosphate. Photosystem 2 activity in isolated chloroplasts was initially decreased, but increased after 30 d. There was a significant increase in the leaf soluble protein content in LNT-treated plants. Hence the photosynthetic performance of plants grown at 15 °C night temperature for 50 d was superior to those grown under natural photoperiod in all parameters studied. The high photosynthetic capacity may contribute to superior rubber yields under LNT. and D. Sundar, A. Ramachandra Reddy.