RNA editing is post-transcriptional modification to RNA molecules. In plants, RNA editing primarily occurs to two energy-producing organelles: plastids and mitochondria. Organelle RNA editing is often viewed as a mechanism of correction to compensate for defects or mutations in haploid organelle genomes. A common type of organelle RNA editing is deamination from cytidine to uridine. Cytidine-to-uridine plastid RNA editing is carried out by the RNA editing complex which consists of at least four types of proteins: pentatricopeptide repeat proteins, RNA editing interacting proteins/multiple organellar RNA editing factors, organelle RNA recognition motif proteins, and organelle zinc-finger proteins. The four types of RNA editing factors work together to carry out RNA editing site recognition, zinc cofactor binding, and cytidine-to-uridine deamination. In addition, three other types of proteins have been found to be important for plastid RNA editing. These additional proteins may play a regulatory or stabilizing role in the RNA editing complex., Y. Lu., and Obsahuje bibliografické odkazy
Personal recollections of Robin Hill as a friend, teacher, farmer, neighbour, botanist, meteorologist and photographer, and of Cambridge University and town atmosphere during the World War II and after it are combined with the author's experience with Hill´s "fish-eye" lens used for hemispherical photography and analysis of plant stand structure
The aim of this study was to assess the impact of the mitochondrial alternative oxidase (AOX) pathway on energy metabolism in chloroplasts, and evaluate the importance of the AOX in alleviating drought-induced photoinhibition in pepper (Capsicum annuum L.). Inhibition of AOX pathway decreased photosynthesis and increased thermal energy dissipation in plants under normal conditions. It indicated that AOX pathway could influence chloroplast energy metabolism. Drought reduced carbon assimilation. Photoinhibition was caused by excess of absorbed light energy in spite of the increase of thermal energy dissipation and cyclic electron flow around PSI (CEF-PSI). Upregulation of AOX pathway in leaves experiencing drought would play a critical role in protection against photoinhibition by optimization of carbon assimilation and PSII function, which would avoid over-reduction of photosynthetic electron transport chain. However, inhibition of AOX pathway could be compensated by increasing the thermal energy dissipation and CEF-PSI under drought stress, and the compensation of CEF-PSI was especially significant., W. H. Hu, X. H. Yan, Y. He, X. L. Ye., and Obsahuje bibliografii
Cross stress of heat and high irradiance (HI) resulted in the accumulation of active oxygen species and photo-oxidative damage to photosynthetic apparatus of wheat leaves during grain development. Pre-treatment with calcium ion protected the photosynthetic system from oxidative damage by reducing O-2 production, inhibiting lipid peroxidation, and retarding electrolyte leakage from cell. Therefore, high Fv/Fm [maximal photochemical efficiency of photosystem 2 (PS2) while all PS2 reaction centres are open], Fm/F0 (another expression for the maximal photochemical efficiency of PS2), ΦPS2 (actual quantum yield of PS2 under actinic irradiation), qP (photochemical quenching coefficient), and PN (net photosynthetic rate) were maintained, and lower qNP (non-photochemical quenching coefficient) of the leaves was kept under heat and HI stress. EGTA (a chelant of calcium ion) and LaCl3 (a blocker of Ca2+ channel in cytoplasmic membrane) had the opposite effect. Thus Ca ion may help protect the photosynthetic system of wheat leaves from oxidative damage induced by the cross stress of heat and HI. and Hui-Jie Zhao, Ji-Fang Tan.
In the frame of the foreseen climate global changes we analysed the physiological responses of Arbutus unedo L. to the variations of carbon dioxide concentration, leaf temperature, and irradiance by measurements of leaf gas exchange and leaf water potential performed both in field and in the laboratory. Stomatal conductance was not affected by increase of leaf temperature. The growth conditions of potted plants likely made stomata more sensitive to the variation of external parameters than naturally growing plants. The interaction between high CO2 concentration and temperature involved important down-regulation mechanisms in the metabolic pathway of the carbon fixation. From an ecological point of view, the ability of A. unedo to adapt to the field stress makes it highly competitive in the Mediterranean plant community. and M. Vitale, F. Manes.
The present work showed that spider mite-infested leaves placed in the light were more attractive to predatory mites than the infested leaves placed in the dark; furthermore, an increase in the light intensity enhanced this attractiveness. However, the increase of the light intensity did not change the attractiveness of the uninfested leaves to predatory mites. The capacity of cyanide-resistant respiration and the photosynthetic rates of both the infested and uninfested leaves increased with increasing light intensities, whereas the photosystem (PS) II chlorophyll (Chl) fluorescence decreased. The increase of the capacity of cyanide-resistant respiration in the infested leaves was more dramatic than that in the uninfested leaves, whereas the values of photosynthetic rates and Chl fluorescence were lower in the infested leaves than those in the uninfested leaves. Treatment of the infested and uninfested leaves with 1 mM salicylhydroxamic acid (SHAM, an inhibitor of cyanide-resistant respiration) decreased photosynthetic rates and caused further reductions in PSII fluorescence, especially under a higher light intensity. In contrast, the effects of SHAM on PSII fluorescence parameters and photosynthetic rates of the infested leaves were more dramatic than on those of the uninfested leaves. The treatment with SHAM did not significantly change the attractiveness of the infested or uninfested leaves to the predatory mites under all of the light intensities tested. These results indicated that cyanide-resistant respiration was not directly associated with the light-induced attraction of predators to plants, but it could play a role in the protection of photosynthesis. Such role might become relatively more important when photosynthesis is impaired by herbivores infestation. and H. Q. Feng ... [et al.].