Chlorophyliase (Chlase) is widely distributed in higher and lower plants and differs in activity. It occurs in various organs. In some plants the enzyme is synthesized in cytoplasm, in others in chloroplasts. Various Chlase forms are known. Participation, in the chlorophyll (Chl) degrading systém belongs to the main fimctions of Chlase. Moreover, it may catalyse Chl biosynthesis and takés part in photosynthesis. The Chlase activity is stimulated by radiant energy, sublethal freezing, heavy metals (Hg, Zn, Cu), Fe and Mn deficiency, and mosaic virus infection. The effect of water content on Chlase activity depends on individual plant organs. Osmotic and saline- osmotic stress decreases Chlase activity, but NaCl can stimulate the activity. The influence of plant age depends on plant genus. Some growth regulators (ethylene, heteroauxin, abscisic acid) increase Chlase activity, others (kinetin, dicarboxylic monoesters, gibberellic acid, gibbérellin A3) inhibit it. The mechanisms of Chlase action are also reviewed.
Chloroplasts utilize photons from solar radiation to synthesize energy-rich molecules of ATPs and NADPHs, which are further used in active cellular processes. Multiprotein complexes (MPCs), including photosystems (PSII and PSI), and the cellular architecture responsible for generation of the proton motive force and the subsequent photophosphorylation, mediate the task of ATP and NADPH synthesis. Both photosystems and other multiprotein assemblies are embedded in thylakoid membranes. Advances in techniques used to study structural biology, biophysics, and comparative genomics and proteomics have enabled us to gain insights of structure, function, and localization of each individual component of the photosynthetic apparatus. An efficient coordination among MPCs is essential for normal functioning of photosynthesis, but there are various stressors that might directly or indirectly interact with photosynthetic components and processes. Cadmium is one of the toxic heavy metals that interact with photosynthetic components and damage photosystems and other MPCs in thylakoids. In plants, iron deficiency shows similar symptoms as those caused by Cd. Our article provides a general overview of chloroplast structure and a critical account of Cd-induced changes in photosystems and other MPCs in thylakoids, and suggests the possible mechanisms involved in mediating these changes. The connection between Cd-induced Fe deficiency and the elevated Cd toxicity under the Fe-deficient condition was also discussed., H. Bashir, M. I. Qureshi, M. M. Ibrahim, M. Iqbal., and Obsahuje seznam literatury
Effects of high irradiance (HI) treatment on chloroplast pigment bleaching and on low temperature excitation and emission fluorescence spectra were studied in thylakoids isolated from 3- or 24-h greening cucumber cotyledons of etiolated seedlings. Irradiation of thylakoids isolated from 3-h greening seedlings with HI (approx. 3500 pmol m'^ s'*) caused chlorophyll (Chl) and carotenoid (Car) breakdown with the initial rates 3.0 and 4.2 mg m’^ s'*, respectively, whereas these values were 1.3 and 0.8 mg m-^ s'^ respectively, in thylakoids isolated from 24-h greening cotyledons. The photosusceptibility decreased in the sequence: protochlorophyll(ide), P-carotene, xanthophylls, Chl a, Chl b. In control seedlings the ratio E472/E437 or E486/E437 was 1.7-1.8-fold higher at the later phase than at the early phase of greening whereas the ratio F730/F684 reached approx. 0.40 or approx. 1.65 after 3- or 24-h greemng, respectively. Treatment of isolated thylakoids with high photon flux density caused a relative increase of the 472 and 486 nm band intensities in the excitation fluorescence spectrum of Chl, whereas the ratio F730/F684 increased only at the later phase investigated.
Many RNA recognition motif (RRM)-containing proteins are known to exist in chloroplasts. Major members of the RRM protein family, which are chloroplast ribonucleoproteins (cpRNPs), have been investigated in seed plants, including tobacco and Arabidopsis thaliana, but never in early land plants, such as bryophytes. In this study, we surveyed RRM proteins encoded in the moss Physcomitrella patens genome and predicted 25 putative chloroplast RRM proteins. Among them, two RRM-containing proteins, PpRBP2a and PpRBP2b, resembled cpRNPs and were thus referred to as cpRNP-like proteins. However, knockout mutants of either one or two PpRBP2 genes exhibited a wild type-like phenotype. Unlike Arabidopsis cpRNPs, the levels of mRNA accumulation in chloroplasts were not affected in the PpRBP2 knockout mutants. In addition, the efficiency of RNA editing was also not altered in the mutants. This suggests that PpRBP2a and 2b may be functionally distinct from Arabidopsis cpRNPs., H. Uchiyama, M. Ichinose, M. Sugita., and Obsahuje bibliografické odkazy
Development of mesophyll cell chloroplasts during ontogeny of second wheat (Triticum aestivum L.) leaf was compared in plants grown in Ml nutrient solution (+N) and in nutrient solution without nitrogen (-N). Chloroplast size and ultrastructure were evaluated quantitatively by means of transmission electron microscopy and stereology. In -N plants compared to +N ones, the life spán of the second leaf was shortened and chloroplast development modified; the most striking feature was the accumulation of starch. Moreover, mature chloroplasts of -N plants were smaller and had smaller relative partial volume of thylakoids and larger relative partial volume of plastoglobules than those of +N plants.
Glechoma longituba (Nakai) Kupr. is a perennial shade plant with pharmaceutical importance. The aim of this study was to investigate the effects of light intensity on the growth, photosynthesis, and accumulation of secondary metabolites in G. longituba grown under six different light environments. The high light intensity decreased the leaf size, specific leaf area, and aboveground dry mass, the number of grana per chloroplast, the number of lamella per granum, the thickness of the grana, the apparent quantum efficiency, the chlorophyll (Chl) content, the concentrations of ursolic and oleanolic acid. The high light increased the stomatal density, the stoma size, the number of chloroplast per a cell, the chloroplast size, the dark respiration rate, the light saturation point, the light compensation point, and the Chl a/b ratio. With the reduction in the light intensity, the light-saturated net photosynthetic rate, the aerial dry mass per plant, and the yields of ursolic and oleanolic acid decreased after an initial increase, peaking at 16 and 33% of sunlight levels. Overall, the 16 and 33% irradiance levels were the most efficient in improving the yields and qualities of the medicinal plant. The lower light demand and growth characteristics suggest that G. longituba is an extremely
shade-tolerant plant and that appropriate light intensity management might be feasible to obtain higher yields of secondary metabolites in agricultural management., L. X. Zhang, Q. S. Guo, Q. S. Chang, Z. B. Zhu, L. Liu, Y. H. Chen., and Obsahuje bibliografii
Prezentujeme případ mladé ženy, jež prodělala v dospělém věku operaci vrozené cysty pravého hepatiku, kterou vzhledem k těsnému kontaktu s velkými cévami nebylo možné kompletně resekovat. Byla provedena parciální resekce a cysto-jejuno-anastomóza (CJA) kdrenáži žluči. Pacientka byla 4 roky bez obtíží. Posléze se dostavily bolesti břicha, subikterus a laboratorní známky cholestázy Kvůli těmto potížím a opakovaným cholangoitidám prodělala řadu vyšetření a intervencí, které měly zajistit ozřejmění příčiny obstrukce a obnovení odtoku žluči. Použité zobrazovací metody neprokázaly jednoznačnou příčinu obtíží, proto bylo přistoupeno k operační revizi, při níž byl peroperační ultrasonografií prokázán tumor v oblasti CJA. Nález byl vzhledem k lokalizaci inoperabilní. Pacientka měla následně zjištěnu diseminaci malignity v játrech i v uzlinách a zemřela 5 měsíců od zjištění maligní diagnózy na hepatorenální selhání. Tento poměrně raritní případ dokládá zvýšené riziko maligního zvratu vrozených malformací žlučových cest především v případě jejich diagnózy a léčby v dospělém věku. V dostupné literatuře existuje jen málo dokumentovaných případů metachronního karcinomu po resekci žlučových cest., We present a case of a young woman, who underwent surgery for congenital bile duct cyst in adulthood. Due to location of the cysts it was impossible to completely remove it. The cyst was partially resected and it was performed cyst-jejunal anastomosis (CJA) to drain of bile. After operation the patient was 4 years without any problems. After this interval appeared pain in the right upper quadrant and subicterus with laboratory evidence of cholestasis. The patient suffered from recurrent cholangitis due to which a number of diagnostic tests and interventions were performed. Used imaging metods did not demonstrate an unequivocal cause of problems, therefore subsequently surgical revision was performed and the in-traoperative ultrasonography demonstrated tumor in anastomosis. The finding was inoperable due to inappropriate location. In the following period liver and lymphnode metastases appeared and patient died five months after diagnosis of malignancy. This relatively rare case illustrates an increased risk of malignant transformation of congenital malformations of the biliary tract. There are very few documented metachronous cancer after resection of the biliary tract in the literature., Eva Korčáková, Hynek Mírka, Vladislav Třeška, Tomáš Skalický, František Šlauf, Zdeněk Chudáček, Šárka Hadravská, and Literatura