The Response of Picea abies Somatic Embryos to UV-B Radiation Depends on the Phase of Maturation

Ultraviolet-B (UV-B) radiation is a key environmental signal which initiates diverse responses that affect the metabolism, development, and viability of plants. In keeping with our previous studies, we concentrated primarily on how UV-B radiation affects Norway spruce [Picea abies (L.) Karst.] somatic embryo maturation and how phenolics and polyamines (PAs) are linked to the defense response invoked by UV-B irradiation. We treated clusters of Norway spruce embryogenic culture (EC) with UV-B during the five stages of embryo maturation (early, cylindrical, precotyledonary, cotyledonary, and mature embryos). For the first time, we take an advantage of the unique environmental scanning electron microscope AQUASEM II to characterize somatic embryos in their native state. The severity of the irradiation effect on embryonal cell viability was shown to be dependent on the intensity of radiation as well as the stage of embryo development, and might be related to the formation of protoderm. The response of early embryos was characterized by an increase in malondialdehyde (MDA), a marked decrease in PA contents and a decline in phenolics. The reduced ability to activate the defense system seems to be responsible not only for the severe cell damage and decrease in viability but also for the inhibition of embryo development. The significant reduction in spermidine (Spd), which has been reported to be crucial for the somatic embryo development of several coniferous species, may be causally linked to the limited development of embryos. The pronounced decrease in cell wall-bound ferulic acid might correspond to failure of somatic embryos to reach more advanced stages of development. Embryos at later stages of development showed stress defense responses that were more efficient against UV-B exposure

The humidity level matters during the desiccation of Norway spruce somatic embryos

In Norway spruce, as in many other conifers, the germination capacity of somatic embryos is strongly influenced by the desiccation phase inserted after maturation. The intensity of drying during desiccation eminently affected the formation of emblings (i.e., seedlings developed from somatic embryos). Compared to non-desiccated embryos, the germination capacity of embryos desiccated at 100% relative humidity was about three times higher, but the reduction of relative humidity to 95 and 90% had a negative effect on the subsequent embryo development. The water loss observed in these embryos did not lead to an increase in lipid peroxidation, as shown by malondialdehyde levels. Another metabolic pathway in plants that mediates a response to abiotic stresses is directed toward the biosynthesis of polyamines (PAs). The activities of PA biosynthetic enzymes increased steadily in embryos during desiccation at 100% relative humidity, whereas they decreased at lower humidity. The total content of free PAs in the embryos gradually decreased throughout desiccation. The increase in free putrescine (Put) and perchloric acid-insoluble Put conjugates was observed in embryos desiccated at lower humidity. These changes were accompanied to some extent by the transcription of the genes for the PA biosynthesis enzymes. Desiccation at 100% relative humidity increased the activity of the cell wall-modifying enzymes β-1,3-glucanases and chitinases; the activities of these enzymes were also significantly suppressed at reduced humidity. The same pattern was observed in the transcription of some β-1,3-glucanase and chitinase genes. Desiccation treatments triggered metabolic processes that responded to water availability, suggesting an active response of the embryo to the reduction in humidity. A positive effect was demonstrated only for desiccation at high relative humidity. Some of the physiological characteristics described can be used as markers of inappropriate relative humidity during somatic embryo desiccation

Pharmacogenetics of warfarin

Department of Biochemical SciencesKatedra biochemických vědFaculty of Pharmacy in Hradec KrálovéFarmaceutická fakulta v Hradci Králov

Somatic embryogenesis of norway spruce (Picea abies (L.) Karst.)

5. CONCLUSIONS . The development of somatic embryos on maturation meďum can be divided at anatomical level into fow developmental stages, differing in the inner struďure: stage of early somatic embryo, cylindricď stage, precotyledonary stageand cotyledonary stage. o The prolonged cultivation of coýledonary errrbryos on maturation medium leads to disintegration of the root cap, connected with starch and phenolic cornpormdsdeposition. o The time course of disctete developmental stagesis affected by PEG 4000; use of 3,75 % PBG speeds up the process of maturation by tvro weeks. Increased level of PEG (7,5%o)leads to the formation of nrpturesin ernbryohypocotyls. The content of non-structural saccharides increases during the cultivation of embryogenic culture on maturation medium due to increasing level of sucrose in developing embryos. The content of hexoses in embryos is low. The addition of 3,75 % PEG 4000 into maturation medium increases the sucrose to hexoses ratio in somatic embryos, the total amotmt of saccharides slightly decreases.7,5 %PEG leadsto hexosesaccumulationin embryos. Insertion of pre-maturation phase (without growth regulators) between proliferation and maturation increases total amount of developed embryos in a majority lines tested. cultivation of embryogenic cultues of rafts with..

Pharmacogenetics of warfarin

Department of Biochemical SciencesKatedra biochemických vědFaculty of Pharmacy in Hradec KrálovéFarmaceutická fakulta v Hradci Králov

Somatic embryogenesis of norway spruce (Picea abies (L.) Karst.)

Katedra experimentální biologie rostlinDepartment of Experimental Plant BiologyFaculty of SciencePřírodovědecká fakult