Caspase-like proteases and their role in programmed cell death in plantsPiszczek, Ewa; Gutman, Wojciech
doi: 10.1007/s11738-007-0086-6pmid: N/A
The investigations performed over recent few years have proved the existence of caspase-like proteases in plants. Three groups of caspase-like proteases: metacaspases, legumain family proteases (VPEs) and saspases have been identified and characterized in plants so far. A considerable amount of evidence supports the role of these enzymes in programmed cell death (PCD) occurring during plant development, their organ senescence as well as hypersensitive response (HR) after pathogen attack. Current knowledge of these enzyme molecular and biochemical structures is summarized in the paper. The homology of caspase-like proteases to animal caspases has been also indicated. Some future perspectives of research concerning the signal pathway during PCD, the regulation of activity and mode of action of these proteases are presented in the article.
Drought response of two bedding plantsChyliński, Wojciech; Łukaszewska, Aleksandra; Kutnik, Katarzyna
doi: 10.1007/s11738-007-0073-ypmid: N/A
Bedding plants are an important part of the urban public space and private gardens. However, they are not always properly watered and suffer from drought stress, especially when grown in containers. In this trial a response to water stress of two commonly used species, impatiens (Impatiens walleriana Hook) and geranium (Pelargonium hortorum L. H. Bailey) were compared. The former is highly herbaceous and prone to wilting whereas the latter has hairy leaves and is better adapted to drought. Plants were grown at three levels of soil water content (SWC): 80% (control), 60% (mild stress) and 30% (severe stress). Drought was maintained during three 10 day cycles, separated by 10 day periods of normal watering. In both species roots were significantly longer in plants grown at 30% SWC as compared to 80% SWC while plant height and flower number were reduced by drought only in impatiens. The initial relative water content (RWC) was lower in geranium and decreased less in response to drought than in impatiens. Ammonium content in leaves of both species increased significantly under stress but the ranges of increase were different in both species. There was a significant increase in the free amino acids content in leaves of impatiens as compared to geranium but this rise was more time than drought dependent. The reduction in the a + b chlorophyll concentration in leaves of impatiens was significantly time and stress dependent while no reaction in geranium was observed. The above results show that changes in leaf RWC merit further attention as a possible indicator of plant response to drought stress in ornamental plants but additional studies are needed before this or other parameters can be used to evaluate new bedding plants for introduction into urban growing conditions, or as selection criteria in breeding for adaptation to demanding growing conditions.
Seasonal ultrasonic acoustic emissions of Quercus ilex L. trees in a Mediterranean forestOgaya, Romà; Peñuelas, Josep
doi: 10.1007/s11738-007-0048-zpmid: N/A
Ultrasonic acoustic emissions were measured in Quercus ilex trees of a Mediterranean forest in Catalonia (NE Spain) each season from summer of 2004 to autumn of 2005. Acoustic emissions were maximum during hot and dry summer periods. Acoustic emissions started below 17% soil moisture, 0.85 RWC, and 2.5 MPa leaf water potential. They were negatively correlated with soil moisture and leaf water potential. The relationship between acoustic emissions and leaf water potential was the strongest, indicating that xylem tension is the most important factor inducing both cavitation (acoustic emissions) and a decrease in leaf water potential. Future increase of xylem cavitation derived from climate change may result in growth and survival limitations for this species in the drier southern limits of its current distribution.
Organospecific responses of lupin seedlings to lead Localization of hydrogen peroxide and peroxidase activityPrzymusiński, Roman; Rucińska-Sobkowiak, Renata; Ilska, Bogna; Gwóźdź, Edward
doi: 10.1007/s11738-007-0049-ypmid: N/A
In an earlier work using tissue printing method, we found that the PR-10 stress protein was observed in leaf petiole of lupin seedling where lead was not detected (Przymusiński et al. 2001). These results suggested the presence of substance(s) mediating a signal transduction from directly affected cells to distant organs. As the hydrogen peroxide was found to be involved in signal transduction pathway, in the present paper, we analysed the level of H2O2 in the organ of lupin seedlings exposed to Pb2+ with spectrophotometric method and tissue printing technique. It was unequivocally demonstrated that the level of H2O2 and the activity of peroxidase increased in every tested organ of lead-treated lupin seedling. Both the level of H2O2 and the activity of POX were correlated with amount of Pb2+ ions in the cells (Przymusiński et al. 2001) and decreased in tissues more and more distant from the site of metal application. On the other hand, there was no correlation between the histological localization of H2O2 and peroxidase. Our results seem to confirm the hypothesis that H2O2 may act as a signalling substance involved in the induction of PR protein synthesis. It was indicated that there is high degree of correlation between the localization of H2O2 and the histological localization of PR-10 proteins (Przymusiński et al. 2001) in every tested organ of lupin seedling. The presented hypothesis is also supported by the fact that H2O2 and PR-10 proteins are detected in organs and tissues where Pb2+ was not found at all.
Enhancing antioxidative capacity of Lepidium meyenii calli by addition of methyl salicylate to culture mediumWang, Ya-Li; Wang, Xiao-Dong; Zhao, Bing; Wang, Yu-Chun
doi: 10.1007/s11738-007-0050-5pmid: N/A
Addition of 0.01–0.2 mM methyl salicylate (MeSA) to the culture media, the antioxidative capacities of maca fresh calli were increased and were 1.19–1.88 times of the control. But MeSA inhibited maca cell growth and this negative effect was dose-dependent. The dry weights of maca calli were 0.60–0.95 times of the control when addition of 0.01–0.2 mM MeSA to the culture media. Elicited by 0.05 mM MeSA, the total phenolic contents in maca calli increased and were 1.25–1.37 times of those in the control in the period from the 10th to the 20th culture day. H2O2 and malondialdehyde (MDA) contents increased as well. At the same time, the activities of antioxidative enzymes had corresponding changes. In conclusions, the antioxidative capacity of maca calli could be enhanced by addition of MeSA to the culture media. Considering the increase of antioxidative capacity and inhibition of maca cell growth, 0.05 mM MeSA was optimal concentration.
Changes in micropore system of roots of wheat and triticale seedlings under aluminum stress as determined using water vapor adsorption—desorptionSzatanik-Kloc, Alicja; Józefaciuk, Grzegorz
doi: 10.1007/s11738-007-0051-4pmid: N/A
Plant root structure including the pore system is severely injured in Al-toxic environments. Experimental water vapor desorption isotherms estimated using vacuum chamber method were used to characterize micropore build-up of roots of wheat (Lanca) and triticale (Debo) 4-day seedlings and its changes after 24 h (8 mg dm−3) aluminum stress. The micropore volumes and average pore radii increased after the stress whereas pore fractal dimensions decreased. The above changes were more pronounced for these roots which were not able to grow further after the stress when compared to the control roots, the total micropore volume was almost twice higher and the fractal dimension reached a value of 2 which is characteristic for flat, two-dimensional surface. The observed alterations of pore system indicate damage of root tissue and possible strong binding of aluminum on cell wall surfaces.
Salt-tolerant reed plants contain lower Na+ and higher K+ than salt-sensitive reed plantsTakahashi, Ryuichi; Nishio, Takayoshi; Ichizen, Nobumasa; Takano, Tetsuo
doi: 10.1007/s11738-007-0052-3pmid: N/A
Reed plants (Phragmites australis Trinius) grow not only in fresh and brackish water areas but also in arid and high salinity regions. Reed plants obtained from a riverside (Utsunomiya) were damaged by 257 mM NaCl, whereas desert plants (Nanpi) were not. When the plants were grown under salt stress, the shoots of the Utsunomiya plants contained high levels of sodium and low levels of potassium, whereas the upper part of the Nanpi plants contained low levels of sodium and high levels of potassium. One month salt stress did not affect potassium contents in either Utsunomiya or Nanpi plants, but it did dramatically increase sodium contents only in the Utsunomiya plants. The ratio of K+ to Na+ was maintained at a high level in the upper parts of the Nanpi plants, whereas the ratio markedly decreased in the Utsunomiya plants in the presence of NaCl. Accumulation of Na+ in the roots and Na+ efflux from the roots were greater in the Nanpi plants than in the Utsunomiya plants. These results suggest that the salt tolerance mechanisms of Nanpi reed plants include an improved ability to take up K+ to prevent an influx of Na+ and an improved ability to exclude Na+ from the roots.
Characterization of olive seed storage proteinsWang, Wei; Dios Alché, Juan; Rodríguez-García, Marìa
doi: 10.1007/s11738-007-0053-2pmid: N/A
At present little is known about olive seed storage proteins (SSPs). A better understanding of olive SSPs will be important for future biotechnology efforts. In the present study, we first developed a protocol relied on chloroform for preparing protein samples free of lipids from lipid-rich olive seeds. Then, we characterized olive SSPs by SDS-PAGE, N-terminal sequencing and immunoblot. Two smaller subunits (20 and 21.5 kD) of SSPs were purified to homogeneity and used for antibody production or N-terminal sequencing. N-terminal sequencing confirmed that major olive SSPs are 11S globulins. Moreover, the components and size distribution of SSPs are identical among several olive cultivars examined, suggesting that their synthesis is highly conserved in this species. Olive SSPs are soluble in aqueous alcohol, with limited solubility in water and dilute salt. Thus, despite their homology with globulins, olive SSPs are similar in solubility to prolamins and different from globulins in other dicot plants. Finally, the accumulation of olive SSPs during fruit maturation was examined. Our results revealed that the accumulation of SSPs is time-dependent and tissue-specific, and only 105 days after pollination (DAP), did individual components of SSPs synthesize substantially, and accumulate rapidly in large quantities over a short period of time. Our results suggest that a 36 kD protein is the precursor of olive SSPs, and 90–105 DAP seems to be a crucial transition period (from a precursor to mature subunits) for the accumulation of SSPs.
Pretreatment in thidiazuron improves the in vitro shoot induction from leaves in Curculigo orchioides Gaertn., an endangered medicinal plantThomas, T.
doi: 10.1007/s11738-007-0055-0pmid: N/A
Leaf regeneration via direct induction of adventitious shoots obtained from an endangered medicinal plant, Curculigo orchioides Gaertn. by pretreating with thidiazuron. C. orchioides is an endangered medicinal herb belonging to the family Hypoxidaceae. Direct inoculation of leaf pieces on MS medium supplemented with various concentrations of BAP (2–8 μM) or TDZ (2–8 μM) alone or in combination with NAA (0.5 and 1.0 μM) produced low shoot induction both in terms of % response and number of shoots per explant. Hence, leaf explants were pretreated with 15, 25 or 50 μM thidiazuron (TDZ), for 6, 24 or 48 h with the aim of improving shoot regeneration from cultured explants. After pretreatment, explants were transferred to an agar solidified MS medium that was supplemented with BAP (4 μM), TDZ (6 μM), BAP (4 μM) + NAA (1.0 μM), TDZ (6 μM) + NAA (0.5 μM). Control explants were incubated directly on the medium without any pretreatment. The pretreatment of explants with 15 μM TDZ for 24 h significantly promoted the formation of adventitious shoots and the maximum response was observed on MS medium supplemented with 6 μM TDZ. In this medium, 96 % cultures responded with an average number of 16.2 adventitious shoots per explant. The percentage of leaf explants producing shoots and the average number of shoots per explant were significantly improved when TDZ pretreated leaves were cultured onto MS medium supplemented with BAP or TDZ alone or in combination with NAA. The rooted plantlets were successfully transplanted to soil with 90% success. The present investigation indicated the stimulatory role of TDZ pretreatment in regulating shoot regeneration from leaf explants of C. orchioides.