Correlation of sequential floral and male gametophyte development and preliminary results on anther culture in <Emphasis Type="Italic">Opuntia ficus-indica</Emphasis>

Before approaching anther culture as a tool to trigger an androgenic response in a new species, it is advisable to characterize and correlate flower and male gametophyte development to enable reproducible identification of the appropriate starting material. Buds and flowers of Opuntia ficus-indica cv. Gialla were classified in eight stages according to their total length at the earlier stages and the length of the corolla in flowers with emerging sepals. Due to the low condensation of chromatin in the microspore nucleus as well as in the vegetative nucleus of the bi- and tricellular pollen along with the high autofluorescence of the intricate exine, DAPI staining turned out not to be feasible in this species. Therefore an approach based on light-microscopy observation of semithin sections was used. These sections were stained with toluidine blue for general structure recognition and I₂KI to study starch deposition. Correlations were made between the sequential floral and male gametophyte development. Using this approach we determined the timing of pollen formation and observed that pollen development is impaired in plants producing seedless fruits. Furthermore, anther culture was carried out with anthers collected from flower buds at stages 2 and 3. Most of the anthers produced callus, however no regeneration was obtained.     

Growth and gas exchange response to water shortage of a maize crop on different soil types

The effect of water shortage on growth and gas exchange of maize grown on sandy soil (SS) and clay soil was studied. The lower soil water content in the SS during vegetative growth stages did not affect plant height, above-ground biomass, and leaf area index (LAI). LAI reduction was observed on the SS during the reproductive stage due to early leaf senescence. Canopy and leaf gas exchanges, measured by eddy correlation technique and by a portable photosynthetic system, respectively, were affected by water stress and a greater reduction in net photosynthetic rate (A _N) and stomatal conductance (g _s) was observed on SS. Chlorophyll and carotenoids content was not affected by water shortage in either condition. Results support two main conclusions: (1) leaf photosynthetic capacity was unaffected by water stress, and (2) maize effectively endured water shortage during the vegetative growth stage.     

A germin-like protein of wheat leaf apoplast inhibits serine proteases

A protein resistant to heat and proteolysis that inhibits serine proteases was isolated from wheat leaf apoplasts. Based on trypsin inhibition, its more active form was a 66-69 kDa oligomer. It was dissociated in an 18-21 kDa monomer having an amino terminal sequence identical to the Box A of germins and germin-like proteins. Like these proteins, it was glycosylated and showed manganese superoxide dismutase activity. The monomer displayed three forms when examined by 2D western blot: two of 19 kDa, pI 5.8 and 6.2; and one of 21 kDa, pI 5.8. It was found that the protein controls serine protease activity in the apoplast of plants challenged with the fungus Septoria tritici.     

Factors controlling the colonial structure of <Emphasis Type="Italic">Pediastrum tetras</Emphasis> (Chlorophyceae)

Accounting for morphological plasticity in phytoplankton populations is relevant for taxonomy, systematic/evolutionary, and ecological studies. In this work, the green alga Pediastrum tetras (Ehrenberg) Ralfs was used to describe the variation in population size structure over its growth cycle and to analyze responses to changes in biotic and abiotic factors. Pediastrum cultures reached a final stable concentration in approximately 10 days. This density (8 × 10⁵ cells ml⁻¹) remained stable for at least another 13 days and the intrinsic growth rate was 0.24 ± 0.01 day⁻¹. In the exponential phase, the relative number of single cells and the proportion of large cells (with vesicles inside) within colonies increased. When density peaked, a relative increase of single cells as well as small cells in new colonies took place. Finally, during the stationary phase, the trend reversed: fewer single cells and a larger cell size (without vesicles) were observed. Results indicated that nutrient supply could affect population structure, diminishing the proportion of eight-cell colonies. Daphnia magna Straus significantly reduced the Pediastrum population density due to predation, and this led to a significant decrease in the density of the largest colonies. In addition, info-chemicals induced a slight increase in the density of the largest colonies compared to the control treatment. Our study suggests a possible trade-off in P. tetras colonial size in natural environments: during the stationary growth period in a lake, Pediastrum populations tend to increase in size for efficient use of nutrients, while they decrease in size in the presence of herbivores. Handling editor: J. Padisak     

ER-stress-induced secretion of circulating glucose-regulated protein 78kDa (GRP78) ameliorates pulmonary artery smooth muscle cell remodelling

Pulmonary arterial hypertension (PAH) is driven by vascular remodelling due to inflammation and cellular stress, including endoplasmic reticulum stress (ER stress). The main ER-stress chaperone, glucose-regulated protein 78 kDa (GRP78), is known to have protective effects in inflammatory diseases through extracellular signalling. The aim of this study is to investigate its significance in PAH. Human pulmonary arterial smooth muscle cells (PASMC) were stimulated with compounds that induce ER stress, after which the secretion of GRP78 into the cell medium was analysed by western blot. We found that when ER stress was induced in PASMC, there was also a time-dependent secretion of GRP78. Next, naïve PASMC were treated with conditioned medium (CM) from the ER-stressed donor PASMC. Incubation with CM from ER-stressed PASMC reduced the viability, oxidative stress, and expression of inflammatory and ER-stress markers in target cells. These effects were abrogated when the donor cells were co-treated with Brefeldin A to inhibit active secretion of GRP78. Direct treatment of PASMC with recombinant GRP78 modulated the expression of key inflammatory markers. Additionally, we measured GRP78 plasma levels in 19 PAH patients (Nice Group I) and correlated the levels to risk stratification according to ESC guidelines. Here, elevated plasma levels of GRP78 were associated with a favourable risk stratification. In conclusion, GRP78 is secreted by PASMC under ER stress and exhibits protective effects from the hallmarks of PAH in vitro. Circulating GRP78 may serve as biomarker for risk adjudication of patients with PAH.Graphical abstractProposed mechanism of ER-stress-induced GRP78 secretion by PASMC. Extracellular GRP78 can be measured as a circulating biomarker and is correlated with favourable clinical characteristics. Conditioned medium from ER-stressed PASMC reduces extensive viability, ROS formation, inflammation, and ER stress in target cells. These effects can be abolished by blocking protein secretion in donor cells by using Brefeldin A. Supplementary InformationThe online version contains supplementary material available at 10.1007/s12192-022-01292-y.     

Melatonin Prevents Oxidative Stress and Hepatocyte Cell Death Induced by Experimental Cholestasis

The induction of oxidative stress precedes liver injury during experimental obstructive jaundice (OJ). In this sense, different evidences suggest that melatonin (MEL), as antioxidant, may be useful in the protection against apoptosis and necrosis during experimental cholestasis. In addition, we will also assess if MEL-dependent protection is related to a recovery of antioxidant status disturbances induced by OJ. Cholestasis was achieved by double ligature and sectioning of the principal bile duct. MEL was injected intraperitoneally (500?μg/kg/day). Lipid peroxidation was evaluated by the measurement of malondialdehyde (MDA) content in liver. Different parameters related to antioxidant status, such as reduced glutathione (GSH), glutathione peroxidase (GPx), catalase and superoxide dismutase (SOD) were determined in liver. Liver injury was assessed by alanine aminotransferase (ALT) in serum, histological examination, DNA fragmentation and TUNEL assay. The activation of perisinusoidal stellate cells was evaluated by immunohistochemical measurement of α-smooth muscle actin in liver sections. The induction of OJ increased all the parameters related to apoptosis and necrosis in liver. The induction of liver injury was associated with stellate cell activation, as well as an increase in MDA (p<0.0001) and a reduction in GSH, GPx, catalase and SOD content (p<0.0001) in liver. MEL reduced hepatic apoptosis and necrosis (p<0.004) with a significant improvement in all oxidative stress markers. In conclusion, our results showed that MEL recovered the antioxidant status and reduced apoptosis and necrosis induced by experimental cholestasis.     

The thermal stability of a castor bean seed acid phosphatase

The effect of temperature on the activity and structural stability of an acid phosphatase (EC 3.1.3.2.) purified from castor bean (Ricinus communis L.) seeds have been examined. The enzyme showed high activity at 45 degrees C using p-nitrophenylphosphate (p-NPP) as substrate. The activation energy for the catalyzed reaction was 55.2 kJ mol(-1) and the enzyme maintained 50% of its activity even after 30 min at 55 degrees C. Thermal inactivation studies showed an influence of pH in the loss of enzymatic activity at 60 degrees C. A noticeable protective effect from thermal inactivation was observed when the enzyme was preincubated, at 60 degrees C, with the reaction products inorganic phosphate-P (10 mM) and p-nitrophenol-p-NP(10 mM). Denaturation studies showed a relatively high transition temperature (Tm) value of 75 degrees C and an influence of the combination of Pi (10 mM) and p-NP (10 mM) was observed on the conformational behaviour of the macromolecule.     

Membrane fluidity of microsomal and thymocyte membranes after X-ray and UV irradiation

A brief literature review shows that ionizing radiation in biological membranes and in pure lipid membranes causes malondialdehyde formation, indicating lipid peroxidation processes. With respect to membrane fluidization by ionizing radiation, in pure lipid membranes rigidization effects are always reported, whereas contradictory results exist for biological membranes. Starting from the assumption that membrane proteins at least partly compensate for radiation effects leading to a rigidization of membrane lipid regions, pig liver microsomes, as a representative protein-rich intracellular membrane system, were irradiated with X-rays or UV-C with doses up to 120 Gy at a dose rate of 0.67 Gy min^–1 and up to 0.73 J cm^–2 at an exposure rate of 16.2 mJ cm^–2 min^–1, respectively. For both irradiation types a weak but significant positive correlation between malondialdehyde formation and membrane fluidity is revealed throughout the applied dose ranges. We conclude that the membraneous protein lipid interface increases its fluidity under radiation conditions. Also, thymocyte ghosts showed an increased fluidity after X-ray irradiation. Fluidity measurements were performed by the pyrene excimer method.