Physiological and morphological characterisation of Limonium species in their natural habitats: Insights into their abiotic stress responses

Background and aims

Morphological and biochemical traits of four halophytes of the genus Limonium were analysed in plants sampled from salt marshes in SE Spain. This work aimed to explore the mechanism(s) behind the adaptation of these species to stressful habitats, with particular emphasis on responses to drought.

Methods

Plants of each species together with soil samples were collected in summer, which is the most stressful season in the Mediterranean. Soil parameters and plant morphological traits were determined, and the levels of several biochemical stress markers in plants were measured using spectrophotometric assays. A multivariate analysis was performed to correlate soil and plant data.

Results

Morphological characteristics regarding the underground system topology and several biochemical traits (higher foliar Ca²⁺, sucrose and glucose, and lower proline, glycine-betaine and fructose) clearly separate L. santapolense individuals from plants of the other three species.

Conclusions

Drought tolerance of L. santapolense in the field is mostly dependent on morphological adaptations: when growing in an arid location, plants of this species develop long taproots that can extract water from the deep, moist layers of the soil.

     

A radioautographic analysis of the prospective cardiac area in the chick blastoderm by means of labeled grafts

Summary Grafting regions of the blastodisc of the chick, labeled with H₃-thymidine at Stages 5 and 6 ofHamilton andHamburger, is a very useful technique for following the morphogenetic movements of the grafted material. Areas (E-M) of the blastodisc of 2.75 by 0.55 mm, grafted in the homologous region of an embryo, participate in its morphogenetic movements. The labeled reversed cardiac area can sometimes be incorporated into the host, and a tubular heart can develop which includes some of the graft tissue, Figs. 3, 4, 5, and 6. The morphogenetic movements shaping the anterior intesinal portal and early foregut can occur despite the reversal of a large rectangle of the endomesoderm, Fig. 6. The coelomic epithelium lining the operated side, a part of the myoepicardium of this side, as well as the endoderm of the ventral portion of the foregut, and, more caudally, half of the anterior intestinal portal are derived from the graft as shown by strong radioactive labeling of the cells, Figs. 3, 4 and 6. The morphogenetic movements of the graft endoderm and mesoderm are independent, the pre-heart mesoderm moving in a cranial direction, while the endoderm extends caudally, Figs. 3 and 4.This study raises an interesting question: Can the original cephalic preconal cardiogenic mesoderm regulate to form sinoatrial tissue (and vice versa) ? The evidence obtained in the present investigation is not extensive enough to warrant conclusions as to the important question of regulation; for this a considerable number of operated embryos is required in which a recognizable normal heart has developed (up to Stage 12–13).This research was supported by a grant from the Association for the Aid of Crippled Children, New York.     

Aspirin treatment of mice infected with Trypanosoma cruzi and implications for the pathogenesis of Chagas disease

Chagas disease, caused by infection with Trypanosoma cruzi, is an important cause of cardiovascular disease. It is increasingly clear that parasite-derived prostaglandins potently modulate host response and disease progression. Here, we report that treatment of experimental T. cruzi infection (Brazil strain) beginning 5 days post infection (dpi) with aspirin (ASA) increased mortality (2-fold) and parasitemia (12-fold). However, there were no differences regarding histopathology or cardiac structure or function. Delayed treatment with ASA (20 mg/kg) beginning 60 dpi did not increase parasitemia or mortality but improved ejection fraction. ASA treatment diminished the profile of parasite- and host-derived circulating prostaglandins in infected mice. To distinguish the effects of ASA on the parasite and host bio-synthetic pathways we infected cyclooxygenase-1 (COX-1) null mice with the Brazil-strain of T. cruzi. Infected COX-1 null mice displayed a reduction in circulating levels of thromboxane (TX)A(2) and prostaglandin (PG)F(2α). Parasitemia was increased in COX-1 null mice compared with parasitemia and mortality in ASA-treated infected mice indicating the effects of ASA on mortality potentially had little to do with inhibition of prostaglandin metabolism. Expression of SOCS-2 was enhanced, and TRAF6 and TNFα reduced, in the spleens of infected ASA-treated mice. Ablation of the initial innate response to infection may cause the increased mortality in ASA-treated mice as the host likely succumbs more quickly without the initiation of the "cytokine storm" during acute infection. We conclude that ASA, through both COX inhibition and other "off-target" effects, modulates the progression of acute and chronic Chagas disease. Thus, eicosanoids present during acute infection may act as immunomodulators aiding the transition to and maintenance of the chronic phase of the disease. A deeper understanding of the mechanism of ASA action may provide clues to the differences between host response in the acute and chronic T. cruzi infection.     

Unraveling cryptic invasion of a freshwater snail in Chile based on molecular and morphological data

Cryptic species may cause biological invasions to be overlooked leading to underestimation of the potential impacts of invaders on the new ecosystems. Identification of freshwater snails is challenging because of the scarcity of discriminative morphological characters and the limited taxonomic knowledge of some taxa. Here, molecular and morphological analyses were performed to investigate the identity of viable populations of the genus Physa in aquatic ecosystems of different basins in northern and central Chile, including habitats where the native species Physa chilensis and Physa nodulosa have been traditionally recognized. Molecular analyses based on mitochondrial DNA sequences from the small subunit 16S rDNA and cytochrome c oxidase subunit 1 identified all specimens sequenced as belonging to the globally invasive species Physa acuta. Microscopic examination of the radula and morphological observations of the reproductive system were congruent with these findings. Highly divergent haplotypes found in El Salto suggest multiple introductions of different lineages of the invader in this locality. It is clear that for future management planning a more reliable assessment of the status of P. chilensis and P. nodulosa is required.     

Unexpected wide substrate specificity of C. perfringens α-toxin phospholipase C

Clostridium perfringens phospholipase C (CpPLC), also called α-toxin, is the main virulence factor for gas gangrene in humans. The lipase activity serves the bacterium to generate lipid signals in the host eukaryotic cell, and ultimately to degrade the host cell membranes. Several previous reports indicated that CpPLC was specific for phosphatidylcholine and sphingomyelin. Molecular docking studies described in this paper predict favorable interactions of the CpPLC active site with other phospholipids, e.g. phosphatidylethanolamine, phosphatidylinositol and, to a lesser extent, phosphatidylglycerol. On the basis of these predictions, we have performed experimental studies showing α-toxin to degrade all the phospholipids mentioned above. The molecular docking data also provide an explanation for the observed lower activity of CpPCL on sphingomyelin as compared to the glycerophospholipids.