Contribution of leaves of different ages to plant carbon balance as affected by potassium supply and water stress

The carbon balances of whole, 21-d old French bean plants (Phaseolus vulgaris L.) grown in standard nutrient solution (1K) and its modifications without (OK) or surplus (2K) potassium were calculated from the daily photosynthetic carbon inputs of individual leaves, and the daily respiratory carbon losses by individual leaves, stalks and petioles, and roots. Under the three K concentrations, maximum net photosynthetic rates (P_n) were found in the 2nd or in the 3rd trifoliate leaves, maximum respiratory rates (R_d) in the youngest, 4th trifoliate leaves; the P_n/R_d ratio decreased with leaf age. In all leaves of 2K plants, leaf dry masses and thicknesses, P_n, P_n/P_d ratios, and stomatal and intracellular conductances were lower than in OK and IK plants. Daily whole-plant net carbon gain was highest in IK plants, whereas in OK and 2K plants it was 98.0 and 81.3 % of IK, respectively. Similar values were found in the parameters of growth analysis, namely in net assimilation rates and relative growth rates. No differences were found in water potential (Ψ _w ) or water saturation deficit (W_sat) in the OK, 1K and 2K plants sufficiently supplied with water or during wilting and resaturation. The decrease in Ψ_w to −0.97 MPa was associated with a 19.9 %, 31.4 % and 23.4 % decrease in P_n of OK, 1K and 2K plants, respectively, but no effect on R_d was found. In the three variants, the short-time effect of mild water stress was fully reversible.     

Extinction Risk Escalates in the Tropics

The latitudinal biodiversity gradient remains one of the most widely recognized yet puzzling patterns in nature [1]. Presently, the high level of extinction of tropical species, referred to as the “tropical biodiversity crisis”, has the potential to erode this pattern. While the connection between species richness, extinction, and speciation has long intrigued biologists [2], [3], these interactions have experienced increased poignancy due to their relevancy to where we should concentrate our conservation efforts. Natural extinction is a phenomenon thought to have its own latitudinal gradient, with lower extinction rates in the tropics being reported in beetles, birds, mammals, and bivalves [4]–[7]. Processes that have buffered ecosystems from high extinction rates in the past may also buffer ecosystems against disturbance of anthropogenic origin. While potential parallels between historical and present-day extinction patterns have been acknowledged, they remain only superficially explored and plant extinction patterns have been particularly neglected. Studies on the disappearances of animal species have reached conflicting conclusions, with the rate of extinction appearing either higher [8] or lower [9] in species richness hotspots. Our global study of extinction risk in vascular plants finds disproportionately higher extinction risk in tropical countries, even when indicators of human pressure (GDP, population density, forest cover change) are taken into account. Our results are at odds with the notion that the tropics represent a museum of plant biodiversity (places of historically lowered extinction) and we discuss mechanisms that may reconcile this apparent contradiction.     

Allosteric modulation of kinases and GPCRs: design principles and structural diversity

Allosteric binding sites, as opposed to traditional orthosteric binding sites, offer unparalleled opportunities for drug discovery by providing high levels of selectivity, mimicking physiological conditions, affording fewer side effects because of desensitization/downregulation, and engendering ligands with chemotypes divergent from orthosteric ligands. For kinases, allosteric mechanisms described to date include alteration of protein kinase conformation blocking productive ATP binding which appear 'ATP competitive' or blocking kinase activation by conformational changes that are 'ATP non-competitive'. For GPCRs, allosteric mechanisms impart multiple modes of target modulation (positive allosteric modulation (PAM), negative allosteric modulation (NAM), neutral cooperativity, partial antagonism (PA), allosteric agonism and allosteric antagonism). Here, we review recent developments in the design principles and structural diversity of allosteric ligands for kinases and GPCRs.     

Methylene blue as an antimalarial agent

Methylene blue has intrinsic antimalarial activity and it can act as a chloroquine sensitizer. In addition, methylene blue must be considered for preventing methemoglobinemia, a serious complication of malarial anemia. As an antiparasitic agent, methylene blue is pleiotropic: it interferes with hemoglobin and heme metabolism in digestive organelles, and it is a selective inhibitor of Plasmodium falciparum glutathione reductase. The latter effect results in glutathione depletion which sensitizes the parasite for chloroquine action. At the Centre de Recherche en Santé de Nouna in Burkina Faso, we study the combination of chloroquine with methylene blue (BlueCQ) as a possible medication for malaria in endemic regions. A pilot study with glucose-6-phosphate dehydrogenase-sufficient adult patients has been conducted recently.     

Estimation of the quantity of bacteria encapsulated in Lentikats Biocatalyst via phospholipid fatty acids content: a preliminary study

The content of phospholipid fatty acids (PLFA) was determined in samples of polyvinyl alcohol lenses (Lentikats Biocatalyst, LB) with encapsulated Paracoccus denitrificans withdrawn during long-term denitrification experiments. The total PLFA content correlated highly with specific denitrification activities of LB as well as biomass estimation based on image analyses of microscopic photos. The results confirmed the applicability of PLFA determination for estimation of the amount of living encapsulated microbial biomass during biotechnological applications.     

Establishment of introduced antagonistic bacteria in the rhizosphere of transgenic potatoes and their effect on the bacterial community

In a field release experiment, rifampicin resistant mutants of two antagonistic plant-associated bacteria were used for seed tuber inoculation of transgenic T4 lysozyme expressing potatoes, transgenic control potatoes and non-transgenic parental potatoes. The T4 lysozyme tolerant Pseudomonas putida QC14-3-8 was originally isolated from the tuber surface (geocaulosphere) of T4 lysozyme producing plants and showed in vitro antibacterial activity to the bacterial pathogen Erwinia carotovora ssp. atroseptica. The T4 lysozyme sensitive Serratia grimesii L16-3-3 was originally isolated from the rhizosphere of parental potatoes and showed in vitro antagonism toward the plant pathogenic fungus Verticillium dahliae. The establishment of the inoculated bacteria in the rhizosphere and geocaulosphere of the different plant lines was monitored over one growing season to assess the effect of T4 lysozyme produced by transgenic potato plants on the survival of both inoculants. Both introduced isolates were able to colonize the rhizo- and geocaulosphere of transgenic plants and non-transgenic parental plants, and established in the rhizosphere at levels of ca. log(10) 5 colony forming units g(-1) fresh weight of root. During flowering of plants, significantly more colony counts of the T4 lysozyme tolerant P. putida were recovered from transgenic T4 lysozyme plants than from the transgenic control and the parental line. At this time, the highest level of T4 lysozyme (% of total soluble protein) was detected. Effects of the inoculants on the indigenous microbial community were monitored by analysis of PCR-amplified fragments of the 16S rRNA genes of the whole bacterial community after separation by denaturing gradient gel electrophoresis (DGGE). At any sampling time, the DGGE pattern of rhizosphere and geocaulosphere communities did not show differences between the inoculated and non-inoculated potatoes. Neither of the introduced strains became a dominant member of the bacterial community. This work was the first approach to assess the establishment of plant growth promoting rhizobacteria and potential biocontrol agents on transgenic plants.     

Fin56-induced ferroptosis is supported by autophagy-mediated GPX4 degradation and functions synergistically with mTOR inhibition to kill bladder cancer cells

Ferroptosis is a form of regulated cell death that emerges to be relevant for therapy-resistant and dedifferentiating cancers. Although several lines of evidence suggest that ferroptosis is a type of autophagy-dependent cell death, the underlying molecular mechanisms remain unclear. Fin56, a type 3 ferroptosis inducer, triggers ferroptosis by promoting glutathione peroxidase 4 (GPX4) protein degradation via a not fully understood pathway. Here, we determined that Fin56 induces ferroptosis and autophagy in bladder cancer cells and that Fin56-triggered ferroptosis mechanistically depends on the autophagic machinery. Furthermore, we found that autophagy inhibition at different stages attenuates Fin56-induced oxidative stress and GPX4 degradation. Moreover, we investigated the effects of Fin56 in combination with Torin 2, a potent mTOR inhibitor used to activate autophagy, on cell viability. We found that Fin56 synergizes with Torin 2 in cytotoxicity against bladder cancer cells. Collectively, our findings not only support the concept that ferroptosis is a type of autophagy-dependent cell death but imply that the combined application of ferroptosis inducers and mTOR inhibitors is a promising approach to improve therapeutic options in the treatment of bladder cancer.Subject terms: Macroautophagy, Macroautophagy     

Length-weight relationships of ornamental fish species from Amanã Lake,Amanã Reserve,Amazonas, Brazil

Length-weight relationships (LWRs) were estimated for 16 ornamental fish species from Amanã Lake and nine tributary streams, in Central Brazilian Amazonia. Sampling was carried out bimonthly for a year (2007–2008), using two sets of four gillnets (20 m × 2 m, 2,5; 3,5; 04; 4,5 cm stretch mesh size); trawls were performed with seine nets (35 m × 6 m, 3 mm stretch mesh size); native fish-traps (fyke-net like fish-traps woven from local lianas), and dip nets (0.5 m × 0.5 m stretch mesh size). Measurements were done for standard length (SL – 0.1 cm precision) and total weight (Wt – 0.01 g precision). This study provides information on the length–weight relationships for all sampled species and, in addition, provides new maximum standard lengths for six species.     

Curcuma pygmaea sp. nov. (Zingiberaceae) from Vietnam and notes on two related species C. parviflora and C. thorelii.

Curcuma pygmaea?korni?k. & ?ída f. (Zingiberaceae), a new species from Vietnam, is described and illustrated. Notes on its closest allies in Curcuma subgenus Hitcheniopsis, C. parviflora Wall. and C. thorelii Gagnep., are provided and a lectotype of C. thorelii is designated.