Rodent seed predation on tree invader species in grassland habitats of the inland Pampa

Woody plant invasion in grassland ecosystems is a worldwide phenomenon, and biotic interactions as competition and predation have been invoked as a possible barrier to woody encroachment in many ecosystems. We evaluated the role of rodents as seed predators in Pampean grasslands, and we assessed the differences in removal by rodents between one native species, Prosopis caldenia (Caldén) and one exotic species, Gleditisia triacanthos (Honey locust). The experiment was conducted at different phases of the rodent population cycle in two grassland communities, a remnant of a native grassland and a post agriculture grassland (old field). The amount of seed loss caused by predation was estimated by a bait-removal experiment in foraging stations. We estimated the frequency of foraging stations with consumption, the overall amount of seed predation and the individual rate of seed predation. The total amount of seed removal and the individual rate of seed removal were higher for P. caldenia than for G. triacanthos, in the native grassland than in the old field, and in autumn when rodent density was maximum. Overall, the role of rodents on woody seed removal varied according to the plant species and depending on the local conditions that vary through time and space.     

Biology of Tupiocoris cucurbitaceus (Hemiptera: Miridae), a predator of the greenhouse whitefly Trialeurodes vaporariorum (Hemiptera: Aleyrodidae) in tomato crops in Argentina

The predator Tupiocoris cucurbitaceus is frequently found attacking Trialeurodes vaporariorum in greenhouses without pesticide applications in Argentina. The objective of these studies was to evaluate some biological characteristics of this species fed on three types of diet (whitefly nymphs, Sitotroga cerealella eggs and a mix of both) and on two host plants (tomato and tobacco), under controlled experimental conditions. Preimaginal developmental time for female and male bugs was shorter in the presence of whiteflies than with only moth eggs. Females lived longer when they ate only whitefly nymphs compared to a mixed diet or only moth eggs. The amount of adult descendants was greater when bugs could eat whiteflies, regardless of the presence of S. cerealella. Embryonic development time, male longevity and sex proportion were not affected by the diet or the host plant. Prey consumption was evaluated for three T. cucurbitaceus life history stages (fourth/fifth instar nymphs, female and male adults) on two types of prey (whitefly nymphs and S. cerealella eggs). On tomato, females were more voracious than males and nymphs. On tobacco, adults and nymphs consumed more S. cerealella than T.vaporariorum nymphs, but again, bug females preyed more than males and nymphs. Results demonstrate that T. cucurbitaceus can survive, develop and reproduce normally using both T. vaporariorum and S. cerealella eggs as prey on tobacco or tomato plants. This information can be useful for managing this predator against T. vaporariorum through conservative or augmentative biological control strategies.     

Slurry bioreactors with simultaneous electron acceptors for bioremediation of an agricultural soil polluted with lindane

The purpose of our study was 2-fold: (i) to evaluate the effect of dominant electron acceptor [either aerobic, methanogenic, or sulfate-reducing slurry bioreactor (SB)] and biostimulation with sucrose on lindane removal from heavy soil and (ii) to assess the effect of the type of combined environments [partially aerated methanogenic (PAM) and simultaneous methanogenic-sulfate reducing (M-SR)] and addition of silicone oil as solvent on lindane removal from a clayish agricultural soil with high levels of organic matter.In the first experiment, the main effect of electron acceptor was significant (p < 0.0001); lindane removals followed the order SR > A ? M SBs. On the other hand, co-substrate sucrose was not significant (p = 0.67). Yet, the interaction was moderately significant (p < 0.007); co-substrate influence was distinct depending on the type of electron acceptor. In our case, co-substrate slightly improved lindane removal in both anoxic SBs (SR and M units), whereas lindane removal in A-SB with sucrose was lower than A-SB without sucrose. Metabolites from lindane transformation in our single electron acceptor SBs were consistent with lindane metabolites reported in the literature for anaerobic and aerobic degradation of the insecticide.In the second experiment, both factors [simultaneous electron acceptor (SEA) combination and solvent addition] were significant (p < 0.0001). Removal of lindane in SEA-SBs, PAM and M-SR without silicone oil was low (～16%). On the other hand, the order of lindane removals in SBs with oil silicone M-SR SB was significantly superior (65%) to that of PAM SB (39%).Finally, in our work, SBs with SEA where one of the anaerobic metabolites is methanogenic were not as successful as SBs with single electron acceptors for removal of lindane from heavy soil.     

Synthesis of Leubethanol derivatives and evaluation against Mycobacterium tuberculosis

Twenty-five derivatives of the natural diterpene leubethanol, including several potential pro-drugs, with changes in the functionality of the aliphatic chain or modifications of the phenolic group, were synthesized and tested in vitro by the MABA technique for their activity against the H37Rv strain of Mycobacterium tuberculosis. Several compounds showed antimycobacterial potencies similar to that of the lead compound and two of them displayed higher selectivity indexes.     

Pannexin-1-mediated intracellular delivery of muramyl dipeptide induces caspase-1 activation via cryopyrin/NLRP3 independently of Nod2

Muramyl dipeptide (MDP), the microbial activator of nucleotide-binding oligomerization domain 2 (Nod2), induces NF-kappaB and MAPK activation, leading to the production of multiple anti-bacterial and proinflammatory molecules. In addition, MDP has been implicated in IL-1beta secretion through the regulation of caspase-1. However, the mechanisms that mediate caspase-1 activation and IL-1beta secretion in response to MDP stimulation remain poorly understood. We show here that fluorescent MDP molecules are internalized in primary macrophages and accumulate in granular structures that colocalize with markers of acidified endosomal compartments. The uptake of MDP was Nod2-independent. Upon ATP stimulation, labeled MDP was rapidly released from acidified vesicles into the cytosol, a process that required functional pannexin-1. Caspase-1 activation induced by MDP and ATP required pannexin-1 and Cryopyrin but was independent of Nod2. Conversely, induction of pro-IL-1beta mRNA by MDP stimulation was abolished in Nod2-deficient macrophages but unimpaired in macrophages lacking Cryopyrin. These studies demonstrate a Nod2-independent mechanism mediated through pore-forming pannexin-1 that is required for intracellular delivery of MDP to the cytosol and caspase-1 activation. Furthermore, the work provides evidence for distinct roles of Nod2 and Cryopyrin in the regulation of MDP-induced caspase-1 activation and IL-1beta secretion.     

Relationship between oxidative stress and mitochondrial function in the post-conditioned heart

The pathways activated by post-conditioning may converge on the mitochondria, in particular on the mitochondrial permeability transition pore. We sought to characterize the inhibition status of the mitochondrial permeability transition early after the post-conditioning maneuver and before long reperfusion was established. We observed that post-conditioning maneuvers applied to isolated rat hearts, after a prolonged ischemia and before reperfusion, promoted cardiac mechanical function recovery and maintained mitochondrial integrity. These effects were evaluated by mitochondrial swelling, calcium transport, and NAD⁺ content measurements; the improvements were established before restoring a long lasting reperfusion period. Mitochondrial integrity was associated with a diminution in oxidative stress, since carbonylation of proteins was prevented and aconitase activity was preserved in the post-conditioned hearts, implying that ROS might mediate mitochondrial dysfunction and mPTP opening. In addition, we found that cytochrome release was significantly abolished in the post-conditioned heart, in contrast with conventionally reperfused hearts.     

Expression of Arabidopsis APETALA1 in tomato reduces its vegetative cycle without affecting plant production

Important agronomic traits such as fruit quality, harvesting efficiency or production largely depend on flowering time. We have analysed the effect of the overexpression of the Arabidopsis APETALA1 MADS-box gene on vegetative and reproductive growth of tomato. Constitutive expression of APETALA1 in tomato plants has major effects on the length of their growth cycle as well as on their growth habit. Transgenic tomato plants initiated flowering after the production of 6 vegetative nodes as compared to 11 nodes for the wild type plants. Most of tomato 35S:AP1 plants also showed determinate growth habit, similar to the phenotype of self pruning tomato mutants, as well as an initial reduction of their axillary growth. Moreover, development and fertility of flowers were not affected in plants expressing AP1. Consequently, fruit formation in transgenic plants grown under greenhouse conditions occurred normally, which permitted a similar fruit yield compared to control plants. Since traits conferred by AP1 expression are dominant, its expression in tomato breeding lines could provide advantages for the development of new hybrid varieties with shorter generation time, determinate growth, and reduced pruning requirements.     

Diversity of airborne <Emphasis Type="Italic">Cladosporium</Emphasis> species isolated from agricultural environments of northern Argentinean Patagonia: molecular characterization and plant pathogenicity

Fungal spores are normal components of external environments. They have been reported to be associated with human, animal and plant diseases causing primary and opportunistic infections. Cladosporium is commonly the most frequently isolated genus from air samples, and its species are considered mainly saprophytic, but there is a wide variety of taxa that can cause adverse effects on human and animal health and also on plants. In this work, we aimed to record Cladosporium spores frequency of isolation in northern Argentinean Patagonia and to perform a molecular characterization based on actin gene complemented with EF1α and ITS genes. The ability of the pathogens to cause disease in pip fruits of Packham’s Triumph and Abate Fetel pears and red delicious apples was determined. Results confirmed Cladosporium spores as the main genera isolated from air samples, and the molecular characterization revealed the existence of 11 species in this region grouped in C. cladosporioides and C. herbarum complexes. Pathogenicity tests revealed that Cladosporium sp. cause disease on fruit. Abate Fetel was the most susceptible to infection. These results compose the first study in Argentina in respect of identification at species level of airborne Cladosporium spores, and furthermore, it is the first report in northern Patagonia and the high valley of Río Negro productive region. This knowledge can help farmers to take preventive measures in order to avoid biological damage.