A Krüppel-like transcription factor gene is involved in salt stress responses in Medicago spp.

Legume plants are able to fix nitrogen in symbiotic association with rhizobia and, like many crops, are sensitive to high salt conditions. However, very few molecular markers can be associated to stress tolerance in legume crops. A Kruppel-like transcription factor, Mtzpt2-1, required for the formation of the nitrogen-fixing region, confers salt tolerance to yeast cells. Here, legume responses to salt stresses were studied using alfalfa and its close relative Medicago truncatula, a model legume species. Salt stress induces the Mszpt2-1 gene both in roots and root harbouring nodules. In addition, Sinorhizobium meliloti strains tolerating up to 700 mM NaCl, were used in nodulation assays to assess salt tolerance of the symbiotic response of M. truncatula. Few nodules, mainly in the upper part of the root, could be detected in plants treated with 200 mM NaCl, suggesting that nodule initiation was particularly sensitive to salt stress. We have also defined for M. truncatula the threshold of NaCl tolerance after which recovery of stressed plants is irreversible under laboratory conditions. After analysing several times of salt treatment (150 mM NaCl), M. truncatula 108R plants stressed for 7 days could not recover (less than 5%), whereas a 4-day treatment allowed at least 75% recovery. Transgenic M. truncatula plants expressing Mtzpt2-1 in antisense configuration are more sensitive to `recover' from salt stress than the wild type. These results identify Mtzpt2-1 as a molecular marker potentially linked to stress tolerance in M. truncatula and suggest its participation in a transcriptional program induced in these plants to cope with salt stress.Facultad de Ciencias ExactasInstituto de Biotecnología y Biología Molecula

A Krüppel-like transcription factor gene is involved in salt stress responses in Medicago spp.

Legume plants are able to fix nitrogen in symbiotic association with rhizobia and, like many crops, are sensitive to high salt conditions. However, very few molecular markers can be associated to stress tolerance in legume crops. A Kruppel-like transcription factor, Mtzpt2-1, required for the formation of the nitrogen-fixing region, confers salt tolerance to yeast cells. Here, legume responses to salt stresses were studied using alfalfa and its close relative Medicago truncatula, a model legume species. Salt stress induces the Mszpt2-1 gene both in roots and root harbouring nodules. In addition, Sinorhizobium meliloti strains tolerating up to 700 mM NaCl, were used in nodulation assays to assess salt tolerance of the symbiotic response of M. truncatula. Few nodules, mainly in the upper part of the root, could be detected in plants treated with 200 mM NaCl, suggesting that nodule initiation was particularly sensitive to salt stress. We have also defined for M. truncatula the threshold of NaCl tolerance after which recovery of stressed plants is irreversible under laboratory conditions. After analysing several times of salt treatment (150 mM NaCl), M. truncatula 108R plants stressed for 7 days could not recover (less than 5%), whereas a 4-day treatment allowed at least 75% recovery. Transgenic M. truncatula plants expressing Mtzpt2-1 in antisense configuration are more sensitive to `recover' from salt stress than the wild type. These results identify Mtzpt2-1 as a molecular marker potentially linked to stress tolerance in M. truncatula and suggest its participation in a transcriptional program induced in these plants to cope with salt stress.Facultad de Ciencias ExactasInstituto de Biotecnología y Biología Molecula

Obstacle tower : a generalization challenge in vision, control, and planning

The rapid pace of recent research in AI has been driven in part by the presence of fast and challenging simulation environments. These environments often take the form of games; with tasks ranging from simple board games, to competitive video games. We propose a new benchmark - Obstacle Tower: a high fidelity, 3D, 3rd person, procedurally generated environment. An agent playing Obstacle Tower must learn to solve both low-level control and high-level planning problems in tandem while learning from pixels and a sparse reward signal. Unlike other benchmarks such as the Arcade Learning Environment, evaluation of agent performance in Obstacle Tower is based on an agent's ability to perform well on unseen instances of the environment. In this paper we outline the environment and provide a set of baseline results produced by current state-of-the-art Deep RL methods as well as human players. These algorithms fail to produce agents capable of performing near human level.peer-reviewe

Proximity to overhead power lines and childhood leukaemia: an international pooled analysis

© 2018, Cancer Research UK. Background: Although studies have consistently found an association between childhood leukaemia risk and magnetic fields, the associations between childhood leukaemia and distance to overhead power lines have been inconsistent. We pooled data from multiple studies to assess the association with distance and evaluate whether it is due to magnetic fields or other factors associated with distance from lines. Methods: We present a pooled analysis combining individual-level data (29,049 cases and 68,231 controls) from 11 record-based studies. Results: There was no material association between childhood leukaemia and distance to nearest overhead power line of any voltage. Among children living < 50 m from 200 + kV power lines, the adjusted odds ratio for childhood leukaemia was 1.33 (95% CI: 0.92–1.93). The odds ratio was higher among children diagnosed before age 5 years. There was no association with calculated magnetic fields. Odds ratios remained unchanged with adjustment for potential confounders. Conclusions: In this first comprehensive pooled analysis of childhood leukaemia and distance to power lines, we found a small and imprecise risk for residences < 50 m of 200 + kV lines that was not explained by high magnetic fields. Reasons for the increased risk, found in this and many other studies, remains to be elucidated

Evidence of positive selection associated with placental loss in tiger sharks

Background: All vertebrates initially feed their offspring using yolk reserves. In some live-bearing species these yolk reserves may be supplemented with extra nutrition via a placenta. Sharks belonging to the Carcharhinidae family are all live-bearing, and with the exception of the tiger shark (Galeocerdo cuvier), develop placental connections after exhausting yolk reserves. Phylogenetic relationships suggest the lack of placenta in tiger sharks is due to secondary loss. This represents a dramatic shift in reproductive strategy, and is likely to have left a molecular footprint of positive selection within the genome. Results: We sequenced the transcriptome of the tiger shark and eight other live-bearing shark species. From this data we constructed a time-calibrated phylogenetic tree estimating the tiger shark lineage diverged from the placental carcharhinids approximately 94 million years ago. Along the tiger shark lineage, we identified five genes exhibiting a signature of positive selection. Four of these genes have functions likely associated with brain development (YWHAE and ARL6IP5) and sexual reproduction (VAMP4 and TCTEX1D2). Conclusions: Our results indicate the loss of placenta in tiger sharks may be associated with subsequent adaptive changes in brain development and sperm production