Isolation and 16S rRNA sequence analysis of the beneficial bacteria from the rhizosphere of rice

The present study deals with the isolation of plant growth promoting rhizobacteria (PGPR) from rice (variety NIAB IRRI-9) and the beneficial effects of these inoculants on two Basmati rice varieties. Nitrogen-fixing activity (acetylene-reduction activity) was detected in the roots and submerged shoots of field-grown rice variety NIAB IRRI-9. Estimation of the population size of diazotrophic bacteria by ARA-based MPN (acetylene reduction assay-based most probable number) in roots and shoots indicated about 10(5)-10(6) counts/g dry weight at panicle initiation and grain filling stages. Four bacterial isolates from rice roots and shoots were obtained in pure culture which produced phytohormone indoleacetic acid (IAA) in the growth medium. Among these, three isolates S1, S4, and R3 reduced acetylene to ethylene in nitrogen-free semi-solid medium. Morphological and physiological characteristics of the isolates indicated that three nitrogen-fixing isolates S1, S4, and R3 belonged to the genus Enterobacter, while the non-fixing isolate R8 belonged to the genus Aeromonas. 16S rRNA sequence of one isolate from root (R8) and one isolate from shoot (S1) was obtained which confirmed identification of the isolates as Aeromonas veronii and Enterobacter cloacae, respectively. The 1517-nucleotide-long sequence of the isolate R8 showed 99% similarity with Aeromonas veronii (accession No. AF099023) while partial 16S rRNA sequence (two stretches of total 1271 nucleotide length) of S1 showed 97% similarity with the sequence of Enterobacter cloacae (accession No. AJ251469). The seedlings of two rice varieties Basmati 385 and Super Basmati were inoculated with the four bacterial isolates from rice and one Azospirillum brasilense strain Wb3, which was isolated from wheat. In the rice variety Basmati 385, maximum increase in root area and plant biomass was obtained in plants inoculated with Enterobacter S1 and Azospirillum Wb3, whereas in the rice variety Super Basmati, inoculation with Enterobacter R3 resulted in maximum increase of root area and plant biomass. Nitrogen fixation was quantified by using 15N isotopic dilution method. Maximum fixation was observed in Basmati 385 with the inoculants Azospirillum Wb3 and Enterobacter S1 where nearly 46% and 41% of the nitrogen was derived from atmosphere (%Ndfa), respectively. In general, higher nitrogen fixation was observed in variety Basmati 385 than in Super Basmati, and different bacterial strains were found more effective as inoculants for the rice varieties Basmati 385 and Super Basmati.     

Chemical Alarm Signals Enhance Survival of Brook Charr (Salvelinus fontinalis) During Encounters with Predatory Chain Pickerel (Esox niger)

A diversity of aquatic organisms release chemical alarm signals when attacked or captured by a predator. These alarm signals are thought to warn other conspecifics of danger and, consequently, may benefit receivers by increasing their survival. Here we experimentally investigated the differences in behaviour and survival of hatchery-reared juvenile brook charr Salvelinus fontinalis that had been exposed to either brook charr skin extract (experimental treatment) or a control of swordtail skin extract (control treatment). Charr exposed to conspecific skin extract exhibited a significant reduction in movement and/or altered their foraging behaviour in the laboratory when compared with charr exposed to swordtail skin extract. We also exposed charr to either water conditioned by a single brook charr disturbed by a predatory bird model or water conditioned by a single undisturbed brook charr. Charr exposed to disturbance signals reduced activity significantly more than charr exposed to chemical stimuli from undisturbed charr. These results demonstrate the existence of both damage-released alarm signals and disturbance signals in brook charr. Wild brook charr also responded to damage-released alarm cues under natural conditions. Charr avoided areas of a stream with minnow traps labelled with conspecific alarm cues vs. control cues. During staged encounters with chain pickerel Esox niger in the laboratory, predator-naive charr fry were better able to evade the predator if they were previously warned by an alarm signal, thus suggesting a survival benefit to receivers. Collectively, these results demonstrate that the presence of alarm signals in brook charr has important implications for understanding predator–prey interactions.     

Structural basis for ubiquitin-mediated dimerization and activation of the ubiquitin protein ligase Cbl-b

Cbl proteins are E3 ubiquitin ligases that are negative regulators of many receptor tyrosine kinases. Cbl-b and c-Cbl contain a ubiquitin-associated (UBA) domain, which is present in a variety of proteins involved in ubiquitin-mediated processes. Despite high sequence identity, Cbl UBA domains display remarkably different ubiquitin-binding properties. Here, we report the crystal structure of the UBA domain of Cbl-b in complex with ubiquitin at 1.9 A resolution. The structure reveals an atypical mechanism of ubiquitin recognition by the first helix of the UBA. Helices 2 and 3 of the UBA domain form a second binding surface, which mediates UBA dimerization in the crystal and in solution. Site-directed mutagenesis demonstrates that Cbl-b dimerization is regulated by ubiquitin binding and required for tyrosine phosphorylation of Cbl-b and ubiquitination of Cbl-b substrates. These studies demonstrate a role for ubiquitin in regulating biological activity by promoting protein dimerization.     

Hetero-Diels-Alder reaction of 1,3-bis(trimethylsilyloxy)-1,3-butadienes with arylsulfonylcyanides. Synthesis and antimicrobial activity of 4-hydroxy-2-(arylsulfonyl)pyridines

Hetero-Diels-Alder reactions of 1,3-bis(silyloxy)-1,3-butadienes with arylsulfonylcyanides afforded a variety of 4-hydroxy-2-(arylsulfonyl)pyridines. Several derivatives show antimicrobial activity against Gram-positive bacteria.     

Conservation gains through HCVF assessments in Bosnia-Herzegovina and Romania

This paper analyses the conservation gains through High Conservation Value Forest (HCVF) assessments in two South-East European countries (Bosnia-Herzegovina and Romania). These are based on the review of the Draft Forest Stewardship Council (FSC) National Standards and HCVF Manuals and the results of the certification process of seven forest management units in the two countries. The review indicates that the application of Principle 9 (High Conservation Value Forests) and Criterion 6.4 of the FSC in Bosnia-Herzegovina and Romania was influenced by the size and nature of tenure (i.e., public or non-public land), rather than geographic location per se. The study also revealed that the assessment of HCVF has, for the first time, raised the question of conservation of cultural, historical and religious values as well as the sustainable management of those forests relevant for the basic needs of communities. These are values not currently covered at the present by the national conservation legislation in either of these two countries. Findings of this study in both countries demonstrates that there are certain conservation gains as a result of the HCVF assessment, especially related to ecosystem services, prevention of soil erosion and conservation of threatened, endangered and endemic species.     

Metal/metalloid stress tolerance in plants: role of ascorbate,its redox couple,and associated enzymes

The enhanced generation of reactive oxygen species (ROS) under metal/metalloid stress is most common in plants, and the elevated ROS must be successfully metabolized in order to maintain plant growth, development, and productivity. Ascorbate (AsA) is a highly abundant metabolite and a water-soluble antioxidant, which besides positively influencing various aspects in plants acts also as an enigmatic component of plant defense armory. As a significant component of the ascorbate-glutathione (AsA-GSH) pathway, it performs multiple vital functions in plants including growth and development by either directly or indirectly metabolizing ROS and its products. Enzymes such as monodehydroascorbate reductase (MDHAR, EC 1.6.5.4) and dehydroascorbate reductase (DHAR, EC 1.8.5.1) maintain the reduced form of AsA pool besides metabolically controlling the ratio of AsA with its oxidized form (dehydroascorbate, DHA). Ascorbate peroxidase (APX, EC 1.11.1.11) utilizes the reduced AsA pool as the specific electron donor during ROS metabolism. Thus, AsA, its redox couple (AsA/DHA), and related enzymes (MDHAR, DHAR, and APX) cumulatively form an AsA redox system to efficiently protect plants particularly against potential anomalies caused by ROS and its products. Here we present a critical assessment of the recent research reports available on metal/metalloid-accrued modulation of reduced AsA pool, AsA/DHA redox couple and AsA-related major enzymes, and the cumulative significance of these antioxidant system components in plant metal/metalloid stress tolerance.     

Links between plant and fungal communities across a deforestation chronosequence in the Amazon rainforest

Understanding the interactions among microbial communities, plant communities and soil properties following deforestation could provide insights into the long-term effects of land-use change on ecosystem functions, and may help identify approaches that promote the recovery of degraded sites. We combined high-throughput sequencing of fungal rDNA and molecular barcoding of plant roots to estimate fungal and plant community composition in soil sampled across a chronosequence of deforestation. We found significant effects of land-use change on fungal community composition, which was more closely correlated to plant community composition than to changes in soil properties or geographic distance, providing evidence for strong links between above- and below-ground communities in tropical forests.