In vitro rapid regeneration of plantlets from nodal explants of Mucuna pruriens– a valuable medicinal plant

A rapid and efficient protocol for the large‐scale propagation of a potential medicinal plant, Mucuna pruriens, through in vitro culture of nodal segment explants obtained from 15‐day‐old aseptic seedlings is described. Of the three different cytokinins, 6‐benzyladenine (BA), kinetin (Kin) and 2‐isopentenyl adenine (2‐iP) evaluated as supplements to Murashige and Skoog (MS) medium, BA at an optimal concentration of 5.0 μM was effective in inducing multiple shoots. Strength of the basal media also influenced the efficiency of shoot regeneration. The frequency of shoot regeneration tended to increase when the salt concentration in the basal media was reduced. Highest number of multiple shoots (23.3) and maximum average length (5.6 cm) were standardised on half‐strength MS medium supplemented with 5.0 μM BA along with 0.5 μM α‐naphthalene acetic acid (NAA) at pH 5.8. Rooting was best induced in shoots excised from proliferated shoot cultures on MS medium augmented with an optimal concentration of 1.0 μM indole‐3‐butyric acid (IBA). The in vitro‐raised plantlets with well‐developed shoots and roots were successfully established in earthen pots containing garden soil and were grown in greenhouse with 90% survival rate. The results of this study provide the first report on in vitro plant regeneration of M. pruriens.     

Iron accumulation in deep cortical layers accounts for MRI signal abnormalities in ALS: correlating 7 Tesla MRI and pathology

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder characterized by cortical and spinal motor neuron dysfunction. Routine magnetic resonance imaging (MRI) studies have previously shown hypointense signal in the motor cortex on T(2)-weighted images in some ALS patients, however, the cause of this finding is unknown. To investigate the utility of this MR signal change as a marker of cortical motor neuron degeneration, signal abnormalities on 3T and 7T MR images of the brain were compared, and pathology was obtained in two ALS patients to determine the origin of the motor cortex hypointensity. Nineteen patients with clinically probable or definite ALS by El Escorial criteria and 19 healthy controls underwent 3T MRI. A 7T MRI scan was carried out on five ALS patients who had motor cortex hypointensity on the 3T FLAIR sequence and on three healthy controls. Postmortem 7T MRI of the brain was performed in one ALS patient and histological studies of the brains and spinal cords were obtained post-mortem in two patients. The motor cortex hypointensity on 3T FLAIR images was present in greater frequency in ALS patients. Increased hypointensity correlated with greater severity of upper motor neuron impairment. Analysis of 7T T(2)(*)-weighted gradient echo imaging localized the signal alteration to the deeper layers of the motor cortex in both ALS patients. Pathological studies showed increased iron accumulation in microglial cells in areas corresponding to the location of the signal changes on the 3T and 7T MRI of the motor cortex. These findings indicate that the motor cortex hypointensity on 3T MRI FLAIR images in ALS is due to increased iron accumulation by microglia.     

In vitro organogenesis from internode derived callus cultures of Capsicum annuum L.

An efficient protocol of shoot organogenesis and plant regeneration from internode derived callus has been developed for Capsicum annuum. Optimal callus was developed from internodal segments on Murashige and Skoog (MS) medium supplemented with 10 μM 2,4-dichlorophenoxy acetic acid (2,4-D) and 2.0 μM 6-benzyladenine (BA). Shoot differentiation was achieved from the surface of callus when transferred on shoot induction medium containing BA and thidiazuron (TDZ) alone or in combination. The highest number of de novo adventitious shoots (25.4?±?1.42) and shoot length (4.6?±?0.37 cm) was recorded on MS medium supplemented with 5.0 μM BA and 2.5 μM TDZ. The individual elongated shoots were rooted well on MS medium supplemented with 1.0 μM Indole-3-butyric acid (IBA). The in vitro raised plantlets with properly developed shoot and roots were acclimatized successfully and grew well in the greenhouse. All the regenerated plants appeared normal with respect to morphology and growth characteristics with 85% survival rate.     

Heat Stress in Wheat during Reproductive and Grain-Filling Phases

Ambient temperatures have increased since the beginning of the century and are predicted to continue rising under climate change. Such increases in temperature can cause heat stress: a severe threat to wheat production in many countries, particularly when it occurs during reproductive and grain-filling phases. Heat stress reduces plant photosynthetic capacity through metabolic limitations and oxidative damage to chloroplasts, with concomitant reductions in dry matter accumulation and grain yield. Genotypes expressing heat shock proteins are better able to withstand heat stress as they protect proteins from heat-induced damage. Heat tolerance can be improved by selecting and developing wheat genotypes with heat resistance. Wheat pre-breeding and breeding may be based on secondary traits like membrane stability, photosynthetic rate and grain weight under heat stress. Nonetheless, improvement in grain yield under heat stress implies selecting genotypes for grain size and rate of grain filling. Integrating physiological and biotechnological tools with conventional breeding techniques will help to develop wheat varieties with better grain yield under heat stress during reproductive and grain-filling phases. This review discusses the impact of heat stress during reproductive and grain-filling stages of wheat on grain yield and suggests strategies to improve heat stress tolerance in wheat.     

Target highlights in CASP13: Experimental target structures through the eyes of their authors

The functional and biological significance of selected CASP13 targets are described by the authors of the structures. The structural biologists discuss the most interesting structural features of the target proteins and assess whether these features were correctly reproduced in the predictions submitted to the CASP13 experiment.     

The poliovirus sensitivity (PVS) gene is on chromosome 19q12----q13.2

Sensitivity to nonmodified poliovirus infection is an autosomal dominant trait, specific to primates. The gene for poliovirus sensitivity (PVS) is encoded on human chromosome 19. In order to sublocalize the PVS gene, we infected rodent-human hybrid cell lines that divide human chromosome 19 into four regions with poliovirus 1 and/or 3. When infected, these hybrid cell lines showed the typical cytopathic effect of poliovirus infection only if they contained 19q12----q13.2 as the smallest region of overlap. Appropriate negative and positive controls were used. PVS may be of relevance to myotonic dystrophy (DM) and the inherited motor neuron diseases: to DM because it localizes to the same region of chromosome 19 and to the inherited motor neuron diseases because it encodes a cell-surface receptor expressed on motor neurons.     

Glutathione contributes to plant defence against parasitic cyst nematodes

Cyst nematodes (CNs) are an important group of root-infecting sedentary endoparasites that severely damage many crop plants worldwide. An infective CN juvenile enters the host's roots and migrates towards the vascular cylinder, where it induces the formation of syncytial feeding cells, which nourish the CN throughout its parasitic stages. Here, we examined the role of glutathione (l -γ-glutamyl-l -cysteinyl-glycine) in Arabidopsis thaliana on infection with the CN Heterodera schachtii. Arabidopsis lines with mutations pad2, cad2, or zir1 in the glutamate–cysteine ligase (GSH1) gene, which encodes the first enzyme in the glutathione biosynthetic pathway, displayed enhanced CN susceptibility, but susceptibility was reduced for rax1, another GSH1 allele. Biochemical analysis revealed differentially altered thiol levels in these mutants that was independent of nematode infection. All glutathione-deficient mutants exhibited impaired activation of defence marker genes as well as genes for biosynthesis of the antimicrobial compound camalexin early in infection. Further analysis revealed a link between glutathione-mediated plant resistance to CN infection and the production of camalexin on nematode infection. These results suggest that glutathione levels affect plant resistance to CN by fine-tuning the balance between the cellular redox environment and the production of compounds related to defence against infection.     

Analysis of copia sequence variation within and between Drosophila species

The sequences of the 5' long-terminal repeat (LTR) and adjacent leader regions of 27 full-length copia elements isolated from natural populations of Drosophila melanogaster, D. simulans, and D. mauritiana are presented. Phylogenetic analyses indicate that although D. melanogaster copia elements are distinct from those of D. simulans and D. mauritiana, the elements of these latter two species are not distinguishable from one another. LTRs and adjacent 5' leader regions of elements isolated from D. simulans and D. mauritiana are structurally similar to one another and carry substantial deletional variation mapping to regions previously identified as being of potential importance for copia expression.      

Toxigenic Vibrio cholerae in the Aquatic Environment of Mathbaria, Bangladesh

Toxigenic Vibrio cholerae, rarely isolated from the aquatic environment between cholera epidemics, can be detected in what is now understood to be a dormant stage, i.e., viable but nonculturable when standard bacteriological methods are used. In the research reported here, biofilms have proved to be a source of culturable V. cholerae, even in nonepidemic periods. Biweekly environmental surveillance for V. cholerae was carried out in Mathbaria, an area of cholera endemicity adjacent to the Bay of Bengal, with the focus on V. cholerae O1 and O139 Bengal. A total of 297 samples of water, phytoplankton, and zooplankton were collected between March and December 2004, yielding eight V. cholerae O1 and four O139 Bengal isolates. A combination of culture methods, multiplex-PCR, and direct fluorescent antibody (DFA) counting revealed the Mathbaria aquatic environment to be a reservoir for V. cholerae O1 and O139 Bengal. DFA results showed significant clumping of the bacteria during the interepidemic period for cholera, and the fluorescent micrographs revealed large numbers of V. cholerae O1 in thin films of exopolysaccharides (biofilm). A similar clumping of V. cholerae O1 was also observed in samples collected from Matlab, Bangladesh, where cholera also is endemic. Thus, the results of the study provided in situ evidence for V. cholerae O1 and O139 in the aquatic environment, predominantly as viable but nonculturable cells and culturable cells in biofilm consortia. The biofilm community is concluded to be an additional reservoir of cholera bacteria in the aquatic environment between seasonal epidemics of cholera in Bangladesh.