Multifaceted Role of Salicylic Acid in Combating Cold Stress in Plants: A Review

Plants face different types of stresses, including biotic and abiotic stresses. Among various abiotic stress, low-temperature stress alters various morphological, cytological, physiological, and other biochemical processes in plants. To thrive in such condition’s plants must adopt some strategy. Out of various strategies, the approach of using plant growth regulators (PGRs) gained a prominent role in the alleviation of multiple stresses. Salicylic acid, application triggers tolerance to both biotic and abiotic stresses via regulation of various morpho-physiological, cytological, and biochemical attributes. SA is shown to alleviate and regulate the various cold-induced changes. Both endogenous and exogenously applied SA show an imperative role in the alleviation of cold-induced changes by activating multiple signaling pathways like ABA-dependent or independent pathway, Ca²⁺ signaling pathway, mitogen-activated protein kinase (MAPKs) pathway, reactive oxygen species (ROS), and reactive nitrogen species (RNS) pathways. Activation of these pathways leads to the amelioration of the cold-induced changes by increasing production of antioxidants, osmolytes, HSPs and other cold-responsive proteins like LEA, dehydrins, AFPs, PR proteins, and various other proteins. This review describes the tolerance of cold stress by SA in plants through the involvement of different stress signaling pathways.

     

High prevalence of asthma symptoms in Warao Amerindian children in Venezuela is significantly associated with open-fire cooking: a cross-sectional observational study

Background

The International Study on Asthma and Allergies in Childhood (ISAAC) reported a prevalence of asthma symptoms in 17 centers in nine Latin American countries that was similar to prevalence rates reported in non-tropical countries. It has been proposed that the continuous exposure to infectious diseases in rural populations residing in tropical areas leads to a relatively low prevalence of asthma symptoms. As almost a quarter of Latin American people live in rural tropical areas, the encountered high prevalence of asthma symptoms is remarkable. Wood smoke exposure and environmental tobacco smoke have been identified as possible risk factors for having asthma symptoms.

Methods

We performed a cross-sectional observational study from June 1, 2012 to September 30, 2012 in which we interviewed parents and guardians of Warao Amerindian children from Venezuela. Asthma symptoms were defined according to the ISAAC definition as self-reported wheezing in the last 12 months. The associations between wood smoke exposure and environmental tobacco smoke and the prevalence of asthma symptoms were calculated by means of univariate and multivariable logistic regression analyses.

Results

We included 630 children between two and ten years of age. Asthma symptoms were recorded in 164 of these children (26%). The prevalence of asthma symptoms was associated with the cooking method. Children exposed to the smoke produced by cooking on open wood fires were at higher risk of having asthma symptoms compared to children exposed to cooking with gas (AOR 2.12, 95% CI 1.18 - 3.84). Four percent of the children lived in a household where more than ten cigarettes were smoked per day and they had a higher risk of having asthma symptoms compared to children who were not exposed to cigarette smoke (AOR 2.69, 95% CI 1.11 - 6.48).

Conclusion

Our findings suggest that children living in rural settings in a household where wood is used for cooking or where more than ten cigarettes are smoked daily have a higher risk of having asthma symptoms.     

Multifactorial diversity sustains microbial community stability

Maintenance of a high degree of biodiversity in homogeneous environments is poorly understood. A complex cheese starter culture with a long history of use was characterized as a model system to study simple microbial communities. Eight distinct genetic lineages were identified, encompassing two species: Lactococcus lactis and Leuconostoc mesenteroides. The genetic lineages were found to be collections of strains with variable plasmid content and phage sensitivities. Kill-the-winner hypothesis explaining the suppression of the fittest strains by density-dependent phage predation was operational at the strain level. This prevents the eradication of entire genetic lineages from the community during propagation regimes (back-slopping), stabilizing the genetic heterogeneity in the starter culture against environmental uncertainty.     

Structural details of proteinase entrapment by human alpha2-macroglobulin emerge from three-dimensional reconstructions of Fab labeled native, half-transformed, and transformed molecules

Three-dimensional electron microscopy reconstructions of native, half-transformed, and transformed alpha2-macroglobulins (alpha2Ms) labeled with a monoclonal Fab Fab offer new insight into the mechanism of its proteinase entrapment. Each alpha2M binds four Fabs, two at either end of its dimeric protomers approximately 145 A apart. In the native structure, the epitopes are near the base of its two chisel-like features, laterally separated by 120 A, whereas in the methylamine-transformed alpha2M, the epitopes are at the base of its four arms, laterally separated by 160 A. Upon thiol ester cleavage, the chisels on the native alpha2M appear to split with a separation and rotation to give the four arm-like extensions on transformed alpha2M. Thus, the receptor binding domains previously enclosed within the chisels are exposed. The labeled structures further indicate that the two protomeric strands that constitute the native and transformed molecules are related and reside one on each side of the major axes of these structures. The half-transformed structure shows that the two Fabs at one end of the molecule have an arrangement similar to those on the native alpha2M, whereas on its transformed end, they have rotated. The rotation is associated with a partial untwisting of the strands and an enlargement of the openings to the cavity. We propose that the enlarged openings permit the entrance of the proteinase. Then cleavage of the remaining bait domains by a second proteinase occurs with its entrance into the cavity. This is followed by a retwisting of the strands to encapsulate the proteinases and expose the receptor binding domains associated with the transformed alpha2M.     

Essential oil composition of aerial parts of Angelica glauca growing wild in North-West Himalaya (India)

Fresh aerial parts of Angelica glauca, growing wild in Kashmir valley in higher Himalaya (Jammu and Kashmir, India), collected at flowering stage from different locations, on hydro-distillation provided a refreshing light pale coloured essential oil with characteristic floral woody flavour. The oil was found to be a complex mixture of mono- and sesquiterpenes and 34 compounds accounting for nearly 97.4% of the oil were characterized with the help of capillary GC, GC-MS, and NMR. Major compounds of the oil were characterized as alpha-phellandrene (13.5%), trans-carveol (12.0%), beta-pinene (11.7%), thujene (7.5%), beta-caryophyllene oxide (7.2%), beta-caryophyllene (7.0%), gamma-terpinene (6.7%), nerolidol (6.5%), beta-bisabolene (5.2%) and germacrene D (4.5%). It is the first report to exploit the essential oil from Himalayan A. glauca herb collected at flowering stage.     

Gluconobacter oxydans: its biotechnological applications

Gluconobacter oxydans is a gram-negative bacterium belonging to the family Acetobacteraceae. G. oxydans is an obligate aerobe, having a respiratory type of metabolism using oxygen as the terminal electron acceptor. Gluconobacter strains flourish in sugary niches e.g. ripe grapes, apples, dates, garden soil, baker's soil, honeybees, fruit, cider, beer, wine. Gluconobacter strains are non-pathogenic towards man and other animals but are capable of causing bacterial rot of apples and pears accompanied by various shades of browning. Several soluble and particulate polyol dehydrogenases have been described. The organism brings about the incomplete oxidation of sugars, alcohols and acids. Incomplete oxidation leads to nearly quantitative yields of the oxidation products making G. oxydans important for industrial use. Gluconobacter strains can be used industrially to produce L-sorbose from D-sorbitol; D-gluconic acid, 5-keto- and 2-ketogluconic acids from D-glucose; and dihydroxyacetone from glycerol. It is primarily known as a ketogenic bacterium due to 2,5-diketogluconic acid formation from D-glucose. Extensive fermentation studies have been performed to characterize its direct glucose oxidation, sorbitol oxidation, and glycerol oxidation. The enzymes involved have been purified and characterized, and molecular studies have been performed to understand these processes at the molecular level. Its possible application in biosensor technology has also been worked out. Several workers have explained its basic and applied aspects. In the present paper, its different biotechnological applications, basic biochemistry and molecular biology studies are reviewed.     

The mouse anterior chamber angle and trabecular meshwork develop without cell death

Background

The iridocorneal angle forms in the mammalian eye from undifferentiated mesenchyme between the root of the iris and cornea. A major component is the trabecular meshwork, consisting of extracellular matrix organized into a network of beams, covered in trabecular endothelial cells. Between the beams, channels lead to Schlemm's canal for the drainage of aqueous humor from the eye into the blood stream. Abnormal development of the iridocorneal angle that interferes with ocular fluid drainage can lead to glaucoma in humans. Little is known about the precise mechanisms underlying angle development. There are two main hypotheses. The first proposes that morphogenesis involves mainly cell differentiation, matrix deposition and assembly of the originally continuous mesenchymal mass into beams, channels and Schlemm's canal. The second, based primarily on rat studies, proposes that cell death and macrophages play an important role in forming channels and beams. Mice provide a potentially useful model to understand the origin and development of angle structures and how defective development leads to glaucoma. Few studies have assessed the normal structure and development of the mouse angle. We used light and electron microscopy and a cell death assay to define the sequence of events underlying formation of the angle structures in mice.

Results

The mouse angle structures and developmental sequence are similar to those in humans. Cell death was not detectable during the period of trabecular channel and beam formation.

Conclusions

These results support morphogenic mechanisms involving organization of cellular and extracellular matrix components without cell death or atrophy.