Interaction between PGPR and PGR for water conservation and plant growth attributes under drought condition

Drought is one of the key restraints to agricultural productivity worldwide and is expected to increase further. Drought stress accompanied by reduction in precipitation pose major challenges to future food safety. Strategies should be develop to enhance drought tolerance in crops like chickpea and wheat, in order to enhance their growth and yield. Drought tolerance strategies are costly and time consuming however, recent studies specify that plant growth promoting rhizobacteria (PGPR) and plant growth regulators (PGRs) can help plants to withstand under harsh environmental condition and enable plants to cope with drought stress. PGPR can act as biofertilizer and bioenhancer for different legumes and non-legumes. The use of PGPR and symbiotic microorganisms, may be valuable in developing strategies to assist water conservation in plants. The use of PGPR has been confirmed to be an ecologically sound way of enhancing crop yields by facilitating plant growth through direct or indirect mechanism. The mechanisms of PGPR for water conservation include secretion of exopolysaccharides, biofilm formation, alternation in phytohormone content, improvement in sugar concentration, enhancing availability of micro- and macronutrients and changes in plant functional traits. Similarly, plant growth regulators (PGRs) are specially noticed in actively growing tissues under stress conditions and have been associated in the control of cell division, embryogenesis, root formation, fruit development and ripening, and reactions to biotic and abiotic stresses and upholding water conservation status in plants. Previous studies also suggest that plant metabolites interact with plant physiology under stress condition and impart drought tolerance. Metabolites like, sugars, amino acids, organic acid and polyols play a key role in drought tolerance of crop plants grown under stress condition. It is concluded from the present study that PGRs in combination with PGPR consortium can be an effective formulation to promote plant growth and maintenance of plant turgidity under drought stress. This review is a compilation of the effect of drought stress on crop plants and described interactions between PGPR/PGRs and plant development, knowledge of water conservation and stress release strategies of PGPR and PGRs and the role of plant metabolites in drought tolerance of crop plants. This review also bridges the gaps that summarizes the mechanism of action of PGPR for drought tolerance of crop plants and sustainability of agriculture and applicability of these beneficial rhizobacteria in different agro-ecosystems under drought stress.     

Variation in the Presence of Anti-<Emphasis Type="Italic">Batrachochytrium dendrobatidis</Emphasis> Bacteria of Amphibians Across Life Stages and Elevations in Ecuador

Amphibian populations are decreasing worldwide due to a variety of factors. In South America, the chytrid fungus Batrachochytrium dendrobatidis (Bd) is linked to many population declines. The pathogenic effect of Bd on amphibians can be inhibited by specific bacteria present on host skin. This symbiotic association allows some amphibians to resist the development of the disease chytridiomycosis. Here, we aimed (1) to determine for the first time if specific anti-Bd bacteria are present on amphibians in the Andes of Ecuador, (2) to monitor anti-Bd bacteria across developmental stages in a focal amphibian, the Andean marsupial tree frog, Gastrotheca riobambae, that deposits larvae in aquatic habitats, and (3) to compare the Bd presence associated with host assemblages including 10 species at sites ranging in biogeography from Amazonian rainforest (450 masl) to Andes montane rainforest (3200 masl). We sampled and identified skin-associated bacteria of frogs in the field using swabs and a novel methodology of aerobic counting plates, and a combination of morphological, biochemical, and molecular identification techniques. The following anti-Bd bacteria were identified and found to be shared among several hosts at high-elevation sites where Bd was present at a prevalence of 32.5%: Janthinobacterium lividum, Pseudomonas fluorescens, and Serratia sp. Bd were detected in Gastrotheca spp. and not detected in the lowlands (sites below 1000 masl). In G. riobambae, recognized Bd-resistant bacteria start to be present at the metamorphic stage. Overall bacterial abundance was significantly higher post-metamorphosis and on species sampled at lower elevations. Further metagenomic studies are needed to evaluate the roles of host identity, life-history stage, and biogeography of the microbiota and their function in disease resistance.     

Pallial origin of basal forebrain cholinergic neurons in the nucleus basalis of Meynert and horizontal limb of the diagonal band nucleus

The majority of the cortical cholinergic innervation implicated in attention and memory originates in the nucleus basalis of Meynert and in the horizontal limb of the diagonal band nucleus of the basal prosencephalon. Functional alterations in this system give rise to neuropsychiatric disorders as well as to the cognitive alterations described in Parkinson and Alzheimer's diseases. Despite the functional importance of these basal forebrain cholinergic neurons very little is known about their origin and development. Previous studies suggest that they originate in the medial ganglionic eminence of the telencephalic subpallium; however, our results identified Tbr1-expressing, reelin-positive neurons migrating from the ventral pallium to the subpallium that differentiate into cholinergic neurons in the basal forebrain nuclei projecting to the cortex. Experiments with Tbr1 knockout mice, which lack ventropallial structures, confirmed the pallial origin of cholinergic neurons in Meynert and horizontal diagonal band nuclei. Also, we demonstrate that Fgf8 signaling in the telencephalic midline attracts these neurons from the pallium to follow a tangential migratory route towards the basal forebrain.     

Extensive dermatophytoses caused by Trichophyton mentagrophytes and Microsporum canis in a patient with AIDS

Retrospective studies have shown the occurrence of episodes of deep or superficial fungal infections in 58 to 81% of HIV/AIDS patients as a result of impairment of cell immunity. We describe a case of disseminated cutaneous dermatophytoses caused by Trichophyton mentagrophytes and Microsporum canis in a patients with AIDS. Diagnostic and therapeutic problems in relation to this unsual presentation are emphasized as well as the importance of an early mycologic diagnosis to prescribe antifungal therapy.     

The effects of l-DOPA on root growth, lignification and enzyme activity in soybean seedlings

In the present study, we investigated the effects of l-DOPA (l-3,4-dihydroxyphenylalanine), an allelochemical exuded from the velvetbean (Mucuna pruriens L DC. var. utilis), on the growth and cell viability of soybean (Glycine max L. Merrill) roots. We analyzed the effects of l-DOPA on phenylalanine ammonia lyase (PAL), cinnamyl-alcohol dehydrogenase (CAD) and cell wall-bound peroxidase (POD) activities as well as its effects on phenylalanine, tyrosine and lignin contents in the roots. 3-day-old seedlings were cultivated in half-strength Hoagland nutrient solution (pH 6.0), with or without 0.5?mM l-DOPA, in a growth chamber at 25?°C for 6, 12, 18 or 24?h with a day/night regime of 1:1, and a photon flux density of 280???mol?m^?2 s^?1. In general, the length, fresh weight and dry weight of the roots decreased followed by a significant loss of cell viability. Phenylalanine, tyrosine and lignin contents as well as PAL, CAD and cell wall-bound POD activities increased after l-DOPA treatment. These results reinforce the susceptibility of soybean to l-DOPA, which increases the enzyme activity in the phenylpropanoid pathway and, therefore, provides precursors for the polymerization of lignin. In brief, these findings suggest that the inhibition of soybean root growth induced by exogenously applied l-DOPA may be due to excessive production of lignin in the cell wall.