VOCs-mediated hormonal signaling and crosstalk with plant growth promoting microbes

Bioinoculant capability enhancement through metabolomics and systems biology approaches

Bioinoculants are eco-friendly microorganisms, and their products are utilized for improving the potential of soil and fulfill the nutrients requirement for the host plant. The agricultural yield has increased due to the use of bioinoculants over chemical-based fertilizers, and thus it generates interest in understanding the innovation process by various methods. By gene-editing tool, the desired gene product can be changed for engineered microbial inoculants. We have also described various modern biotechnological tools like constraint-based modeling, OptKnock, flux balance analysis and modeling of the biological network for enhancing the bioinoculant capability. These fluxes give the fascinating perception of the metabolic network in the absence of comprehensive kinetic information. These tools also help in the stimulation of the metabolic networks by incorporation of enzyme-encoding genes. The present review explains the use of systems biology and gene-editing tools for improving the capability of bioinoculants. Moreover, this review also emphasizes on the challenges and future perspective of systems biology and its multidisciplinary facets.

An overview on improvement of crop productivity in saline soils by halotolerant and halophilic PGPRs

Salinity of water and soil are of the most important factors limiting the production of crops. Moreover, with the increasing population of the planet and saline fields worldwide there is no choice but to use saline soil and water in the near future. Therefore, to increase plant growth under saline stress condition, provision of sustainable and environmentally friendly management for the use of saline water and soil resources is necessary. The development of saline resistant plants is a potent approach to solve this problem. Generally, soil salinity negatively affects the plant growth through ion toxicity, oxidative stress, osmotic stress and ethylene generation. In recent years, scientists through genetic engineering techniques, which are based on molecular and physiological characteristics of plants, have made salt tolerance plants. However, the validation of the present technique is restricted to laboratory condition and it is not easily applied in the agronomy research under field environment. Another option would be to isolate and utilize salinity resistant microorganisms from the rhizosphere of halophyte plants, namely plant growth-promoting rhizobacteria (PGPR). The mechanisms of these bacteria includes; ACC-deaminase and exopolysachared production, osmolite accumulation, antioxidant system activation, ion hemostasis and etc. In this review, we will discuss mechanisms of PGPR in producing tolerate plants under salt stress and how to improve the plant-microbe interactions in future for increasing agricultural productivity to feed all of the world's people.

Induced Systemic Resistance (ISR) and Fe Deficiency Responses in Dicot Plants

Plants develop responses to abiotic stresses, like Fe deficiency. Similarly, plants also develop responses to cope with biotic stresses provoked by biological agents, like pathogens and insects. Some of these responses are limited to the infested damaged organ, but other responses systemically spread far from the infested organ and affect the whole plant. These latter responses include the Systemic Acquired Resistance (SAR) and the Induced Systemic Resistance (ISR). SAR is induced by pathogens and insects while ISR is mediated by beneficial microbes living in the rhizosphere, like bacteria and fungi. These root-associated mutualistic microbes, besides impacting on plant nutrition and growth, can further boost plant defenses, rendering the entire plant more resistant to pathogens and pests. In the last years, it has been found that ISR-eliciting microbes can induce both physiological and morphological responses to Fe deficiency in dicot plants. These results suggest that the regulation of both ISR and Fe deficiency responses overlap, at least partially. Indeed, several hormones and signaling molecules, like ethylene (ET), auxin, and nitric oxide (NO), and the transcription factor MYB72, emerged as key regulators of both processes. This convergence between ISR and Fe deficiency responses opens the way to the use of ISR-eliciting microbes as Fe biofertilizers as well as biopesticides. This review summarizes the progress in the understanding of the molecular overlap in the regulation of ISR and Fe deficiency responses in dicot plants. Root-associated mutualistic microbes, rhizobacteria and rhizofungi species, known for their ability to induce morphological and/or physiological responses to Fe deficiency in dicot plant species are also reviewed herein.

Bioinoculants for Bioremediation Applications and Disease Resistance: Innovative Perspectives

Soil microbial species that act as PGPR or bioinoculants have the capability of improving plant health and promoting its growth. They facilitate plants for uptake nutrients from their surroundings. They provide resistivity to pathogenic pests and also play many roles in the bioremediation process. Bioremediation is the biological approach for the elimination of toxic contaminants by the approach of beneficial microbes. By the consortium of beneficial microbes and plant, a large number of heavy metal and organic contaminants can be controlled. With this advancement of bioremediation, microbial species that act as bioinoculants also help in the enhancement of induced systemic resistance (ISR) and their consortium triggers it by controlling SA, JA, ET and hormonal signaling pathways. Here, this review discusses the progress made on these areas and how the beneficial microbes that act as bioinoculants towards triggering bioremediation and ISR mechanism.