Anukool Vaishnav

Putative bacterial volatile-mediated growth in soybean (Glycine max L. Merrill) and expression of induced proteins under salt stress

Plant root‐associated rhizobacteria elicit plant immunity referred to as induced systemic tolerance (IST) against multiple abiotic stresses. Among multibacterial determinants involved in IST, the induction of IST and promotion of growth by putative bacterial volatile compounds (VOCs) is reported in the present study.

Bacterial-Mediated Tolerance and Resistance to Plants Under Abiotic and Biotic Stresses

Plant growth-promoting bacteria (PGPB) are capable of alleviating environmental stress and eliciting tolerance in plants to promote their growth. Several PGPB elicit physical and/or chemical changes related to plant defense in the form of induced systemic resistance (ISR) under biotic stress. Researchers emphasized that PGPB-elicited ISR has suppressed plant diseases caused by a range of pathogens in both the greenhouse and field. PGPB-elicited physical and chemical changes in plants result in enhanced tolerance to drought, salt, and other factors that have been described as a form of induced systemic tolerance under abiotic stress. This review will focus on recent research concerning interactions between PGPB and plants under biotic and abiotic stresses. The use of PGPB requires precise understanding of the interactions between plant-bacteria, among bacteria-microbiota, and how biotic and abiotic factors influence these relationships. Consequently, continued research is needed to develop new approaches to ameliorate the efficiency of PGPB and to understand the ecological, genetic, and biochemical relationships in their habitat.

PGPR-mediated expression of salt tolerance gene in soybean through volatiles under sodium nitroprusside.

Increasing evidence shows that nitric oxide (NO), a typical signaling molecule plays important role in development of plant and in bacteria‐plant interaction. In the present study, we tested the effect of sodium nitroprusside (SNP)‐a nitric oxide donor, on bacterial metabolism and its role in establishment of PGPR‐plant interaction under salinity condition. In the present study, we adopted methods namely, biofilm formation assay, GC‐MS analysis of bacterial volatiles, chemotaxis assay of root exudates (REs), measurement of electrolyte leakage and lipid peroxidation, and quantitative reverse transcription–polymerase chain reaction (qRT–PCR) for gene expression. GC‐MS analysis revealed that three new volatile organic compounds (VOCs) were expressed after treatment with SNP. Two VOCs namely, 4‐nitroguaiacol and quinoline were found to promote soybean seed germination under 100 mM NaCl stress. Chemotaxis assay revealed that SNP treatment, altered root exudates profiling (SS‐RE), found more attracted to Pseudomonas simiae bacterial cells as compared to non‐treated root exudates (S‐RE) under salt stress. Expression of Peroxidase (POX), catalase (CAT), vegetative storage protein (VSP), and nitrite reductase (NR) genes were up‐regulated in T6 treatment seedlings, whereas, high affinity K+ transporter (HKT1), lipoxygenase (LOX), polyphenol oxidase (PPO), and pyrroline‐5‐carboxylate synthase (P5CS) genes were down‐regulated under salt stress. The findings suggest that NO improves the efficiency and establishment of PGPR strain in the plant environment during salt condition. This strategy may be applied on soybean plants to increase their growth during salinity stress.

Molecular Mechanism of Benign Microbe-Elicited Alleviation of Biotic and Abiotic Stresses for Plants

In continuous agricultural systems, crop yields are directly dependent on the inherent soil fertility with microbial processes that governs the mineralization and mobilization of nutrients required for plant growth. The impact of different crop species that are used in various combinations is likely to be an important factor in determining the structure of plant benign microbial communities that function in nutrient cycling, the production of plant growth hormones, and suppression of root diseases. In the present scenario, a perceived role of biotechnology is to introduce multiple choreographed genes into plants that would elicit multiple benefits to the plants such as resistance to stress, productivity, and quality. Microbial genomes that have coevolved with native plant species may already be choreographed and compatible with a wide range of plant genomes and available in this vast unexplored genetic reservoir. Understanding of microbial genome and how it communicates with plant genome for their mutual welfare could lead to innovative methods of plant improvement. Increased adverse effects of abiotic and biotic stresses impacting productivity in principal crops are being witnessed all over the world. Extreme events like prolonged droughts, intense rains and flooding, heat waves, and frost damages are likely to further increase in future due to climate change. A wide range of adaptations and mitigation strategies are required to cope with such impacts. Efficient resource management and crop improvement for evolving better breeds can help to overcome abiotic stresses to some extent. However, such strategies being long drawn and cost intensive, there is a need to develop simple and low cost-effective biological methods for the management of abiotic stress, which can be used on long-term basis. Therefore, studies are needed to elucidate the molecular mechanisms that result from treatment of plants with benign microbes under stress conditions and only then will the full benefits of plant-microbe interaction be understood.

Role of Functional Bacterial Phylum Proteobacteria in Glycine max Growth Promotion Under Abiotic Stress: A Glimpse on Case Study

The PGPR elicit plant immunity referred to as induced systemic tolerance (IST) to cope up with abiotic stresses. The common modes of PGPR include fixing N2, increasing the availability of nutrients in the rhizosphere, positively influencing root growth, promoting beneficial plant–microbe symbioses and succumb diseases. The present review deals case study of salt-tolerant rhizobacteria with respect to its functional plant growth promotional activities. Genomic DNA was isolated from bacterial strain AK-1, and gene-specific primers were used to amplify the 16S ribosomal DNA, ACC deaminase gene (acdS gene), IAA gene (ipdC gene), P-solubilizing gene (gcd and gad gene), ectoine production gene (EctC gene) and glycine betaine gene (betA gene). Gene amplification using specific gene primers showed sharp bands of the specific genes near to desired amplicon size. Bacterial-inoculated plants were exhibited superior tolerance against salt stress, as shown by their higher plant biomass, water content, chlorophyll content and lower osmotic stress injury as compared to non-inoculated plants during salt stress. Increased proline accumulation and antioxidant activity in bacterial-inoculated plants also contributed to salt tolerance. This study was conducted to assess the PGPR that are associated with the rhizosphere of soybean grown in semiarid areas of Rajasthan. We also sought to identify and characterize representative PGPR with respect to growth-promoting attributes and studied their salinity tolerance.

PGPR-Mediated Amelioration of Crops Under Salt Stress

Soil salinity is a major abiotic factor which adversely affects the crop growth and productivity worldwide. Higher salt concentration caused ion imbalance and hyperosmotic stress which often lead to oxidative stress in plants. Soil salinization is mainly due to the poor irrigation management practices and natural causes. A total 20 % of the world’s cultivated lands and almost half of all irrigated lands are affected by high salinity. This chapter begins by stressing the importance of research into plant salt tolerance. After a brief outline of salinity-induced damage to both agricultural yield and growth of plants, strategies which plants adopt to deal with salinity are discussed, and current biotechnological efforts towards producing salt-tolerant crops are summarized. Particular attention is paid towards the application of plant growth-promoting bacteria in agriculture system for producing salt stress-tolerant crops and a fundamental understanding towards the mechanisms of beneficial plant–microbe interaction in the presence of salt.

Regulation of Ethylene Level in Mungbean (Vigna radiata L.) by 1-Aminocyclopropane-1-Carboxylic Acid (ACC)-Deaminase containing Bacterial Strain under Salt Stress

The plant hormone ethylene is a gaseous hormone which is found in the all higher plants is an important modulator for normal plant growth and developmental process as well as a key feature in the response of different abiotic and biotic stresses (Abeles et al., 1992). Ethylene is an inhibitor for plant growth but at very low concentration it may promote plant growth in a large number of ways such as promoting root initiation in many plant species including Arabidopsis (Pierik et al., 2006). In the presence of wide range of environmental stresses like salinity (Mayak et al., 2004a), drought (Mayak et International Journal of Current Microbiology and Applied Sciences ISSN: 2319-7706 Volume 5 Number 11 (2016) pp. 275-283 Journal homepage: http://www.ijcmas.com