Shekhar Jain

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.

Plant Growth-Promoting Microbial-Mediated Induced Systemic Resistance in Plants: Induction, Mechanism, and Expression

In the agroecosystem, plants are an attractive source of nutrients and life environment for many microbes. Pathogenic as well as nonpathogenic microbes get colonized to the plants resulting in various diseases and beneficial effects on plant growth or stress resistance, respectively. Plants are generally resistant to the majority of phytopathogens due to the presence of an efficient and complex immune system which is able to deal with most microbial invaders ubiquitously present in the environment. Plant growth-promoting microbes (PGPMs) elicit a higher level of resistance in addition to an indigenous immune system in the form of induced systemic resistance in plants and provide a heightened level of protection. Induced systemic resistance is a pre-activated induced resistance in plants leading to defense-related protein activation which is independent of salicylic acid and dependent on jasmonic acid and ethylene. Nonexpressor of pathogenesis-related protein 1 (NPR1) works as a master regulator of hormonal defense signaling pathway leading to activation of pathogenesis-related and defense-related protein that depends on the preceding signals. This chapter focuses on recent research study concerning interaction between PGPMs and plants under biotic stress condition.

RNAi induced silencing of pathogenicity genes of Fusarium spp. for vascular wilt management in tomato

The necessity to develop new strategies for the control of Fusarium wilt of tomato signifies the identification of pathogencity genes and ascertaining their role to use them as molecular tools for fungicide development or to develop transgenics. Semi-quantitative gene expression studies have identified two pathogenicity genes, FOW2 and chsV, reported as ZnII)2Cys6-type transcription regulator and class V chitin synthase, respectively, as potential ones for being secreted all the time. The roles of these genes in the pathogenicity of Fusarium oxysporum and F. solani have been established by RNA interference (RNAi)-induced silencing (knockdown). The silencing vector encoding hairpin RNA of each of the gene fragment was constructed in a two-step PCR-based cloning, and introduced into the fungal genomic DNA. Silencing of either of the genes resulted in less virulent fungal phenotypes with altered physiological characteristics like sporulation and growth on solid media and a reduction in mRNA expression. The results therefore demonstrate the applicability of these pathogenicity genes as useful molecular targets for exploitation in Fusarium wilt control in tomato.

Bacterial Mediated Plant Protection: Induced Systemic Resistance in Soybean

Soybean (Glycine max L. Merrill) is world’s most important source of the highest protein content among leguminous crops. Several pathogens like fungi, bacteria and viruses attack on the soybean plant and cause different diseases leading to the great losses in the yield. At global level a wide-ranging research has been done to build up resistance varieties against biotic stresses by means of genetic engineering. In the present scenario an alternative strategy has developed wherein bacteria played a key role to the plants successful survival against pathogen stress. Plant growth promoting rhizobacteria (PGPR) elicited a higher level of resistance in addition to indigenous immune system in the form of induced systemic resistance (ISR) in plants and offers heightened level of protection. ISR is the prior activation of induced resistance in plants leading to triggering of jasmonic acid and ethylene mediated signaling pathways. Nonexpressor of pathogenesis related protein 1 (NPR1) work as a master regulator of hormonal defense signaling pathway leading to activation of pathogenesis related and defense related protein depend on the preceding signals. This review chapter will focus on research study done on soybean concerning interaction between PGPRs and plants under biotic stress condition.

Bacterial Volatiles in Promotion of Plant Under Biotic Stress

Confined to a narrow region but rich in nutrients, rhizosphere is always favorable to interactions between microorganisms and plants. While many soil microorganisms have no obvious effects on plants, some have negative as well as positive effects on plant growth. Plant growth-promoting rhizobacteria (PGPR) are beneficial microbes which have been fruitfully applied in agriculture to enhance seedling emergence, plant weight, crop yield, and disease resistance. Among these, some PGPR strains mediate plant growth promotion in direct and/or indirect manner by releasing volatile organic compounds (VOCs). Bacteria emitted a wide array of volatiles ranging from inorganic such as hydrogen cyanide (HCN) and nitric oxide (NO) to organic such as hydrocarbon, ketone, acids, terpenes, etc. Bacterial VOCs promote plant growth by eliciting different signaling pathway and show correlation with plant growth hormones also. In particular, 2,3-butanediol and acetoin were reported for the heightened level of plant growth promotion and triggering induced resistance against fungal pathogens. This chapter focuses on recent research study and role of bacterial volatiles in plant growth promotion and protection against pathogens.

Bacteria-Mediated Elicitation of Induced Resistance in Plants upon Fungal Phytopathogen

Plants are sessile organism and primary producer of the ecosystem and communicate with above- and belowground communities that consist of benign/pathogenic microbes. Among these interactions, phytopathogenic fungi and oomycetes are the major causative agents of infectious crop plant diseases. To control these pathogens is extremely difficult, and a very small percentage of applied fungicides used for crop protection reach the target pathogen. To combat with such pathogen, higher level of resistance in addition to indigenous immune system is required which is elicited by plant growth-promoting bacteria (PGPB) in the form of induced systemic resistance in plants. Induced systemic resistance is prior activation of resistance in plants through PGPB via root priming that leads to defense-related protein activation which is independent of salicylic acid and dependent on jasmonic acid and ethylene. In case of it, nonexpressor of pathogenesis-related protein 1 (NPR1) plays the most important role by regulating hormonal defense signaling pathway leading to activation of pathogenesis-related and defense-related protein depending on the preceding signals. PGPB-elicited induced resistance showed that some of the bacterial determinants are responsible for the elicitation of induced systemic resistance (ISR). Although PGPB seem to actively suppress local host defense responses in the roots, it also produces elicitors that are responsible for the onset of systemic immunity. This chapter focuses on recent research study concerning the interaction between PGPB and plants under biotic stress condition.

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