Bacillus subtilis NBRI-W9 simultaneously activates SAR and ISR against Fusarium chlamydosporum NBRI-FOL7 to increase wilt resistance in tomato.

AIMS: The study aimed to determine the pathogenicity of Fusarium species currently prevalent in tomato fields having history of chemical fungicide applications and determine the bio-efficacy of Bacillus subtilis NBRI-W9 as a potent biological control agent. METHODS AND RESULTS: Fusarium was isolated from surface-sterilized infected tomato plants collected from fields. Pathogenicity of 30 Fusarium isolates was determined by in vitro and in vivo assays. Following Koch's postulates, F. chlamydosporum (FOL7) was identified as a virulent pathogen. The biological control of FOL 7 by B. subtilis NBRI-W9 (W9) and the colonization potential of W9 were established using spontaneous rifampicin-resistant mutants. W9 showed 82% inhibition of FOL7 on a dual-culture plate and colonization levels in tomato plants of ∼5.5, ∼3.3, and ∼2.2 log10 CFU/g in root, stem, and leaf tissue, respectively. Antagonistic activity was shown by scanning electron microscopy (SEM) and cell-wall-degradative enzymes. W9 reduced FOL7 infection in net-house and field experiments by 60% and 41%, respectively. Biochemical investigation, defence enzymes, defence gene expression analysis, SEM, and field studies provide evidence of hyperparasitism and induced resistance as the mode of biological control. The study also demonstrates that the potent biocontrol agent W9, isolated from Piper, can colonize tomato plants, control fungal disease by inducing induced systemic resistance (ISR) and systemic acquired resistance (SAR) simultaneously, and increase crop yield by 21.58% under field conditions. CONCLUSIONS: This study concludes that F. chlamydosporum (NBRI-FOL7) is a potent, fungicide-resistant pathogen causing wilt in tomatoes. NBRI-W9 controlled FOL7 through mycoparasitism and simultaneously activated ISR and SAR in plants, providing an attractive tool for disease control that acts at multiple levels.

Endophytic biofungicide Bacillus subtilis (NBRI-W9) reshapes the metabolic homeostasis disrupted by the chemical fungicide, propiconazole in tomato plants to provide sustainable immunity against non-target bacterial pathogens.

Chemical and microbial fungicides (Bio/fungicide) act differentially on plant systems. The present work assessed the metabolic profile of tomato plants vis-a-vis endophytic diversity after spraying of Propiconazole (PCZ) and endophytic biofungicide Bacillus subtilis (W9). Bio/fungicides were sprayed on tomato plants and evaluated for phenotypic, biochemical, and metabolic profiles after one week. In W9 treatment, a significant increase in relative abundance of several metabolites was observed including sugars, sugar alcohols, fatty-acids, organic-acids, and amino-acids. Polysaccharides and fatty acids showed a significant positive correlation with Rhizobiales, Burkholderiales, Bacillales, and Lactobacillales, respectively (p < 0.05). The PCZ and W9 treated plant's metabolic status significantly affected their resistance to non-target, bacterial pathogen P. syringae. Compared to PCZ and control, W9 treatment reduced the ROS deposition and expression of antioxidants gene GPx, PO (~0.1-1.7fold). It enhanced the genes related to the Phenylpropanoid pathway (∼1.6-5.2 fold), PR protein (~1.2-3.4 fold), and JA biosynthesis (~1.7-4.3 fold), resulting in reduced disease incidence. The results provide novel insights into the effects of endophytic biofungicide and chemical fungicides on the plant's metabolic status, its relation to the endophytes, and role in altering the plant's immune system.

Comprehensive analysis of OsJAZ gene family deciphers rhizobacteria-mediated nutrient stress modulation in rice.

The JASMONATE-ZIM DOMAIN (JAZ) repressors are crucial proteins in jasmonic acid signaling pathway that are critical for plant growth. Therefore, the present study aimed to identify and characterize OsJAZs in the rice genome, revealing their structural attributes, regulatory elements, miRNA interactions, and subcellular localization. 23 JAZ transcripts across the 6 chromosomes of rice genome were identified having conserved domains and different physiochemical characteristics. Phylogenetically classified into five clades, they showed highest syntenic relationship with P. virgatum. The non-synonymous/synonymous values ranged from 0.44 to 1.21 suggesting purifying/stabilizing selection in OsJAZs. The study examined the 1.5 kb promoter region for cis-regulatory elements, and also identified 92 miRNAs targets. Furthermore, homology modeling provided insights into the 3D-structures of JAZ proteins while in-silico gene expression analysis revealed their functional diversity in various tissues and developmental stages. Additionally, qRT-PCR analysis highlighted their involvement in stress adaptation to sub-optimum nutrient conditions induced by plant-beneficial rhizobacteria Bacillus amyloliquefaciens (SN13) in two rice varieties. Distinct OsJAZ expression patterns in the two varieties correlated with altered root architecture, xylem structure, and lignification. These findings affirmed that specific up-or down-regulation of OsJAZs might play critical role in SN13 induced changes in the two varieties that enabled them to survive under stress.

Carbendazim Modulates the Metabolically Active Bacterial Populations in Soil and Rhizosphere.

The impact of fungicide residues on non-target soil bacterial communities is relatively unexplained. We hypothesize that the persistence of fungicide residues in the soil will affect the soil bacterial populations. Persistence depends on biotic and abiotic factors, primarily determined by agricultural activities. Activities such as fallow soil (F), farmyard manure (FYM) amendment, rice straw (RS) mulching, and cultivation of maize (Zea mays) and clover (Trifolium alexandrinum) were used as treatments. The soil CO2 efflux showed no effect of Carbendazim on dormant bacteria (unwatered condition). However, in irrigated condition, Carbendazim enhanced the CO2 efflux by 8, 164, 131, 249, and 182% in fallow, FYM, RS, maize, and Trifolium treatments, respectively. However, 16S rRNA metagenome study after 30 days of carbendazim treatment showed that maize rhizosphere microflora was most susceptible, decreasing the Shannon diversity index from 0.321 to 0.165. Diversity indices generally increased in maize and RS treatments, and Proteobacteria was the most prominent bacterial phyla in the maize rhizosphere. The microbial communities separated into distinct groups on the Principal Co-ordinate analysis (PCoA) plot. The separation on scale 1 (35%) and scale 2 (13%) was based, respectively, on microbial activity and carbendazim treatments. Functionally Maize+Carbendazim treatment showed the highest enzyme activities dehydrogenase (82.25%), acid phosphatase (78.10%), alkaline phosphatase (48.26%), ß-glucosidase (59.99%), protease (126.65%), and urease (50.66%) compared to fallow soil. Overall, Carbendazim enhanced non-target bacterial activity in metabolically active niches, while it did not affect the dormant microflora. Thus, organic amendments and cultivation of fungicide-contaminated soil may help render the contaminant through bacterial activity.

Mitigation of arsenic toxicity in rice by the co-inoculation of arsenate reducer yeast with multifunctional arsenite oxidizing bacteria.

The study aimed to explicate the role of microbial co-inoculants for the mitigation of arsenic (As) toxicity in rice. Arsenate (AsV) reducer yeast Debaryomyces hansenii NBRI-Sh2.11 (Sh2.11) with bacterial strains of different biotransformation potential was attempted to develop microbial co-inoculants. An experiment to test their efficacy (yeast and bacterial strains) on plant growth and As uptake was conducted under a stressed condition of 20 mg kg-1 of arsenite (AsIII). A combination of Sh2.11 with an As(III)-oxidizer, Citrobacter sp. NBRI-B5.12 (B5.12), resulted in ∼90% decrease in grain As content as compared to Sh2.11 alone (∼40%). Reduced As accumulation in rice roots under co-treated condition was validated with SEM-EDS analysis. Enhanced As expulsion in the selected combination under in vitro conditions was found to be correlated with higher As content in the soil during their interaction with plants. Selected co-inoculant mediated enhanced nutrient uptake in association with better production of indole acetic acid (IAA) and gibberellic acid (GA) in shoot, support microbial co-inoculant mediated better biomass under stressful condition. Boosted defense response in association with enhanced glutathione-S-transferase (GST) and glutathione reductase (GR), activities under in vitro and in vivo conditions were observed. These results indicated that the As(III) oxidizer-B5.12 accelerated the As detoxification property of the As(V) reducer-Sh2.11. Henceforth, the results confer that the coupled reduction-oxidation process of the co-inoculant reduces the accumulation of As in rice grain. These co-inoculants can be further developed for field trials to achieve higher biomass with alleviated As toxicity in rice.

An Insight into the Endophytic Bacterial Community of Tomato after Spray Application of Propiconazole and Bacillus subtilis Strain NBRI-W9.

Propiconazole (PCZ) is a commonly sprayed fungicide against fungal pathogens. Being systemic in action, it reaches subcellular layers and impacts the endophytes. Although PCZ is a fungicide, it is hypothesized to exert an inhibitory effect on the bacterial endophytes. Therefore, this study aims to get an insight into the perturbations caused by the systemically acting antifungal agents PCZ and Bacillus subtilis (W9) and the consequences thereof. The current study compared the 16S rRNA microbial diversity, abundance, and functions of the endophytic bacterial community of tomato in response to PCZ, W9, and PCZ+W9 application. The implications of these treatments on the development of bacterial speck disease by Pseudomonas syringae were also studied. The culturable endophyte population fluctuated after (bio)fungicide application and stabilized by 72 h. At 72 h, the endophyte population was ~3.6 × 103 CFUg-1 in control and ~3.6 × 104 in W9, ~3.0 × 102 in PCZ, and ~5.3 × 103 in PCZ+W9 treatment. A bacterial community analysis showed a higher relative abundance of Bacillales, Burkholderiales, Rhizobiales, Pseudomonadales, and Actinomycetales in the W9 treatment compared with that in the PCZ treatment and control. Phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt) analysis showed enhanced metabolic pathways related to secretion, stress, chemotaxis, and mineral nutrition in the W9 treatment. Disease severity was greater in PCZ than that in the W9 treatment. Disease severity on tomato plants showed strong negative correlations with Sphingomonas (r = -0.860) and Janthinobacterium (r = -0.810), indicating that the natural biocontrol communities are agents of plant resistance to diseases. Outcomes show that systemic chemicals are a potential threat to the nontarget endophytes and that plants became susceptible to disease on endophyte decline; this issue could be overcome by the application of microbial inoculums. IMPORTANCE Endophytes are plant inhabitants acting as its extended genome. The present study highlights the importance of maintaining plant endophytes for sustainable disease resistance in plants. The impact of chemical fungicides and biofungicides was shown on tomato endophytes, in addition to their implications on plant susceptibility to bacterial speck disease. The observations point toward the deleterious effects of systemic pesticide application on endophyte niches that disrupt their diversity and functions compromising plant immunity.

Synergistic action of Trichoderma koningiopsis and T. asperellum mitigates salt stress in paddy.

Intensive cultivation increases the salinity and alkalinity of soil leading to its degradation. Such soil lead to abiotic stress conditions in plants causing ROS-mediated cellular damage. Microbes constitute an important group of bio-stimulants, which are promising alternatives to reduce ROS-mediated abiotic stresses and improve plant growth. In the present study synergistic activity of stress-tolerant Trichoderma koningiopsis NBRI-PR5 (MTCC 25372) and T. asperellum NBRI-K14 (MTCC 25373) (TrichoMix) was assessed in paddy crop under salt stress conditions. Improved soil microbial biomass carbon (MBC), total organic carbon (TOC), and available nutrients N/P/K by 2-3 folds was observed in the pot experiment using the TrichoMix. It restored the heterogeneous microbial population of the paddy rhizosphere during salt stress and modulated the soil enzyme activities. The anatomical distortions in rice roots due to salt stress were stabilized in presence of the TrichoMix. Different stress marker genes (OsMAPK5, OsAPX, OsGST, OsUSP, OsBADH, OsLYSO, OsNRAMP6, and OsBz8) were differentially modulated by the TrichoMix in presence of salt stress as compared to the control. The TrichoMix increased the yield by 10% in marginally stressed fields; however, it enhanced the yield by approximately 60% when used with the 50% recommended dose of NPK. In the integrated treatment, Fe and Zn were fortified by approximately 40% and 29% respectively in the grains. From the present study, it was concluded that the TrichoMix stimulated the rice plants to accumulate osmoprotectants, improved the anatomical features, modulated the plant defense system, and improved the grain yield and quality. Therefore, the NBRI-PR5 and NBRI-K14 mixture may be used as a bio-stimulant to increase productivity in the rapidly deteriorating soil and reduce the NPK inputs. Supplementary Information: The online version contains supplementary material available at 10.1007/s12298-022-01192-6.

Comprehensive illustration of transcriptomic and proteomic dataset for mitigation of arsenic toxicity in rice (Oryza sativa L.) by microbial consortium.

The present article represents the data for analysis of microbial consortium (P.putida+C.vulgaris) mediated amelioration of arsenic toxicity in rice plant. In the current study the transcriptome profiling of treated rice root and shoot was performed by illumina sequencing (Platform 2000). To process the reads and to analyse differential gene expression, Fastxtoolkit, NGSQCtoolkit, Bowtie 2 (version 2.1.0), Tophat program (version 2.0.8), Cufflinks and Cuffdiff programs were used. For Proteome profiling, total soluble proteins in shoot of rice plant among different treatments were extracted and separated by 2D poly acrylamide gel electrophoresis (PAGE) and then proteins were identified with the help of MALDI-TOF/TOF. In gel based method of protein identification, the isoelectric focusing machine (IPGphor system,Bio-Rad USA), gel unit (SDS-PAGE) and MALDI-TOF/TOF (4800 proteomic analyzer Applied Biosystem, USA) were used for successful separation and positive identification of proteins. To check the differential abundance of proteins among different treatments, PDQuest software was used for data analysis. For protein identification, Mascot search engine (http://www.matrixscience.com) using NCBIprot/SwissProt databases of rice was used. The analyzed data inferred comprehensive picture of key genes and their respective proteins involved in microbial consortium mediated improved plant growth and amelioration of As induced phyto-toxicity in rice. For the more comprehensive information of data, the related full-length article entitled "Microbial consortium mediated growth promotion and Arsenic reduction in Rice: An integrated transcriptome and proteome profiling" may be accessed.

Nitric oxide-mediated alleviation of arsenic stress involving metalloid detoxification and physiological responses in rice (Oryza sativa L.).

Rice is a staple crop, and food chain contamination of arsenic in rice grain possesses a serious health risk to billions of population. Arsenic stress negatively affects the rice growth, yield and quality of the grains. Nitric oxide (NO) is a major signaling molecule that may trigger various cellular responses in plants. The protective role of NO during arsenite (AsIII) stress and its relationship with plant physiological and metabolic responses is not explored in detail. Exogenous NO, supplemented through the roots in the form of sodium nitroprusside, has been shown to provide protection vis-à-vis AsIII toxicity. The NO-mediated variation in physiological traits such as stomatal density, size, chlorophyll content and photosynthetic rate maintained the growth of the rice plant during AsIII stress. Besides, NO exposure also enhanced the lignin content in the root, decreased total arsenic content and maintained the activities of antioxidant isoenzymes to reduce the ROS level essential for protecting from AsIII mediated oxidative damage in rice plants. Further, NO supplementation enhanced the GSH/GSSG ratio and PC/As molar ratio by modulating PC content to reduce arsenic toxicity. Further, NO-mediated modulation of the level of GA, IAA, SA, JA, amino acids and phenolic metabolites during AsIII stress appears to play a central role to cope up with AsIII toxicity. The study highlighted the role of NO in AsIII stress tolerance involving modulation of metalloid detoxification and physiological pathways in rice plants.

Root system architecture, physiological analysis and dynamic transcriptomics unravel the drought-responsive traits in rice genotypes.

Drought is the major abiotic factors that limit crop productivity worldwide. To withstand stress conditions, plants alter numerous mechanisms for adaption and tolerance. Therefore, in the present study, 106 rice varieties were screened for drought tolerance phenotype via exposing different concentrations of polyethylene glycol 6000 (PEG) in the hydroponic nutrient medium at the time interval of 1, 3, and 7 days to evaluate the changes in their root system architecture. Further, based on root phenotype obtained after PEG-induced drought, two contrasting varieties drought-tolerant Heena and -sensitive Kiran were selected to study transcriptional and physiological alterations at the same stress durations. Physiological parameters (photosynthesis rate, stomatal conductance, transpiration), and non-enzymatic antioxidants (carotenoids, anthocyanins, total phenol content) production indicated better performance of Heena than Kiran. Comparatively higher accumulation of carotenoid and anthocyanin content and the increased photosynthetic rate was also observed in Heena. Root morphology (length, numbers of root hairs, seminal roots and adventitious roots) and anatomical data (lignin deposition, xylem area) enable tolerant variety Heena to better maintain membrane integrity and relative water content, which also contribute to comparatively higher biomass accumulation in Heena under drought. In transcriptome profiling, significant drought stress-associated differentially expressed genes (DEGs) were identified in both the varieties. A total of 1033 and 936 uniquely upregulated DEGs were found in Heena and Kiran respectively. The significant modulation of DEGs that were mainly associated with phytohormone signaling, stress-responsive genes (LEA, DREB), transcription factors (TFs) (AP2/ERF, MYB, WRKY, bHLH), and genes involved in photosynthesis and antioxidative mechanisms indicate better adaptive nature of Heena in stress tolerance. Additionally, the QTL-mapping analysis showed a very high number of DEGs associated with drought stress at AQHP069 QTL in Heena in comparison to Kiran which further distinguishes the drought-responsive traits at the chromosomal level in both the contrasting varieties. Overall, results support the higher capability of Heena over Kiran variety to induce numerous genes along with the development of better root architecture to endure drought stress.

Auxin-salicylic acid cross-talk ameliorates OsMYB-R1 mediated defense towards heavy metal, drought and fungal stress.

The MYB TF family is an immensely large and functionally diverse class of proteins involved in the regulation of cell cycle, cell morphogenesis to stress signaling mechanism. The present study deciphered the hormonal cross-talk of wound inducible and stress-responsive OsMYB-R1 transcription factor in combating abiotic [Cr(VI) and drought/PEG] as well as biotic (Rhizoctonia solani) stress. OsMYB-R1 over-expressing rice transgenics exhibit a significant increase in lateral roots, which may be associated with increased tolerance under Cr(VI) and drought exposure. In contrast, its loss-of-function reduces stress tolerance. Higher auxin accumulation in the OsMYB-R1 over-expressed lines further strengthens the protective role of lateral roots under stress conditions. RNA-seq. data reveals over-representation of salicylic acid signaling molecule calcium-dependent protein kinases, which probably activate the stress-responsive downstream genes (Peroxidases, Glutathione S-transferases, Osmotins, Heat Shock Proteins, Pathogenesis Related-Proteins). Enzymatic studies further confirm OsMYB-R1 mediated robust antioxidant system as catalase, guaiacol peroxidase and superoxide dismutase activities were found to be increased in the over-expressed lines. Our results suggest that OsMYB-R1 is part of a complex network of transcription factors controlling the cross-talk of auxin and salicylic acid signaling and other genes in response to multiple stresses by modifying molecular signaling, internal cellular homeostasis and root morphology.

Functional characterization of tau class glutathione-S-transferase in rice to provide tolerance against sheath blight disease.

Glutathione-S-transferase (GST) is an important defense gene that confers resistance against several abiotic and biotic stresses. The present study identifies a tau class GST in rice (Oryza sativa L.), OsGSTU5 (Os09g20220), which provided tolerance against sheath blight (SB) disease, caused by a necrotrophic fungus, Rhizoctonia solani (RS). Overexpression and knockdown rice transgenic lines of OsGSTU5 were generated and tested for the severity of infection during sheath blight disease. The results obtained after RS infection showed that the lesion cover area and hyphal penetration were more in knockdown line and lesser in the overexpression line. Analysis of reactive oxygen species (ROS) accumulation showed more spots of H2O2 and O2- in knockdown lines compared to overexpressed lines. Later, RS transcript level was analyzed in RS-infected transgenic lines, which manifested that the knockdown line had higher RS transcripts in comparison to the control line and least RS transcripts were observed in the overexpressed line. In conclusion, rice transgenic lines overexpressing OsGSTU5 were found to be more tolerant, while the knockdown lines were more prone to Rhizoctonia infection compared to control lines.

Transcriptome and proteome analyses reveal selenium mediated amelioration of arsenic toxicity in rice (Oryza sativa L.).

Arsenic (As), a chronic poison and non-threshold carcinogen, is a food chain contaminant in rice, posing yield losses as well as serious health risks. Selenium (Se), a trace element, is a known antagonist of As toxicity. In present study, RNA seq. and proteome profiling, along with morphological analyses were performed to explore molecular cross-talk involved in Se mediated As stress amelioration. The repair of As induced structural deformities involving disintegration of cell wall and membranes were observed upon Se supplementation. The expression of As transporter genes viz., NIP1;1, NIP2;1, ABCG5, NRAMP1, NRAMP5, TIP2;2 as well as sulfate transporters, SULTR3;1 and SULTR3;6, were higher in As + Se compared to As alone exposure, which resulted in reduced As accumulation and toxicity. The higher expression of regulatory elements like AUX/IAA, WRKY and MYB TFs during As + Se exposure was also observed. The up-regulation of GST, PRX and GRX during As + Se exposure confirmed the amelioration of As induced oxidative stress. The abundance of proteins involved in photosynthesis, energy metabolism, transport, signaling and ROS homeostasis were found higher in As + Se than in As alone exposure. Overall, present study identified Se responsive pathways, genes and proteins involved to cope-up with As toxicity in rice.

PGPR-induced OsASR6 improves plant growth and yield by altering root auxin sensitivity and the xylem structure in transgenic Arabidopsis thaliana.

Plant-growth-promoting rhizobacteria (PGPR) improve plant growth by altering the root architecture, although the mechanisms underlying this alteration have yet to be unravelled. Through microarray analysis of PGPR-treated rice roots, a large number of differentially regulated genes were identified. Ectopic expression of one of these genes, OsASR6 (ABA STRESS RIPENING6), had a remarkable effect on plant growth in Arabidopsis. Transgenic lines over-expressing OsASR6 had larger leaves, taller inflorescence bolts and greater numbers of siliques and seeds. The most prominent effect was observed in root growth, with the root biomass increasing four-fold compared with the shoot biomass increase of 1.7-fold. Transgenic OsASR6 over-expressing plants showed higher conductance, transpiration and photosynthesis rates, leading to an ˜30% higher seed yield compared with the control. Interestingly, OsASR6 expression led to alterations in the xylem structure, an increase in the xylem vessel size and altered lignification, which correlated with higher conductance. OsASR6 is activated by auxin and, in turn, increases auxin responses and root auxin sensitivity, as observed by the increased expression of auxin-responsive genes, such as SAUR32 and PINOID, and the key auxin transcription factor, ARF5. Collectively, these phenomena led to an increased root density. The effects of OsASR6 expression largely mimic the beneficial effects of PGPRs in rice, indicating that OsASR6 activation may be a key factor governing PGPR-mediated changes in rice. OsASR6 is a potential candidate for the manipulation of rice for improved productivity.

Poikilodermatous Mycosis Fungoides with Erosive Lesions.

Mycosis fungoides (MF) is the commonest form of cutaneous T-cell lymphoma. Many clinical subtypes and variants of MF have been described, one of which is poikilodermatous MF variant. Erosions and bullous lesions in a patient with poikilodermatous MF is a rare presentation. We present one such rare case of poikilodermatous MF with erosive lesions in a 40-year-old male.

A multifaceted rhizobacterium Paenibacillus lentimorbus alleviates nutrient deficiency-induced stress in Cicer arietinum L.

Nutrient deficiency in soil is one of the limiting factors responsible for stunted growth and poor flowering/fruiting of crops which result in decline in overall agricultural productivity. However, one important strategy to overcome the problem of nutrient deficiency and to avoid use of chemical fertilizers is the use of plant growth promoting rhizobacteria (PGPR). Paenibacillus lentimorbus NRRL B-30488 (hereafter B-30488), an efficient PGPR has been reported to have various plant growth promoting traits that help crops to mitigate various environmental stresses. Therefore, the present work was designed to examine the application of B-30488 on chickpea growth under nutrient stress condition. Plants inoculated with B-30488 showed positive modulation in physio-biochemical behaviour and mineral nutrient uptake for better growth and development. Alteration in gene expression and metabolic profile under nutrient stress condition in chickpea also supported the stress amelioration capability of B-30488. Principal component analysis statistically proved that improved growth performance of chickpea plants under nutrient stress was mainly due to B-30488 induced modulation of metabolic pathways. To the best of our knowledge, this is the first study for analysis of growth promotion and stress alleviation in chickpea plants subjected to nutrient stress in presence of PGPR B-30488.

Paenibacillus lentimorbus induces autophagy for protecting tomato from Sclerotium rolfsii infection.

During biotic stress, plants use several mechanisms to protect themselves that include the production of reactive oxygen species (ROS), induction of pathogenesis-related proteins and cell death. Some plant growth promoting rhizobacteria (PGPR) are known to act as bio-control agents that protect crops against pathogens. The biocontrol activity of PGPR Paenibacillus lentimorbus (B-30488) against Sclerotium rolfsii showed previously where several defense-related genes were upregulated with ROS induction in tomato. We further evaluate the other possibility, i.e. role of autophagy in enhancing defense in tomato using PGPR. Confocal microscopy revealed the presence of an acidotropic dye Mono Dansyl Cadaverine (MDC) stained autophagosomes in B-30488 treated healthy and infected plants. These autophagosomes almost disappeared in plants treated with an autophagy inhibitor chloroquine. The results were also confirmed by ultrastructural analysis of leaf tissues using transmission electron microscopy. Enhanced expression of autophagy-related genes was also monitored in B-30488 primed fungal infected tissues as compared to control by qRT-PCR. Results of ROS accumulation, fluorescence, confocal and transmission electron microscopy and gene expression analysis revealed induction of autophagy using B-30488 as a biocontrol agent suggesting a role in enhancing disease resistance in tomato. Overall, the present study indicated a role of B-30488 as a biocontrol in enhancing disease resistance in tomato and also assists a better understanding of fungal pathogenesis that is expected to be useful in developing new strategies for disease control.

Chlorella vulgaris and Pseudomonas putida interaction modulates phosphate trafficking for reduced arsenic uptake in rice (Oryza sativa L.).

Rice grown in arsenic (As) contaminated areas contributes to high dietary exposure of As inducing multiple adverse effects on human health. The As contamination and application of phosphate fertilizers during seedling stage creates a high P and As stress condition. The flooded paddy fields are also conducive for algal growth and microbial activity. The present study proposes potential role of microalgae, Chlorella vulgaris (CHL) and bacteria, Pseudomonas putida (RAR) on rice plant grown under excess As and phosphate (P) conditions. The results show synchronized interaction of CHL + RAR which, reduces As uptake through enhanced P:As and reduced As:biomass ratio by modulating P trafficking. Gene expression analysis of different phosphate transporters exhibited correlation with reduced As uptake and other essential metals. The balancing of reactive oxygen species (ROS), proline accumulation, hormone modulation, and As sequestration in microbial biomass were elucidated as possible mechanisms of As detoxification. The study concludes that RAR and CHL combination mitigates the As stress during P-enriched conditions in rice by: (i) reducing As availability, (ii) modulating the As uptake, and (iii) improving detoxification mechanism of the plant. The study will be important in assessing the role and applicability of P solubilizing biofertilizers in these conditions.