Silicate solubilizing and plant growth promoting bacteria interact with biogenic silica to impart heat stress tolerance in rice by modulating physiology and gene expression

Heat stress caused due to increasing warming climate has become a severe threat to global food production including rice. Silicon plays a major role in improving growth and productivity of rice by aiding in alleviating heat stress in rice. Soil silicon is only sparingly available to the crops can be made available by silicate solubilizing and plant-growth-promoting bacteria that possess the capacity to solubilize insoluble silicates can increase the availability of soluble silicates in the soil. In addition, plant growth promoting bacteria are known to enhance the tolerance to abiotic stresses of plants, by affecting the biochemical and physiological characteristics of plants. The present study is intended to understand the role of beneficial bacteria viz. Rhizobium sp. IIRR N1 a silicate solublizer and Gluconacetobacter diazotrophicus, a plant growth promoting bacteria and their interaction with insoluble silicate sources on morpho-physiological and molecular attributes of rice (Oryza sativa L.) seedlings after exposure to heat stress in a controlled hydroponic system. Joint inoculation of silicates and both the bacteria increased silicon content in rice tissue, root and shoot biomass, significantly increased the antioxidant enzyme activities (viz. superoxidase dismutase, catalase and ascorbate peroxidase) compared to other treatments with sole application of either silicon or bacteria. The physiological traits (viz. chlorophyll content, relative water content) were also found to be significantly enhanced in presence of silicates and both the bacteria after exposure to heat stress conditions. Expression profiling of shoot and root tissues of rice seedlings revealed that seedlings grown in the presence of silicates and both the bacteria exhibited higher expression of heat shock proteins (HSPs viz., OsHsp90, OsHsp100 and 60 kDa chaperonin), hormone-related genes (OsIAA6) and silicon transporters (OsLsi1 and OsLsi2) as compared to seedlings treated with either silicates or with the bacteria alone. The results thus reveal the interactive effect of combined application of silicates along with bacteria Rhizobium sp. IIRR N1, G. diazotrophicus inoculation not only led to augmented silicon uptake by rice seedlings but also influenced the plant biomass and elicited higher expression of HSPs, hormone-related and silicon transporter genes leading to improved tolerance of seedling to heat stress

Estimation of Calcium and Iron Levels in Gingival Crevicular Fluid and Serum in Periodontal Health and Disease

Introduction: Gingival Crevicular Fluid (GCF) has been referred to as a promising medium for detection of markers for periodontal disease activity. Analysis of GCF shows minute changes in biomarker levels well before the onset of clinical signs and symptoms; which helps to even predict a person’s predisposition towards periodontal disease occurrence. The elemental analysis of human blood serum is noteworthy in routine clinical practice as well as in medical research. Aim: This study was done to determine the changes in calcium and iron levels in GCF and serum in human subjects with normal periodontal health and those with disease. Materials and Methods: This was a cross-sectional study conducted from March 2019 to December 2019. Eight study subjects (four healthy subjects and four periodontitis cases) were selected from the patients reporting to the Department of Periodontics at Tagore Dental College and Hospital, Chennai. The subjects were chosen based on inclusion and exclusion criteria and all patients were subjected to a clinical examination wherein the Probing Depth (PD) and Clinical Attachment Level (CAL) were recorded by a single examiner using William’s Periodontal probe. The GCF samples were collected by Capillary Tubing method. Blood was collected by venipuncture and centrifuged to provide serum samples. Dual viewing Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) was used to estimate Calcium and Iron in GCF and serum. SPSS version 21.0 was used for statistical analysis. Mann Whitney U test was used for comparing the groups. A p-value less than 0.05 was considered statistically significant. Results: Serum iron levels were significantly less in periodontitis patients than healthy subjects (p-value 0.043). GCF iron level (p-value 0.386), GCF calcium level (p-value 0.149) and serum calcium level (p-value 0.564) did not show any major variation among subjects with normal periodontal health and those with disease. Conclusion: The findings of this study showed that iron and calcium are present in GCF and serum samples of healthy persons and patients with chronic periodontitis which can be detected using ICP-OES. A significant difference in serum iron levels between health and disease could indicate a patient’s predisposition towards developing periodontitis. Calcium levels in GCF and serum do not point towards periodontal disease activity

In-situ synthesis of CN@La(OH)3 nanocomposite for improved the charge separation and enhanced the photocatalytic activity towards Cr(VI) reduction under visible light

In this work, we report for the first time a novel graphitic carbon nitride (CN) composited with different weight percentages (5–15%) of La(OH)3 (CN@La(OH)3) for photocatalytic reduction of hexavalent chromium (Cr(VI)) in aqueous solution. In situ fabrication of the CN@La(OH)3 photocatalysts were carried out via a hydrothermal method. The La(OH)3 nanoparticles were deposited onto the surface of CN nanosheets to form heterojunction, as confirmed by series of techniques. Compared to the pure CN and different weight percentages of CN@La(OH)3 nanocomposite, the CN@La(OH)3(10%) nanocomposite exhibited remarkable photocatalytic reduction performance for Cr(VI) under visible light illumination. Such excellent photocatalytic reduction activity ascribed to the more photocatalytic active sites, high visible light harvesting capacity and improved electron-hole separation and transfer efficiency which was confirmed by photocurrent, impedance and photoluminescence results. The photoreduction efficiency and the reduction rate constant was 98.7% and 0.0263 min−1 within 50 min. A possible reaction mechanism for the effective reduction of carcinogenic Cr(VI) is put forward tentatively. Moreover, the developed CN@La(OH)3(10%) nanocomposite also possessed high structural stability and recyclability after five photocatalytic cycles. This work may open up the way into the robust photocatalysis of Cr(VI) in wastewater treatment application

Table_4_Understanding plant–microbe interaction of rice and soybean with two contrasting diazotrophic bacteria through comparative transcriptome analysis.docx

Understanding the beneficial plant–microbe interactions is becoming extremely critical for deploying microbes imparting plant fitness and achieving sustainability in agriculture. Diazotrophic bacteria have the unique ability to survive without external sources of nitrogen and simultaneously promote host plant growth, but the mechanisms of endophytic interaction in cereals and legumes have not been studied extensively. We have studied the early interaction of two diazotrophic bacteria, Gluconacetobacter diazotrophicus (GAB) and Bradyrhizobium japonicum (BRH), in 15-day-old seedlings of rice and soybean up to 120 h after inoculation (hai) under low-nitrogen medium. Root colonization of GAB in rice was higher than that of BRH, and BRH colonization was higher in soybean roots as observed from the scanning electron microscopy at 120 hai. Peroxidase enzyme was significantly higher at 24 hai but thereafter was reduced sharply in soybean and gradually in rice. The roots of rice and soybean inoculated with GAB and BRH harvested from five time points were pooled, and transcriptome analysis was executed along with control. Two pathways, “Plant pathogen interaction” and “MAPK signaling,” were specific to Rice-Gluconacetobacter (RG), whereas the pathways related to nitrogen metabolism and plant hormone signaling were specific to Rice-Bradyrhizobium (RB) in rice. Comparative transcriptome analysis of the root tissues revealed that several plant–diazotroph-specific differentially expressed genes (DEGs) and metabolic pathways of plant–diazotroph-specific transcripts, viz., chitinase, brassinosteroid, auxin, Myeloblastosis (MYB), nodulin, and nitrate transporter (NRT), were common in all plant–diazotroph combinations; three transcripts, viz., nitrate transport accessory protein (NAR), thaumatin, and thionin, were exclusive in rice and another three transcripts, viz., NAC (NAM: no apical meristem, ATAF: Arabidopsis thaliana activating factor, and CUC: cup-shaped cotyledon), ABA (abscisic acid), and ammonium transporter, were exclusive in soybean. Differential expression of these transcripts and reduction in pathogenesis-related (PR) protein expression show the early interaction. Based on the interaction, it can be inferred that the compatibility of rice and soybean is more with GAB and BRH, respectively. We propose that rice is unable to identify the diazotroph as a beneficial microorganism or a pathogen from an early response. So, it expressed the hypersensitivity-related transcripts along with PR proteins. The molecular mechanism of diazotrophic associations of GAB and BRH with rice vis-à-vis soybean will shed light on the basic understanding of host responses to beneficial microorganisms.</p

Table_8_Understanding plant–microbe interaction of rice and soybean with two contrasting diazotrophic bacteria through comparative transcriptome analysis.docx

Understanding the beneficial plant–microbe interactions is becoming extremely critical for deploying microbes imparting plant fitness and achieving sustainability in agriculture. Diazotrophic bacteria have the unique ability to survive without external sources of nitrogen and simultaneously promote host plant growth, but the mechanisms of endophytic interaction in cereals and legumes have not been studied extensively. We have studied the early interaction of two diazotrophic bacteria, Gluconacetobacter diazotrophicus (GAB) and Bradyrhizobium japonicum (BRH), in 15-day-old seedlings of rice and soybean up to 120 h after inoculation (hai) under low-nitrogen medium. Root colonization of GAB in rice was higher than that of BRH, and BRH colonization was higher in soybean roots as observed from the scanning electron microscopy at 120 hai. Peroxidase enzyme was significantly higher at 24 hai but thereafter was reduced sharply in soybean and gradually in rice. The roots of rice and soybean inoculated with GAB and BRH harvested from five time points were pooled, and transcriptome analysis was executed along with control. Two pathways, “Plant pathogen interaction” and “MAPK signaling,” were specific to Rice-Gluconacetobacter (RG), whereas the pathways related to nitrogen metabolism and plant hormone signaling were specific to Rice-Bradyrhizobium (RB) in rice. Comparative transcriptome analysis of the root tissues revealed that several plant–diazotroph-specific differentially expressed genes (DEGs) and metabolic pathways of plant–diazotroph-specific transcripts, viz., chitinase, brassinosteroid, auxin, Myeloblastosis (MYB), nodulin, and nitrate transporter (NRT), were common in all plant–diazotroph combinations; three transcripts, viz., nitrate transport accessory protein (NAR), thaumatin, and thionin, were exclusive in rice and another three transcripts, viz., NAC (NAM: no apical meristem, ATAF: Arabidopsis thaliana activating factor, and CUC: cup-shaped cotyledon), ABA (abscisic acid), and ammonium transporter, were exclusive in soybean. Differential expression of these transcripts and reduction in pathogenesis-related (PR) protein expression show the early interaction. Based on the interaction, it can be inferred that the compatibility of rice and soybean is more with GAB and BRH, respectively. We propose that rice is unable to identify the diazotroph as a beneficial microorganism or a pathogen from an early response. So, it expressed the hypersensitivity-related transcripts along with PR proteins. The molecular mechanism of diazotrophic associations of GAB and BRH with rice vis-à-vis soybean will shed light on the basic understanding of host responses to beneficial microorganisms.</p

Table_11_Understanding plant–microbe interaction of rice and soybean with two contrasting diazotrophic bacteria through comparative transcriptome analysis.xlsx

Understanding the beneficial plant–microbe interactions is becoming extremely critical for deploying microbes imparting plant fitness and achieving sustainability in agriculture. Diazotrophic bacteria have the unique ability to survive without external sources of nitrogen and simultaneously promote host plant growth, but the mechanisms of endophytic interaction in cereals and legumes have not been studied extensively. We have studied the early interaction of two diazotrophic bacteria, Gluconacetobacter diazotrophicus (GAB) and Bradyrhizobium japonicum (BRH), in 15-day-old seedlings of rice and soybean up to 120 h after inoculation (hai) under low-nitrogen medium. Root colonization of GAB in rice was higher than that of BRH, and BRH colonization was higher in soybean roots as observed from the scanning electron microscopy at 120 hai. Peroxidase enzyme was significantly higher at 24 hai but thereafter was reduced sharply in soybean and gradually in rice. The roots of rice and soybean inoculated with GAB and BRH harvested from five time points were pooled, and transcriptome analysis was executed along with control. Two pathways, “Plant pathogen interaction” and “MAPK signaling,” were specific to Rice-Gluconacetobacter (RG), whereas the pathways related to nitrogen metabolism and plant hormone signaling were specific to Rice-Bradyrhizobium (RB) in rice. Comparative transcriptome analysis of the root tissues revealed that several plant–diazotroph-specific differentially expressed genes (DEGs) and metabolic pathways of plant–diazotroph-specific transcripts, viz., chitinase, brassinosteroid, auxin, Myeloblastosis (MYB), nodulin, and nitrate transporter (NRT), were common in all plant–diazotroph combinations; three transcripts, viz., nitrate transport accessory protein (NAR), thaumatin, and thionin, were exclusive in rice and another three transcripts, viz., NAC (NAM: no apical meristem, ATAF: Arabidopsis thaliana activating factor, and CUC: cup-shaped cotyledon), ABA (abscisic acid), and ammonium transporter, were exclusive in soybean. Differential expression of these transcripts and reduction in pathogenesis-related (PR) protein expression show the early interaction. Based on the interaction, it can be inferred that the compatibility of rice and soybean is more with GAB and BRH, respectively. We propose that rice is unable to identify the diazotroph as a beneficial microorganism or a pathogen from an early response. So, it expressed the hypersensitivity-related transcripts along with PR proteins. The molecular mechanism of diazotrophic associations of GAB and BRH with rice vis-à-vis soybean will shed light on the basic understanding of host responses to beneficial microorganisms.</p

Table_9_Understanding plant–microbe interaction of rice and soybean with two contrasting diazotrophic bacteria through comparative transcriptome analysis.xlsx

Understanding the beneficial plant–microbe interactions is becoming extremely critical for deploying microbes imparting plant fitness and achieving sustainability in agriculture. Diazotrophic bacteria have the unique ability to survive without external sources of nitrogen and simultaneously promote host plant growth, but the mechanisms of endophytic interaction in cereals and legumes have not been studied extensively. We have studied the early interaction of two diazotrophic bacteria, Gluconacetobacter diazotrophicus (GAB) and Bradyrhizobium japonicum (BRH), in 15-day-old seedlings of rice and soybean up to 120 h after inoculation (hai) under low-nitrogen medium. Root colonization of GAB in rice was higher than that of BRH, and BRH colonization was higher in soybean roots as observed from the scanning electron microscopy at 120 hai. Peroxidase enzyme was significantly higher at 24 hai but thereafter was reduced sharply in soybean and gradually in rice. The roots of rice and soybean inoculated with GAB and BRH harvested from five time points were pooled, and transcriptome analysis was executed along with control. Two pathways, “Plant pathogen interaction” and “MAPK signaling,” were specific to Rice-Gluconacetobacter (RG), whereas the pathways related to nitrogen metabolism and plant hormone signaling were specific to Rice-Bradyrhizobium (RB) in rice. Comparative transcriptome analysis of the root tissues revealed that several plant–diazotroph-specific differentially expressed genes (DEGs) and metabolic pathways of plant–diazotroph-specific transcripts, viz., chitinase, brassinosteroid, auxin, Myeloblastosis (MYB), nodulin, and nitrate transporter (NRT), were common in all plant–diazotroph combinations; three transcripts, viz., nitrate transport accessory protein (NAR), thaumatin, and thionin, were exclusive in rice and another three transcripts, viz., NAC (NAM: no apical meristem, ATAF: Arabidopsis thaliana activating factor, and CUC: cup-shaped cotyledon), ABA (abscisic acid), and ammonium transporter, were exclusive in soybean. Differential expression of these transcripts and reduction in pathogenesis-related (PR) protein expression show the early interaction. Based on the interaction, it can be inferred that the compatibility of rice and soybean is more with GAB and BRH, respectively. We propose that rice is unable to identify the diazotroph as a beneficial microorganism or a pathogen from an early response. So, it expressed the hypersensitivity-related transcripts along with PR proteins. The molecular mechanism of diazotrophic associations of GAB and BRH with rice vis-à-vis soybean will shed light on the basic understanding of host responses to beneficial microorganisms.</p

Table_6_Understanding plant–microbe interaction of rice and soybean with two contrasting diazotrophic bacteria through comparative transcriptome analysis.xlsx

Understanding the beneficial plant–microbe interactions is becoming extremely critical for deploying microbes imparting plant fitness and achieving sustainability in agriculture. Diazotrophic bacteria have the unique ability to survive without external sources of nitrogen and simultaneously promote host plant growth, but the mechanisms of endophytic interaction in cereals and legumes have not been studied extensively. We have studied the early interaction of two diazotrophic bacteria, Gluconacetobacter diazotrophicus (GAB) and Bradyrhizobium japonicum (BRH), in 15-day-old seedlings of rice and soybean up to 120 h after inoculation (hai) under low-nitrogen medium. Root colonization of GAB in rice was higher than that of BRH, and BRH colonization was higher in soybean roots as observed from the scanning electron microscopy at 120 hai. Peroxidase enzyme was significantly higher at 24 hai but thereafter was reduced sharply in soybean and gradually in rice. The roots of rice and soybean inoculated with GAB and BRH harvested from five time points were pooled, and transcriptome analysis was executed along with control. Two pathways, “Plant pathogen interaction” and “MAPK signaling,” were specific to Rice-Gluconacetobacter (RG), whereas the pathways related to nitrogen metabolism and plant hormone signaling were specific to Rice-Bradyrhizobium (RB) in rice. Comparative transcriptome analysis of the root tissues revealed that several plant–diazotroph-specific differentially expressed genes (DEGs) and metabolic pathways of plant–diazotroph-specific transcripts, viz., chitinase, brassinosteroid, auxin, Myeloblastosis (MYB), nodulin, and nitrate transporter (NRT), were common in all plant–diazotroph combinations; three transcripts, viz., nitrate transport accessory protein (NAR), thaumatin, and thionin, were exclusive in rice and another three transcripts, viz., NAC (NAM: no apical meristem, ATAF: Arabidopsis thaliana activating factor, and CUC: cup-shaped cotyledon), ABA (abscisic acid), and ammonium transporter, were exclusive in soybean. Differential expression of these transcripts and reduction in pathogenesis-related (PR) protein expression show the early interaction. Based on the interaction, it can be inferred that the compatibility of rice and soybean is more with GAB and BRH, respectively. We propose that rice is unable to identify the diazotroph as a beneficial microorganism or a pathogen from an early response. So, it expressed the hypersensitivity-related transcripts along with PR proteins. The molecular mechanism of diazotrophic associations of GAB and BRH with rice vis-à-vis soybean will shed light on the basic understanding of host responses to beneficial microorganisms.</p