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Oxidative stress is common consequence of abiotic stress in plants as well as cyanobacteria caused by generation of reactive oxygen species (ROS), an inevitable product of respiration and photosynthetic electron transport. ROS act as signalling molecule at low concentration however, when its production exceeds the endurance capacity of antioxidative defence system, the organisms suffer oxidative stress. A highly toxic metabolite, methylglyoxal (MG) is also produced in cyanobacteria in response to various abiotic stresses which consequently augment the ensuing oxidative damage. Taking recourse to the common lineage of eukaryotic plants and cyanobacteria, it would be worthwhile to explore the regulatory role of glyoxalase system and antioxidative defense mechanism in combating abiotic stress in cyanobacteria. This review provides comprehensive information on the complete glyoxalase system (GlyI, GlyII and GlyIII) in cyanobacteria. Furthermore, it elucidates the recent understanding regarding the production of ROS and MG, noteworthy link between intracellular MG and ROS and its detoxification via synchronization of antioxidants (enzymatic and non-enzymatic) and glyoxalase systems using glutathione (GSH) as common co-factor.

WD40 domain-containing proteins are one of the eukaryotes' most ancient and ubiquitous protein families. Little is known about the presence and function of these proteins in cyanobacteria in general and Anabaena in particular. In silico analysis confirmed the presence of WD40 repeats. Gene expression analysis indicated that the transcript levels of both the target proteins were up-regulated up to 4 fold in Cd and drought and 2-3 fold in heat, salt, and UV-B stress. Using a fluorescent oxidative stress indicator, we showed that the recombinant proteins were scavenging reactive oxygen species (ROS) (4-5 fold) more efficiently than empty vectors. Chromatin immunoprecipitation analysis (ChIP) and electrophoretic mobility shift assay (EMSA) revealed that the target proteins function as transcription factors after binding to the promoter sequences. The presence of kinase activity (2-4 fold) in the selected proteins indicated that these proteins could modulate the functions of other cellular proteins under stress conditions by inducing phosphorylation of specific amino acids. The chosen proteins also demonstrated interaction with Zn, Cd, and Cu (1.4-2.5 fold), which might stabilize the proteins' structure and biophysical functions under multiple abiotic stresses. The functionally characterized Alr0671 and All2352 proteins act as transcription factors and offer tolerance to agriculturally relevant abiotic stresses.Alr0671 and All2352 are novel WD40 proteins of Anabaena capable of regulating biochemical functions and abiotic stress tolerance by acting as a transcription factor and mediating DNA-protein interaction.

Background:Cyanobacteria are excellent model to understand the basic metabolic processes taking place in response to abiotic stress. The present study involves characterization of a hypothetical protein Alr0765 of Anabaena PCC7120 comprising CBS-CP12 domain and deciphering its role in abiotic stress tolerance.Methods:Molecular cloning, heterologous expression and protein purification using affinity chromatography was performed to obtain native purified protein Alr0765. Energy sensing property of Alr0765 was inferred from its binding affinity with different ligand molecules as analyzed by FTIR and TNP-ATP binding assay. AAS and real time-PCR were applied to evaluate the iron acquisition property and cyclic voltammetry was employed to check redox sensitivity of the target protein. Transcript level under different abiotic stresses as well as spot assay, CFU count, ROS level and cellular H2O2level were used to show potential role of Alr0765 in abiotic stress tolerance. In-silico analysis of Alr0765 included molecular function probability analysis, multiple sequence analysis, protein domain and motif finding, secondary structure analysis, protein ligand interaction, homologous modeling, model refinement and verification and molecular docking was performed with COFACTOR, PROMALS-3D, InterProScan, MEME, TheaDomEx, COACH, Swiss modeller, Modrefiner, PROCHECK, ERRAT, MolProbity, ProSA, TM-align, and Discovery studio respectively.Results:Transcript levels of alr0765 significantly increased by 20, 13, 15, 14.8, 12, 7, 6 and 2.5 fold when Anabaena PCC7120 treated with LC50 dose of heat, arsenic, cadmium, butachlor, salt, mannitol (drought), UV-B, and methyl viologen respectively, with respect to control (untreated). Heterologous expression resulted in 23KDa protein observed on the SDS-PAGE. Immunoblotting and MALDI-TOF-MS/MS followed by MASCOT search analysis confirmed the identity of the protein and ESI/MS revealed the purified protein was a dimer. Binding possibility of Alr0765 with ATP was observed with almost 6-fold increment in relative fluorescence during TNP-ATP binding assay with a ƛ max of 538 nm. FTIR spectra revealed modification in protein confirmation upon binding of Alr0765 with ATP, ADP, AMP and NADH. A 10-fold higher accumulation of iron was observed in digests of E. coli with recombinant vector after induction as compared to control affirms the iron acquisition property of protein. Moreover, generation of redox potential of 146 mV by Alr0765 suggested its probable role in maintaining redox status of the cell under environmental constraints. As per CFU count recombinant E. coli BL21 cells showed about 14.7, 7.3, 6.9, 1.9, 3, 4.9 fold higher number of colonies under heat, cadmium (CdCl2), arsenic (Na3AsO4), salt (NaCl), UV-B and drought (mannitol) respectively compared to pET21a harboring E. coli BL21 cells. Deterioration in cellular ROS level and total cellular H2O2concentration validated stress tolerance ability of Alr0765. In-silico analysis unraveled novel findings and attested experimental findings in determining the role of Alr0765.Conclusion:Alr0765 is a novel CBS-CP12 domain protein that maintains cellular energy level and iron homeostasis provide tolerance against multiple abiotic stresses.

Treatment of Enterobacter infections is complex and often associated with development of resistance when wrong antibiotics are chosen for treatment despite in vitro susceptibility. This infectious diseases grand round highlights two cases, how antimicrobial and diagnostic stewardship approach could detect and prevent development of such resistance in - vivo.

Abiotic stresses enhance cellular reactive oxygen species (ROS) level which results in toxic methylglyoxal (MG) production. Glyoxalases catalyze the conversion of toxic MG into non-toxic lactic acid whose properties and function are still unknown in cyanobacteria. This is the first attempt to characterize All0580 from Anabaena sp. PCC7120 as GlyII using in silico and wet lab approaches. Data of functional complementation of E. coli GlyII mutant (ΔgloB), enzyme kinetics and ESI-MS analysis suggested that All0580 harbors distinctive GlyII activity. The catalytic efficiency of All0580 (3 × 106 M−1 s−1) is higher than Arabidopsis GlyII. AAS analysis revealed the presence of a binuclear Zn/Fe centre in All0580 active site. The qRT-PCR of the target gene revealed maximum up-regulation in salinity followed by drought, arsenic, heat, and UV-B stresses. BL21/pET-21a-all0580 showed 1.5 to 10 fold increased growth and up to 4 fold decreased intracellular MG level as compared to BL21/pET-21a cells under various abiotic stresses and MG. A 39% drop in ROS generation by BL21/pET-21a-all0580 under MG stress suggested its potential to manage MG toxicity. Above attributes suggest that the hypothetical protein All0580 is a novel GlyII of cyanobacteria which heterologously confers tolerance to multiple abiotic stresses in E. coli.

In- silico and functional genomics approaches have been used to determine cellular functions of two hypothetical proteins All1122 and Alr0750 of Anabaena sp. PCC 7120. Motif analysis and multiple sequence alignment predicted them as typical α/β ATP binding universal stress family protein-A (UspA) with G-(2×)-G-(9×)-G(S/T) as conserved motif. qRT-PCR data under UV-B, NaCl, heat, As, CdCl2, mannitol and methyl viologen registered approximately 1.4 to 4.3 fold induction of all1122 and alr0750 thus confirming their multiple abiotic stress tolerance potential. The recombinant E. coli (BL21) cells harboring All1122 and Alr0750 showed 12-41% and 23-41% better growth respectively over wild type control under said abiotic stresses thus revalidating their stress coping ability. Functional complementation on heterologous expression in UspA mutant E. coli strain LN29MG1655 (ΔuspA::Kan) attested their UspA family membership. This study tempted us to suggest that recombinant Anabaena PCC 7120 over expressing all1122 and alr0750 might contribute to the nitrogen economy in paddy fields experiencing array of abiotic stresses including drought and nutrient limitation.

Background Dengue and malaria co-infection has been reported in several case reports. We aim to study effect of malaria co-infection on clinical outcomes of dengue infection. Methods Records of 623 children with dengue infection, based on NS-1 antigen and IgM ELISA testing, were collected. Malaria co-infection was identified in 20 cases, based on peripheral blood smear examination. Clinical and hematological parameters were compared in two groups (malaria co-infection vs. dengue mono-infection). Results Duration of hospitalization was significantly higher in co-infected group. Significantly higher proportion of malaria co-infection cases had hepatosplenomegaly, hemoglobin ≤8 g/dl, serum albumin ≤3 g/dl, serum bilirubin ≥1 mg/dl, serum aspartate aminotransferase ≥500 U/l and serum alanine aminotransferase ≥300 U/l. Number of transfusions (PRBC and platelets) required in malaria co-infection group was higher. Conclusion Malaria co-infection in dengue impacts clinical presentation, hematological parameters, requirement of blood transfusion and morbidity. High index of suspicion is warranted while evaluating febrile patients.

INTRODUCTION: Dengue presents with a variable clinical course, ranging from mild illness to potentially fatal hemorrhage and shock. We aimed to evaluate the capabilities of various hematological parameters observed early in the course of illness for predicting the clinical outcomes of illness. METHODS: We retrospectively analyzed the records of children admitted in the pediatric inpatient services of the institute with dengue between 2017 and 2019. We determined the relationships between the hematological parameters observed during the first evaluation and the various clinical outcomes. RESULTS: We evaluated data from 613 patients (age range, 26 days to 17 years). Of these, 29.85% exhibited fever with warning signs, and 8.97% had severe dengue. Lower values of hemoglobin, platelet count, mean corpuscular volume, mean corpuscular hemoglobin concentration, and mean platelet volume, and higher values of total leukocyte count (TLC), hematocrit, and red cell distribution width variably correlated with numerous clinical outcomes-duration of hospital stay, development of complications, requirement of blood component transfusion, inotropic support, and mortality. Among the parameters, TLC ≥20,000/mL and initial platelet count ≤20,000/mL significantly associated with mortality, with odds ratios (95% confidence interval) of 11.81 (4.21-33.80) and 5.53 (1.90-16.09), respectively. CONCLUSIONS: Hematological parameters observed early during dengue infection may predict its clinical outcomes in infected children. Initial high TLC and low platelet count are potential predictors of fatal outcomes in the course of disease.

Introduction: Management of newborns who suffer perinatal asphyxia is primarily based on supportive management, of which fluid and electrolyte management plays a very important role. We studied the role of restriction of fluids in the first 72 h in term neonates suffering from moderate to severe perinatal asphyxia. Methods: Term newborns with moderate to severe perinatal asphyxia were randomised to receive full or restricted fluids (25 newborns each) during the first 72 h of life. The primary outcome measures were mortality and neurological status at discharge. Results: Mortality among the full (FF) and restricted fluid (RF) groups was not significantly different, 4 in the FF group and 3 in the RF group with a relative risk (RR) of 1.52 [confidence interval (CI) 0.38-6.04]. The neurological status at discharge was also comparable in both the groups with RR (CI) 0.61 (0.22-1.7). Conclusion: Routine restriction of fluids in term neonates with moderate to severe perinatal asphyxia does not have any advantage.

Background: According to World Health Organization (2013) approximately 35% of the under-fivemortalities are due to nutrition related factors & 4.4% of deaths are due to severe wasting. It has been found that Vitamin D levels are low in children with malnourished and very sick children. Even the prevalence of vitamin D deficiency is very high in Indian subcontinent. In WHO recommendations for the management of severe acute malnutrition there is no role of vitamin D supplementation. Objective: To study the effect of vitamin D supplementation on severe acute malnourished children admitted in nutritional rehabilitation Centre. Design: Single blinded Randomized controlled, parallel group trial. Setting: Nutritional Rehabilitation Centre (NRC) of a tertiary care hospital. Participants: 70 severe acute malnourished children aged 6 months to 59 months admitted in the NRC were randomized by computer generated random table. Intervention: 6 lakhs IU vitamin D was given intramuscularly on day one of therapy after an informed consent to the study group and other group was given only management of SAM. Main Outcome measure: outcome indicators of NRC i.e. cure rate, death rate, non-responders, relapse rate. Results: There was no significant difference in the outcome indicators of NRC i.e cured, death, non-response and relapse rate (p=0.32) and average weight gain (p= 0.38) and length of stay (p=0.42) between the two groups at discharge but wasting (p=0.02 on first, p=0.008 on third and p=0.04 on fourth follow ups respectively) improved significantly on follow ups. Conclusions: vitamin D supplementation does not have any significant improvement in the outcome indicators at discharge but significantly improves wasting on follow up.

Salmonella Paratyphi B infection is rare in newborns. We present the case of a 26 d old baby with Salmonella Paratyphi B sepsis. The baby responded well to 14 d of antibiotics. A prompt blood culture sample should always be taken before starting antibiotics.

Aldo/keto reductases (AKRs) constitute a multitasking protein family that catalyzes diverse metabolic transformations including detoxification of stress generated reactive aldehydes. Yet this important protein family is poorly understood particularly in cyanobacteria, the ecologically most diverse and significant group of micro-organisms. Present study is an attempt to characterize all putative AKRs of Anabaena sp. PCC 7120. In silico analysis, it revealed the presence of at least four putative AKRs in Anabaena PCC7120 genome. All four proteins share less than 40% sequence identity with each other and also with the identified members of AKR superfamily and hence deserve to be assigned in new families. Dissimilarity in sequences is also reflected through their substrate specificity. While reduction of trans-2-nonenal, a LPO-derived reactive aldehyde was common across the four proteins, these proteins were found to be activated during heat, salt, Cd, As, and butachlor treatments, and their ectopic expression in Escherichia coli conferred tolerance to the above abiotic stresses. These findings affirm the role of AKRs in providing a broad tolerance to environmental stresses conceivably by detoxifying the stress-generated reactive aldehydes.

In silico derived properties on experimental validation revealed that hypothetical protein Alr2954 of Anabaena sp. PCC7120 is ADP-ribose pyrophosphatase, which belongs to nudix hydrolase superfamily. Presence of ADP-ribose binding site was attested by ADP-ribose pyrophosphatase activity (K m 44.71 ± 8.043 mM, V max 7.128 ± 0.417 μmol min−1 mg protein−1, and K cat/K m 9.438 × 104 μM−1 min−1). Besides ADP-ribose, the enzyme efficiently hydrolyzed various nucleoside phosphatases such as 8-oxo-dGDP, 8-oxo-dADP, 8-oxo-dGTP, 8-oxo-dATP, GDP-mannose, ADP-glucose, and NADH. qRT-PCR analysis of alr2954 showed significant expression under different abiotic stresses reconfirming its role in stress tolerance. Thus, Alr2954 qualifies to be a member of nudix hydrolase superfamily, which serves as ADP-ribose pyrophosphatase and assists in multiple abiotic stress tolerance.

In an attempt to mine cyanobacterial genes of potential biotechnological applications, the hypothetical protein All4894 of Anabaena PCC7120, following cloning, heterologous expression, purification and biochemical analysis, revealed the presence of a thermostable β-glucosidase. The glycosylated protein showed apparent molecular mass of ~18.0 kDa, while the purified enzyme depicted activity over wide pH (2.0–9.0) range and 85% stability up to 100 °C. All4894 encoding fascilin-1 domain showed higher specific activity to natural substrate cellobiose (Km = 0.75 mM and Vmax = 0.416 mMmin−1 mg−1) as compared to p-nitrophenyl-β-D-glucopyranoside. Quantitative reverse transcription polymerase chain reaction analysis (qRT-PCR) of all4894 revealed 4.0 to 16.0 fold elevated transcript under salinity, heat, arsenic, cadmium, UV-B and butachlor. The ectopic expression of All4894 in E. coli BL21 (DE3) reaffirmed its stress management capability. In view of the multiple functional attributes i.e. cell adhesion and abiotic stress tolerance All4894 may be regarded as “moonlighting protein” having a novel biomolecule for biotechnological applications including bioethanol production.

Cyanobacteria due to their remarkable evolutionary advances such as the presence of oxygenic photosynthesis have been considered as an ideal system for plant-based studies in order to assess fundamental biochemical processes like carbon and nitrogen assimilation and photosynthesis processes. Moreover, the exclusive ability of both photosynthesis and nitrogen fixation together with adaptability to various environmental fluctuations of few genera makes them ubiquitous. Cyanobacterial genes involved in carbon metabolism, fatty acid biosynthesis, and pigment biosynthesis have been exploited as substitute for homologous gene sources, targeting enhanced plant productivity and nutritional values. Present chapter sheds light on key contributions of cyanobacterial biodiversity and biotechnology along with the future prospects for developing transgenic crops of high yield and nutritive value utilizing cyanobacterial genes.

We studied 48 children receiving abacavir-based HAART regimen, over a period of one-year for side effects and failure rates. None of the children developed hypersensitivity reaction. The CD4 count significantly improved from the time of enrolment till 12 months of therapy while the failure rate was 14.5%.

To compare the efficacy of double dose (20 μg) with standard dose (10 μg) of hepatitis B vaccine in HIV-infected children. Unvaccinated HIV-infected children were randomized to receive 3 doses of double dose (N=27) or standard dose (N=28) of recombinant Hepatitis B vaccine. Anti-HBs antibody titres were measured 3 mo after the last dose. An antibody titre ≥10 mIU/mL 12 weaks after the third dose was considered as serporotection. Seroprotection was achieved by 17 (60.7%) children in standard dose group against 20 (74%) in the double dose group [RR (95%CI) 0.8 (0.17-1.7); P=0.29]. CD4 count < 500 cells/mm3 was significantly associated with lower rates of seroprotection. Double dose of hepatitis B vaccine does not seem to provide any advantage when compared to standard dose in HIV-infected children.

Cyanobacteria, a group of photosynthetic prokaryotes, have drawn the attention of agricultural scientists due to their notable key features such as the presence of oxygenic photosynthesis along with nitrogen fixation, ease in genetic manipulation and excellent adaptability to various environmental vagaries. Moreover, they have been recognized as an opulent source of various bioactive compounds possessing antibacterial, antiviral, antifungal and anticancer activities. They are also contributing positively in bioremediation and sustainable development of ecosystem. Furthermore, the presence of novel genes opens new ways for generation of transgenic crops with improved productivity and nutritional values. In view of the above, the present chapter is an attempt to cast light on cyanobacterial assistance and their potential role in sustainable development of agriculture and ecosystem.

The stem rust resistance gene Sr26 imparts resistance to all the virulent pathotypes of stem rust (Puccinia graminis f. sp. tritici) including a new race of pathogen named TTKSK (syn.Ug99). Wheat genotypes including non-carrier Kalyan Sona (-Sr26) and carrier Kite (+Sr26) of the Sr26 gene were analysed using polymerase chain reactions and a RAPD marker OPAE07620 was found to link with the desired trait. Linkage between the marker OPAE07620 and rust resistance phenotype was confirmed by analyzing F2 population obtained from a cross between a resistant and susceptible genotype. The Random Amplified Polymorphic DNA (RAPD) marker was converted into sequence characterized amplified region (SCAR) marker SCOPAE07620. The marker was validated in another segregating population and 45 wheat genotypes including carrier and non-carriers of Sr26 gene. The marker developed in this study can be used for pyramiding of the Sr26 gene with other major resistance genes that are effective against the TTKSK lineage (Ug99) which will help in attaining durable resistance against a disease that poses a serious threat to global wheat production.

Abiotic stresses enhance the cellular level of reactive oxygen species (ROS) which consequently leads to toxic methylglyoxal (MG) production. Glyoxalases (GlyI & GlyII) catalyze the conversion of toxic MG into non-toxic lactic acid but their properties and functions have been overlooked in cyanobacteria. This is the first attempt to conduct a genome-wide analysis of GlyI protein (PF00903) from Anabaena sp. PCC7120. Out of total nine GlyI domain possessing proteins, only three (Alr2321, Alr4469, All1022) harbour conserve His/Glu/His/Glu metal binding site at their homologous position and are deficient in conserved region specific for Zn2+ dependent members. Their biochemical, structural and functional characterization revealed that only Alr2321 is a homodimeric Ni2+ dependent active GlyI with catalytic efficiency 11.7 × 106 M−1 s−1. It has also been found that Alr2321 is activated by various divalent metal ions and has maximum GlyI activity with Ni2+ followed by Co2+ > Mn2+ > Cu2+ and no activity with Zn2+. Moreover, the expression of alr2321 was found to be maximally up-regulated under heat (19 fold) followed by cadmium, desiccation, arsenic, salinity and UV-B stresses. BL21/pGEX-5X2-alr2321 showed improved growth under various abiotic stresses as compared to BL21/pGEX-5X2 by increased scavenging of intracellular MG and ROS levels. Taken together, these results suggest noteworthy links between intracellular MG and ROS, its detoxification by Alr2321, a member of GlyI family of Anabaena sp. PCC7120, in relation to abiotic stress.

There is paucity of knowledge about the immunogenicity of vaccines in infants who have been exposed to HIV in-utero but have remained uninfected. The authors studied the immunogenicity of 3 doses of recombinant hepatitis B vaccine at 6,10,14 wk of age in HIV exposed but uninfected (HEU) infants. After 3 mo of last dose of the vaccine, out of 26 infants, 23 (89.5 %) infants were found to be responders (Anti HBs IgG titres ≥ 10 mIU/ml) and 3 (11.5 %) babies remained non responders (Anti HBs IgG titres < 10 mIU/ml). The proportion of babies who were non responders were higher when compared to similar studies done on unexposed and uninfected infants, suggesting a poorer immunogenicity of hepatitis B vaccine in these infants.

Objective: The aim was to study the thrombocytopenia in human immunodeficiency virus (HIV) infected children and its relation with WHO clinical and immunological HIV/AIDS staging. Study Design: Observational analytic cross-sectional study. Materials and Methods: 47 ambulatory and clinically stable HIV-infected children (confirmed by enzyme-linked immunosorbent assay for HIV-1 and HIV-2) aged 18 months-18 years attending the out-patient Department of anti-retroviral therapy center at tertiary care setting, were included in this study. Detailed history was taken, and thorough clinical examination was done in all cases. Blood sample for complete blood count and CD4 count was taken. Primary Outcome: Thrombocytopenia in HIV-infected children. Secondary Outcome: WHO clinical and immunological HIV/AIDS staging in HIV-infected children and its relation to thrombocytopenia. Results: Of 47 studied children, thrombocytopenia was found in 14 (29.78%) cases. Patients with thrombocytopenia were found in all stages of the disease; however, it was strongly associated with increasing immunological stages (correlation coefficient, r = 0.948). Conclusion: Thrombocytopenia commonly occurs in children with HIV and its occurrence increases with an increase in WHO clinical and immunological HIV/AIDS staging. Key words: Human immunodeficiency virus, Immunological human immunodeficiency virus/AIDS staging, Thrombocytopenia, WHO clinical human immunodeficiency virus/AIDS staging

The present study provides data on the insertion of an extra copy of phytochelatin synthase (alr0975) in Anabaena sp. PCC 7120. The recombinant strain (AnFPN-pcs) compared to wild type showed approximately 22.3% increase in growth rate under UV-B, NaCl, heat, CuCl2, carbofuran, and CdCl2. It also registered 2.25-fold enhanced nitrogenase activity and 5-fold higher phytochelatin production. A comparison of the protein profile of wild type with the recombinant strain revealed that recombinant strain accumulated proteins belonging to the following categories: (i) detoxification (nutrient stress induced DNA binding protein, Mn-SOD, Alr0946 (CalA)), (ii) protein folding and modification (molecular chaperone DnaK, FKBP-type peptidyl-prolyl cis-trans isomerase), (iii) nucleotide and amino acid biosynthesis (dihydroorotase and Ketol-acid reductoisomerase), (iv) photosynthesis and respiration (coproporphyrinogen III oxidase, phycocyanin alpha chain, ferredoxin-NADP+ reductase), and (v) transport (sugar transport ATP-binding protein). Thus, it can be concluded that, above category proteins with their respective role in scavenging reactive oxygen species, proper folding of unfolded proteins, and protection of protein from degradation, sustained carbon fixation and energy pool and active transport of sugar together conceivably help the recombinant cyanobacterium (AnFPN-pcs) to cope with abiotic stress employed in the present study. Such recombinant strains have potential for future use as biofertilizer.

The study explores the significance of peroxides in regulating the CO2- and N2-fixation capacities in Anabaena sp. PCC7120. To this end Anabaena strains were generated carrying an extra copy of ahpC (An+ahpC) or by deleting from their endogenous functional ahpC (AnΔahpC). AhpC levels were 2.2- to 6.0-fold higher in An+ahpC than in wild type. An+ahpC revealed 1.4- to 2-fold upregulation of photosystems I and II, nitrogenase, superoxide dismutase and catalase activities while same activities were 1.3- to 2.5-fold downregulated in the insertional mutant (AnΔahpC) compared to the wild type. Peroxide, superoxide and malondialdehyde contents were low in An+ahpC and high in AnΔahpC. Growth was inhibited in AnΔahpC by approximately 40-60% compared to a 33-40% enhanced growth in An+ahpC under selected stresses. Most interestingly, heterocyst frequency was increased in An+ahpC. In order to address transcriptional and posttranscriptional effects, transcripts of genes including groEL, fld, kat, gor, gst, dps, bfr, tf, sodA, dnaK, prx, uspA, pcs and apx were quantified and found to be increased 1.33- to 7.70-fold in unstressed and 1.76- to 13.80-fold in stressed An+ahpC. In a converse manner, they were downregulated by 1.20- to 7.50-fold in unstressed and 1.23 to 10.20-fold in stressed AnΔahpC. It is concluded that the level of AhpC controls a major set of metabolic and developmental genes in normal and stress conditions and thus likely is in the core of the redox regulatory system of Anabaena.

Alkylhydroperoxide reductase (AhpC), a 1-Cys peroxiredoxin is well known for maintaining the cellular homeostasis. Present study employs proteome approach to analyze and compare alterations in proteome of Anabaena PCC7120 in overexpressing (An + ahpC), deletion (An ∆ ahpC) and its wild type. 2-DE based analysis revealed that the major portion of identified protein belongs to energy metabolism, protein folding, modification and stress related proteins and carbohydrate metabolism. The two major traits discernible from An + ahpC were (i) augmentation of photosynthesis and nitrogen fixation (ii) modulation of regulatory network of antioxidative proteins. Increased accumulation of proteins of light reaction, dark reaction, pentose phosphate pathway and electron transfer agent FDX for nitrogenase in An + ahpC and their simultaneous downregulation in AnΔahpC demonstrates its role in augmenting photosynthesis and nitrogen fixation. Proteomic data was nicely corroborated with physiological, biochemical parameters displaying upregulation of nitrogenase (1.6 fold) PSI (1.08) and PSII (2.137) in An + ahpC. Furthermore, in silico analysis not only attested association of AhpC with peroxiredoxins but also with other players of antioxidative defense system viz. thioredoxin and thioredoxin reductase. Above mentioned findings are in agreement with 33–40% and 40–60% better growth performance of An + ahpC over wild type and An ∆ ahpC respectively under abiotic stresses, suggesting its role in maintenance of metabolic machinery under stress. Significance Present work explores key role of AhpC in mitigating stress in Anabaena PCC7120 through combined proteomic, biochemical and in silico investigations. This study is the first attempt to analyze and compare alterations in proteome of Anabaena PCC7120 following addition (overexpressing strain An + ahpC) and deletion (mutant An ∆ ahpC) of AhpC against its wild type. The effort resulted in two major traits in An + ahpC as (i) augmentation of photosynthesis and nitrogen fixation (ii) modulation of regulatory network of antioxidative proteins.