The heparin-binding hemagglutinin protein of Mycobacterium tuberculosis is a nucleoid-associated protein.

Nucleoid-associated proteins (NAPs) regulate multiple cellular processes such as gene expression, virulence, and dormancy throughout bacterial species. NAPs help in the survival and adaptation of Mycobacterium tuberculosis (Mtb) within the host. Fourteen NAPs have been identified in Escherichia coli; however, only seven NAPs are documented in Mtb. Given its complex lifestyle, it is reasonable to assume that Mtb would encode for more NAPs. Using bioinformatics tools and biochemical experiments, we have identified the heparin-binding hemagglutinin (HbhA) protein of Mtb as a novel sequence-independent DNA-binding protein which has previously been characterized as an adhesion molecule required for extrapulmonary dissemination. Deleting the carboxy-terminal domain of HbhA resulted in a complete loss of its DNA-binding activity. Atomic force microscopy showed HbhA-mediated architectural modulations in the DNA, which may play a regulatory role in transcription and genome organization. Our results showed that HbhA colocalizes with the nucleoid region of Mtb. Transcriptomics analyses of a hbhA KO strain revealed that it regulates the expression of ∼36% of total and ∼29% of essential genes. Deletion of hbhA resulted in the upregulation of ∼73% of all differentially expressed genes, belonging to multiple pathways suggesting it to be a global repressor. The results show that HbhA is a nonessential NAP regulating gene expression globally and acting as a plausible transcriptional repressor.

Iron reprogrammes the root system architecture by regulating OsWRKY71 in arsenic-stressed rice (Oryza sativa L.).

Iron (Fe) has been critically reported to act as a signal that can be interpreted to activate the molecular mechanisms involved in root developmental processes. Arsenic (As) is a well-known metalloid that restricts the growth and productivity of rice plants by altering their root architecture. Since root system architecture (RSA) under As stress targets WRKY transcription factors (TFs) and their interaction partners, the current investigation was carried out to better understand the Fe-dependent dynamics of RSA and its participation in this process. Here, we analyzed the effects of As and Fe (alone or in combination) exposed to hydroponically grown rice roots of 12-day-old plants. Our research showed that adding As to Fe changed how OsWRKY71 was expressed and improved the morphology and anatomy of the rice roots in Ratna and Lalat varieties. As + Fe treatment also manifested the biochemical parameters. OsWRKY71, revealed an up-regulation (Fe alone and As + Fe conditions) and down-regulation (As stress) in both varieties, in comparison to the controls. The improved root anatomy and root oxidizability indicated the enhanced capability of Lalat over the Ratna variety to induce OsWRKY71 for the better development of RSA during As + Fe treatment. Further, OsWRKY71 has revealed the presence of gibberellin-responsive cis-regulatory elements (GAREs) in its promoter region, indicating the involvement of OsWRKY71 in the gibberellin pathway. Molecular docking revealed that OsWRKY71 and SLR1 (DELLA protein) interact positively, which supports the hypothesis that Fe alters RSA by regulating OsWRKY71 through the gibberellin pathway in As-stressed rice.

Metabolomic profiling reveals key factors and associated pathways regulating the differential behavior of rice (Oryza sativa L.) genotypes exposed to geogenic arsenic.

Arsenic (As) toxicity is an escalating problem; however, information about the metabolic events controlling the varied pattern of As accumulation in rice genotypes within their natural environment is still lacking. The present study is thus an advancement in unravelling the response of such rice genotypes. Soil-water-rice samples were analyzed for As accumulation using ICP-MS. Furthermore, we implemented metabolomics through LC-MS/MS and UHPLC to identify metabolic signatures regulating As content by observing the metalloid's composition in rice agrosystem. Results showed that rice genotypes differed significantly in their levels of metabolites, with Mini mansoori and Pioneer having the highest levels. Mini mansoori contained least As which might have been regulated by Ala, Ser, Glu, Phe, Asn, His, Ile, Lys, Gln, Trp, Tyr, chlorogenic, p-coumaric, trans-ferulic, rutin, morin, naringenin, kampferol, and myricetin, while Asp, Arg, Met, syringic, epigalocatechin, and apigenin contributed to the greater As acclimatization ability of Pioneer. Multivariate tools separated the rice genotypes into two major clusters: Pioneer-Mini mansoori and Damini-Sampoorna-Chintu. KEGG identified three major metabolic pathways (aminoacyl-tRNA, phenylpropanoid, and secondary metabolites biosynthesis route) linked with As tolerance and adaptation mechanisms in rice. Overall, these two genotypes symbolize their As hostile and accommodating attitudes probably due to the accumulated metabolites and the physicochemical attributes of the soil-water. Thus, thorough understanding of the metabolic reactions to As may facilitate the emergence of As tolerant/resilient genotypes. This will aid in the selection of molecular markers to cultivate healthier rice genotypes in As-contaminated areas.

WRKY transcription factors: a promising way to deal with arsenic stress in rice.

Arsenic (As) is a global carcinogenic contaminant, and is one of the significant environmental constraints that limits the development and yield of crop plants. It is always tagged along with rice as rice takes up As and tends to accumulate it in grains. This amassment makes a way for As to get into the food chain that leads to unforeseen human health risks. Being viewed as parallel with toxicity, As in rice is an important global risk that calls for an urgent solution. WRKY Transcription Factors (TFs) seems to be promising in this area. The classical and substantial progress in the molecular mechanism of WRKY TFs, strengthened the understanding of innovative solutions for dealing with As in rice. Here, we review the potential of WRKY TFs under As stressed rice as a genetic solution and also provide insights into As and rice. Further, we develop an understanding of WRKY TF gene family and its regulation in rice. To date, studies on the role of WRKY TFs under As stressed rice are lacking. This area needs to be explored more so that this gene family can be utilized as an effective genetic tool that can break the As cycle to develop low or As free rice cultivar.

An insight into the act of iron to impede arsenic toxicity in paddy agro-system.

Surplus research on the widespread arsenic (As) revealed its disturbing role in obstructing the metabolic function of plants. Also, the predilection of As towards rice has been an interesting topic. Contrary to As, iron (Fe) is an essential micronutrient for all life forms. Past findings propound about the enhanced As-resistance in rice plants during Fe supplementation. Thus, considering the severity of As contamination and resulting exposure through rice crops, as well as the studied cross-talks between As and Fe, we found this topic of relevance. Keeping these in view, we bring this review discussing the presence of As-Fe in the paddy environment, the criticality of Fe plaque in As sequestration, and the effectiveness of various Fe forms to overcome As toxicity in rice. This type of interactive analysis for As and Fe is also crucial in the context of the involvement of Fe in cellular redox activities such as oxidative stress. Also, this piece of work highlights Fe biofortification approaches for better rice varieties with optimum intrinsic Fe and limited As. Though elaborated by others, we lastly present the acquisition and transport mechanisms of both As and Fe in rice tissues. Altogether we suggest that Fe supply and Fe plaque might be a prospective agronomical tool against As poisoning and for phytostabilization, respectively.

Bacillus anthracis chain length, a virulence determinant, is regulated by membrane localized serine/threonine protein kinase PrkC.

Anthrax is a zoonotic disease caused by Bacillus anthracis, a spore-forming pathogen that displays a chaining phenotype. It has been reported that the chaining phenotype acts as a virulence factor in B. anthracis In this study, we identify a serine/threonine protein kinase of B. anthracis, PrkC, the only kinase localized at the bacteria-host interface, as a determinant of B. anthracis chain length. In vitro, prkC disruption strain (BAS ΔprkC) grew as shorter chains throughout the bacterial growth cycle. A comparative analysis between the parent strain and BAS ΔprkC indicated that the levels of proteins, BslO and Sap, associated with the regulation of the bacterial chain length, were upregulated in BAS ΔprkC BslO is a septal murein hydrolase that catalyzes daughter cell separation and Sap is an S-layer structural protein required for the septal localization of BslO. PrkC disruption also has a significant effect on bacterial growth, cell wall thickness, and septa formation. Upregulation of ftsZ in BAS ΔprkC was also observed. Altogether, our results indicate that PrkC is required for maintaining optimum growth, cell wall homeostasis and most importantly - for the maintenance of the chaining phenotype.IMPORTANCEChaining phenotype acts as a virulence factor in Bacillus anthracis This is the first study that identifies a 'signal transduction protein' with an ability to regulate the chaining phenotype in Bacillus anthracis We show that the disruption of the lone surface-localized serine/threonine protein kinase, PrkC, leads to the shortening of the bacterial chains. We report upregulation of the de-chaining proteins in the PrkC disruption strain. Apart from this, we also report for the first time that PrkC disruption results in an attenuated cell growth, a decrease in the cell wall thickness and aberrant cell septa formation during the logarithmic phase of growth - a growth phase where PrkC is expressed maximally.

Protective role of nitric oxide on nitrogen-thiol metabolism and amino acids profiling during arsenic exposure in Oryza sativa L.

Nitric oxide (NO) being a signaling molecule inside the plant cells, play significant role in signaling cascades and protection against environmental stresses. However, the protective role of NO in alleviating As toxicity in rice plants is currently not available. In the present study, the level of NO, nitrogen (N), inorganic N (nitrate, ammonium), thiols {TT (Total thiols), NPT (Nonprotein thiol)} and AAs contents along with N assimilating enzymes (NR, GDH, GOGAT) were analyzed after exposure of AsIII/NO treatment alone, and in combination. NO supplementation enhanced the content of N, inorganic N & thiol contents, NR, GOGAT activities, when compared with AsIII exposure alone. In AsIII exposed rice seedlings, content of AAs (except His, Arg, Met) reduced over the control, while supplementation of SNP improved AAs contents, compared to AsIII treatment alone. In conclusion, rice seedlings supplemented with NO tolerate the AsIII toxicity by reducing the N related parameters, thiol contents, altering the AA profile and enhanced the nutritional quality by increasing EAAs (essential amino acids) and NEAAs (non-essential amino acids).

Nitric oxide and abscisic acid protects against PEG-induced drought stress differentially in Brassica genotypes by combining the role of stress modulators, markers and antioxidants.

The present study was designed to see the effect of exogenous nitric oxide (NO) and abscisic acid (ABA) and their interaction on physiological and biochemical activities in leaves and roots of two Indian mustard (Brassica juncea) cultivars [cv. Pusa Jagannath (PJN) and Varuna (VAR)] exposed to polyethylene glycol (PEG)-induced drought stress. Seven days old hydroponically grown seedlings were treated with PEG (10%), sodium nitroprusside, a NO donor [NO (100 µM)] and abscisic acid [ABA (10 µM)], using different combinations as: Control, ABA, NO, PEG, PEG + ABA, PEG + NO, and PEG + NO + ABA. Results revealed that in response to PEG-induced drought stress leaf relative water content, chlorophyll, carotenoid and protein content decreased with increased production of O2-●, MDA, H2O2, cysteine content and non-enzymatic antioxidants (including proline, flavonoid, phenolic, anthocyanin, and ascorbic acid), whereas, the enzymatic antioxidants (including SOD, CAT, APX, GR) showed the response range from no effect to increase or decrease in certain enzymes in both Brassica cultivars. The application of NO or/and ABA in PEG-stressed cultivars showed that both enzymatic and non-enzymatic antioxidants responded differently to attenuate oxidative stress in leaves and roots of both cultivars. Overall, PJN had the antioxidant protection mainly through the accumulation of non-enzymatic antioxidants, whereas VAR showed tolerance by the enhancement of both enzymatic and non-enzymatic antioxidant activities. Altogether, the study concluded that the independent NO and its interaction with ABA (PEG + NO and PEG + NO + ABA) were much effective than independent ABA (PEG + ABA) in lowering PEG-drought stress in Brassica cultivars.

Nitric oxide alters nitrogen metabolism and PIN gene expressions by playing protective role in arsenic challenged Brassica juncea L.

Plants have ability to adapt themselves through altering their growth process. In the present study, we examined exogenous application of nitric oxide (NO) on nitrogen metabolism and auxin (PIN) gene expression, and its possible role in alleviation of arsenic (As) toxicity in Brassica juncea seedlings. Seven days old hydroponically grown B. juncea seedlings were exposed to AsIII (150 µM), Sodium nitroprusside (NO donor, 100 µM), AsIII + SNP and control (without metal)for 48 h. Experimental results revealed that AsIII stress: enhanced the level of nitrite, NiR activity, NO3- and NH4+content as well as NADH-GOGAT activity; but GDH level decreased; enhanced content of amino acids; upregulated gene expression level of N metabolism and downregulated polar auxin transporter genes (PIN); inhibited plant growth and morphological parameters; increased MDA, H2O2, cysteine, proline content, enzymatic antioxidants (SOD, CAT, APX; GSH, TT, NPT); and decreased nutrient content. AsIII + SNP combination reduced the accumulation of As; improved growth; chlorophyll, protein and mineral nutrient content by scavenging ROS generation; maintained amino acids content; downregulated expression of N metabolism genes and upregulated expression of auxin transporter (PIN) genes . Additional biochemical data depicts reduction in the level of nitrogen related enzymatic activities, and other stress related parameters. Overall, this study provides an integrated view that exogenous SNP (NO donor) supplementation alleviated the inhibitory role of AsIII in B. juncea seedlings by altering nutrients, amino acids and auxin redistribution via expression of nitrogen and PIN gene profiling.

Waste water irrigation in the regulation of soil properties, growth determinants, and heavy metal accumulation in different Brassica species.

To evaluate the impact of waste water (WW) irrigation, four Brassica species, namely B. campestris, B. juncea, B. napus, and B. nigra, were grown for 2 years in the agricultural field. First-year experiment (2014-2015) was conducted with the comparative effect of WW and ground water (GW) under a uniform dose of NPK (N80P45K45, kg ha-1). WW irrigation proved efficacious over GW to increase growth, physiological, and yield parameters. Increase in all parameters was due to the use of WW which leads to the improvement in the physico-chemical properties of soil as compared to resulted soil from GW application. Second-year experiment (2015-2016) therefore deals with WW irrigation only but under interaction with two levels of NPK fertilizers (N80P45K45 and N60P30K30, kg ha-1). Results of this year revealed that maximum enhancement in growth, physiological, and yield parameters was observed at WW × N60P30K30 and the input of WW × N80P45K45 was not of benefit. WW × N60P30K30 treatment was beneficial also because, at this treatment level, the accumulation of Cr, Cu, Pb, Ni, and Cd in leaf and seed was comparatively lesser in amount than that of WW × N80P45K45. The study concluded even though the use of WW was applicable to save freshwater, enhance soil nutrient status, and make N, P, and K balance at their lower inputs, WW irrigation caused accumulation of heavy metals in all Brassica crops far above the safe limits during a quite longer irrigation time (70 days and 105 days after sowing (DAS)). However, WW was safe to use only up to 35 DAS. Therefore, the study suggested that there should be regular monitoring of heavy metal concentrations in irrigation water as well as in various crop vegetables.

An update on nitric oxide and its benign role in plant responses under metal stress.

Pollution due to heavy metal(loid)s has become common menace across the globe. This is due to unprecedented frequent geological changes coupled with increasing anthropogenic activities, and population growth rate. Heavy metals (HMs) presence in the soil causes toxicity, and hampers plant growth and development. Plants being sessile are exposed to a variety of stress and/or a network of different kinds of stresses throughout their life cycle. To sense and transduce these stress signal, the signal reactive nitrogen species (RNS) particularly nitric oxide (NO) is an important secondary messenger next to only reactive oxygen species (ROS). Nitric oxide, a redox active molecule, colourless simple gas, and being a free radical (NO) has the potential in regulating multiple biological signaling responses in a variety of plants. Nitric oxide can counteract HMs-induced ROS, either by direct scavenging or by stimulating antioxidants defense team; therefore, it is also known as secondary antioxidant. The imbalance or cross talk of/between NO and ROS concentration along with antioxidant system leads to nitrosative and oxidative stress, or combination of both i.e., nitro-oxidative stress. Endogenous synthesis of NO also takes place in plants in the presence of heavy metals. During HM stress the different organelles of plant cells can biosynthesize NO in parallel to the ROS, such as in mitochondria, chloroplasts, peroxisomes, cytoplasm, endoplasmic reticulum and apoplasts. In view of the above, an effort has been made in the present review article to trace current knowledge and latest advances in chemical properties, biological roles, mechanism of NO action along with the physiological, biochemical, and molecular changes that occur in plants under different metal stress. A brief focus is also carried on ROS properties, roles, and their production.

Bacterial Virulence Factors: Secreted for Survival.

Virulence is described as an ability of an organism to infect the host and cause a disease. Virulence factors are the molecules that assist the bacterium colonize the host at the cellular level. These factors are either secretory, membrane associated or cytosolic in nature. The cytosolic factors facilitate the bacterium to undergo quick adaptive-metabolic, physiological and morphological shifts. The membrane associated virulence factors aid the bacterium in adhesion and evasion of the host cell. The secretory factors are important components of bacterial armoury which help the bacterium wade through the innate and adaptive immune response mounted within the host. In extracellular pathogens, the secretory virulence factors act synergistically to kill the host cells. In this review, we revisit the role of some of the secreted virulence factors of two human pathogens: Mycobacterium tuberculosis-an intracellular pathogen and Bacillus anthracis-an extracellular pathogen. The advances in research on the role of secretory factors of these pathogens during infection are discussed.

HupB, a nucleoid-associated protein of Mycobacterium tuberculosis, is modified by serine/threonine protein kinases in vivo.

HU, a widely conserved bacterial histone-like protein, regulates many genes, including those involved in stress response and virulence. Whereas ample data are available on HU-DNA communication, the knowledge on how HU perceives a signal and transmit it to DNA remains limited. In this study, we identify HupB, the HU homolog of the human pathogen Mycobacterium tuberculosis, as a component of serine/threonine protein kinase (STPK) signaling. HupB is extracted in its native state from the exponentially growing cells of M. tuberculosis H37Ra and is shown to be phosphorylated on both serine and threonine residues. The STPKs capable of modifying HupB are determined in vitro and the residues modified by the STPKs are identified for both in vivo and the in vitro proteins through mass spectrometry. Of the identified phosphosites, Thr(65) and Thr(74) in the DNA-embracing ß-strand of the N-terminal domain of HupB (N-HupB) are shown to be crucial for its interaction with DNA. In addition, Arg(55) is also identified as an important residue for N-HupB-DNA interaction. N-HupB is shown to have a diminished interaction with DNA after phosphorylation. Furthermore, hupB is shown to be maximally expressed during the stationary phase in M. tuberculosis H37Ra, while HupB kinases were found to be constitutively expressed (PknE and PknF) or most abundant during the exponential phase (PknB). In conclusion, HupB, a DNA-binding protein, with an ability to modulate chromatin structure is proposed to work in a growth-phase-dependent manner through its phosphorylation carried out by the mycobacterial STPKs.

Arsenate induced differential response in rice genotypes.

To study the differential response in two rice genotypes (PB1 and IR-64), hydroponically grown 14 days old plants were exposed to 50, 150 and 300µM As(V) for 24 and 96h. Accumulation of As was not significantly higher in PB1 variety except at higher concentration (300µM) and duration (96h), but up regulation of gene transcripts were higher as compared to IR-64. Inhibition in seed germination, root-shoot length, chlorophyll and protein content was observed in both varieties with increasing concentration and exposure time. PB1 variety was found more capable to detoxify As(V) through induction of antioxidant defense system and other stress related parameters (cysteine, proline content). SDS-PAGE and semi quantitative RT-PCR analysis showed significant changes in protein profile and gene expression analysis. The results suggests that various studied parameters and transcripts accumulation showed a combinatorial type of tolerance mechanism in PB1 variety to provide better protection against As(V) stress.

Deciphering the regulation of transporters and mitogen-activated protein kinase in arsenic and iron exposed rice.

This study investigates the influence of arsenic (As) and iron (Fe) on the molecular aspects of rice plants. The mRNA-abundance of As (OsLsi, OsPHT, OsNRAMP1, OsABCC1) and Fe (OsIRT, OsNRAMP1, OsYSL, OsFRDL1, OsVIT2, OsSAMS1, OsNAS, OsNAAT1, OsDMAS1, OsTOM1, OsFER) related genes has been observed in 12-d old As and Fe impacted rice varieties. Analyses of phytosiderophores synthesis and Fe-uptake genes affirm the existence of specialized Fe-uptake strategies in rice with varieties PB-1 and Varsha favouring strategy I and II, respectively. Expression of OsNAS3, OsVIT2, OsFER and OsABCC1 indicated PB-1's tolerance towards Fe and As. Analysis of mitogen-activated protein kinase cascade members (OsMKK3, OsMKK4, OsMKK6, OsMPK3, OsMPK4, OsMPK7, and OsMPK14) revealed their importance in the fine adjustment of As/Fe in the rice system. A conditional network map was generated based on the gene expression pattern that unfolded the differential dynamics of both rice varieties. The mating based split ubiquitin system determined the interaction of OsIRT1 with OsMPK3, and OsLsi1 with both OsMPK3 and OsMPK4. In-silico tools also confirmed the binding affinities of OsARM1 with OsLsi1, OsMPK3 and OsMPK4, and of OsIDEF1/OsIRO2 with OsIRT1 and OsMPK3, supporting our hypothesis that OsARM1, OsIDEF1, OsIRO2 were active in the connections discovered by mbSUS.

Iono-metabolomic guided elucidation of arsenic induced physiological and metabolic dynamics in wheat genotypes.

Despite the growing concerns about arsenic (As) toxicity, information on wheat adaptability in such an aggravating environment is limited. Thus, the present investigation based on an iono-metabolomic approach is aimed to decipher the response of wheat genotypes towards As toxicity. Wheat genotypes procured from natural conditions were characterized as high As-contaminated (Shri ram-303 and HD-2967) and low As-contaminated (Malviya-234 and DBW-17) based on ICP-MS As accumulation analysis. Reduced chlorophyll fluorescence attributes, grain yield and quality traits, and low grain nutrient status were accompanied by remarkable grain As accumulation in high As-contaminated genotypes, thus imposing a higher potential cancer risk and hazard quotient. Contrarily, in low As-contaminated genotypes, the richness of Zn, N, Fe, Mn, Na, K, Mg, and Ca could probably have supported less grain As accumulation, imparting better agronomic and grain quality traits. Additionally, from metabolomic analysis (LC-MS/MS and UHPLC), abundances of alanine, aspartate, glutamate, quercetin, isoliquiritigenin, trans-ferrulic, cinnamic, caffeic, and syringic bestow Malviya-234 as the best edible wheat genotype. Further, the multivariate statistical analysis (HCA, PCA, and PLS-DA) revealed certain other key metabolites (rutin, nobletin, myricetin, catechin, and naringenin) based genotypic discrimination that imparts strength to genotypes for better adaptation in harsh conditions. Out of the 5 metabolic pathways ascertained through topological analysis, the two main pathways vital for plant's metabolic adjustments in an As-induced environment were: 1. The alanine, aspartate and glutamate metabolism pathway, and 2. The flavonoid biosynthesis pathway. This is also evident from network analysis, which stipulates amino acid metabolism as a prominent As regulatory factor closely associated with flavonoids and phenolics. Therefore, the present findings are useful for wheat breeding programs to develop As adaptive genotypes that are beneficial for crop improvement and human health.

Unraveling the molecular aspects of iron-mediated OsWRKY76 signaling under arsenic stress in rice.

Arsenic (As) is a significant environmental element that restricts the growth and production of rice plants. Although the role of iron (Fe) to sequester As in rice is widely known, the molecular mechanism regarding As-Fe interaction remains opaque. Here, we show the differential response of two rice varieties (Ratna and Lalat) in terms of their morphological and biochemical changes in the presence of As and Fe. These results together with in-silico screening, gene expression analysis, and protein-protein interaction studies suggest the role of OsWRKY76 in Fe-mediated As stress alleviation. When OsWRKY76 is activated by MAPK signaling, it inhibits the gene expression of Fe transporters OsIRT1 and OsYSL2, which reduces the amount of Fe accumulated. However, MAPK signaling and OsWRKY76 remain down-regulated during Fe supplementation with As, which subsequently encourages the up-regulation of OsIRT1 and OsYSL2. This results in greater Fe content and decreased As accumulation and toxicity. The lower H2O2 and SOD, CAT, and APX activities were likewise seen under the As + Fe condition. Overall, results revealed the molecular aspects of Fe-mediated control of OsWRKY76 signaling and showed that Ratna is a more As tolerant variety than Lalat. Lalat, however, performs better in As stress due to the presence of Fe.

Micronutrient seed priming: new insights in ameliorating heavy metal stress.

Plants need to survive with changing environmental conditions, be it different accessibility to water or nutrients, or attack by insects or pathogens. Few of these changes, especially heavy metal stress, can become more stressful and needed strong countermeasures to ensure survival of plants. Priming, a pre-sowing hydration treatment, involves pre-exposure of plants to an eliciting component which enhance the plant's tolerance to later stress events. By considering the role of micronutrients in aiding plants to cope up under adverse conditions, this review addresses various aspects of micronutrient seed priming in attenuating heavy metal stress. Priming using micronutrients is an adaptive strategy that boosts the defensive capacity of the plant by accumulating several active or inactive signaling proteins, which hold considerable importance in signal amplification against the triggered stimulus. Priming induced 'defence memory' persists in both present generation and its progeny. Therefore, it is considered a promising approach by seed technologist for commercial seed lots to enhance the vigour in terms of seed germination potential, productivity and strengthening resistance response against metalloid stress. The present review provides an overview regarding the potency of priming with micronutrient to ameliorate harmful effects of heavy metal stress, possible mechanism how attenuation is accomplished, role of priming in enhancing crop productivity and inducing defence memory against the metalloid stress stimulus.

Interaction of Mycobacterium tuberculosis elongation factor Tu with GTP is regulated by phosphorylation.

During protein synthesis, translation elongation factor Tu (Ef-Tu) is responsible for the selection and binding of the cognate aminoacyl-tRNA to the acceptor site on the ribosome. The activity of Ef-Tu is dependent on its interaction with GTP. Posttranslational modifications, such as phosphorylation, are known to regulate the activity of Ef-Tu in several prokaryotes. Although a study of the Mycobacterium tuberculosis phosphoproteome showed Ef-Tu to be phosphorylated, the role of phosphorylation in the regulation of Ef-Tu has not been studied. In this report, we show that phosphorylation of M. tuberculosis Ef-Tu (MtbEf-Tu) by PknB reduced its interaction with GTP, suggesting a concomitant reduction in the level of protein synthesis. Overexpression of PknB in Mycobacterium smegmatis indeed reduced the level of protein synthesis. MtbEf-Tu was found to be phosphorylated by PknB on multiple sites, including Thr118, which is required for optimal activity of the protein. We found that kirromycin, an Ef-Tu-specific antibiotic, had a significant effect on the nucleotide binding of unphosphorylated MtbEf-Tu but not on the phosphorylated protein. Our results show that the modulation of the MtbEf-Tu-GTP interaction by phosphorylation can have an impact on cellular protein synthesis and growth. These results also suggest that phosphorylation can change the sensitivity of the protein to the specific inhibitors. Thus, the efficacy of an inhibitor can also depend on the posttranslational modification(s) of the target and should be considered during the development of the molecule.

Arsenic stress activates MAP kinase in rice roots and leaves.

The toxic metalloid arsenite has become a potential threat to rice growing regions leading to serious contamination in food chain. In the present study effect of different physiological concentration of arsenite that is toxic and triggers the molecular events were evaluated in rice seedlings. Along with severe effect on the growth of rice seedling, production of reactive oxygen species (ROS) and nitric oxide (NO) in arsenite treated rice roots was also observed. Activation of a 42kDa mitogen activated protein kinase (MAPK/MPK) by arsenite was observed in rice leaves and 42 and 44kDa in roots in dose dependent manner. The activated MAPK could be immunoprecipitated with anti-phospho-tyrosine antibody, 4G10. The kinetic of MAPK activation by arsenite was found to be dose dependent. Transcript analysis of MAPK family and immunokinase assay in arsenite treated rice seedling revealed significant level of induction in OsMPK3 transcripts in leaves and OsMPK3, OsMPK4 transcripts in roots. Among MAPK kinase (MKKs) gene family, OsMKK4 transcripts were found to be induced in arsenite treated rice leaves and roots. In-silico homology modeling and docking analysis supported OsMPK3-OsMKK4 interaction. The data indicates that arsenite stress is transduced through MAPK signaling cascade in rice.