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.

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.

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.

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.

Sulphur potentiates selenium to alleviate arsenic-induced stress by modulating oxidative stress, accumulation and thiol-ascorbate metabolism in Brassica juncea L.

The present study was designed to see the influence of selenium (Se) and sulphur (S) in the alleviation of arsenic (As)-induced stress in Brassica juncea plant. Se-induced alterations in physiological and biochemical responses due to deficient S (DS), normal S (NS) and additional S (AS) conditions were evaluated in 14-day-old seedlings of B. juncea variety Varuna. During the last 7 days of the 14-day-old seedlings, supplementation with arsenite (AsIII, 300 µM) alone and its combination with selenite (SeIV, 50 µM) along with different S treatments was done which are as follows: (i) control; (ii) As; (iii) As+Se+DS; (iv) As+Se + NS; (v) As+Se + AS. Experimental results showed that the application of AS in spite of NS supplied with Se influenced plant growth, oxidative stress and thiol-ascorbate-related parameters more prominently under As stress. The plants with As+Se+AS treatment exhibited lower ROS (superoxide and hydrogen peroxide ion), malondialdehyde (MDA) accumulation and lipoxygenase activity with increased activities of superoxide dismutase, catalase and ascorbate peroxidase compared with As+Se+NS condition. These plants also exhibited an increase in cysteine, non-protein thiols and phytochelatins, along with reduced, oxidised and redox content of glutathione and ascorbate. Furthermore, the application of S along with Se increased the activities of glutathione reductase, glutathione S-transferase, glutathione peroxidase, monodehydroascorbate and dehydroascorbate to minimise As stress. However, we observed that these responses were reversed under As+Se+DS condition and induced oxidative stress, which was almost similar to As only treatment. It indicated that AS nutrition potentiated Se to alleviate As-inhibited plant growth by modulating antioxidants including thiol-ascorbate-based mechanism and reducing As accumulation in B. juncea plants.

Facets of iron in arsenic exposed Oryza sativa varieties: A manifestation of plant's adjustment at morpho-biochemical and enzymatic levels☆.

Rice consumption is one of the primary sources of arsenic (As) exposure as the grains contain relatively higher concentration of inorganic As. Abundant studies on the ability of iron (Fe) plaque in hampering As uptake by plants has been reported earlier. However, little is known about its role in the mitigation of As mediated oxidative damage in rice plants. The present study highlights the effect of As and Fe co-supplementation on growth response, oxidative stress, Fe uptake related enzymes and nutrient status in rice varieties. Eight different Indica rice varieties were screened and finally four varieties (Varsha, Jaya, PB-1 and IR-64) were selected for detailed investigations. Improved germination and chlorophyll/protein levels during As+Fe co-exposure indicate healthier plants than As(III) treated ones. Interestingly Fe was found act both as an antagonist and also as a synergist of As treatments. It acted by reducing As translocation and improving the nutritional levels and enhancing the oxidative stress. Fe uptake related enzymes (nitrite reductase and ferric chelate reductase) and phytosiderophores analysis revealed that Fe supplementation can reduce its deficiency in rice plants. Morpho-biochemical, oxidative stress and nutrient analysis symbolizes higher tolerance of PB-1 towards As, while Varsha being most sensitive, efficiently combated the As(III) stress in the presence of Fe.

Arsenic affects the production of glucosinolate, thiol and phytochemical compounds: A comparison of two Brassica cultivars.

Arsenic (As), a non-essential metalloid, severely affects the normal functioning of plants, animals and humans. Plants play a crucial role in metabolic, physiological and numerous detoxification mechanisms to cope up with As induced stress. This study aimed to examine the differential response in two Brassica juncea cultivars, Varuna and Pusa Jagannath (PJn) exposed to different doses of As (50, 150, 300 µM) for 48 h duration. Change in morphological traits, concentration of individual as well as total GSL, sulfur related thiol proteins, sulfur content, and phytochemicals were analyzed in both cultivars. Accumulation pattern of As showed dose dependent accumulation in both the cultivars, being more in PJn. Our finding revealed that both cultivars were tolerant at low concentrations of As, while at higher concentration Varuna excelled over PJn. The increased tolerance of Varuna cultivar exposed to 150 and 300 µM concentration of As, correlated with its increased thiol related proteins, sulfur content and phytochemicals, which serves as defence strategy in the plant against oxidative stress. Differential pattern of total as well as individual GSLs content was observed in both Varuna and PJn cultivars. Varuna cultivar showed higher level of total and aliphatic GSLs, which serves as defence compound with other detoxification machineries to combat As stress. Our findings provide foundation for developing metalloid tolerant crops by analyzing the role of different genes involved in GSL mechanism and signaling pathways in different organs of plant.

Impact of silicon on Indian mustard (Brassica juncea L.) root traits by regulating growth parameters, cellular antioxidants and stress modulators under arsenic stress.

Arsenic (As) is an emerging pollutant causing inhibition in growth and development of plants resulting into phytotoxicity. On the other hand, silicon (Si) has been suggested as a modulator in abiotic and biotic stresses that, enhances plant's physiological adaptations in response to several stresses including heavy metal stress. In this study, we used roots of hydroponically grown 14 day old seedlings of Brassica juncea var. Varuna treated with 150 µM As, 1.5 mM Si and both in combination for 96 h duration. Application of Si modulated the effect of As by improving morphological traits of root along with the development of both primary and lateral roots. Changes observed in root traits showed positive correlation with As induced cell death, accumulation of reactive oxygen species (ROS), nitric oxide (NO) and intracellular superoxide radicals (O2(-)). Addition of 1.5 mM Si during As stress increased accumulation of As in roots. Mineral nutrient analysis was done using energy-dispersive X-ray fluorescence (EDXRF) technique and positively correlated with increased cysteine, proline, MDA, H2O2 and activity of antioxidant enzymes (SOD, CAT and APX). The results obtained from the above biochemical approaches support the protective and active role of Si in the regulation of As stress through the changes in root developmental process.