Breeding rice for yield improvement through CRISPR/Cas9 genome editing method: current technologies and examples.

The impending climate change is threatening the rice productivity of the Asian subcontinent as instances of crop failures due to adverse abiotic and biotic stress factors are becoming common occurrences. CRISPR-Cas9 mediated genome editing offers a potential solution for improving rice yield as well as its stress adaptation. This technology allows modification of plant's genetic elements and is not dependent on foreign DNA/gene insertion for incorporating a particular trait. In this review, we have discussed various CRISPR-Cas9 mediated genome editing tools for gene knockout, gene knock-in, simultaneously disrupting multiple genes by multiplexing, base editing and prime editing the genes. The review here also presents how these genome editing technologies have been employed to improve rice productivity by directly targeting the yield related genes or by indirectly manipulating various abiotic and biotic stress responsive genes. Lately, many countries treat genome-edited crops as non-GMOs because of the absence of foreign DNA in the final product. Thus, genome edited rice plants with improved yield attributes and stress resilience are expected to be accepted by the public and solve food crisis of a major portion of the globe. Supplementary Information: The online version contains supplementary material available at 10.1007/s12298-024-01423-y.

A rapid and robust colorimetric method for measuring relative abundance of auxins in plant tissues.

INTRODUCTION: Auxin estimation in plant tissues is a crucial component of auxin signaling studies. Despite the availability of various high-throughput auxin quantification methods like LC-MS, GC-MS, HPLC, biosensors, and DR5-gus/gfp-based assays, auxin quantification remains troublesome because these techniques are very expensive and technology intensive and they mostly involve elaborate sample preparation or require the development of transgenic plants. OBJECTIVES: To find a solution to these problems, we made use of an old auxin detection system to quantify microbe derived auxins and modified it to effectively measure auxin levels in rice plants. MATERIALS AND METHODS: Auxins from different tissues of rice plants, including root samples of seedlings exposed to IAA/TIBA or subjected to different abiotic stresses, were extracted in ethanol. The total auxin level was measured by the presently described colorimetric assay and counterchecked by other auxin estimation methods like LC-MS or gus staining of DR5-gus overexpressing lines. RESULTS: The presented colorimetric method could measure (1) the auxin levels in different tissues of rice plants, thus identifying the regions of higher auxin abundance, (2) the differential accumulation of auxins in rice roots when auxin or its transport inhibitor was supplied exogenously, and (3) the levels of auxin in roots of rice seedlings subjected to various abiotic stresses. The thus obtained auxin levels correlated well with the auxin levels determined by other methods like LC-MS or gus staining and the expression pattern of auxin biosynthesis pathway genes. CONCLUSIONS: The auxin estimation method described here is simple, rapid, cost-effective, and sensitive and allows for the efficient detection of relative auxin abundances in plant tissues.

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.

A simplified and improved protocol of rice transformation to cater wide range of rice cultivars.

The latest CRISPR-Cas9-mediated genome editing technology is expected to bring about revolution in rice yield and quality improvement, and thus validation of rice transformation protocols using CRISPR-Cas9-gRNA constructs is the need of the hour. Moreover, regeneration of more number of transgenic rice plants is prerequisite for developing genome-edited rice lines, as recalcitrant rice varieties were shown to have lower editing efficiencies which necessities screening of large number of transgenic plants to find the suitable edits. In the present study, we have simplified the Agrobacterium-mediated rice transformation protocol for both Indica and Japonica rice cultivars using CRISPR/Cas9 empty vector construct, and the protocols have been suitably optimized for getting large numbers of the regenerated plantlets within the shortest possible time. The Japonica transgenic lines were obtained within 65 days and for the Indica cultivars, it took about 76-78 days. We also obtained about 90% regeneration efficiency for both Japonica and Indica cultivars. The transformation efficiency was about 97% in the case of Japonica and 69-83% in the case of Indica rice cultivars. Furthermore, we screened the OsWRKY24 gene editing efficiency by transforming rice cultivars with CRISPR/Cas9 construct harbouring sgRNA against OsWRKY24 gene and found about 90% editing efficiency in Japonica rice cultivars, while 30% of the transformed Indica cultivars were found to be edited. This implicated the presence of a robust repair mechanism in the Indica rice cultivars.

Phosphorylation of AGO1a by MAP kinases is required for miRNA mediated resistance against Xanthomonas oryzae pv. oryzae infection in rice.

Bacterial leaf blight is a devastating disease caused by Xanthomonas oryzae pv. oryzae (Xoo) which causes severe crop loss in rice. The molecular mechanism that initiates defense against such pathogens remains unexplored. Reports have suggested crucial role of several miRNAs in regulating immune responses in plants. Argonaute (AGO) proteins have been implicated in imparting immunity against pathogens by using small RNAs as guide molecules. Here, we show that phosphorylation of rice AGO1a by MAP kinases is required for miRNA expression regulation during Xoo infection. AGO1a is induced in response to pathogen infection and is under the control of SA signaling pathway. The pathogen responsive MAP kinases MPK3, MPK4 and MPK6, interact with AGO1a in planta and can phosphorylate the protein in vitro. Overexpression of AGO1a extends disease resistance against Xoo in rice and leads to a higher accumulation of miRNAs. Conversely, overexpression of a non phosphorylatable mutant protein aggravates disease susceptibility and remarkably suppresses the miRNA expression levels. At a molecular level, phosphorylation of AGO1a by MAP kinase is required for increased accumulation of miRNAs during pathogen challenge. Taken together, the data suggests that OsAGO1a is a direct phosphorylation target of MAP kinases and this phosphorylation is crucial for its role in imparting disease resistance.

Regulation of photosynthesis by mitogen-activated protein kinase in rice: antagonistic adjustment by OsMPK3 and OsMPK6.

Photosynthesis is the basis of almost all life on earth and is the main component of crop yield that contributes to the carbohydrate partitioning to the grains. Maintaining the photosynthetic efficiency of plants in challenging environmental conditions by regulating the associated factors is a potential research arena which will help in the improvement of crop yield. Phosphorylation is known to play a pivotal role in the regulation of photosynthesis. Mitogen Activated Protein Kinases (MAPKs) cascade although known to regulate a diverse range of processes does not have any exact reported function in the regulation of photosynthesis. To elucidate the regulatory role of MAPKs in photosynthesis we investigated the changes in net photosynthesis rate and related parameters in DEX inducible over-expressing (OE) lines of two members of MAPK gene family namely, OsMPK3 and OsMPK6 in rice. Interestingly, significant changes were found in net photosynthesis rate and related physiological parameters in OsMPK3 and OsMPK6-OE lines compared to its wild-type relatives. OsMPK3 and OsMPK6 have regulatory effects on nuclear-encoded photosynthetic genes. Untargeted metabolite profiling reveals a higher accumulation of sugars and their derivatives in MPK6 overexpressing plants and a lower accumulation of sugars and organic acids in MPK3 overexpressing plants. The accumulation of amino acids was found in abundance in both MPK3 and MPK6 overexpressing plants. Understanding the effects of MPK3 and MPK6 on the CO2 assimilation of rice plants under normal growth conditions, will help in devising strategies that can be extended for crop improvement. Supplementary Information: The online version contains supplementary material available at 10.1007/s12298-023-01383-9.

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.

Rice Mitogen-Activated Protein Kinase regulates serotonin accumulation and interacts with cell cycle regulators under prolonged UV-B exposure.

Stress conditions such as UV-B exposure activates MAPKs in Arabidopsis and rice. UV-B radiation is hazardous to plant as it causes photosystem disruption, DNA damage and ROS generation. Here we report its effect on biological pathways by studying the global changes in transcript profile in rice seedling exposed to UV-B radiation for 1 h and 16 h. Short UV-B exposure (1 h) led to moderate changes, while a drastic change in transcript landscape was observed after long term UV-B exposure (16 h) in rice seedlings. Prolonged UV-B exposure negatively impacts the expression of cell cycle regulating genes and several other metabolic pathways in developing seedlings. MAP kinase signaling cascade gets activated upon UV-B exposure similar to reports in Arabidopsis indicating conservation of its function in both dicot and monocot. Expression analysis in inducible overexpression transgenic lines of MPK3 and MPK6 shows higher transcript abundance of phytoalexin biosynthesis gene like Oryzalexin D synthase and Momilactone A synthase, along with serotonin biosynthesis genes. An accumulation of serotonin was observed upon UV-B exposure and its abundance positively correlates with the MPK3 and MPK6 transcript level in the respective over-expression lines. Interestingly, multiple cell cycle inhibitor proteins including WEE1 and SMR1 interact with MPK3 and MPK6 thus, implying a major role of this pathway in cell cycle regulation under stress condition. Overall overexpression of MPK3 and MPK6 found to be detrimental for rice as overexpression lines shows higher cell death and compromised tolerance to UV-B.

MAP kinases may mediate regulation of the cell cycle in rice by E2F2 phosphorylation.

E2F is the key transcription factor that determines the proliferative status of cells by regulating the G1/S phase of the cell cycle. In this study, we show that in rice (Oryza sativa), OsE2F2 is a phosphorylation target of MAP kinases. The MAP kinases OsMPK3, OsMPK4, and OsMPK6 interact with and phosphorylate OsE2F2. Next, we determined the serine and threonine residues that could play a role in the phosphorylation of OsE2F2. Subsequently, our study suggests a possible link between MAP kinase-mediated OsE2F2 phosphorylation and its impact on DNA proliferation in the roots of rice seedlings. Finally, we found positive feedback regulation of OsMPK4 by OsE2F2. Therefore, our study hints at the potential impact of MAP kinase signaling on the cell cycle of rice plants.

Revisiting the role of MAPK signalling pathway in plants and its manipulation for crop improvement.

The mitogen-activated protein kinase (MAPK) pathway is an important signalling event associated with every aspect of plant growth, development, yield, abiotic and biotic stress adaptation. Being a central metabolic pathway, it is a vital target for manipulation for crop improvement. In this review, we have summarised recent advancements in understanding involvement of MAPK signalling in modulating abiotic and biotic stress tolerance, architecture and yield of plants. MAPK signalling cross talks with reactive oxygen species (ROS) and abscisic acid (ABA) signalling events in bringing about abiotic stress adaptation in plants. The intricate involvement of MAPK pathway with plant's pathogen defence ability has also been identified. Further, recent research findings point towards participation of MAPK signalling in shaping plant architecture and yield. These make MAPK pathway an important target for crop improvement and we discuss here various strategies to tweak MAPK signalling components for designing future crops with improved physiology and phenotypes.

A Rare Case of Incidentally Diagnosed Pulmonary Inflammatory Myofibroblastic Tumour with Dramatic Response to Crizotinib in a Postpartum Woman.

Introduction: Inflammatory myofibroblastic tumours are rare neoplasms which most commonly affect children and young adults. With an intermediate malignant potential, they are typically detected in the abdomen, lung, mediastinum, head and neck, gastrointestinal tract, and genitourinary tract. Case description: We describe the case of a 33-year-old postpartum woman incidentally diagnosed with a pulmonary inflammatory myofibroblastic tumour following complaints of poorly controlled hypertension a week after caesarean section. She was ALK-negative and received an ALK inhibitor with complete resolution of the lesion. A ROS1-TFG fusion confirmed the diagnosis of an inflammatory myofibroblastic tumour after CT-guided fine needle aspiration. Discussion: This case highlights an uncommon presentation posing a diagnostic and therapeutic challenge and the potential treatment option of crizotinib. LEARNING POINTS: Inflammatory myofibroblastic tumour (IMT) is a rarely reported neoplasm arising in the abdominal soft tissues, the lung, mediastinum, head, neck, gastrointestinal tract, and genitourinary tract, with intermediate malignant potential.IMT is definitively diagnosed only after histological examination following surgical biopsy, based on immunohistochemical markers and the molecular characteristics of the tumour, but small biopsies may have a role in a large lesion.IMT did not cause any complications during gestation.Therapeutic approaches include surgical resection and chemotherapy, including with crizotinib, an ALK tyrosine kinase inhibitor.

Root-Expressed Rice PAP3b Enhances Secreted APase Activity and Helps Utilize Organic Phosphate.

Phosphate (Pi) deficiency leads to the induction of purple acid phosphatases (PAPs) in plants, which dephosphorylate organic phosphorus (P) complexes in the rhizosphere and intracellular compartments to release Pi. In this study, we demonstrate that OsPAP3b belongs to group III low-molecular weight PAP and is low Pi-responsive, preferentially in roots. The expression of OsPAP3b is negatively regulated with Pi resupply. Interestingly, OsPAP3b was found to be dual localized to the nucleus and secretome. Furthermore, OsPAP3b is transcriptionally regulated by OsPHR2 as substantiated by DNA-protein binding assay. Through in vitro biochemical assays, we further demonstrate that OsPAP3b is a functional acid phosphatase (APase) with broad substrate specificity. The overexpression (OE) of OsPAP3b in rice led to increased secreted APase activity and improved mineralization of organic P sources, which resulted in better growth of transgenics compared to the wild type when grown on organic P as an exogenous P substrate. Under Pi deprivation, OsPAP3b knock-down and knock-out lines showed no significant changes in total P content and dry biomass. However, the expression of other phosphate starvation-induced genes and the levels of metabolites were found to be altered in the OE and knock-down lines. In addition, in vitro pull-down assay revealed multiple putative interacting proteins of OsPAP3b. Our data collectively suggest that OsPAP3b can aid in organic P utilization in rice. The APase isoform behavior and nuclear localization indicate its additional role, possibly in stress signaling. Considering its important roles, OsPAP3b could be a potential target for improving low Pi adaptation in rice.

MKKK20 works as an upstream triple-kinase of MKK3-MPK6-MYC2 module in Arabidopsis seedling development.

The mitogen-activated protein kinase (MAPK) cascade is involved in several signal transduction processes in eukaryotes. Here, we report a mechanistic function of MAP kinase kinase kinase 20 (MKKK20) in light signal transduction pathways. We show that MKKK20 acts as a negative regulator of photomorphogenic growth at various wavelengths of light. MKKK20 not only regulates the expression of light signaling pathway regulatory genes but also gets regulated by the same pathway genes. The atmyc2 mkkk20 double mutant analysis shows that MYC2 works downstream to MKKK20 in the regulation of photomorphogenic growth. MYC2 directly binds to the promoter of MKKK20 to modulate its expression. The protein-protein interaction study indicates that MKKK20 physically interacts with MYC2, and this interaction likely suppresses the MYC2-mediated promotion of MKKK20 expression. Further, the protein phosphorylation studies demonstrate that MKKK20 works as the upstream kinase of MKK3-MPK6-MYC2 module in photomorphogenesis.

Bacterial distribution in Twilight zone of the Indian sector of Southern Ocean: V3- V4 rDNA hypervariable region data.

Twilight zones in oceans represent the oceanic waters between 200 m to 1000 m in depth, wherein sunlight is diffused and intensity is <1% of surface value. The activities and diversity of marine micro-organisms in this unique zone are understudied, especially in the Indian Sector of the Southern Ocean. For a better understanding of the microbial environment and diversity in the twilight zone of the Indian sector of Southern Ocean, samples were collected from 200m depth in eddy-influenced waters of Subtropical Front (STF), Sub-Antarctic Front (SAF), Polar Front (PF), waters off Kerguelen (Kw), and Prydz Bay (Pb) waters. In this article, next-generation sequencing (NGS) based amplicon data of 16s rDNA bacterial samples are presented. Hypervariable V3-V4 regions were sequenced using Hiseq platform, and data was processed using Mothur v 1.48.0, and database Silva 138.1nr. Total of nine different phyla is reported from the Southern Ocean at 200m, whereas at order level Synechococcales was found in STF waters only and SAR 11_ Clades were present in all stations.

RAV1 family members function as transcriptional regulators and play a positive role in plant disease resistance.

Phytopathogens pose a severe threat to agriculture and strengthening the plant defense response is an important strategy for disease control. Here, we report that AtRAV1, an AP2 and B3 domain-containing transcription factor, is required for basal plant defense in Arabidopsis thaliana. The atrav1 mutant lines demonstrate hyper-susceptibility against fungal pathogens (Rhizoctonia solani and Botrytis cinerea), whereas AtRAV1 overexpressing lines exhibit disease resistance against them. Enhanced expression of various defense genes and activation of mitogen-activated protein kinases (AtMPK3 and AtMPK6) are observed in the R. solani infected overexpressing lines, but not in the atrav1 mutant plants. An in vitro phosphorylation assay suggests AtRAV1 to be a novel phosphorylation target of AtMPK3. Bimolecular fluorescence complementation and yeast two-hybrid assays support physical interactions between AtRAV1 and AtMPK3. Overexpression of the native as well as phospho-mimic but not the phospho-defective variant of AtRAV1 imparts disease resistance in the atrav1 mutant A. thaliana lines. On the other hand, overexpression of AtRAV1 fails to impart disease resistance in the atmpk3 mutant. These analyses emphasize that AtMPK3-mediated phosphorylation of AtRAV1 is important for the elaboration of the defense response in A. thaliana. Considering that RAV1 homologs are conserved in diverse plant species, we propose that they can be gainfully deployed to impart disease resistance in agriculturally important crop plants. Indeed, overexpression of SlRAV1 (a member of the RAV1 family) imparts disease tolerance against not only fungal (R. solani and B. cinerea), but also against bacterial (Ralstonia solanacearum) pathogens in tomato, whereas silencing of the gene enhances disease susceptibility.

Appraisal of groundwater arsenic on opposite banks of River Ganges, West Bengal, India, and quantification of cancer risk using Monte Carlo simulations.

This study was conducted to inspect the spatial distribution, source identification, and risk assessment of groundwater arsenic (As) in different blocks that lie on the opposite banks of river Bhagirathi (a distributary of river Ganges), Murshidabad, West Bengal, India. It has been observed that the blocks that lie towards the eastern bank of river Bhagirathi have elevated arsenic and comparatively more reducing groundwater (lower oxidation-reduction potential and high iron). About 66% of groundwater samples across the district have arsenic concentration higher than the World Health Organization (WHO) permissible limit. Speciation of groundwater arsenic reveals that about 90% of arsenic species were present as arsenic (III). Further, principal component analysis (PCA) was employed to identify the controlling factors that favor the release of arsenic. PC1 comprises EC, TDS, As, Fe, TOC, and HCO3- with moderate loadings, which suggests microbially mediated degradation of organic matter (OM), helps in reductive dissolution of arsenic-bearing Fe-Mn oxyhydroxides. Results pointed out severe groundwater arsenic poisoning; hence, a health risk assessment was performed for the exposure of arsenic in groundwater, using incremental lifetime cancer risk (ILCR) models coupled with Monte Carlo simulations. On the eastern bank of river Bhagirathi, incremental lifetime cancer risk (ILCR) due to oral exposure (5th to 95th percentile values) ranged from 1.30538E - 04 to 9.31398E - 03 with a mean of 2.84194E - 03 for adults, which is 2841 times higher than the USEPA high safety risk guidelines of one in 1 million. The outcomes of the results will be useful for the policymakers and regulatory boards in defining the actual impact and deciding the pre-remediation goals.

Characterization and expression profiling of PIN auxin efflux transporters reveal their role in developmental and abiotic stress conditions in rice.

The auxin efflux transporter proteins called PINs ferry auxin from its source to sinks in particular directions depending on their polar localizations in the plasma membrane, thus facilitating the development of the entire plant architecture. The rice genome has 12 PIN genes distributed over eight chromosomes. To study their roles in plant development, abiotic stress responsiveness, and shaping an auxin-dependent root architecture, a genome-wide analysis was carried out. Based on phylogeny, cellular localization, and hydrophilic loop domain size, the PINs were categorized into canonical and noncanonical PINs. PINs were found expressed in all of the organs of plants that emphasized their indispensable role throughout the plant's life cycle. We discovered that PIN5C and PIN9 were upregulated during salt and drought stress. We also found that regardless of its cellular level, auxin functioned as a molecular switch to turn on auxin biosynthesis genes. On the contrary, although PIN expression was upregulated upon initial treatment with auxin, prolonged auxin treatment not only led to their downregulation but also led to the development of auxin-dependent altered root formation in rice. Our study paves the way for developing stress-tolerant rice and plants with a desirable root architecture by genetic engineering.

Delusion of pregnancy: Conception in brain.

Delusional disorders are common psychiatric disorders, but a delusion of pregnancy is a rare condition. Four cases that presented at a single tertiary care psychiatry center with delusion of pregnancy as a part of different psychological disorders are illustrated here. These cases were seen over a period of 6 months and had varied presentations and associated psychopathologies. Three of the four patients showed rapid recovery to treatment, but one patient was lost to follow-up. The heterogeneity in the presentation, sociodemographic profile of the patients and even in the symptom profile and response to treatment in this condition is highlighted and discussed in this case series.

Bacterial distribution in the Equatorial Indian Ocean using Amplicon sequencing of V3-V4 rDNA hypervariable region data.

The Equatorial Indian Ocean (EIO) is a complex system strongly influenced by Indian Monsoon. During a RAMA (Research Moored Array for African-Asian-Australian Monsoon Analysis and Prediction) mooring maintenance expedition during the Southwest monsoon (August-September 2016) onboard ORV Sagar Kanya, seawater samples from the surface, deep chlorophyll maxima (DCM) and 200m were collected for bacterioplankton community structure. Herein we document our amplicon data of the bacterial community at 4 stations (4.01°S, 1.60°S, 0.36°N and 1.78°N) along the 67°00' E transect. The samples were subjected to next-generation sequencing (NGS), followed by processing with Mothur v 1.48.0, and the taxonomic classification prepared with Silva 138.1nr reference database. Our data indicates Alphaproteobacteria (48 %) and Cyanobacteria (33 %) dominance in the surface and DCM samples.

Profiling and occupational health risk assessment study on coal ashes in terms of polycyclic aromatic hydrocarbons (PAHs).

Profiling and cancer risk assessment on the polycyclic aromatic hydrocarbons (PAHs) content of coal ashes produced by the major coal combustion plants from the eastern coalfield region in India was conducted. Thirteen PAHs were detected on coal ashes collected from ash deposition sites of major thermal power plants and the profiling of the PAHs was done. Benzo[a]pyrene equivalents (BaPeq) for individual PAHs were calculated and applied to the probabilistic assessment model from US EPA (1989). Monte Carlo simulations were conducted to assess the risk of inhabitants exposed to PAHs through the dust of the coal ash deposition site. In fly ash, the range of total amount of carcinogenic PAHs was from 3.50 to 6.72 µg g-1 and for the bottom ash, the range was 8.49 to 14.91 µg g-1. Bottom ashes were loaded with ample amounts of 5- and 6-ring carcinogenic PAHs, whereas fly ashes were dominated by medium molecular weight PAHs. The simulated mean cancer risks from fly ashes were 2.187 E-06 for children and 3.749 E-06 for adults. For the case of bottom ash, the mean risks were 1.248 E-05 and 2.173 E-05 respectively for children and adults. Among all the three exposure routes, dermal contact was the major and caused 81% of the total cancer risk. The most sensitive parameters were exposure duration and relative skin adherence factor for soil, which contributed the most to total variation. The 90% risks calculated from the bottom ashes (2.617 E-05 for children and 4.803 E-05 for adults) are marginally above the acceptable limit (>1.000 E-06) according to US EPA. In this study, a comprehensive risk assessment on carcinogenic PAHs present in coal ashes was done for the first time that may be helpful to develop potential strategies against occupational cancer risk.