Browsing by Author "Fatima, Urooj"

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AtGBF3 confers tolerance to Arabidopsis thaliana against combined drought and Pseudomonas syringae stress
(Elsevier B.V., 2019) Dixit, Sandeep Kumar; Gupta, Aarti; Fatima, Urooj; Senthil-Kumar, Muthappa
In field conditions, plants are often exposed to a combination of abiotic and biotic stresses, for instance, drought and pathogen infection. Transcriptome studies on Arabidopsis thaliana and other plants under individual and combined drought and pathogen stresses have unveiled the activation of shared molecular defense mechanisms. These shared plant responses are characterized by commonly regulated genes under both individual as well as combined stresses. Therefore, the identification of commonly regulated genes during individual and combined stress conditions can reveal plant responses towards combined stress. Available transcriptome studies on combined-stressed plants have hinted at G-Box Binding Factor 3 (GBF3) as one of the regulatory components of the shared response. However, the mechanistic understanding of the role of AtGBF3 under combined drought and pathogen stress is not yet decoded. In the current study, we used genetic approaches to identify the role of AtGBF3 in conferring tolerance to individual and combined drought and pathogen stress. Atgbf3 mutant plants showed increased susceptibility, while AtGBF3-overexpressing plants were tolerant under individual and combined drought and Pseudomonas syringae pv. tomato infection stresses as compared to wild-type plants. We further analyzed the global transcriptome of Atgbf3 mutant plants under combined stress to identify its downstream targets. We also established a high-throughput method to apply combined polyethylene glycol and pathogen stress on Murashige and Skoog medium-grown plants to further validate the role of AtGBF3 in combined stress.
AtSWEET11 and AtSWEET12 transporters function in tandem to modulate sugar flux in plants
(John Wiley & Sons, 2023) Fatima, Urooj; Balasubramaniam, D.; Khan, Wajahat Ali; Kandpal, Manu; Vadassery, Jyothilakshmi; Arockiasamy, Arulandu; Senthil-Kumar, Muthappa
The sugar will eventually be exported transporter (SWEET) members in Arabidopsis, AtSWEET11 and AtSWEET12 are the important sucrose efflux transporters that act synergistically to perform distinct physiological roles. These two transporters are involved in apoplasmic phloem loading, seed filling, and sugar level alteration at the site of pathogen infection. Here, we performed the structural analysis of the sucrose binding pocket of AtSWEET11 and AtSWEET12 using molecular docking followed by rigorous molecular dynamics (MD) simulations. We observed that the sucrose molecule binds inside the central cavity and in the middle of the transmembrane (TM) region of AtSWEET11 and AtSWEET12, that allows the alternate access to the sucrose molecule from either side of the membrane during transport. Both AtSWEET11 and AtSWEET12, shares the similar amino acid residues that interact with sucrose molecule. Further, to achieve more insights on the role of these two transporters in other plant species, we did the phylogenetic and the in-silico analyses of AtSWEET11 and AtSWEET12 orthologs from 39 economically important plants. We reported the extensive information on the gene structure, protein domain and cis-acting regulatory elements of AtSWEET11 and AtSWEET12 orthologs from different plants. The cis-elements analysis indicates the involvement of AtSWEET11 and AtSWEET12 orthologs in plant development and also during abiotic and biotic stresses. Both in silico and in planta expression analysis indicated AtSWEET11 and AtSWEET12 are well-expressed in the Arabidopsis leaf tissues. However, the orthologs of AtSWEET11 and AtSWEET12 showed the differential expression pattern with high or no transcript expression in the leaf tissues of different plants. Overall, these results offer the new insights into the functions and regulation of AtSWEET11 and AtSWEET12 orthologs from different plant species. This might be helpful in conducting the future studies to understand the role of these two crucial transporters in Arabidopsis and other crop plants.
AtSWEET11 and AtSWEET12: the twin traders of sucrose
(Elsevier B.V., 2022) Fatima, Urooj; Anjali, Anjali; Senthil-Kumar, Muthappa
AtSWEET11 and AtSWEET12 are central players in phloem loading and long-distance sucrose translocation. During drought stress, these transporters enhance sucrose transport from shoot to root, increasing root proliferation. Chen et al. have now unravelled novel aspects of sucrose transport regulation, occurring via AtSWEET11 and AtSWEET12 phosphorylation and oligomerisation.
Dual localization of JA receptor, CaCOI2, explains JA perception dynamics in chickpea
(John Wiley & Sons, 2025) Singh, Ajit Pal; Bhatia, Chitra; Singh, Ekampreet; Singh, Amit Kumar; Fatima, Urooj; Senthil-Kumar, Muthappa; Giri, Jitender
Jasmonates (JAs) are a group of oxylipin-derived phytohormones involved in various biotic and abiotic stress responses and regulate plant development. JAs are perceived by receptor proteins called coronatine insensitive (COI). These JA receptors encode F-box proteins that form the SCFCOI ubiquitin ligase complex (comprising Skp, Cullin, and F-box) and activate JA signaling by promoting the degradation of the transcriptional repressor JAZ (JA associated ZIM domain containing) proteins via the 26S proteasomal pathway. However, JA signaling is not well understood in chickpea, a vital legume. In this study, we identified two potential chickpea JA receptors, named CaCOI1 and CaCOI2, and characterized CaCOI2 as a functional JA receptor. Subcellular localization experiments revealed that CaCOI2 is localized outside the nucleus but moves into the nucleus upon JA perception to activate signaling. Using domain-swapping experiments between CaCOI1 and CaCOI2, we demonstrated that the leucine-rich repeat region of the receptors, which interacts with bioactive JA such as JA-Isoleucine, also plays a crucial role in controlling the subcellular localization of CaCOI proteins. Our findings identify a functional JA receptor in chickpea and reveal new aspects of JA signaling and perception, which may also be relevant to other plants.
The ins and outs of SWEETs in plants: current understanding of the basics and their prospects in crop improvement
(Springer Nature Publishing AG, 2021) Anjali, Anjali; Fatima, Urooj; Senthil-Kumar, Muthappa
Sugar will eventually be exported transporters (SWEETs), a newly discovered class of sugar transporters, play a significant role in sugar efflux processes across various kingdoms of life. In fact, SWEETs have a long evolutionary path from prokaryotes to higher plants. In plants, they are involved in developmental processes, including nectar secretion, pollen nutrition, and seed filling. While the role of SWEETs has been well studied in biotic stresses, particularly their manipulation by pathogens for sugar acquisition, they have also been linked to many abiotic stresses. Although the phylogenetic relationships and solved structures of SWEETs in different plants have been revealed, their regulation remains unexplored. The current review deals with all the exciting discoveries around SWEETs, including their classification and diversity, and bridges the gaps in their evolutionary story, from bacterial semiSWEETs to eukaryotic SWEETs. We also critically examine SWEETs at genomic, transcriptomic, and proteomic levels, as evinced by recently published examples from grain, millet, and horticultural crops. In addition, we highlight the possibilities of utilizing SWEETs in applications such as bioethanol production and disease diagnostic markers. We attempt to elucidate and unify findings related to the yet unsolved puzzle of SWEET regulation in plants to improve crop production and protection for sustainable agriculture.
Morpho-pathological and global transcriptomic analysis reveals the robust nonhost resistance responses in chickpea interaction with Alternaria brassicae
(American Phytopathological Society, 2019) Fatima, Urooj; Bhorali, Priyadarshini; Senthil-Kumar, Muthappa
Alternaria blight, caused by Alternaria brassicae, causes considerable yield loss in Brassica crops. While several blight-resistant varieties have been developed using resistance sources from host germplasm, none of them are entirely successful in imparting durable resistance. This has prompted the exploration of novel gene pools of nonhost plant species. Nonhost resistance (NHR) is a durable form of resistance, comprising pre- and post-invasion layers of defense. We aimed to identify the molecular basis of NHR to A. brassicae and identify the layers of NHR operating in a nonhost, chickpea (Cicer arietinum). To elucidate the layers of NHR operating against A. brassicae, we compared the histopathology and infection patterns of A. brassicae in C. arietinum and Brassica juncea. Delayed conidial germination, impeded hyphal growth, suppressed appressorium formation, and limited hyphal penetration occurred in the nonhost plant compared to the host plant, implying the involvement of the pre-invasion layer of NHR in C. arietinum. Next, we investigated the molecular basis of robust NHR in C. arietinum challenged with A. brassicae by microarray-based global transcriptome profiling. Genes involved in stomatal closure, cuticular wax biosynthesis, cell wall modification, and secondary metabolite production (contributing to pre-invasion NHR), as well as reactive oxygen species (ROS) and cell death (contributing to post-invasion NHR), were found to be upregulated. Consistent with transcriptomic analysis, the morpho-pathological analysis revealed stomatal closure, ROS accumulation, and localized cell death in C. arietinum as the defense strategies against A. brassicae. Thus, we identified NHR-contributing genes with potential applications in blight resistance gene transfer to B. juncea.
Non-host resistance to plant viruses: What do we know?
(Elsevier B.V., 2020) Baruah, Aiswarya; Sivalingam, Palaiyur Nanjappan; Fatima, Urooj; Senthil-Kumar, Muthappa
Non-host resistance (NHR) is a prevalent mode of plant defense against invading pathogens, including viruses. Being hard to circumvent, NHR has considerable potential to provide durable resistance against virus infection. This review systematically analyzes recent research findings demonstrating NHR mechanisms and chronologically enumerates the defense strategies contributing to NHR. Conventionally, the NHR mechanisms that operate by restricting viral entry and multiplication are termed “true NHR.” Here, we propose NHR mechanisms operating beyond viral multiplication in non-host plants as “apparent NHR.” This review elucidates both categories of NHR and provides insights into the mechanisms involved in NHR.
Perspectives on the utilization of resistance mechanisms from host and nonhost plants for durable protection of Brassica crops against Alternaria blight
(PeerJ, Inc., 2019) Fatima, Urooj; Bhorali, Priyadarshini; Borah, S.; Senthil-Kumar, Muthappa
Background: Alternaria brassicae, the causal organism of Alternaria blight, is a necrotroph infecting crops of the Brassicaceae family at all growth stages. To circumvent this problem, several disease management strategies are being used in the field, and disease-resistant varieties have also been developed. However, no strategy has proven completely successful, owing to the high variability in virulence among A. brassicae isolates, which causes a diverse spectrum of symptoms. Nonhost resistance (NHR) is a robust and broad-spectrum defense mechanism available in plants, and the exploitation of gene pools from plant species that are nonhost to A. brassicae could serve as novel sources of resistance. Methodology: We searched the literature using key words relevant to this study in various search engines, such as PubMed, Web of Science, and Google Scholar, as well as certain journal websites. The literature was retrieved, sorted, and mined to extract data pertinent to the present review. Results: In this review, we have comprehensively covered the recent progress made in developing Alternaria blight resistance in Brassica crops by exploiting host germplasm. We also enumerate the potential NHR sources available for A. brassicae and the NHR layers possibly operating against this pathogen. In addition, we propose different strategies for identifying NHR-related genes from nonhost plants and testing their relevance in imparting broad-spectrum resistance when transferred to host plants. Conclusion: This review will help broaden the current knowledge base pertaining to the resistance sources available in host germplasm, the exploitation of NHR mechanisms, and their applications in protecting Brassica crops from Alternaria blight. The insights might also be applicable to a wider repertoire of plant pathogens.
Plant and pathogen nutrient acquisition strategies
(Frontiers Media S.A., 2015) Fatima, Urooj; Senthil-Kumar, Muthappa
Nutrients are indispensable elements required for the growth of all living organisms including plants and pathogens. Phyllosphere, rhizosphere, apoplast, phloem, xylem, and cell organelles are the nutrient niches in plants that are the target of bacterial pathogens. Depending upon nutrients availability, the pathogen adapts various acquisition strategies and inhabits the specific niche. In this review, we discuss the nutrient composition of different niches in plants, the mechanisms involved in the recognition of nutrient niche and the sophisticated strategies used by the bacterial pathogens for acquiring nutrients. We provide insight into various nutrient acquisition strategies used by necrotrophic, biotrophic, and hemibiotrophic bacteria. Specifically we discuss both modulation of bacterial machinery and manipulation of host machinery. In addition, we highlight the current status of our understanding about the nutrient acquisition strategies used by bacterial pathogens, namely targeting the sugar transporters that are dedicated for the plant’s growth and development. Bacterial strategies for altering the plant cell membrane permeability to enhance the release of nutrients are also enumerated along with in-depth analysis of molecular mechanisms behind these strategies. The information presented in this review will be useful to understand the plant–pathogen interaction in nutrient perspective.
Structure and regulation of SWEET transporters in plants: An update
(Elsevier B.V., 2020) Anjali, Anjali; Fatima, Urooj; Manu, M.S.; Ramasamy, Sureshkumar; Senthil-Kumar, Muthappa
Sugar will eventually be exported transporters (SWEETs), a novel family of sugar transporters found in both eukaryotes and prokaryotes, facilitate sugar flux across the cell membrane. Although these transporters were first discovered in plants, their homologs have been reported in different organisms. SWEETs have critical roles in various developmental processes, including phloem loading, nectar secretion, and pathogen nutrition. The structure of bacterial homologs, called SemiSWEETs, has been well studied thus far. Here, we provide an overview of SWEET protein structure and dynamic function by analyzing the solved crystal structures and predicted models that are available for a few SWEETs in a monocot plant (rice) and dicot plant (Arabidopsis thaliana). Despite the advancement in structure-related studies, the regulation of SWEETs remains unknown. In light of reported regulatory mechanisms of a few other sugar transporters, we propose the regulation of SWEETs at the post-translational level. We then enumerate the potential post-translational modification sites in SWEETs using computational tools. Overall, in this review, we critically analyze SWEET protein structure in plants to predict the post-translational regulation of SWEETs. Such findings have a direct bearing on plant nutrition and defense and targeting the regulation at these levels will be important in crop improvement.
Tissue water status and bacterial pathogen infection: how they are correlated?
(Springer, 2017) Fatima, Urooj; Senthil-Kumar, Muthappa
Tissue water status plays an important role in determining the fate of plant-pathogen interaction. Water availability is one of the factors that determine the multiplication of bacteria on the surface and inside the plants. Plant-water relations are highly influenced by soil water status, and drought stress is known to severely impact plant-pathogen interaction. Water, as a limiting factor, is differentially manipulated by both plants and pathogens during compatible and incompatible interactions. Plants stimulate the localized loss of water at the site of infection for limiting the bacterial multiplication. On the other hand, foliar and vascular bacterial pathogens employ different strategies to alter the plant water status and eventually establish the infection in plants. Foliar pathogens manipulate their own machinery in response to water-limited condition in plants. They also modulate the plant machinery in order to promote disease by increasing the water soaking between the cells. Similarly, vascular pathogens use different strategies such as clogging of vessels and embolism of xylem elements that leads to wilting of plant. Here, we discuss the current knowledge on impact of drought stress during plant interaction with foliar or vascular pathogen interactions.