Browsing by Author "Kumar, Kamal"

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An alternative approach in Gateway ® cloning when the bacterial antibiotic selection cassettes of the entry clone and destination vector are the same
(Springer, 2013) Kumar, Kamal; Yadav, Saurabh; Purayannur, Savithri; Verma, Praveen K.
The Gateway(®) recombination technology has revolutionized the method of gene cloning for functional analyses and high-throughput ORFeome projects. In general, Gateway cloning is highly efficient because after LR recombination and bacterial transformation, only cells containing the recombinant destination clone are selected on an antibiotic selection plate. However, when the antibiotic resistance gene for bacterial selection is the same in the entry and destination vectors, the direct selection of recombinant destination clones on an antibiotic plate is difficult. Here, we demonstrate an efficient and comprehensive approach to obtain positive destination clones directly on an antibiotic selection plate in this situation. The strategy involves polymerase chain reaction (PCR)-mediated amplification of the entry clone using entry vector-specific primers that bind outside the attL sequences and the subsequent use of this purified PCR product for LR recombination with the destination vector. Our results suggest that cloning of linear DNA fragments into circular destination vectors through LR recombination is an efficient method for inserts up to 7 kb in size. Using this approach, the yield of colony PCR positive destination clones was 100 % for genes of various sizes tested in our experiments.
Ascochyta rabiei: A threat to global chickpea production
(John Wiley & Sons, 2022) Singh, Ritu; Kumar, Kamal; Purayannur, Savithri; Chen, Weidong; Verma, Praveen K.
The necrotrophic fungus Ascochyta rabiei causes Ascochyta blight (AB) disease in chickpea. A. rabiei infects all aerial parts of the plant, which results in severe yield loss. At present, AB disease occurs in most chickpea-growing countries. Globally increased incidences of A. rabiei infection and the emergence of new aggressive isolates directed the interest of researchers toward understanding the evolution of pathogenic determinants in this fungus. In this review, we summarize the molecular and genetic studies of the pathogen along with approaches that are helping in combating the disease. Possible areas of future research are also suggested.
Broadening the horizon of crop research: a decade of advancements in plant molecular genetics to divulge phenotype governing genes
(Springer Nature Publishing AG, 2022) Singh, Ritu; Kumar, Kamal; Bharadwaj, Chellapilla; Verma, Praveen K.
The modern crop improvement programs rely heavily on two major steps—trait-associated QTL/gene/marker’s identification and molecular breeding. Thus, it is vital for basic and translational crop research to identify genomic regions that govern the phenotype of interest. Until the advent of next-generation sequencing, the forward-genetic techniques were laborious and time-consuming. Over the last 10 years, advancements in the area of genome assembly, genotyping, large-scale data analysis, and statistical algorithms have led faster identification of genomic variations regulating the complex agronomic traits and pathogen resistance. In this review, we describe the latest developments in genome sequencing and genotyping along with a comprehensive evaluation of the last 10-year headways in forward-genetic techniques that have shifted the focus of plant research from model plants to diverse crops. We have classified the available molecular genetic methods under bulk-segregant analysis-based (QTL-seq, GradedPool-Seq, QTG-Seq, Exome QTL-seq, and RapMap), target sequence enrichment-based (RenSeq, AgRenSeq, and TACCA), and mutation-based groups (MutMap, NIKS algorithm, MutRenSeq, MutChromSeq), alongside improvements in classical mapping and genome-wide association analyses. Newer methods for outcrossing, heterozygous, and polyploid plant genetics have also been discussed. The use of k-mers has enriched the nature of genetic variants which can be utilized to identify the phenotype-causing genes, independent of reference genomes. We envisage that the recent methods discussed herein will expand the repertoire of useful alleles and help in developing high-yielding and climate-resilient crops.
Comparative structural modelling of a monothiol GRX from chickpea: insight in iron-sulfur cluster assembly
(Elsevier, 2012) Yadav, Saurabh; Kushwaha, Hemant Ritturaj; Kumar, Kamal; Verma, Praveen K.
Glutaredoxins (GRXs) are small, ubiquitous, multifunctional, heat-stable and glutathione-dependent thiol-disulphide oxidoreductases, classified under thioredoxin-fold superfamily. In the green lineage, GRXs constitute a complex family of proteins. Based on their active site, GRXs are classified into two subfamilies: dithiol and monothiol. Monothiol GRXs contain 'CGFS' as a redox active motif and assist in maintaining redox state and iron homeostasis within the cell. Using RACE strategy, a full length cDNA of chickpea (Cicer arietinum) glutaredoxin 3 (CarGRX3) was cloned and sequenced. The cDNA contains open reading frame of 537 bp encoding 178 amino acids and exhibits features of other known 'CGFS' type GRXs. Based on the multiple sequence alignment among CarGRX3 and monothiol GRXs of other photosynthetic organisms, the characteristic motif (KGX4PXCGFSX([29/30/32])KX4WPTXPQX4GX3GGXDI) with 18 invariant residues was observed. The proposed structure of CarGRX3 was compared with structurally resolved monothiol GRXs of other organisms. The CarGRX3 and nearest Arabidopsis homolog (AtGRXcp) shares 76% sequence identity which was reflected by their 3D-structure conservation. The structure of chickpea monothiol GRX (CarGRX3) coordinates glutathione ligated [2Fe-2S] cluster in a homodimeric form, highlighting the structural basis for iron-sulfur cluster (ISC) assembly and delivery to acceptor proteins. The present study on CarGRX3 model highlighted the utility of the theoretical approaches to understand complex biological phenomena such as glutathione docking and incorporation of GSH-ligated [2Fe-2S] cluster.
Constructing synthetic pathways in plants: Strategies and tools
(Elsevier B.V., 2020) Dwivedi, Anuj; Kumar, Kamal; Verma, Praveen K.
Plants, being primary producers, are the ultimate choice for the synthetic biology and metabolite engineering. For thousands of years, conventional methods allowed plants to meet various human requirements. Synthetic biology is a combination of engineering and biological science that facilitates with large number of new opportunities toward generation of reprogrammed cell with new biological behavior. The application of this technology can enhance traditional crop production and maximize the desired biomass production in required plants. Efforts in establishments of such individual plant systems will result in pioneering in various applications, such as generation of food, fuel, fiber, and biomedical therapies. The primary goal of this chapter is to discuss the advancement in strategies and tools form the core of synthetic pathway construction. However, synthetic biology in plant system is still at infancy stage and thus implications of synthetic biology strategies deployed in crops for biomass production have been discussed.
Differential transcript accumulation in chickpea during early phases of compatible interaction with a necrotrophic fungus Ascochyta rabiei
(Springer Science, 2012) Jaiswal, Purnima; Cheruku, Jyothi Reddy; Kumar, Kamal; Yadav, Saurabh; Singh, Archana; Kumari, Pragati; Dube, Sunil Chandra; Upadhyaya, Kailash C.; Verma, Praveen K.
The initial phases of the disease establishment are very crucial for the compatible interactions. Pathogens must overcome the responses generated by the host for the onset of disease invasion. The compatible interaction is inadequately represented in plant-pathogen interaction studies. To gain broader insight into the early responses elicited by chickpea blight fungus Ascochyta rabiei during compatible interaction; we isolated early responsive genes of chickpea using PCR based suppression subtractive hybridization (SSH) strategy. We obtained ~250 unique genes after homology search and redundancy elimination. Based on their potential cellular functions, these genes were broadly classified into eleven different categories viz. stress, signaling, gene regulation, cellular metabolism and genes of unknown functions. Present study revealed few unexpected genes which have a possible role in induced immunity and disease progression. We employed macroarray, northern blot, real-time PCR and cluster analysis to develop transcript profiles. Most of the genes analyzed were early induced and were transcriptionally upregulated upon 24 h post inoculation. Our approach has rendered the isolation of early responsive genes involved in signaling and regulation of metabolic changes upon fungal infection. The information obtained will help to dissect the molecular mechanisms during compatible chickpea-Ascochyta interactions.
Functional characterization of genes involved in legume nodulation using hairy root cultures
(Springer Nature Publishing AG, 2020) Singh, Jawahar; Kumar, Kamal; Verma, Praveen K.
Legumes, the second most important crop to humans possess unique ability to fix atmospheric nitrogen, making them one of the major contributors to sustainable agriculture. In legumes, molecular characterization of genes by stable transformation is difficult due to their recalcitrant nature to the whole-plant regeneration in desired varieties. The Agrobacterium rhizogenes-mediated generation of transgenic hairy roots or composite plants may facilitate a rapid and convenient alternative to study nodule biology. Functional analysis of genes involved in legume nodulation has been proven as successful for model legumes, viz., Medicago truncatula and Lotus japonicus, using transgenic hairy roots. Besides sharing some common features of nodulation among legumes, the symbiotic signaling is a complex and specific process. Here, we describe an improved protocol for hairy root transformation of a legume crop chickpea (Cicer arietinum L.) and the method to study nodulation to uncover the signaling components. Using the described protocol, transgenic hairy roots were generated in chickpea and selected based on the red fluorescence protein (RFP) microscopy. This protocol can be extended to other underutilized legumes.
Genetic engineering to improve biotic stress tolerance in plants
(Springer Nature, 2017) Purayannur, Savithri; Kumar, Kamal; Verma, Praveen K.
Genetic engineering of plants for resistance is an effective method to counter pathogens and pests owing to the specificity and efficiency of the technology. The genes that have been used to genetically engineer resistance are as diverse as the diseases they act against. In cases where gene-for-gene resistance coded by resistance (R) genes exists, engineering resistance in plants becomes a straight path. Different classes of R genes have been engineered to provide resistance against viruses, bacteria, filamentous phytopathogens, and nematodes. Where the resistance mechanism is not R gene mediated, myriad of other mechanisms have been tried. These include the use of genes coding for antimicrobial compounds against bacterial and filamentous pathogens. The cloning of transcription factors, receptor genes, proteases, and genes involved in the systemic acquired resistance (SAR) has also been found to be effective. RNA silencing against specific genes involved in pathogenicity has proved to be an efficacious strategy against viruses and nematodes. Posttranscriptional silencing of genes coding for viral coat proteins has been successful, both scientifically and commercially. The most extensively used technology till date has been the introduction of cry genes from the bacterium Bacillus thuringiensis into plants to render them resistant against insect pests. Advances in molecular biology have paved the way for new strategies, the phenomenon of host-induced gene silencing (HIGS) being an interesting example. Amidst all the hue and cry raised against genetic modification of crops, it is necessary to highlight the scientific principles involved so as to make full use of a technology that could very well solve the problem of food shortage.
Genomics of filamentous phytopathogens: new insight in pathogenesis and virulence
(Westville Pub., New Delhi, 2012) Kumar, Kamal; Verma, Praveen K.
Plants being the primary producers are always engaged in complex dialogue with other organisms. From the start of agricultural practices, plant diseases have concerned humans as they limit the supply of food and with the growing population this concern has elevated. A general observation in nature is that most plants are resistant to most pathogens or a pathogen can only cause disease on one or a few related plant species. This observation suggests that plants possess a defense system against potential pathogens and only few adapted or evolved pathogens can breach this multi-layered defense. Understanding the molecular and biochemical complexities of plant-pathogen interactions and applying obtained knowledge for sustainable agriculture is the aim of research projects around the globe. In this aspect, the sequencing projects of many filamentous pathogens (oomycetes and fungi) have revealed the information about an arsenal of molecules that are the key pathogenicity determinants on plants. In this chapter, we have presented recent findings on the evolution and functions of these protein molecules delivered by filamentous pathogens for successful pathogenesis on host plants. This area of molecular plant pathology is emerging very fast as effectors and cognate host proteins are the front-runners in this co-evolving host-pathogen interaction.
Global transcriptome and co-expression analysis reveals robust host defence pathway reprogramming and identifies key regulators of early phases of Cicer-Ascochyta interactions
(American Phytopathological Society, 2022) Singh, Ritu; Dwivedi, Aditi; Singh, Yeshveer; Kumar, Kamal; Ranjan, Aashish; Verma, Praveen K.
Ascochyta blight (AB) caused by a filamentous fungus Ascochyta rabiei is a major threat to global chickpea production. The mechanisms underlying chickpea response to A. rabiei remain elusive. Here, we investigated the comparative transcriptional dynamics of AB-resistant and susceptible chickpea genotypes upon A. rabiei infection to understand the early host defence response. Our findings revealed that AB-resistant plants underwent rapid and extensive transcriptional reprogramming compared to susceptible host. At early stage (24-hpi), mainly cell wall remodeling and secondary metabolite pathways were highly activated, while DEGs related with signaling components viz. protein kinases, transcription factors, and hormonal pathways show remarkable upsurge at 72-hpi, especially in resistant genotype. Notably, our data suggests imperative role of JA, ET, and ABA signaling in providing immunity against A. rabiei. Furthermore, gene co-expression networks and modules corroborated the importance of cell wall remodeling, signal transduction, and phytohormone pathways. The hub genes such as MYB14, PRE6, and MADS-SOC1 discovered in these modules might be the master regulators governing chickpea immunity. Overall, we not only provide novel insights for comprehensive understanding of immune signaling components mediating AB resistance/susceptibility at early Cicer-Ascochyta interactions, but also offer a valuable resource for developing AB-resistant chickpea.
Modulation of fungal virulence through CRZ1 regulated F-BAR-dependent actin remodeling and endocytosis in chickpea infecting phytopathogen Ascochyta rabiei
(PLOS, 2021) Sinha, Manisha; Shree, Ankita; Singh, Kunal; Kumar, Kamal; Singh, Shreenivas Kumar; Kumar, Vimlesh; Verma, Praveen K.
Polarized hyphal growth of filamentous pathogenic fungi is an essential event for host penetration and colonization. The long-range early endosomal trafficking during hyphal growth is crucial for nutrient uptake, sensing of host-specific cues, and regulation of effector production. Bin1/Amphiphysin/Rvs167 (BAR) domain-containing proteins mediate fundamental cellular processes, including membrane remodeling and endocytosis. Here, we identified a F-BAR domain protein (ArF-BAR) in the necrotrophic fungus Ascochyta rabiei and demonstrate its involvement in endosome-dependent fungal virulence on the host plant Cicer arietinum. We show that ArF-BAR regulates endocytosis at the hyphal tip, localizes to the early endosomes, and is involved in actin dynamics. Functional studies involving gene knockout and complementation experiments reveal that ArF-BAR is necessary for virulence. The loss-of-function of ArF-BAR gene results in delayed formation of apical septum in fungal cells near growing hyphal tip that is crucial for host penetration, and impaired secretion of a candidate effector having secretory signal peptide for translocation across the endoplasmic reticulum membrane. The mRNA transcripts of ArF-BAR were induced in response to oxidative stress and infection. We also show that ArF-BAR is able to tubulate synthetic liposomes, suggesting the functional role of F-BAR domain in membrane tubule formation in vivo. Further, our studies identified a stress-induced transcription factor, ArCRZ1 (Calcineurin-responsive zinc finger 1), as key transcriptional regulator of ArF-BAR expression. We propose a model in which ArCRZ1 functions upstream of ArF-BAR to regulate A. rabiei virulence through a mechanism that involves endocytosis, effector secretion, and actin cytoskeleton regulation.
The nuclear effector ArPEC25 from the necrotrophic fungus Ascochyta rabiei targets the chickpea transcription factor CaβLIM1a and negatively modulates lignin biosynthesis, increasing host susceptibility
(Oxford University Press, 2023) Singh, Shreenivas Kumar; Shree, Ankita; Verma, Sandhya; Singh, Kunal; Kumar, Kamal; Srivastava, Vikas; Singh, Ritu; Saxena, Samiksha; Singh, Agam Prasad; Pandey, Ashutosh; Verma, Praveen K.
Fungal pathogens deploy a barrage of secreted effectors to subvert host immunity, often by evading, disrupting, or altering key components of transcription, defense signaling, and metabolic pathways. However, the underlying mechanisms of effectors and their host targets are largely unexplored in necrotrophic fungal pathogens. Here, we describe the effector protein Ascochyta rabiei PEXEL-like Effector Candidate 25 (ArPEC25), which is secreted by the necrotroph A. rabiei, the causal agent of Ascochyta blight disease in chickpea (Cicer arietinum), and is indispensable for virulence. After entering host cells, ArPEC25 localizes to the nucleus and targets the host LIM transcription factor CaβLIM1a. CaβLIM1a is a transcriptional regulator of CaPAL1, which encodes phenylalanine ammonia lyase, the regulatory, gatekeeping enzyme of the phenylpropanoid pathway. ArPEC25 inhibits the transactivation of CaβLIM1a by interfering with its DNA binding ability, resulting in negative regulation of the phenylpropanoid pathway and decreased levels of intermediates of lignin biosynthesis, thereby suppressing lignin production. Our findings illustrate the role of fungal effectors in enhancing virulence by targeting a key defense pathway that leads to the biosynthesis of various secondary metabolites and antifungal compounds. This study provides a template for the study of less explored necrotrophic effectors and their host target functions.
Phylogenomic analysis of MKKs and MAPKs from 16 legumes and detection of interacting pairs in chickpea divulge MAPK signalling modules
(Nature Publishing Group, 2017) Purayannur, Savithri; Kumar, Kamal; Kaladhar, Vemula Chandra; Verma, Praveen K.
The mitogen-activated protein kinase (MAPK)-mediated phosphorylation cascade is a vital component of plant cellular signalling. Despite this, MAPK signalling cascade is less characterized in crop legumes. To fill this void, we present here a comprehensive phylogeny of MAPK kinases (MKKs) and MAPKs identified from 16 legume species belonging to genistoid (Lupinus angustifolius), dalbergioid (Arachis spp.), phaseoloid (Glycine max, Cajanus cajan, Phaseolus vulgaris, and Vigna spp.), and galegoid (Cicer arietinum, Lotus japonicus, Medicago truncatula, Pisum sativum, Trifolium spp., and Vicia faba) clades. Using the genes of the diploid crop chickpea (C. arietinum), an exhaustive interaction analysis was performed between MKKs and MAPKs by split-ubiquitin based yeast two-hybrid (Y2H). Twenty seven interactions of varying strengths were identified between chickpea MKKs and MAPKs. These interactions were verified in planta by bimolecular fluorescence complementation (BiFC). As a first report in plants, four intra-molecular interactions of weak strength were identified within chickpea MKKs. Additionally; two TEOSINTE-BRANCHED1/CYCLOIDEA/PCF (TCP) transcription factors of class I were identified as novel down-stream interacting partners of seven MAPKs. We propose that this highly reliable MAPK interaction network, presented here for chickpea, can be utilized as a reference for legumes and thus will help in deciphering their role in legume-specific events.
Plant pathogen interactions: crop improvement under adverse conditions
(Springer, 2013) Kumar, Kamal; Verma, Praveen K.
Alleviating the crop loss due to biotic stress is the primary aim of plant biologists to achieve sustainable evergreen revolution in order to feed rapidly growing population. In nature, continuous evolution of plants while interacting with pathogens has generated a complex immune system that consists of preformed barriers and induced responses. The induced responses are further subdivided based upon the recognition of microbe-associated molecular patterns and effectors produced by pathogens; however, overlap exists between the downstream signaling pathways. In last decade, great deal of information about molecular aspects of plant–pathogen interactions has been generated which can be utilized for improving crops through genetic manipulation. Plant breeding has helped in the isolation of species-specific resistance components (R genes) from many plants. The molecular breeding techniques have also helped in pyramiding several components to a single variety, especially QTLs responsible for plant resistance, high yield, and nutritional quality. The identification of nonhost components in model plants and incorporation of genetically modified crops in our cropping system have raised hopes that nonhost resistance can be utilized for generating broad-spectrum pathogen tolerance breaking the barriers of species level resistance. This chapter describes the recent molecular aspects of plant–pathogen interactions focusing on the nonhost resistance components. Additionally, strategies like specific regulation of induced defense responses, manipulation of susceptibility factors, and host-induced gene silencing (HIGS) are discussed. The development of GM crops using such strategies will help in generating higher yields against pathogen infestations.
Transcript profiling reveals potential regulators for oxidative stress response of a necrotrophic chickpea pathogen Ascochyta rabiei
(Springer Nature Publishing AG, 2020) Maurya, Ranjeet; Singh, Yeshveer; Sinha, Manisha; Singh, Kunal; Mishra, Pallavi; Singh, Shreenivas Kumar; Verma, Sandhya; Prabha, Kanchan; Kumar, Kamal; Verma, Praveen K.
Necrotrophic pathogens experience host-generated oxidative stress during pathogenesis. They overcome such hostile environment by intricate mechanisms which are largely understudied. In this article, reference-based transcriptome analysis of a devastating Ascochyta Blight (AB) disease causing chickpea pathogen Ascochyta rabiei was explored to get insights into survival mechanisms under oxidative stress. Here, expression profling of mock-treated and menadione-treated fungus was carried out by RNA-Seq approach. A signifcant number of genes in response to oxidative stress were overrepresented, suggestive of a robust and coordinated defense system of A. rabiei. A total 73 diferentially expressed genes were fltered out from both the transcriptomes, among them 64 were up-regulated and 9 were found down-regulated. The gene ontology and KEGG mapping were conducted to comprehend the possible regulatory roles of diferentially expressed genes in metabolic networks and biosynthetic pathways. Transcript profling, KEGG pathway and gene ontology-based enrichment analysis revealed 12 (16.43%) stress responsive factors, 25 (34.24%) virulence associated genes, 10 (13.69%) putative efectors and 28 (38.35%) important interacting proteins associated with various metabolic pathways. In addition, genes with diferential expression were further explored for underlying putative pathogenicity factors. We identifed fve genes ST47_g10291, ST47_g9396, ST47_g10294, ST47_g4395, and ST47_g7191 that were common to stress and fungal pathogenicity. The factors recognized in this work can be used to establish molecular tools to explain the regulatory gene networks engaged in stress response of fungal pathogens and disease management.
WRKY domain-encoding genes of a crop legume chickpea (Cicer arietinum): comparative analysis with Medicago truncatula WRKY family and characterization of group-III gene(s)
(Oxford University Press, 2016) Kumar, Kamal; Srivastava, Vikas; Purayannur, Savithri; Kaladhar, V. Chandra; Cheruvu, Purnima Jaiswal; Verma, Praveen K.
The WRKY genes have been identified as important transcriptional modulators predominantly during the environmental stresses, but they also play critical role at various stages of plant life cycle. We report the identification of WRKY domain (WD)-encoding genes from galegoid clade legumes chickpea (Cicer arietinum L.) and barrel medic (Medicago truncatula). In total, 78 and 98 WD-encoding genes were found in chickpea and barrel medic, respectively. Comparative analysis suggests the presence of both conserved and unique WRKYs, and expansion of WRKY family in M. truncatula primarily by tandem duplication. Exclusively found in galegoid legumes, CaWRKY16 and its orthologues encode for a novel protein having a transmembrane and partial Exo70 domains flanking a group-III WD. Genomic region of galegoids, having CaWRKY16, is more dynamic when compared with millettioids. In onion cells, fused CaWRKY16-EYFP showed punctate fluorescent signals in cytoplasm. The chickpea WRKY group-III genes were further characterized for their transcript level modulation during pathogenic stress and treatments of abscisic acid, jasmonic acid, and salicylic acid (SA) by real-time PCR. Differential regulation of genes was observed during Ascochyta rabiei infection and SA treatment. Characterization of A. rabiei and SA inducible gene CaWRKY50 showed that it localizes to plant nucleus, binds to W-box, and have a C-terminal transactivation domain. Overexpression of CaWRKY50 in tobacco plants resulted in early flowering and senescence. The in-depth comparative account presented here for two legume WRKY genes will be of great utility in hastening functional characterization of crop legume WRKYs and will also help in characterization of Exo70Js.