Fig 4 - uploaded by Gulzar S Sanghera
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Formation of RISC assembly complexes. The asymmetric siRNA molecule bound by Dcr2 and R2D2 which sense the stability at both ends of siRNA duplex. This initiation complex is known as RDI complex (Dcr2 –R2D2 initiation complex).Dcr2 is eventually exchanged with Ago2, which by virtue of its PIWI domain cleaves the passenger strand which results in the formation of an active RISC loading complex.
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... This RNA silencing process is called quelling in fungi (Duan et al. 2012). RNA-mediated gene silencing involved in switching off the expression of specific genes of fungi responsible for pathogenicity and is an advanced approach for enhancing resistance against fungi (Sanghera et al. 2009). Plant pathogenic fungi develop direct connections with their host plants via a specialized structure known as haustorium which act as an interface for signal exchange as well as nutrient uptake (Panstruga 2003). ...
Take-all disease is the most important root disease in wheat caused by the fungus Gaeumannomyces graminis var. tritici. Considering economic importance of wheat, the disease is a serious problem worldwide. The effective and economically feasible control of the disease is a major problem around the globe. Strategies based on chemical control of take-all have been inefficient due to that the control of soil-borne pathogen is depending on the use of soil fumigants of broad-spectrum gaseous as methyl bromide, chloropicrin, metam sodium which are unacceptable in agriculture. The discovery of suppressive soils involving major plant–microbe interactions resulted in some significant advances, particularly in elucidating the role of the enzymes. These microbes through several mechanisms including the biocontrol, antibiosis, systemic resistance in plants (ISR) have made advanced progress in identifying major factors involved host range and pathogenicity determining as well as recognizing the mechanism that explains disease suppression. Moreover, the high-throughput sequencing techniques open new avenues for microbial control of plant disease considering, for example, the engineering plant microbiome to improve the plant health and food security.KeywordsWheatRoot diseaseSoil-borne pathogenBiological control
Gaeumannomyces graminis
... This RNA silencing process is called quelling in fungi (Duan et al. 2012). RNA-mediated gene silencing involved in switching off the expression of specific genes of fungi responsible for pathogenicity and is an advanced approach for enhancing resistance against fungi (Sanghera et al. 2009). Plant pathogenic fungi develop direct connections with their host plants via a specialized structure known as haustorium which act as an interface for signal exchange as well as nutrient uptake (Panstruga 2003). ...
The climate change and ever-increasing population has stressed the plant scientists to devise economically viable, ecologically safe and socially acceptable agricultural practices that can keep the menace of plant disease losses under economic threshold levels. In the recent past, the philosophy of crop protection has shifted from the use of environmentally unsafe chemical pesticides to the eco-friendly approaches. The conventional methods of plant disease management like cultural practices, biological control, chemical control, and natural resistance are still in practice, but are not adequate to control many destructive diseases. The sustenance of disease resistant varieties under variable eco-systems remained a challenge to the breeders due to the fast-evolving nature of many plant pathogens resulting in the breakdown of the R-genes. This emphasized the plant breeders to have a wide range of genetic options to diversify the resistance traits having potential to reduce the pressure of pest evolution. Hence the approaches for the genetic improvement of crops are expanded from simple selection to the genome editing. The recombinant DNA technology and genetic transformation techniques offered unique opportunities to transfer resistance genes beyond crop plant gene pools. The effective strategies for engineering disease resistance include exploitation of genes related to pathogenesis-related protein (PR proteins), upregulation of plant structural defense mechanism, disarming host susceptibility genes and to express proteins or antimicrobial compounds that are harmful to the pathogens. The RNA-mediated gene silencing is another approach to switch off specific genes by inserting double-stranded RNA and has been successfully exploited in disease management especially the viral pathogens. With the advent of genome editing technologies, now it is possible to edit crop genome by editing the sequences of a specific gene instead of complete gene deletion and it can be exploited to modify the genes associated with plant immunity. To achieve the targets of developing eco-friendly and durable pathogen management, there is a need to design strategies that can complement conventional and modern techniques.
... The high level of genetic complexity in sugarcane creates challenges in the application of both conventional and molecular breeding to the genetic improvement of sugarcane. as a sugar and energy crop [56]. Recent technology developments indicate the potential to greatly increase our understanding of the sugarcane plant disease management by application of emerging technologies like tissue culture, genetic transformation [55], RNAi [60], quarm quenching [33], ABC transporters [34], microarray [68] etc. ...
Sugarcane is an important agro-industrial crop cultivated for sugar and other by-products. The future of sustainable agriculture will rely on the integration of biotechnology with traditional agricultural practices. Diseases can be caused by a variety of plant pathogens including fungi, others and their management requires the use of techniques in transgenic technology, molecular biology, and genetics. These include: genes that express proteins, peptides, or antimicrobial compounds that are directly toxic to pathogens or that reduce their growth in situ; gene products that directly inhibit pathogen virulence products or enhance plant structural defense genes, that directly or indirectly activate general plant defense responses; and resistance genes involved in the hypersensitive response and in the interactions with a virulence factors. This chapter discusses the key recent approaches to manage different pathogens within the context of recent developments in biotechnology and plant science.
... and (4) Low fertility, seed set, and germination rates. As for genetic engineering and gene transfer, over the past few decades, this approach has been used to complement conventional breeding [6]. Undoubtedly, advances in modern technologies such as transcriptomics, proteomics, and metabolomics are likely to benefit breeding and genetic engineering strategies from an understanding of plant metabolic pathways and the role of key genes associated with their regulation. ...
... RNA mediated gene silencing is a quite advanced approach for enhancing resistance against fungi. It is a tool for reverse genetics which is involved in switching of the expression of certain genes by targeting specific genes of fungi responsible for pathogenicity [54] . The expression of genes is silenced either at transcriptional or post-transcriptional level i.e., epigenetic modification at transcriptional level and degradation of specific nucleotide sequences of mRNA through introduction of dsRNA at post transcriptional level [55] . ...
Pathogenic fungi are associated with devastating plant diseases since centuries, causing huge epidemics in history. Plant pathogenic fungi have been managed by employing multiple strategies including chemical control, biological control, organic management etc. Despite, being a quick mean to provide an effective control, chemical management has hazardous effects on human health and environment. Fungal pathogens can be managed by using transgenic technology, molecular technology and other approaches aiming at genetic manipulation. Genetic engineering technology has been widely researched in recent era and many transgenic plants with remarkable resistance against potential fungal pathogens have been developed. Transgenic plants have the advantage of being environment friendly. Transgenic technology has aimed at engineering for the expression of many anti-fungal genes including pathogenesis related (PR) proteins, phytoalexins, hydrolytic enzymes, antimicrobial peptides and resistance (R) genes. The expression of these anti-fungal genes was successfully imparted into plants via, transgenic technology contributing to significant resistance against fungal pathogens. Another approach include RNA silencing "switching off" the expression of specific genes by introducing double stranded RNA's is gaining huge importance since last decade. Many fungal genes encoding for pathogenecity factors have been sequenced successfully. The application of RNA silencing against fungal pathogens is still limited. In this review all strategies which have been employed so far to enhance resistance against fungi will be discussed briefly.
... Genetic engineering technology has proved to be beneficial in managing fungal (Lin et al., 2004;Wani, 2010, Parkhi et. al., 2010aand 2010bKumar et al., 2012), viral (Wani and Sanghera, 2010b) and bacterial (Jube and Borthakur, 2007;Sanghera et al., 2009) diseases in plants. Additionally, genetic engineering has the potential to increase disease tolerance to a range of pathogens, with no side effect on beneficial soil microbes (Liu et al., 2005).Genetic engineering of diseaseresistance through transfer of plant defense-related genes or pathogen-originated genes into crops is valuable in terms of cost, efficacy and reduction of pesticide usage (Shah et al., 1997;Salmeron and Vernooij, 1998;Rommens and Kishore, 2000;Stuiver and Custers, 2001). ...
In the world of plants the non-expresser of pathogenesis-related gene 1 (NPR1) is a key regulator of salicylic acid (SA) mediated systemic acquired resistance (SAR). It also plays an important role in the Jasmonic acid (JA) induced systemic resistance (ISR) signaling pathway and also arbitrates the crosstalk between SA-JA defense pathways to fine-tune defense responses of whole plant system. NPR1 is one of the most agronomically important genes which are under extensive research for development of transgenic with broad spectrum disease resistance. In this study, we have isolated NPR1
gene from genomic DNA of Arabidopsis thaliana ecotype Col-0. 2277 bp AtNPR1 PCR product with single complete open reading frame has been cloned in pJET1.2 cloning vector and sequence characterized. AtNPR1 encode a putative functional protein of 593 amino acids long. Sequence analysis in NCBI CDD domain reveals presence of important Ankyrin repeats domain and a BTB/POZ domain, found in some regulatory proteins and both of which mediate protein-protein interactions. Among the SARrelated gene with vast potential in disease resistance, AtNPR1 is a leading candidate represents promising results in engineering resistance to broad-spectrum of pathogens.
... Small RNAs, including microRNAs (miRNAs) (Bartel, 2004), small interfering RNAs (siRNAs) (Baulcombe, 2004), and transacting siRNAs (tasiRNAs), mediate post-transcriptional regulation, RNA-directed DNA methylation, and chromatin remodeling. RNA interference (RNAi) is an evolutionarily conserved mechanism for modulating gene expression (Sanghera et al., 2010). Evidence for the involvement of RNA-mediated gene regulation in heterosis came from characterization of five miRNA families in maize, and some miRNAs are differentially expressed between hybrid and its parental inbred lines (Mica et al., 2006) proposed that if siRNAs from one inbred do not match genes from the other inbred, the resulting hybrid could exhibit novel patterns of gene expression, including overdominance or under-dominance. ...
Abstarct: Heterosis, or hybrid vigor, an unsolved puzzle and a 'miraculous' agricultural phenomenon, refers to the phenomenon in which hybrid progeny of two inbred varieties exhibits enhanced growth or agronomic performance. Converse of hybrid vigour is 'inbreeding depression' caused by increased homozygosity of individuals, which reduces survival and fertility of offspring. Agricultural heterosis was observed nearly 100 years ago when hybrid plants out yielded their inbred parents and today this "hybrid vigor" is a major provider for global food production. One of the most promising approaches to unravel the genetic basis for heterosis at the molecular level emerged through the availability of molecular markers, as they have provided a powerful approach to map and subsequently identify genes involved in complex traits. Molecular marker technology was used to identify the genomic regions that contribute to heterosis for a trait of interest. The advancements in functional genomics have created a novel avenue to study the genetic basis of heterosis at the gene-expression level. The genetic basis of heterosis has been debated with respect to the relative importance of dominance, overdominance and epistasis; where one of the problems has been the use of whole genome segregating populations where interactions often mask the effects of individual quantitative trait loci. In this review the phenomenon of heterosis and the modern concept of its genetic and molecular basis will be discussed.
... Expression of dsRNA for a secreted Meloidogyne parasitism gene 16D10 decreased eggs per gram of root by 69-93%. The comprehensive information on this technology was further elaborated by Sanghera et al. (2010a) who reviewed the potential exploitation of RNAi in commercial nematode control through trans-genic plant-delivered dsRNA. examples showing the utilization of transgenic technology to develop nematode tolerant transgenic in different crops are given in Table 5. ...
Population growth and climate change posed a challenge to breed designer crops in an environment having biotic and abiotic threats. Though, integrated pest and disease management has placed hopes on host plant resistance, the evolution of new races and biotypes for important pathogens and parasites of plants is still a growing threat to crop production worldwide. Use of agrochemicals for control of crop pests and diseases is however inefficient and environmentally unsound. The conventional host-plant resistance to various biotic stresses involves quantitative traits at several loci. The advent of molecular genetic technologies have advanced our understanding regarding biotic stress resistance mechanisms. With the advent of genetic transformation techniques, it has become possible to clone and insert genes into the crop plants to confer resistance to different biotic stresses. Reinforcement of resistance against insect- pests and pathogens attack using genetic engineering has proven to be an effective strategy to develop resistant crop plants and that could offer a remedy, allowing more precise targeting of pest and disease management. Present paper deals with the reports where the function of a specific gene towards improving the performance of a plant against different biotic stresses like pests, diseases (fungal, bacterial, viral) and nematodes have been analysed using transgenic approach.
... Small RNAs, including microRNAs (miRNAs) (Bartel, 2004), small interfering RNAs (siRNAs) (Baulcombe, 2004), and transacting siRNAs (tasiRNAs), mediate post-transcriptional regulation, RNA-directed DNA methylation, and chromatin remodeling. RNA interference (RNAi) is an evolutionarily conserved mechanism for modulating gene expression (Sanghera et al., 2010). Evidence for the involvement of RNA-mediated gene regulation in heterosis came from characterization of five miRNA families in maize, and some miRNAs are differentially expressed between hybrid and its parental inbred lines (Mica et al., 2006) proposed that if siRNAs from one inbred do not match genes from the other inbred, the resulting hybrid could exhibit novel patterns of gene expression, including overdominance or under-dominance. ...
Heterosis, or hybrid vigor, an unsolved puzzle and a ‘miraculous’ agricultural phenomenon, refers to the
phenomenon in which hybrid progeny of two inbred varieties exhibits enhanced growth or agronomic performance.
Converse of hybrid vigour is ‘inbreeding depression’ caused by increased homozygosity of individuals, which
reduces survival and fertility of offspring. Agricultural heterosis was observed nearly 100 years ago when hybrid
plants out yielded their inbred parents and today this “hybrid vigor” is a major provider for global food production.
One of the most promising approaches to unravel the genetic basis for heterosis at the molecular level emerged
through the availability of molecular markers, as they have provided a powerful approach to map and subsequently
identify genes involved in complex traits. Molecular marker technology was used to identify the genomic regions
that contribute to heterosis for a trait of interest. The advancements in functional genomics have created a novel
avenue to study the genetic basis of heterosis at the gene-expression level. The genetic basis of heterosis has been
debated with respect to the relative importance of dominance, overdominance and epistasis; where one of the
problems has been the use of whole genome segregating populations where interactions often mask the effects of
individual quantitative trait loci. In this review the phenomenon of heterosis and the modern concept of its genetic
and molecular basis will be discussed.
... Expression of dsRNA for a secreted Meloidogyne parasitism gene 16D10 decreased eggs per gram of root by 69–93%. The comprehensive information on this technology was further elaborated by Sanghera et al. (2010a) who reviewed the potential exploitation of RNAi in commercial nematode control through transgenic plant-delivered dsRNA. examples showing the utilization of transgenic technology to develop nematode tolerant transgenic in different crops are given inTable 5. ...
