Differential expression of microRNAs in response to infection in differentially responding genotypes of papaya ( L.) and its wild relative.

Papaya ringspot virus (PRSV) is one of the most devastating viruses of papaya that has significantly hampered papaya production across the globe. Although PRSV resistance is known in some of its wild relatives, such as and in some of the improved papaya genotypes, the molecular basis of this resistance mechanism has not been studied and understood. Plant microRNAs are an important class of small RNAs that regulate the gene expression in several plant species against the invading plant pathogens.

A novel tasi RNA-based micro RNA-induced gene silencing strategy to tackle multiple pests and pathogens in cotton (Gossypium hirsutum L.).

This study demonstrates the combinatorial management of multiple pests through a trans-acting siRNA (tasiRNA)-based micro RNA-induced gene silencing (MIGS) strategy. Transgenic cotton events demonstrated improved efficacy against cotton leaf curl disease, cotton leaf hopper and root-knot nematode. Cotton (Gossypium hirsutum L.

RNA-Based Vaccination of Plants for Control of Viruses.

Plant viruses cause nearly half of the emerging plant diseases worldwide, contributing to 10-15% of crop yield losses. Control of plant viral diseases is mainly accomplished by extensive chemical applications targeting the vectors (i.e.

Characterization of the functional domains of nuclear shuttle protein (NSP) of Indian cassava mosaic virus using green fluorescent protein as reporter.

Indian cassava mosaic virus (ICMV), responsible for the cassava mosaic disease in India, harbours two circular genomic components, DNA-A and DNA-B; the former being responsible for the encapsidation and replication and the latter for intra- and inter-cellular movement of the viral DNA. Two proteins, encoded by DNA-B, the movement protein (MP) and the nuclear shuttle protein (NSP), act in concert on the newly replicated viral DNA to move it from the nucleus to the cell periphery. To map the functional domains of NSP, the intra-cellular localization of its full-length protein and deletion derivatives was studied in the epidermal cells of detached leaves of the laboratory host plant, Nicotiana benthamiana, where the target proteins were transiently expressed as GFP fusions.

The Citrus yellow mosaic badnavirus ORFI functions as a RNA-silencing suppressor.

Citrus yellow mosaic badnavirus (CMBV) causes mosaic disease in all economically important citrus cultivars of India, with losses reaching up to 70%. CMBV belongs to the genus Badnavirus, family Caulimoviridae, possessing a circular double-stranded (ds) DNA genome with six open reading frames (ORFs I to VI), whose functions are yet to be deciphered. The RNA-silencing suppressor (RSS) activity has not been assigned to any CMBV ORF as yet.

Micro RNA-induced gene silencing strategy for the delivery of siRNAs targeting Meloidogyne incognita in a model plant Nicotiana benthamiana.

Background: Occurrence of multiple biotic stresses on crop plants result in drastic yield losses which may have severe impact on the food security. It is a challenge to design strategies for simultaneous management of these multiple stresses. Hence, establishment of innovative approaches that aid in their management is critical.

DsRNA-mediated protection against two isolates of Papaya ringspot virus through topical application of dsRNA in papaya.

Papaya ringspot virus (PRSV) infections in papaya result in heavy yield losses, severely affecting the papaya industry worldwide, and hence warranting for effective control measures. In the past, transgenic papaya cultivars were developed that overexpressed parts of the PRSV genome and exhibited high levels of virus resistance. In the present study, a non-transgenic approach was employed, in which in vitro produced dsRNA molecules derived from a PRSV isolate from South India (PRSV-Tirupati) was tested for dsRNA-mediated protection against two isolates of PRSV through topical application of the dsRNA on papaya.

Sequence diversity studies of papaya ringspot virus isolates in South India reveal higher variability and recombination in the 5'-terminal gene sequences.

Papaya ringspot virus (PRSV) is one of the most devastating viruses which causes huge damage to papaya plantations across the globe. PRSV is a positive sense RNA virus encoding for a polyprotein that is processed into ten proteins. In this study for the first time we analyzed the variability for 15 PRSV isolates from a selected geographical region of a South Indian state Karnataka, which is under intensive papaya cultivation.

First Complete Genome Sequence of a Distinct Papaya Ringspot Virus Isolate from the Northeastern Region of India.

This is the first report of a (PRSV) isolate from the northeastern region of India. The nucleotide sequence identity of PRSV-Meghalaya was in the range of 72.6 to 82.

RNAi-derived transgenic resistance to Mungbean yellow mosaic India virus in cowpea.

Cowpea is an important grain legume crop of Africa, Latin America, and Southeast Asia. Leaf curl and golden mosaic diseases caused by Mungbean yellow mosaic India virus (MYMIV) have emerged as most devastating viral diseases of cowpea in Southeast Asia. In this study, we employed RNA interference (RNAi) strategy to control cowpea-infecting MYMIV.

Variability of Emaravirus Species Associated with Sterility Mosaic Disease of Pigeonpea in India Provides Evidence of Segment Reassortment.

Sterility mosaic disease (SMD) of pigeonpea is a serious constraint for cultivation of pigeonpea in India and other South Asian countries. SMD of pigeonpea is associated with two distinct emaraviruses, Pigeonpea sterility mosaic virus 1 (PPSMV-1) and Pigeonpea sterility mosaic virus 2 (PPSMV-2), with genomes consisting of five and six negative-sense RNA segments, respectively. The recently published genome sequences of both PPSMV-1 and PPSMV-2 are from a single location, Patancheru from the state of Telangana in India.

Emergence of a Latent Indian Cassava Mosaic Virus from Cassava Which Recovered from Infection by a Non-Persistent Sri Lankan Cassava Mosaic Virus.

The major threat for cassava cultivation on the Indian subcontinent is cassava mosaic disease (CMD) caused by cassava mosaic geminiviruses which are bipartite begomoviruses with DNA A and DNA B components. Indian cassava mosaic virus (ICMV) and Sri Lankan cassava mosaic virus (SLCMV) cause CMD in India. Two isolates of SLCMV infected the cassava cultivar Sengutchi in the fields near Malappuram and Thiruvananthapuram cities of Kerala State, India.

Artificial microRNA-derived resistance to Cassava brown streak disease.

Artificial miRNAs (amiRNA) were generated targeting conserved sequences within the genomes of the two causal agents of Cassava brown streak disease (CBSD): Cassava brown streak virus (CBSV) and Ugandan cassava brown streak virus (UCBSV). Transient expression studies on ten amiRNAs targeting 21nt conserved sequences of P1(CBSV and UCBSV), P3(CBSV and UCBSV), CI(UCBSV), NIb(CBSV and UCBSV), CP(UCBSV) and the un-translated region (3'-UTR) were tested in Nicotiana benthamiana. Four out of the ten amiRNAs expressed the corresponding amiRNA at high levels.

Mapping and identification of cassava mosaic geminivirus DNA-A and DNA-B genome sequences for efficient siRNA expression and RNAi based virus resistance by transient agro-infiltration studies.

Geminiviruses are among the most serious pathogens of many economically important crop plants and RNA interference (RNAi) is an important strategy for their control. Although any fragment of a viral genome can be used to generate a double stranded (ds) RNA trigger, the precursor for generation of siRNAs, the exact sequence and size requirements for efficient gene silencing and virus resistance have so far not been investigated. Previous efforts to control geminiviruses by gene silencing mostly targeted AC1, the gene encoding replication-associated protein.

Cassava brown streak disease: a threat to food security in Africa.

Cassava brown streak disease (CBSD) has emerged as the most important viral disease of cassava (Manihot esculenta) in Africa and is a major threat to food security. CBSD is caused by two distinct species of ipomoviruses, Cassava brown streak virus and Ugandan cassava brown streak virus, belonging to the family Potyviridae. Previously, CBSD was reported only from the coastal lowlands of East Africa, but recently it has begun to spread as an epidemic throughout the Great Lakes region of East and Central Africa.

Studies on differential behavior of cassava mosaic geminivirus DNA components, symptom recovery patterns, and their siRNA profiles.

Cassava mosaic disease caused by cassava mosaic geminiviruses (CMGs) with bipartite genome organization is a major constraint for production of cassava in the African continent and the Indian sub-continent. Currently, there are eleven recognized species of CMGs, and several diverse isolates represent them, with vast amount of sequence variability, reflecting into diversity of symptom severity/phenotypes. Here, we make a systematic effort to study the infection dynamics of several species of CMGs and their isolates.

Pigeonpea sterility mosaic virus: a legume-infecting Emaravirus from South Asia.

Unlabelled: Pigeonpea sterility mosaic virus (PPSMV), a species of the genus Emaravirus, is the causal agent of sterility mosaic disease (SMD) of pigeonpea [Cajanus cajan (L.) Millsp]. This disease, dubbed the 'green plague', as the infected plants remain in the vegetative state without flower production, has been reported from India and a few other South-East Asian countries.

Tropical food legumes: virus diseases of economic importance and their control.

Diverse array of food legume crops (Fabaceae: Papilionoideae) have been adopted worldwide for their protein-rich seed. Choice of legumes and their importance vary in different parts of the world. The economically important legumes are severely affected by a range of virus diseases causing significant economic losses due to reduction in grain production, poor quality seed, and costs incurred in phytosanitation and disease control.

Light intensity and temperature affect systemic spread of silencing signal in transient agroinfiltration studies.

RNA silencing is a sequence-specific post-transcriptional gene inactivation mechanism that operates in diverse organisms and that can extend beyond its site of initiation, owing to the movement of the silencing signal, called non-autonomous gene silencing. Previous studies have shown that several factors manifest the movement of the silencing signal, such as the size (21 or 24 nucleotides) of the secondary small interfering RNA (siRNA) produced, the steady-state concentration of siRNAs and their cognate messenger RNA (mRNA) or a change in the sink-source status of plant parts affecting phloem translocation. Our study shows that both light intensity and temperature have a significant impact on the systemic movement of the silencing signal in transient agroinfiltration studies in Nicotiana benthamiana.

RNAi-mediated resistance to Cassava brown streak Uganda virus in transgenic cassava.

Cassava brown streak disease (CBSD), caused by Cassava brown streak Uganda virus (CBSUV) and Cassava brown streak virus (CBSV), is of new epidemic importance to cassava (Manihot esculenta Crantz) production in East Africa, and an emerging threat to the crop in Central and West Africa. This study demonstrates that at least one of these two ipomoviruses, CBSUV, can be efficiently controlled using RNA interference (RNAi) technology in cassava. An RNAi construct targeting the near full-length coat protein (FL-CP) of CBSUV was expressed constitutively as a hairpin construct in cassava.

Comparison of phenotypes produced in response to transient expression of genes encoded by four distinct begomoviruses in Nicotiana benthamiana and their correlation with the levels of developmental miRNAs.

Background: Whitefly-transmitted geminiviruses (begomoviruses) are a major limiting factor for the production of numerous dicotyledonous crops throughout the world. Begomoviruses differ in the number of components that make up their genomes and association with satellites, and yet they cause strikingly similar phenotypes, such as leaf curling, chlorosis and stunted plant growth. MicroRNAs (miRNAs) are small endogenous RNAs that regulate plant growth and development.

A common set of developmental miRNAs are upregulated in Nicotiana benthamiana by diverse begomoviruses.

Background: Begomoviruses are single-stranded DNA viruses that cause economically important diseases of many crops throughout the world and induce symptoms in plants, including enations, leaf curling and stunting, that resemble developmental abnormalities. MicroRNAs (miRNAs) are small endogenous RNAs that are involved in a variety of activities, including plant development, signal transduction and protein degradation, as well as response to environmental stress, and pathogen invasion.

Results: The present study was aimed at understanding the deregulation of miRNAs upon begomovirus infection.

RNAi-mediated resistance to diverse isolates belonging to two virus species involved in Cassava brown streak disease.

Cassava brown streak disease (CBSD) is emerging as one of the most important viral diseases of cassava (Manihot esculenta) and is considered today as the biggest threat to cassava cultivation in East Africa. The disease is caused by isolates of at least two phylogenetically distinct species of single-stranded RNA viruses belonging to the family Potyviridae, genus Ipomovirus. The two species are present predominantly in the coastal lowland [Cassava brown streak virus (CBSV); Tanzania and Mozambique] and highland [Cassava brown streak Uganda virus (CBSUV); Lake Victoria Basin, Uganda, Kenya and Malawi] in East Africa.

Transmission studies with Cassava brown streak Uganda virus (Potyviridae: Ipomovirus) and its interaction with abiotic and biotic factors in Nicotiana benthamiana.

Cassava brown streak disease (CBSD), caused by two distinct species, Cassava brown streak Uganda virus (CBSUV) and Cassava brown streak virus (CBSV), is a major constraint to cassava (Manihot esculenta Crantz) production in Africa. Absence of infectious clones of CBSUV or CBSV and the lack of efficient means of mechanical transmission of CBSD has hampered laboratory studies of this disease. Mechanical transmission, achieved mainly by plant sap inoculation, is a widely used technique for characterizing plant viruses.

Distinct evolutionary histories of the DNA-A and DNA-B components of bipartite begomoviruses.

Background: Viruses of the genus Begomovirus (family Geminiviridae) have genomes consisting of either one or two genomic components. The component of bipartite begomoviruses known as DNA-A is homologous to the genomes of all geminiviruses and encodes proteins required for replication, control of gene expression, overcoming host defenses, encapsidation and insect transmission. The second component, referred to as DNA-B, encodes two proteins with functions in intra- and intercellular movement in host plants.