Exogenous dsRNA-mediated field protection against Pigeonpea sterility mosaic emaravirus

Journal of Plant Biochemistry and Biotechnology - Pigeonpea sterility mosaic emaraviruses (PPSMVs) cause sterility mosaic disease in pigeonpea which significantly reduce the crop yield. Currently...     

Correction to: Exogenous dsRNA-mediated field protection against Pigeonpea sterility mosaic emaravirus

Journal of Plant Biochemistry and Biotechnology - Unfortunately, the title of the article was incorrectly published in the original publication. The correct title is updated.     

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. The origin of the DNA-B component remains unclear. The study described here was initiated to investigate the relationship between the DNA-A and DNA-B components of bipartite begomoviruses with a view to unraveling their evolutionary histories and providing information on the possible origin of the DNA-B component.     

Comparative characterization of small RNAs derived from an emaravirus and a geminivirus infecting pigeonpea

High throughput sequencing technologies, supported by bioinformatics tools are employed to retrieve small RNA sequence information derived from the nucleic acids of plant infecting viruses. In addition to characterization of the small RNAs to understand the biology of the virus, the small RNA sequence can be assembled to reconstitute viral genome sequence. For the first time the semiconductor based Ion Proton sequencing technology is used to sequence the small RNAs from pigeonpea (Cajanus cajan) plants infected by two distinct viruses with RNA and DNA as their genomes. The reconstitution of the viral genome sequence revealed that the pigeonpea plant from Kalaburagi (erstwhile Gulbarga, Karnataka state) was infected by an emaravirus species Pigeonpea sterility mosaic emaravirus 1 (PPSMV-1) and another plant from New Delhi was infected by a begomovirus species Mungbean yellow mosaic India virus (MYMIV). Characterization and comparison of small RNA sequences derived from both the viruses showed vast differences in their pattern of accumulation and their size classes. In the case of PPSMV-1, the 21 nt sized siRNAs accumulated at far greater levels followed by 22 and 24 nt siRNAs. Whereas in MYMIV, the proportion of accumulation of each size class of siRNAs was similar. Further the distribution of small RNAs across the genomes of PPSMV-1 and MYMIV was mapped and the density of small RNA accumulation showed a positive correlation with the GC content of viral sequence.     

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. In this study, we demonstrate that CBSD can be efficiently controlled using RNA interference (RNAi). Three RNAi constructs targeting the highland species were generated, consisting of the full-length (FL; 894 nucleotides), 397-nucleotide N-terminal and 491-nucleotide C-terminal portions of the coat protein (CP) gene of a Ugandan isolate of CBSUV (CBSUV-[UG:Nam:04]), and expressed constitutively in Nicotiana benthamiana. After challenge with CBSUV-[UG:Nam:04], plants homozygous for FL-CP showed the highest resistance, followed by the N-terminal and C-terminal lines with similar resistance. In the case of FL, approximately 85% of the transgenic plant lines produced were completely resistant. Some transgenic lines were also challenged with six distinct isolates representing both species: CBSV and CBSUV. In addition to nearly complete resistance to the homologous virus, two FL plant lines showed 100% resistance and two C-terminal lines expressed 50-100% resistance, whereas the N-terminal lines succumbed to the nonhomologous CBSV isolates. Northern blotting revealed a positive correlation between the level of transgene-specific small interfering RNAs detected in transgenic plants and the level of virus resistance. This is the first demonstration of RNAi-mediated resistance to CBSD and protection across very distant isolates (more than 25% in nucleotide sequence) belonging to two different species: Cassava brown streak virus and Cassava brown streak Uganda virus.     

Controlled micelle conjugation via charged peptide amphiphiles

Abstract We report the first demonstration of nonionic detergent micelle conjugation and phase separation using purpose‐synthesized, peptide amphiphiles, C₁₀‐(Asp)₅ and C₁₀‐(Lys)₅. Clustering is achieved in two different ways. Micelles containing the negatively charged peptide amphiphile C₁₀‐(Asp)₅ are conjugated (a) via a water‐soluble, penta‐Lys mediator or (b) to micelles containing the C₁₀‐(Lys)₅ peptide amphiphile. Both routes lead to phase separation in the form of oil‐rich globules visible in the light microscope. The hydrophobic nature of these regions leads to spontaneous partitioning of hydrophobic dyes into globules that were found to be stable for weeks to months. Extension of the conjugation mechanism to micelles containing a recently discovered, light‐driven proton pump King Sejong 1‐2 (KS1‐2) demonstrates that a membrane protein may be concentrated using peptide amphiphiles while preserving its native conformation as determined by characteristic UV absorption. The potential utility of these peptide amphiphiles for biophysical and biomedical applications is discussed.     

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. The study described here was aimed at investigating the effects of each virus encoded gene on the levels of developmental miRNAs to identify common trends between distinct begomoviruses.

Results

All genes encoded by four distinct begomoviruses (African cassava mosaic virus [ACMV], Cabbage leaf curl virus [CbLCuV], Tomato yellow leaf curl virus [TYLCV] and Cotton leaf curl virus/Cotton leaf curl betasatellite [CLCuV/CLCuMB]) were expressed from a Potato virus X (PVX) vector in Nicotiana benthamiana. Changes in the levels of ten miRNAs in response to the virus genes were determined by northern blotting using specific miRNA probes. For the monopartite begomoviruses (TYLCV and CLCuMV) the V2 gene product was identified as the major symptom determinant while for bipartite begomoviruses (ACMV and CbLCuV) more than one gene appears to contribute to symptoms and this is reflected in changes in miRNA levels. The phenotype induced by expression of the βC1 gene of the betasatellite CLCuMB was the most distinct and consisted of leaf curling, vein swelling, thick green veins and enations and the pattern of changes in miRNA levels was the most distinct.

Conclusions

Our results have identified symptom determinants encoded by begomoviruses and show that developmental abnormalities caused by transient expression of begomovirus genes correlates with altered levels of developmental miRNAs. Additionally, all begomovirus genes were shown to modulate miRNA levels, the first time this has been shown to be the case.