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Rajeevkumar S.,Central Institute of Medicinal and Aromatic Plants Research Center | Anunanthini P.,Bharathiar University | Sathishkumar R.,Bharathiar University
Frontiers in Plant Science | Year: 2015

Epigenetic silencing is a natural phenomenon in which the expression of genes is regulated through modifications of DNA, RNA, or histone proteins. It is a mechanism for defending host genomes against the effects of transposable elements and viral infection, and acts as a modulator of expression of duplicated gene family members and as a silencer of transgenes. A major breakthrough in understanding the mechanism of epigenetic silencing was the discovery of silencing in transgenic tobacco plants due to the interaction between two homologous promoters. The molecular mechanism of epigenetic mechanism is highly complicated and it is not completely understood yet. Two different molecular routes have been proposed for this, that is, transcriptional gene silencing, which is associated with heavy methylation of promoter regions and blocks the transcription of transgenes, and post-transcriptional gene silencing (PTGS), the basic mechanism is degradation of the cytosolic mRNA of transgenes or endogenous genes. Undesired transgene silencing is of major concern in the transgenic technologies used in crop improvement. A complete understanding of this phenomenon will be very useful for transgenic applications, where silencing of specific genes is required. The current status of epigenetic silencing in transgenic technology is discussed and summarized in this mini-review. © 2015 Rajeevkumar, Anunanthini and Sathishkumar. Source


Campos M.D.,University of Evora | Nogales A.,University of Evora | Cardoso H.G.,University of Evora | Kumar S.R.,University of Evora | And 4 more authors.
Frontiers in Genetics | Year: 2016

Stress-adaptive cell plasticity in target tissues and cells for plant biomass growth is important for yield stability. In vitro systems with reproducible cell plasticity can help to identify relevant metabolic and molecular events during early cell reprogramming. In carrot, regulation of the central root meristem is a critical target for yield-determining secondary growth. Calorespirometry, a tool previously identified as promising for predictive growth phenotyping has been applied to measure the respiration rate in carrot meristem. In a carrot primary culture system (PCS), this tool allowed identifying an early peak related with structural biomass formation during lag phase of growth, around the 4th day of culture. In the present study, we report a dynamic and correlated expression of carrot AOX genes (DcAOX1 and DcAOX2a) during PCS lag phase and during exponential growth. Both genes showed an increase in transcript levels until 36 h after explant inoculation, and a subsequent down-regulation, before the initiation of exponential growth. In PCS growing at two different temperatures (21°C and 28°C), DcAOX1 was also found to be more expressed in the highest temperature. DcAOX genes' were further explored in a plant pot experiment in response to chilling, which confirmed the early AOX transcript increase prior to the induction of a specific anti-freezing gene. Our findings point to DcAOX1 and DcAOX2a as being reasonable candidates for functional marker development related to early cell reprogramming. While the genomic sequence of DcAOX2a was previously described, we characterize here the complete genomic sequence of DcAOX1. © 2016 Campos, Nogales, Cardoso, Kumar, Nobre, Sathishkumar and Arnholdt-Schmitt. Source


Mallavarapu G.R.,Renaissance Temple Bells | Syamasundar K.V.,Central Institute of Medicinal and Aromatic Plants Research Center | Rameshc S.,Research Center | Rajeswara Rao B.R.,Central Institute of Medicinal and Aromatic Plants Research Center
Natural Product Communications | Year: 2012

The essential oils isolated from vetiver [Vetiveria zizanioides (L.) Nash.] roots collected from four locations in south India were analyzed by GC-FID and GCMS. Eighty constituents, representing 94.5-97.8% of the oils, have been identified. The oils from Bangalore, Hyderabad, Kundapur, and Mettupalayam were rich in sesquiterpenes and oxygenated sesquiterpenes with cedrane, bisabolane, eudesmane, eremophilane, and zizaane skeletons. The main components of the four essential oils were: eudesma-4,6-diene (δ-selinene) + β-vetispirene (3.9-6.1%), β-vetivenene (0.9-9.4%), 13-nor-trans-eudesma-4(15),7-dien-11- one + amorph-4-en-10-ol (5.0-6.4%), trans-eudesma-4(15),7-dien-12-ol (vetiselinenol) + (E)-opposita-4(15),7(11)-dien-12-ol (3.7-5.9%), eremophila-1(10),11-dien- 2α-ol (nootkatol) + ziza-6(13)-en-12-ol (khusimol) (16.1-19.2%), and eremophila-1(10),7(11)-dien-2α-ol (isonootkatol) + (E)-eremophila-1(10),7(11)-12-ol (isovalencenol) (5.6-6.9%). The important compounds that impart the characteristic vetiver odor are: khusimene, δ-selinene, β-vetivenene, cyclocopacamphan-12-ol (epimers A and B), vetiselinenol, khusimol, isovalencenol, khusimone, α-vetivone, and β-vetivone. The chemical profiles of the oils are comparable to Haitian vetiver oil. Source


Rajeswara Rao B.R.,Central Institute of Medicinal and Aromatic Plants Research Center | Rajput D.K.,Central Institute of Medicinal and Aromatic Plants Research Center | Mallavarapu G.R.,A602 Renaissance Temple Bells
Food Chemistry | Year: 2011

Wild and cultivated Murraya koenigii leaf essential oils collected from ten Indian locations were investigated for their chemical diversity. The essential oil yields ranged from 1.2-2.5 ml/kg biomass. GC and GC-MS analyses revealed ninety compounds, constituting 93.8-99.9% of the essential oils. The highest concentrations of α-pinene (55.7%) and β-pinene (10.6%) were found in the essential oil of wild plants. α-Pinene (13.5-35.7%) and/or β-phellandrene (14.7-50.2%) were the dominant essential oil constituents of seven locations. (E)-Caryophyllene (26.5%, 31.5%) and α-selinene (9.5%, 10.4%) were the principal essential oil components of two locations. The odour profiles of the essential oils were distinctly different. Tetradecanoic acid, hexadecanoic acid, piperitone, cada-1,4-diene,1,10-di-epi-cubenol, γ-eudesmol, α-muurolol, (Z,E)-farnesol and (Z,Z)-farnesol are identified for the first time in curry leaf essential oil. The chemical diversity of the oils offers opportunity to flavourists to choose curry leaves and essential oils with preferential flavour composition. © 2010 Elsevier Ltd. All rights reserved. Source


Rao B.R.R.,Central Institute of Medicinal and Aromatic Plants Research Center | Rajput D.K.,Central Institute of Medicinal and Aromatic Plants Research Center
Industrial Crops and Products | Year: 2011

A field investigation was carried out on red sandy soil in the semi-arid tropical climate of south India to investigate the response of industrially important, multi-harvest, aromatic crop palmarosa {. Cymbopogon martinii (Roxb.) Wats. var. motia Burk., family: Poaceae} to foliar application (2.5. g/L single application for each harvest at 700. L nutrient solution per hectare) of magnesium (Mg), manganese (Mn), iron (Fe), zinc (Zn), boron (B) and their residual effect on the succeeding harvest. During the experimental period, palmarosa crop afforded four harvests, 49.5-70.6. t/ha total biomass yield (fresh weight), 211.4-384.2. kg/ha total essential oil yield and Rs. 232,540-422,620/ha (US$ 4844.6-8804.6/ha) gross returns. Fifth harvest (no nutrients were applied) performed to examine the residual effect of Mg and micronutrients applied to the previous four harvests revealed the absence of residual effect pointing to the need for application of nutrients to individual harvests. Foliar application of Mg and micronutrients significantly increased the yield attributes (plant height, tiller number/plant, leaf number/plant), biomass yield, essential oil yield and gross returns of palmarosa. Mg and micronutrients enhanced the total biomass yields by 37.0-42.6% and the total essential oil yields by 44.6-81.7% in comparison to the control (water spray). All the treatments produced good quality essential oils with 1.5-3.2% linalool, 79.7-85.8% geraniol and 4.5-10.3% geranyl acetate. Mg and B additions declined linalool (%) in the second and fourth harvests and increased geraniol (%) in the first harvest. Mg and micronutrients application improved geraniol (%) in the second harvest. Except Zn, all the other nutrients decreased geranyl acetate (%) in the second harvest, but in the third and fourth harvests Mn and B increased geranyl acetate (%). © 2010 Elsevier B.V. Source

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