Koppolu Raja Rajesh Kumar

Publications (5)17.89 Total impact

• Article: Establishment of efficient and rapid regeneration system for some diploid wild species of Arachis

  Tantravahi Srinivasan, Koppolu Raja Rajesh Kumar, Pulugurtha Bharadwaja Kirti
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  ABSTRACT: Though peanut tissue culture has advanced to a considerable extent using a number of explants with the subsequent production of transgenic plants, wild Arachis species appeared to be recalcitrant to using similar explants. In this study, the use of cotyledonary nodes as explants prepared from 7-day old seedlings resulted in the development of a simple and rapid regeneration protocol for five diploid wild species including A. diogoi, A. stenosperma, A. duranensis, A. cardenasii and A. correntina belonging to the genus Arachis for producing multiple shoots. Shoot bud initiation was observed 10 to 15days after culture initiation. Responding cotyledonary nodes with shoot buds were subcultured to lower levels of cytokinin and finally to MS basal medium for further shoot development and elongation. Production of multiple shoots was observed in all the five diploid species with a maximum of 9 to 16 shoots were obtained per explant in the primary cultures. The number of shoot buds increased significantly with repeated explant subculturing with recovery up to 45 shoots from responding explants. These shoots were rooted efficiently on MS medium supplemented with 1mgl−1 naphthalene acetic acid and the time taken from explanting to the transfer of shoots to potting mixture was about 12weeks. All rooted shoots were successfully established in soil in glass house and further transferred to field. These plants survived to maturity and set seed. KeywordsWild Arachis species-Cotyledonary node explants-Shoot regeneration-BA-6-Benzyl amino purine-KIN–6-Fufuryl amino purine-TDZ–thidiazuron
  Plant Cell Tissue and Organ Culture 04/2012; 101(3):303-309. · 3.09 Impact Factor
• Article: Differential gene expression in Arachis diogoi upon interaction with peanut late leaf spot pathogen, Phaeoisariopsis personata and characterization of a pathogen induced cyclophilin.

  Koppolu Raja Rajesh Kumar, Pulugurtha Bharadwaja Kirti
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  ABSTRACT: The wild relatives of peanut are resistant to various economically important diseases including late leaf spot (LLS) caused by Phaeoisariopsis personata, compared with the susceptible cultivated peanut (Arachis hypogaea L.). The interaction of the late leaf spot pathogen, Phaeoisariopsis personata and the highly resistant, diploid peanut wild species, Arachis diogoi was analyzed at the molecular level by differential gene expression studies. Genes up-regulated with in 48 h of pathogen challenge were isolated as partial cDNAs. Some of the isolated genes, which are shown to be involved in the first line of defense in plants, were further characterized with respect to their transcriptional regulation in response to pathogen. Among the isolated clones, two were found to encode cyclophilin like proteins. One of the two isolated partial cDNAs encoding cyclophilin like proteins was extended using 5' RACE. The full length cDNA, designated as AdCyp, was 886 bp in length and encodes a polypeptide of 172 amino acids. Southern hybridization suggests that AdCyp is possibly coded by a single gene and at least one more identical gene is present in Arachis diogoi genome. AdCyp exhibits evolutionary conservation across the kingdoms. Phylogenetic analysis showed that AdCyp belongs to the subgroup I of Group I in cyclophilins. A translational fusion of GFP-AdCyp was found to localize to both cytosol and nucleus. AdCyp transcripts were found to accumulate in response to the treatments with pathogen as well as phytohormones. Constitutive heterologous expression of AdCyp resulted in enhanced resistance to Ralstonia solanacearum and reduced susceptibility towards Phytophthora parasitica var. nicotianae in transgenic tobacco and the resistance was associated with higher transcript levels of various defense related genes.
  Plant Molecular Biology 02/2011; 75(4-5):497-513. · 4.15 Impact Factor
• Article: A mitogen-activated protein kinase, AhMPK6 from peanut localizes to the nucleus and also induces defense responses upon transient expression in tobacco.

  Koppolu Raja Rajesh Kumar, Pulugurtha Bharadwaja Kirti
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  ABSTRACT: Mitogen-activated protein kinase (MAPK) cascades are one of the well studied signaling networks in plants. In this study a full length cDNA from Arachis hypogaea (peanut) encoding a mitogen-activated protein kinase was cloned using RACE-PCR approach. The cDNA was designated as AhMPK6 based on its high identity with AtMPK6 of Arabidopsis. The AhMPK6 encodes a 397 amino acid polypeptide that shows high similarity with MsSIMK, NtSIPK, OsSIPK of Medicago, tobacco and rice respectively. Phylogenetic analysis suggests that AhMPK6 belongs to the A2 subgroup of MAPK family. When expressed as a translational fusion with GFP, AhMPK6 displayed predominant nuclear localization. The conditional overexpression of AhMPK6 resulted in hypersensitive response (HR)-like cell death in tobacco, with a simultaneous upregulation of HR-marker gene transcripts and various defense response gene transcripts. The AhMPK6 induced gene expression suggests an overlapping or partially redundant function with previously reported AhMPK3.
  Plant Physiology and Biochemistry 06/2010; 48(6):481-6. · 2.84 Impact Factor
• Article: Constitutive expression of a trypsin protease inhibitor confers multiple stress tolerance in transgenic tobacco.

  Tantravahi Srinivasan, Koppolu Raja Rajesh Kumar, Pulugurtha Bharadwaja Kirti
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  ABSTRACT: Protease inhibitors have been reported to confer insect resistance in transgenic plants, except for a rice protease inhibitor that conferred drought tolerance in transgenic rice plants. We have cloned a protease inhibitor of tobacco that is expressed under treatment with ABA, hydrogen peroxide, methyl jasmonate and wounding. The cDNA codes for a six-domain serine protease inhibitor with a deduced sequence of 396 amino acids. We have generated transgenic tobacco plants expressing the protease inhibitor constitutively under the 35S promoter. When analyzed in the T(2) generation, these transgenic plants exhibited tolerance to sodium chloride, variable pH and sorbitol, together with the expected resistance to the insect pests Spodoptera litura and Helicoverpa armigera. The transgenic plants showed enhanced seed germination, root length and root-shoot ratio, significantly enhanced total chlorophyll content and reduced thiobarbituric acid-reactive substances under stress. Under sodium chloride treatment, the transgenic plants have enhanced protease inhibitor activity. The transgenic plants exhibited a higher potassium content and an optimum Na+/K+ ratio. To our knowledge, this is the first report of transgenic plants with constitutive protease inhibitor expression showing tolerance to a wide range variable pH in the culture medium along with other stresses.
  Plant and Cell Physiology 02/2009; 50(3):541-53. · 4.70 Impact Factor
• Article: Constitutive expression of Arabidopsis NPR1 confers enhanced resistance to the early instars of Spodoptera litura in transgenic tobacco.

  Gargi Meur, Madhusudhan Budatha, Tantravahi Srinivasan, Koppolu Raja Rajesh Kumar, Aparna Dutta Gupta, Pulugurtha Bharadwaja Kirti
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  ABSTRACT: In Arabidopsis, NPR1 (AtNPR1) regulates salicylic acid (SA)-mediated activation of PR genes at the onset of systemic acquired resistance. AtNPR1 also modulates SA-induced suppression of jasmonic acid-responsive gene expression, and npr1 mutants manifest enhanced herbivore resistance. We have raised stable transgenic tobacco lines, expressing AtNPR1 constitutively, which showed elevated expression of PR1 and PR2 genes upon SA treatment. Herbivore bioassays with a generalist polyphagous pest, Spodoptera litura, revealed that the transgenic lines exhibited enhanced resistance compared to the wild-type plants, particularly with respect to younger larval populations. Insect-mediated injury induced several protease inhibitors (PIs), more significantly a 40-kDa serine PI in all the tobacco lines, but the induction was higher in the transgenic plants. We show in this communication that heterologous expression of AtNPR1 provides enhanced resistance to early larval populations of the herbivore, Spodoptera in transgenic tobacco plants.
  Physiologia Plantarum 05/2008; 133(4):765-75. · 3.11 Impact Factor