• Arun Kumar

      Articles written in Journal of Genetics

    • Further investigations on cytology of members of commelinaceae with special reference to the role of polyploidy and the origin of ecotypes

      Arun Kumar Sharma Archana Sharma

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    • Chromosome studies in species ofDracaena with special reference to their means of speciation

      Arun Kumar Sharma Praphulla Chandra Datta

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      Detailed study of the structure and behaviour of chromosomes in the somatic tissue of twenty-one species of the genusDracaena has been made and the “normal” chromosome numbers of all these species have been reported for the first time in this paper.

      The previous and the present records suggest that most of the species possess a number of chromosomal biotypes. These biotypes mainly differ with respect to their chromosome numbers.

      Relationship between species showing multiples of different series of chromosome numbers, viz. eight, ten, thirteen, seventeen and nineteen has been indicated.

      On the basis of the fact that a general resemblance in gross morphology of chromosomes and similarity in total amount of chromatin length are present amongst different species of the genusDracaena, it has been suggested that the species of this genus represent a homogeneous assemblage in spite of the fact that inconstancy in chromosome number is noted within a species.

      The different lines have mainly been assumed to have come out through continued production of aneuploid numbers during evolution. The presence of a number of chromosomal biotypes indicates that such aneuploid numbers often arise.

      Minor differences in details of chromosome morphology, and the presence of super-numerary constrictions in certain species, have been regarded as proving that structural changes of chromosomes have also played a distinct role in evolution of the species.

      As the different species ofDracaena are propagated exclusively through vegetative means, the only explanation for the origin of biotypes which can be suggested is that the recorded variant nuclei enter into the formation of new daughter shoots from which new individuals originate with different genomic constitutions. As flowers are scarcely noted and sexual reproduction is entirely ineffective with respect to propagation, this seems to be the only way through which speciation is effected here.

    • Cytotaxonomic investigation with the aid of an improved method on the family verbenaceae with special reference to the lines of evolution

      Arun Kumar Sharma Satyabrata Mukhopadhyay

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    • Interrelationships and evolution of the tribe Aloineae as reflected in its cytology

      Arun Kumar Sharma Ranajit Mallick

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    • Cytological studies on Indian representatives of the genusViola

      Amiyangshu Chatterjee Arun Kumar Sharma

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      The present investigations on the chromosome study of ten Indian representatives ofViola have revealed interesting data from cytotaxonomical and cytoecological standpoints. The existence of two distinctly different chromosome series in the same species, rather uncommon for this genus, has been recorded inV.serpens (2n= 18 and 48) andV. biflora (2n = 12 and 20). Such intraspecific variations imply that differences in numerical series of chromosomes should not necessarily play an important role in categorizing species assemblages. They have also been noted inV. tricolor (2n = 42 and 46) and polyploid cytotypes have been recorded inV. hookeri (n = 9 and 36). On the basis of chromosome data, it has been stated that the retention ofV. odorata andV. tricolor under the section Erpetion as followed by Engler and Prantl, is not desirable. De Candolle in his system kept the two genera under two separate sections. Remarkable similarity betweenV. serpens ( 2n = 18 and 48) andV. distans ( 2n = 44) in chromosome morphology has been shown.

      From a study of the chromosomes of different ecotypes it has been shown that inViola extreme climatic conditions are tolerated by diploids, whereas the polyploids abound in comparatively moderate climate, which is rather uncommon for other genera.

    • Genetic control of leaf-blade morphogenesis by the INSECATUS gene in Pisum sativum

      Sushil Kumar Swati Chaudhary Vishakha Sharma Renu Kumari Raghvendra Kumar Mishra Arvind Kumar Debjani Roy Choudhury Ruchi Jha Anupama Priyadarshini Arun Kumar

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      To understand the role of INSECATUS (INS) gene in pea, the leaf blades of wild-type, ins mutant and seven other genotypes, constructed by recombining ins with uni-tac, af, tl and mfp gene mutations, were quantitatively compared. The ins was inherited as a recessive mutant allele and expressed its phenotype in proximal leaflets of full size leaf blades. In ins leaflets, the midvein development was arrested in distal domain and a cleft was formed in lamina above this point. There was change in the identity of ins leaflets such that the intercalary interrupted midvein bore a leaf blade. Such adventitious blades in ins, ins tl and ins tl mfp were like the distal segment of respective main leaf blade. The ins phenotype was not seen in ins af and ins af uni-tac genotypes. There was epistasis of uni-tac over ins. The ins, tl and mfp mutations interacted synergistically to produce highly pronounced ins phenotype in the ins tl mfp triple mutant. The role(s) of INS in leaf-blade organogenesis are: positive regulation of vascular patterning in leaflets, repression of UNI activity in leaflet primordia for ectopic growth and in leaf-blade primordium for indeterminate growth of rachis, delimitation of proximal leaflet domain and together with TL and MFP homeostasis for meristematic activity in leaflet primordia. The variant apically bifid shape of the affected ins leaflets demonstrated that the leaflet shape is dependent on the venation pattern.

    • Genetic diversity of Cahi DRB and DQB genes of caprine MHC class II in Sirohi goat


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      The objective of this study was to assess the genetic diversity of the Sirohi goat for DRB and DQB1 loci, and to study their association with antibody response induced by the Peste des petits ruminants (PPR) vaccine. A total of 360 Sirohi kids were studied using single stranded confirmation polymorphism (SSCP) followed by polymerase chain reaction sequence-based typing (PCR-SBT) for DRB and DQB1 diversities. The competitive enzyme-linked immuno-sorbent assay (C-ELISA) was used to evaluate immune response post-PPR vaccination. Study revealed rich diversity of major histocompatibility complex (MHC) region in goat. A total of 18 DRB and 15 DQB1 alleles were obtained which were new. Alleles DRB*0104 and DQB1*0101 were the most common. The approach of SSCP combined with PCR-SBT reflects cost-effective and most powerful approach to decipher the genetic diversity in complex MHC region. Study revealed variation in DRB and DQB1 genes in Sirohi flock along with high Wu–Kabat index. A totalof 16 of the 89 amino acid residue sites in DRB and 19 of 86 residue sites in DQB1 had more than three amino acid substitutions. Positive evolutionary selection was evident in Sirohi forMHC region. Nonsignificant association of DRB and DQB1 genotypes with PPR virus (PPRV) vaccine response revealed complexity of the phenotype and importance of other factors for vaccine response. Rich diversity of DRB and DQB1 genes reflects the fitness of the population and importance of this locus for future selection programmes.

    • Genetics of nonalcoholic fatty liver disease in Asian populations


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      Nonalcoholic fatty liver disease (NAFLD) is characterized by the accumulation of fat in the liver without any history of chronic alcohol consumption. It encompasses a wide spectrum of diseases that range from simple steatosis to nonalcoholicsteatohepatitis. NAFLD is strongly associated with obesity, insulin resistance / type-2 diabetes mellitus and the metabolic syndrome. NAFLD is a complex disorder; environmental and genetic factors interact with NAFLD manifestation and determine its progression. In this review, an attempt was made to provide current information on the genetic variants of NAFLD in Asian populations. Literature search was performed by using PubMed, Medline and Google Scholar database. Candidate gene, validation and genomewide association studies (GWASs) were included in this review. A total of 41 studies fulfilled inclusion criteria of which 12 candidate gene studies exclusively focussed on the PNPLA3 gene and 17 other studies on other important candidate genes such as NCANCILP2, PPARG,AGTR1, FABP1, APOC3 etc. reported significant association with NAFLD. Eight validation studies identified associations of variants on PNPLA3, LYPLAL1, TM6SF2, ADIPOR2, STAT3, GCKR, SAMM50 etc. with NAFLD. Thus, so far, four GWASs have been conducted in Asian population that reported PNPLA3, SAMM50, PARVB and GATAD2A genes which were significantly associated with NAFLD. Findings indicate that PNPLA3, APOC3, PPARG, NCAN and GCKR genes emerge out to be the important biological markers associated with NAFLD.

    • Variability of the EG95 antigen-coding gene of Echinococcus granulosus in animal and human origin: implications for vaccine development


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      In the present study, the genetic variability of the EG95 protein-coding gene in several animal and human isolates of Echinococcus granulosus was investigated. A total of 24 isolates collected from cattle, buffalo, sheep, goat, dog and man were amplified by Eg95-coding gene-specific primers. From the generated sequence information, a conceptual amino acid sequence was deduced. Phylogenetically, the Eg95 coding gene belongs to the Eg95-1/Eg95-2/Eg95-3/Eg95-4 cluster. Further confirmation on the maximum composite likelihood analysis revealed that the overall transition/transversion bias was 2.913. This finding indicated thatthere is bias towards transitional and transversional substitution. Using artificial neural networks, a B-cell epitope was predicted on primary sequence information. Stretches of amino acid residues varied between animal and human isolates when hydrophobicity was considered. Flexibility also varied between larval and adult stages of the organism. This observation is important to develop vaccines. However, cytotoxic T-lymphocyte epitopes on primary sequence data remained constant in all isolates. In this study, agretope identification started with hydrophobic amino acids. Amino acids with the same physico-chemical properties were present in the middle. The conformational propensity of the Eg95-coding gene of 156 amino acid residues had α-turns and β-turns, and α-amphipathic regions up to 129, 138–156 and 151–155 residues, respectively. The results indicated potential T-cell antigenic sites. The overall Tajima’s D value was negative (−2.404165), indicative of negative selection pressure.

    • Genetics of novel brown planthopper Nilaparvata lugens (Stål) resistance genes in derived introgression lines from the interspecific cross O. sativa var. Swarna × O. nivara


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      The brown planthopper (BPH) Nilaparvata lugens (Stål) (Homoptera: Delphacidae) is considered a threat to rice (Oryza sativa ssp.) crop in many parts of the world including India. Among the BPH-resistance (R) genes so far reported in rice, most of them are ineffective against BPH biotype 4 predominant in the Indian sub-continent. In this study, we show the introgression line RPBio4918-230S was identified as BPH resistant after five years of rigorous screening at seedling stage and two years at tillering and reproductive stages. The inheritance of resistance indicated that two recessive genes are involved at seedling and reproductive stages. The allelic relation with known genes using linked reported markers suggested that the genes present in RPBio4918-230S are different. We report here the genetics of the two newly introgressed BPH resistance genes from O. nivara in the background of Swarna which are effective at all the important growth stages. The genes have been tentatively named as bph39(t) and bph40(t). The honeydew area (feeding rate) and days to wilt parameters observed at 30 days after sowing in BC1F3 indicated that newly introgressed genes have both antibiosis and tolerance mechanisms for resistance. The BPH resistance genes identified in this study would facilitate the breeding of broad spectrum and durable resistance in rice against BPH biotype 4.

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