• R. P. Sharma

      Articles written in Journal of Genetics

    • Maternal effect embryonic lethal mutants identified in the 37D2-38A1 region of chromosome 2 ofDrosophila melanogaster

      S. Chandrashekaran R. P. Sharma

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      The genome region represented byDeficiency (2L) E55 inDrosophila melanogaster has been implicated in maternal gene activity, based on high levels of F1 embryonic mortality in hemizygousDf(2L) E55/+female x+/+male matings. Extensive mutagenesis screens were conducted to detect any maternal embryonic lethal loci in theDf (2L) E55, 37D2-38A1 cytological region. Consequently, seven maternal effect embryonic lethal loci have been identified. Five of them altered the ventral embryonic cuticle pattern in various ways. In addition to these, a new ovarian tumour mutant has also been identified in the same region. This demonstrates that maternal haplo insufficiency of theDf (2L) E55/+females, leading to embryonic mortality, is due to theen bloc removal of the wild type alleles of these mutants, whose activity is required in the female for ovarian organisation and embryonic development.

    • A substitution mutation in OsCCD7 cosegregates with dwarf and increased tillering phenotype in rice

      Krishnanand P. Kulkarni Chandrapal Vishwakarma Sarada P. Sahoo John M. Lima Manoj Nath Prasad Dokku Rajesh N. Gacche Trilochan Mohapatra S. Robin N. Sarla M. Seshashayee Ashok K. Singh Kuldeep Singh Nagendra K. Singh R. P. Sharma

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      Dwarf plant height and tillering ability are two of the most important agronomic traits that determine the plant architecture, and have profound influence on grain yield in rice. To understand the molecular mechanism controlling these two traits, an EMS-induced recessive dwarf and increased tillering1 (dit1) mutant was characterized. The mutant showed proportionate reduction in each internode as compared to wild type revealing that it belonged to the category of dn-type of dwarf mutants. Besides, exogenous application of GA3 and 24-epibrassinolide, did not have any effect on the phenotype of the mutant. The gene was mapped on the long arm of chromosome 4, identified through positional candidate approach and verified by cosegregation analysis. It was found to encode carotenoid cleavage dioxygenase7 (CCD7) and identified as an allele of htd1. The mutant carried substitution of two nucleotides CC to AA in the sixth exon of the gene that resulted in substitution of serine by a stop codon in the mutant, and thus formation of a truncated protein, unlike amino acid substitution event in htd1. The new allele will facilitate further functional characterization of this gene, which may lead to unfolding of newer signalling pathways involving plant development and architecture.

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