• Helena Mathews

      Articles written in Journal of Genetics

    • Transformation ofBrassica juncea byAgrobacterium tumefaciens harbouring plasmid pTiT37 and its ‘rooty’ mutant pTiT37.14a/a

      Helena Mathews P S Rao C R Bhatia

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      Indian mustard (Brassica juncea Linn., Czern and Coss) plants were inoculated withAgrobacterium tumefaciens strain A208 harbouring either plasmid pTiT37 or pTiT37.14a/a. The latter carries an insertion at the ‘rooty’ locus (gene 4 orcyt) of the T-DNA governing cytokinin biosynthesis. The tumours induced by pTiT37.14a/a were small and formed many roots. Forin vitro culture, these transformed cells required supplementation of the basal medium with IAA and kinetin in the initial stages though after six sub-cultures they were also hormone autotrophic.In vitro cultures showed profuse rooting like the inplanta tumours. Unlike transformed tobacco and carrot cells,Brassica juncea cells transformed by pTiT37.14a/a could not be induced to differentiate into shoots. In contrast, the cells transformed by the wild type pTiT37 were hormone autotrophic and occasionally differentiated into shoots but could not be induced to produce roots. These results demonstrate how a single gene mutation affecting cytokinin biosynthesis can alter the inplanta as well as thein vitro response of a transformed cell of the same genotype.

    • Monohybrid and dihybrid segregations in the progenies of tobacco transformed for kanamycin resistance with a Ti-vector system

      Patricia Viegas Helena Mathews C. R. Bhatia N. K. Notani

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      A chimeric DNA construction having nopaline synthase promoter, coding sequences of neomycin phosphotransferase gene conferring resistance to antibiotic kanamycin and OCS (octopine synthase) polyadenylation sequences bracketed by T-DNA ends was transferred to tobacco. Leaf discs were infected withA. tumefaciens containing disarmed, cointegrate plasmid pGV3850:: 1103 and allowed to form a callus in the presence of kanamycin. Shoots regenerated from infected leaf discs either through the callus or arising directly were further selected for their ability to root in kanamycin-containing media. Among the nine transgenic plants that were progeny tested, the transferred bacterial gene segregated as monohybrid ratio (3 KanR: 1 Kans) in seven. Segregation data of two plant progenies indicated the presence of two independent loci of KanR DNA insertion (15 KanR: 1 Kans). Back-cross segregation data were consistent with the monohybrid or independent assortment of duplicate factors. Thus in the two cases, a minimum independent integration of two copies of T-DNA each with a KanR marker is inferred.

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