Plant Genome II Conference
Town & Country Conference Center, San Diego, CA, January, 1994.
PG-II: RIBOSOMAL RNA GENE REPEAT LINKED TO ADAPTABILITY OF A INDICA
RICE CULTIVAR (BHASAMANIK) TO DEEPWATER ECOLOGY
RIBOSOMAL RNA GENE REPEAT LINKED TO ADAPTABILITY OF A INDICA
RICE CULTIVAR (BHASAMANIK) TO DEEPWATER ECOLOGY.
Rajat K. Chaudhuri, A Das, D Roy, I Chaudhuri, M Singh and Dilip
Mukhopadhyay. Molecular Biology Laboratory, Botany Department,
Calcutta University, Calcutta-700019, India.
Repeated DNA sequences are found to be the main cause for
variation in the size of genomes among different species of the
same genus (Chaudhuri and Chaudhuri, 1993. Penn. Acad. Sci.).
Highly repetitive DNA sequences are sometimes found to be species
specific. Ribosomal RNA genes of rice are organised as tandem
repeats - the variation of which is by length variation in
intergenic spacer (IGS) DNA sequences. While analysing ribosomal
RNA gene sequences of indica and japonica rice (Oryza sativa)
cultivars, we have noted polymorphism in restriction repeats.
This observation finds support in observations made by Densley
and others (Cordesse et al., 1992. TAG 83: 864-870). With the
idea that rDNA IGS sequences may be linked to quantitative
character or to adaptation to ecological condition, we have
studied their distribution, as restriction repeats, in a
salt-tolerant (Matla) and a submergence-tolerant (Bhasamanik)
rice cultivars and observed a difference in Eco RI restriction
repeat distribution in them. The result suggests Bhasamanik
genome has undergone a significant change in Eco RI restriction
sites while the Matla genome shows a constant feature of other
indica rice cultivar genomes after Eco RI digestion and
hybridization with rice ribosmal RNA gene probe. This
observation substantiates the findings of Rocheford et al. (TAG
79: 790-800, 1990) with maize where they could tag a 200 hp IGS
sequence to yield.
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