Gene Expression and Nucleolar Dominance in Hexaploid Triticale and T. Aestivum

Abstract

ABSTRACTThe expression of rRNA genes located in the nucleolar organizing region (NOR) present in the short arm of chromosome 1R from rye (Secale cereale L.) was examined in several hexaploid genotypes of T. aestivum cv. Chinese Spring (AABBDD), Triticale 171 (AABBRR), sphaerococcum mutant form MT47–2D(2R) and Secale cereale (RR). By silver staining and in situ (FISH) hybridization with the DNA probe pTa71, was established a corresponance between the expression and organization patterns of rDNA domains in metaphase and interphase cells. We show here that the substitution of the rye chromosome 2R by a chromosome from hexaploide wheat 2D (triticale–2D(2R) in MT47sph, prevents suppression of the rye-origin rDNA and leads to activity of all six major rDNA loci. In spite of that in triticale 171, containing 28 chromosomes of wheat origin and 14 from rye, rDNA of rye origin is not normally expressed, while the 1B- and 6B- origin rDNA from wheat shows strong expression.