Gene-dosage compensation of endosperm proteins in hexaploid wheat Triticum aestivum.

Several aneuploid lines and one intervarietal substitution line of the hexaploid wheat Triticum aestivum (2n = 6x = 42; genomes AABBDD) cv. Chinese Spring were used to study the effects of different doses of chromosomes 1B, 1D, or 1A on the amount of the high molecular weight ("HMW") glutenins and gliadins of endosperm. These homeologous chromosomes carry HMW glutenin and gliadin gene clusters on their long and short arms, respectively. Increasing the dosage of chromosome 1B of Chinese Spring in plants having in their 3n endosperm zero or the normal three doses of the homeologue 1D, as well as in plants carrying in their endosperm one dose of 1B of the cultivar Timstein, had a dual effect: on one hand, a nonlinear increase in the amount of each subunit encoded by the chromosome whose dosage was elevated and, on the other hand, a compensating nonspecific decrease in the amount of other HMW glutenin and gliadin subunits encoded either by the homeoalleles on 1D or by the homoalleles on 1B of Timstein, respectively. Deletion of chromosome arm 1BL, which carries only a few HMW glutenin genes, had no significant effect on the amount of HMW glutenins encoded by 1DL and HMW gliadins encoded by 1DS and 1BS. However, deletion of 1BS or 1DS, each carrying many gliadin genes, caused a significant but nonspecific increase in the HMW glutenins and gliadins encoded by the remaining arms of 1B and 1D. The possible mechanism and evolutionary implications of gene-dosage compensation in polyploid wheat are discussed.