Application of the gene dosage balance hypothesis to auxin-related ribosomal mutants in Arabidopsis.

Several proteomic studies in Arabidopsis have shown the presence of heterogeneous ribosomal populations in different tissues. However, the phenotypic consequences of the imbalance of those ribosomal populations, and the regulatory mechanisms activated to control specific ratios between them, have yet to be evaluated. In our previous report, the phenotypic characterization of the ribosomal protein family L4 (RPL4) in Arabidopsis suggests that the maintenance of proper auxin-regulated developmental responses requires the simultaneous presence of RPL4A- and RPL4D-containing ribosomes. Based on the analysis of the compensatory mechanisms within the RPL4 family proteins in the rpl4a and rpl4d backgrounds, we propose the Gene Dosage Balance Hypothesis (GDBH) as a regulatory mechanism for ribosomal complexes in Arabidopsis. By using the concepts of dosage compensation and hierarchy, GDBH is able to explain the severity and specificity of different ribosomal mutant phenotypes associated with the same ribosomal complex.