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Figure 8 | BMC Plant Biology

Figure 8

From: RACK1 genes regulate plant development with unequal genetic redundancy in Arabidopsis

Figure 8

The model of unequal genetic redundancy of RACK1 genes in regulating plant development. Arabidopsis genome contains three RACK1 homologous genes, designated as RACK1A, RACK1B and RACK1C, respectively, which encode three highly similar proteins. RACK1 genes regulate plant development likely in a continuous quantitative manner. RACK1A is likely the ancestral gene whereas RACK1B and RACK1C are the duplicate genes, because RACK1A retains the most functions of RACK1 genes. The expression of RACK1 follows a general trend of RACK1A > RACK1B > RACK1C. A certain threshold of gene activity is likely required for the RACK1 genes to have any influence on plant development, and the gene activity can be saturated once an excess of gene activity is reached. Because the loss-of-function mutations in RACK1B or RACK1C or both do not confer any defects in plant development while enhancing the developmental defects of rack1a mutants, the residual activities of RACK1B and RACK1C are likely above this threshold but below the point of saturation. RACK1 genes mutually regulate each other's transcription. Both the difference in gene expression and the cross-regulation are likely the molecular determinants of unequal genetic redundancy of RACK1 genes in regulating plant development. The model is schematically based on the possible explanations for unequal genetic redundancy provided by Briggs et al. (2006) [16].

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