Abstract
Recent genetic evidence has highlighted developmental roles of ribosomes. The ribosome consists of about 80 ribosomal proteins (r-proteins) and in Arabidopsis thaliana each r-protein has two or more paralogues. Due to the genetic complexity of r-protein genes, precise mechanisms of developmental regulation by the ribosome are not known. We previously reported the isolation of a number of r-protein defective mutants. We found that most of them commonly exhibited developmental phenotypes such as impaired cell proliferation in leaves and abaxialization of leaves in the asymmetric leaves1 (as1) and as2 backgrounds. These results suggest that the ribosome itself plays a role in these developmental processes. However, we found an interesting exception: mutations in RPL4D did not detectably affect cell proliferation in leaves but very strongly enhanced abaxialization of leaves in the as2 background. This finding suggests that RPL4D has a unique role within the ribosome to control specific gene expression. To further understand the developmental roles of RPL4D, genetic, developmental and expression analyses of RPL4D are in progress.
