Role of SMU Homologues in Pre-mRNA Splicing During Maize and Arabidopsis Development

• Main Author: Chung, Taijoon
• Other Authors: Larkins, Brian A.
• Language: EN
• Published: The University of Arizona. 2006
• Online Access: http://hdl.handle.net/10150/195508

A maize (Zea mays ssp. mays) opaque mutant, mto38 (Mutator-taggedopaque 38), was shown to cosegregate with a Mutator-tagged genomicfragment. Sequence analysis of the DNA indicated that it contained a genesimilar to the smu-2 (suppressor of mec-8 unc-52) gene in nematodes. Previous studies showed that the mutations in either thenematode smu-1 or smu-2 genes affect splicing of the unc-52 pre-mRNA, and SMU-1 protein interacts with SMU-2 protein. In addition, human homologues of SMU-1 and SMU-2 proteins wereidentified from human spliceosome. Thus, animal SMU-1 and SMU-2 homologuesappear to play a role in pre-mRNA splicing. Plant SMU-1 and SMU-2 homologueshave not been characterized. This study demonstrated that a Mutator insertion in Zmsmu2 (Zea mays homologue of nematode smu-2) geneis responsible for multiple mutant phenotypes. Transcript profiling of mto38/zmsmu2-1endosperm revealed that defective rRNA processing and inefficient proteinsynthesis in the mutant can explain the mutant endosperm phenotypes.Furthermore, splicing of multiple pre-mRNAs is altered in zmsmu2-1endosperm, indicating a regulatory role for ZmSMU2 in pre-mRNA splicing. Thisstudy also describes the AtSMU1 and AtSMU2 genes, which encodethe Arabidopsis homologues of nematode SMU-1 and SMU-2, respectively.The SMU-2 homologues of Arabidopsis and maize physically interact with their corresponding SMU-1 homologues. Genetic analysis indicated that the AtSMU1 and AtSMU2 genes are in the same genetic pathway, and mutations in AtSMU1 and AtSMU2 also result in altered splicing of pre-mRNAs, as was true for zmsmu2. Taken together, the data presented in this study indicate a rolefor plant SMU-2 homologues in pre-mRNA splicing.