Abstract
NMD (Nonsense-mediated mRNA Decay) mRNA surveillance conserved among eukaryotes is involved in degradation of aberrant mRNAs that contain premature termination codon (PTC) and in the translation-dependent processing of mRNAs with various structural features. Knockout of AtUPF1 or AtUPF2 encoding major factors of NMD in Arabidopsis are lethal and lba1 missense mutant of AtUPF1 shows pleiotropic phenotypes. mRNAs that increased in lba1 and atupf3-1 compared to the wild type were enriched with PTC+-mRNAs produced by alternative splicing and mRNAs with short ORF in the 5'-untranslated region. Among them, alternatively spliced PTC+-mRNA of TFIIIA and uORF-containing mRNA of SAC51 encoding a bHLH protein seem to be direct targets of NMD, since they showed longer half-lives in lba1 and atupf3-1 compared to the wild type and their degradation was translation-dependent. Seeds of lba1 and atupf3-1 were larger at long axis than the wild-type seeds, which was due to the longer distance between the ovule primordia formed on septum during pistil development. We are searching for mRNAs that are targets of NMD and involved in the determination of periodical pattern of ovule primordia formation.
