Abstract
U12 intron-specific spliceosomes contain U11 and U12 small nuclear ribonucleoproteins and mediate the removal of U12 introns from precursor-mRNAs. Among the several proteins unique to the U12-type spliceosomes, an Arabidopsis thaliana AtU11/U12-31K protein has been shown to be indispensible for proper U12 intron splicing and for normal growth and development of Arabidopsis plants. Here, we assessed the functional roles of the rice (Oryza sativa) OsU11/U12-31K protein in U12 intron splicing and development of plants. The U11/U12-31K transcripts were abundantly expressed in the shoot apical meristems (SAMs) of Arabidopsis and rice. Ectopic expression of OsU11/U12-31K in AtU11/U12-31K-defecient Arabidopsis mutant complemented the incorrect U12 intron splicing and abnormal development phenotypes of the Arabidopsis mutant plants. Impaired cell division activity in the SAMs and inflorescence stems observed in the AtU11/U12-31K-deficient mutant was completely recovered to normal by the expression of OsU11/U12-31K. Similar to Arabidopsis AtU11/U12-31K, rice OsU11/U12-31K was determined to harbor RNA chaperone activity. Collectively, the present findings provide evidence for the emerging idea that the U11/U12-31K protein is an indispensible RNA chaperone that functions in U12 intron splicing and is necessary for normal development of monocotyledonous plants as well as dicotyledonous plants.
Highlights
Splicing of both the major class of U2-dependent introns and minor class of U12-dependent introns is an indispensible step in the regulation of gene expression in eukaryotes
By functional complementation of OsU11/ U12-31K in the AtU11/U12-31K-defecient Arabidopsis mutant plants, we provide evidence demonstrating that U11/U12-31K proteins are functionally conserved RNA chaperones in Arabidopsis thaliana and rice, which are crucial for correct U12 intron splicing and normal development of monocotyledonous plants as well as dicotyledonous plants
Since AtU11/U12-31K affected the formation of primary inflorescence stems and meristem activity, we investigated in more detail the expression patterns of the U11/U12-31K gene in Arabidopsis and rice by in situ hybridization analysis
Summary
Splicing of both the major class of U2-dependent introns and minor class of U12-dependent introns is an indispensible step in the regulation of gene expression in eukaryotes. During minor spliceosome formation, the U11 and U12 small nuclear ribonucleoproteins (snRNPs) form a stable U11/U12 di-snRNP complex [15,16], and seven unique proteins, denoted 65K, 59K, 48K, 35K, 31K, 25K and 20K, associate with the U11/U12 di-snRNPs [11,17]. These minor spliceosome-associated proteins were found to be well conserved in animals and plants, and in plants they are conserved in both dicotyledonous and monocotyledonous plants [11,18,19]
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