The Arabidopsis U12-Type Spliceosomal Protein U11/U12-31K Is Involved in U12 Intron Splicing via RNA Chaperone Activity and Affects Plant Development  

Abstract

U12 introns are removed from precursor-mRNA by a U12 intron-specific spliceosome that contains U11 and U12 small nuclear ribonucleoproteins. Although several proteins unique to the U12-type spliceosome have been identified, the manner by which they affect U12-dependent intron splicing as well as plant growth and development remain largely unknown. Here, we assessed the role of U11/U12-31K, a U12-type spliceosomal protein in Arabidopsis thaliana. T-DNA-tagged homozygote lines for U11/U12-31K could not be obtained, and heterozygote mutants were defective for seed maturation, indicating that U11/U12-31K is essential for the normal development of Arabidopsis. Knockdown of U11/U12-31K by artificial microRNA caused a defect in proper U12 intron splicing, resulting in abnormal stem growth and development of Arabidopsis. This defect in proper splicing was not restricted to specific U12-type introns, but most U12 intron splicing was influenced by U11/U12-31K. The stunted inflorescence stem growth was recovered by exogenously applied gibberellic acid (GA), but not by cytokinin, auxin, or brassinosteroid. GA metabolism-related genes were highly downregulated in U11/U12-31K knockdown plants. Importantly, U11/U12-31K was determined to harbor RNA chaperone activity. We propose that U11/U12-31K is an RNA chapereone that is indispensible for proper U12 intron splicing and for normal growth and development of plants.

MaizeRough Endosperm3Encodes an RNA Splicing Factor Required for Endosperm Cell Differentiation and Has a Nonautonomous Effect on Embryo Development

“…Most plant genes contain introns that must be removed for protein expression; therefore, RNA splicing should be an essential function for cell viability. Consistent with this reasoning, lossof-function alleles of core splicing factors are gametophyte or seed lethal (Liu et al, 2009;Wang and Okamoto, 2009;Kim et al, 2010).…”

“…In plants, a variety of RNA splicing factors have been shown to have specific roles in abiotic stress tolerance and flowering time (reviewed in Lorković , 2009). Mutants and misexpression transgenics of both U2 and U12 splicing factors can have pleiotropic developmental defects (Lopato et al, 1999;Kalyna et al, 2003;Ali et al, 2007;Chung et al, 2007;Coury et al, 2007;Kim et al, 2010). Most plant genes contain introns that must be removed for protein expression; therefore, RNA splicing should be an essential function for cell viability.…”

LSM Proteins Provide Accurate Splicing and Decay of Selected Transcripts to Ensure NormalArabidopsisDevelopment

“…It has been described that the proteins involved in mRNA decapping, DCP1, DCP2, VCS, and DCP5, as well as the splicing factors STA1, U11/U112-31K, and ERECTA MRNA UNDER-EXPRESSED, play an essential role in Arabidopsis development, their absence being lethal (Lee et al, 2006;Xu et al, 2006;Goeres et al, 2007;Xu and Chua, 2009;Furumizu et al, 2010;Kim et al, 2010). Arabidopsis plants deficient in LSM1 and LSM8 proteins also display quite severe development alterations, but they are viable.…”

“…Furthermore, only a few genes were analyzed for splicing defects in the lsm4 mutant (Zhang et al, 2011). The fact that not all mRNAs exhibit reduced degradation rates in lsm1a lsm1b plants nor splicing defects in lsm8 mutants indicates that the cytoplasmic and nuclear LSM complexes from Arabidopsis, as described for other components of the Arabidopsis machineries involved in mRNA degradation and processing (Xu et al, 2006;Goeres et al, 2007;Xu and Chua, 2009;Kim et al, 2010;Rymarquis et al, 2011), act on selected targets. How selected mRNAs are targeted to these complexes remains largely unknown.…”

InsP6-Sensitive Variants of the Gle1 mRNA Export Factor Rescue Growth and Fertility Defects of the ipk1 Low-Phytic-Acid Mutation in Arabidopsis

“…To test whether Gle1 activates the RNA helicase activity of LOS4, we performed in vitro nucleic acid-melting assays with LOS4-His and MBP-Gle1 recombinant proteins using 78-nucleotide-long, 9-bp-containing, hairpin-shaped molecular beacons (Kim et al, 2007(Kim et al, , 2010. In the presence of ATP, the beacon itself (control) or the addition of LOS4-His did not increase beacon fluorescence ( Figure 4F).…”