The DEAD-box RNA helicase ZmRH48 is required for the splicing of multiple mitochondrial introns,mitochondrial complex biosynthesis,and seed development in maize

RNA helicases participate in nearly all aspects of RNA metabolism by rearranging RNAs or RNA–protein complexes in an adenosine triphosphatedependent manner. Due to the large RNA helicase families in plants, the precise roles of many RNA helicases in plant physiology and development remain to be clarified. Here, we show that mutations in maize(Zea mays) DEAD-box RNA helicase48(Zm RH48) impair the splicing of mitochondrial introns, mitochondrial complex biosynthesis,and seed development. Loss of Z...     

The nad4L-orf25 gene cluster is conserved and expressed in sugar beet mitochondria

We have found that a gene coding for NADH dehydrogenase subunit 4L and a presumed gene, orf25, are linked and co-transcribed with each other in sugar beet mitochondria. Ten and twelve C-to-U editing events were observed in the mRNAs of nad4L and orf25, respectively; the amino-acid sequence specified after editing is better-conserved in comparison with the homologues of other organisms. It is interesting to note that the translation initiation codon of nad4L is created by editing. The conservation of the nad4L-orf25 linkage was examined by PCR-amplification of the intergenic region. We obtained successful PCR products from five dicots (spinach, apple, snapdragon, petunia and tobacco) and two monocots (tulip and pineapple), but not in two poaceous plants, rice and maize. The intergenic region, when present, was found to be well-conserved in its sequence, suggesting a monophyletic origin of this linkage. Our result, together with previous reports of Arabidopsis and four poaceous species, favour the argument that the nad4L-orf25 linkage is conserved throughout angiosperms except in the Poaceae. Received: 12 April 1999 / Accepted: 22 June 1999     

Assigning DYW-type PPR proteins to RNA editing sites in the funariid mosses Physcomitrella patens and Funaria hygrometrica

The plant‐specific pentatricopeptide repeat (PPR) proteins with variable PPR repeat lengths (PLS‐type) and protein extensions up to the carboxyterminal DYW domain have received attention as specific recognition factors for the C‐to‐U type of RNA editing events in plant organelles. Here, we report a DYW‐protein knockout in the model plant Physcomitrella patens specifically affecting mitochondrial RNA editing positions cox1eU755SL and rps14eU137SL. Assignment of DYW proteins and RNA editing sites might best be corroborated by data from a taxon with a slightly different, yet similarly manageable low number of editing sites and DYW proteins. To this end we investigated the mitochondrial editing status of the related funariid moss Funaria hygrometrica. We find that: (i) Funaria lacks three mitochondrial RNA editing positions present in Physcomitrella, (ii) that F. hygrometrica cDNA sequence data identify nine DYW proteins as clear orthologues of their P. patens counterparts, and (iii) that the ‘missing’ 10th DYW protein in F. hygrometrica is responsible for two mitochondrial editing sites in P. patens lacking in F. hygrometrica (nad3eU230SL, nad4eU272SL). Interestingly, the third site of RNA editing missing in F. hygrometrica (rps14eU137SL) is addressed by the DYW protein characterized here and the presence of its orthologue in F. hygrometrica is explained through its simultaneous action on site cox1eU755SL conserved in both mosses.