The first intron of rice EPSP synthase enhances expression of foreign gene

The first intron (EPI) of rice 5-enolpyruvylshikimate 3-phosphate synthase gene was isolated by PCR from one clone with genomic EPSP synthase gene. Sequence analysis showed that the first intron is 704 bp in length with 36.2% G+C content. To investigate its effect on expression of foreign gene, we inserted the first intron between CaMV35S promoter and β-glucuronidase (GUS) gene. The transient expression results showed that GUS could be expressed effectively with EPI. The GUS activity in transgenic tobacco shows that the EPI can greatly enhance the expression level of β-glucuronidase (P < 0.01) compared with transgenic tobacco without the first intron, and 3-to 6-fold increase in GUS activity in some transgenic tobaccos. Northern blot indicated the first intron was spliced from GUS pre-mRNA, and the steady-state mRNA levels of GUS with EPI in transgenic tobaccos were higher than that in transgenic tobacco without EPI, which suggested that the first intron of EPSP was a non-translated intron.     

Phylogenetic Analysis of New Plant Myosin Sequences

We have sampled a large number of plant taxa, ranging from brown algae to angiosperms, for the presence of myosin sequences. Using phylogenetic analysis, we show that all but two of the new plant myosin sequences fall into two of three preexisting myosin classes. We identified two outlying sequences, which do not fall into any preexisting myosin class. Additionally, all genomic sequences encoding class XI myosins contain an intron in the region studied, suggesting that this genomic region has been conserved over at least 1 billion years of plant evolution. With these data, we can rapidly and consistently classify partial myosin sequences from plants. Our data show that plant myosins do not have clear orthologues in other kingdoms, providing interesting insights into the diversification of myosins.     

A repressor element in the 5'-untranslated region of human Pax5 exon 1A

Five members of the RecQ helicase family, RECQL, WRN, BLM, RTS and RECQL5, have been found in human and three of them (WRN, BLM and RTS) were disclosed to be the genes responsible for Werner, Bloom and Rothmund–Thomson syndromes, respectively. RECQL5 (RecQ helicase protein-like 5) was isolated as the fifth member of the family in humans through a search of homologous expressed sequence tags. The gene is expressed with at least three alternative splicing products, , β and γ. Here, we isolated mouse RECQL5β and determined the DNA sequence of full-length cDNA as well as the genome organization and chromosome locus. The mouse RECQL5β gene consists of 2949 bp coding 982 amino acid residues. Comparison of amino acid sequence among human (Homo sapiens), mouse (Mus musculus), Drosophila melanogaster and Caenorhabditis elegans RECQL5β homologs revealed three portions of highly conserved regions in addition to the helicase domain. Nineteen exons are dispersed over 40 kbp in the genome and all of the acceptor and donor sites for the splicing of each exon conform to the GT/AG rule. The gene is localized to the mouse chromosome 11E2, which has a syntenic relation to human 17q25.2-q25.3 where human RECQL5β exists. Our genetic characterizations of the mouse RECQL5β gene will contribute to functional studies on the RECQL5β products.     

Jam packed genomes--a preliminary,comparative analysis of nucleomorphs

There are two ways eukaryotic cells can permanently acquire chloroplasts. They can take up a cyanobacterium and turn it into a chloroplast or they can engulf an alga that already has a chloroplast. The second method is far more common and there are at least seven major groups of protists that have obtained their chloroplasts, this way. In most cases little remains of the engulfed alga apart from its chloroplast, but in two groups, the cryptomonads and chlorarachniophytes, a small remnant nucleus of the engulfed alga is still present. These tiny nuclei, called nucleomorphs, are the smallest and most compact eukaryotic genomes known and recently the nucleomorph of the cryptomonad alga Guillardia theta, was completely sequenced (551 kilobases). The nucleomorph of the chlorarachniophyte Bigellowiella natans (380 kilobases), is also being sequenced and is about half complete. We discuss some of the similarities and differences that are emerging between these two nucleomorph genomes. Both genomes contain just three chromosomes that encode mainly housekeeping genes and a few proteins for chloroplast functions. The bulk of nucleomorph gene coding capacity, therefore, appears to be devoted to self perpetuation and creating gene and protein expression machineries to make a small number of essential chloroplast proteins. We discuss reasons why both nucleomorphs are extraordinarily compact and why their gene sequences are evolving rapidly.     

A novel mitochondrial DEAD box protein (Mrh4) required for maintenance of mtDNA in Saccharomyces cerevisiae

In a screen of nuclear genes that assist splicing of mitochondrial localized group II introns in yeast we isolated low-copy number suppressors of splicing and respiratory-deficient point mutants of intron aI5gamma, the last intron of the gene encoding cytochrome c oxidase subunit I. One of the genes found contains the open reading frame (ORF) YGL064c that has previously been proposed to encode a putative RNA helicase of the DEAD box family. Deletion of the ORF gives rise to 100% cytoplasmic petites, indicating that the protein plays an essential role in the mitochondrial RNA metabolism. Overexpression of YGL064c-GFP fusions clearly revealed a mitochondrial localization of the protein. The gene encodes the fourth putative RNA helicase of Saccharomyces cerevisiae implicated in a mitochondrial function and was therefore termed MRH4 (for mitochondrial RNA helicase).     

Globin genes are present in Ciona intestinalis

The key position of the Ciona intestinalis basal to the vertebrate phylogenetic tree brings up the question of which respiratory proteins are used by the tunicate to facilitate oxygen transport and storage. The publication of the Ciona draft genome sequence suggests that globin genes are completely missing and that-like some molluscs and arthropods-the sea squirt uses hemocyanin instead of hemoglobin for respiration. However, we report here the presence and expression of at least four distinct globin gene/protein sequences in Ciona. This finding is in agreement with the ancestral phylogeny of the vertebrate globins. Moreover, it seems likely that the Ciona hemocyanin-like sequences have enzymatic instead of respiratory functions.