ABSTRACT
Transcription of the single-copy rice mitochondrial atp9 gene has been analyzed. We propose that there is a 0.65 kb primary transcript that is processed to an abundant 0.45 kb mRNA; a sequence motif at the 5' terminus of the 0.65 kb transcript shares 9 out of 11 nucleotides homology to the consensus promoter proposed for maize. There are several 3' termini based on RNase protection, and these termini map within or just distal to inverted repeats that could fold into a double stem-loop structure.
Subject(s)
Adenosine Triphosphatases/genetics , Mitochondria/enzymology , Oryza/genetics , Transcription, Genetic , Base Sequence , DNA, Mitochondrial , Molecular Sequence Data , Nucleic Acid Conformation , Oryza/enzymology , Oryza/ultrastructure , RNA/chemistry , Restriction MappingABSTRACT
Rice mitochondrial DNA contains an intact copy and a pseudogene copy of a apocytochrome b gene (cob-1 and cob-2, respectively). Using primer extension and capping analyses, the transcriptional start site has been mapped; an 11-base motif at the transcription start site closely matches the consensus promoter motifs proposed for maize, wheat and soybean mitochondrial genes. Although both copies are identical in the 5' upstream region and through most of the coding region, only cob-1-specific mRNA is detected on RNA gel-blots. Run-on transcription analysis indicates, however, that both cob-1 and cob-2 mRNAs are synthesized in vivo but less cob-2 is accumulated. At its mapped 3' terminus the cob-1 transcript possesses a sequence that could fold into a double stem-loop structure. The possible roles of a double stem-loop structure in mitochondrial gene expression are discussed.
Subject(s)
Apoproteins/genetics , Cytochrome b Group/genetics , Mitochondria/enzymology , Oryza/enzymology , Pseudogenes , Base Sequence , Blotting, Northern , Blotting, Southern , Cytochromes b , DNA, Mitochondrial , Gene Expression , Molecular Sequence Data , Nucleic Acid Hybridization , RNA/chemistry , Restriction Mapping , Sequence Homology, Nucleic AcidABSTRACT
Southern hybridization analysis using homologous maize probes indicated that orf25 and coxIII are closely linked in the mitochondrial genome of rice (Oryza sativa) cultivar IR36. The two coding regions were found on the same 5.1 kb BamHI fragment, and this fragment was cloned, mapped and partially sequenced. Using probes for each gene derived from the rice clone, a 2.4 kb dicistronic mRNA transcript was found containing both orf25 and coxIII coding regions. Multiple 5' ends were identified by primer extension analysis and a double stem/loop structure was mapped to the 3' end. The orf25 coding region shares greater than 85% identity with orf25 sequences from maize, tobacco and wheat, suggesting that orf25 may code for a conserved protein product.
Subject(s)
DNA, Mitochondrial/genetics , Oryza/genetics , Plant Proteins/genetics , Transcription, Genetic/genetics , Amino Acid Sequence , Base Sequence , Blotting, Northern , Blotting, Southern , Cloning, Molecular , Gene Library , Molecular Sequence Data , Nucleic Acid Conformation , Oligonucleotide Probes , Plant Proteins/chemistry , Sequence Homology, Nucleic AcidSubject(s)
DNA, Mitochondrial/genetics , Genes, Plant , Mitochondria/enzymology , Mitochondrial Proton-Translocating ATPases , Oryza/genetics , Plant Proteins/genetics , Proteolipids/genetics , Proton-Translocating ATPases/genetics , Amino Acid Sequence , Arabidopsis Proteins , Base Sequence , Molecular Sequence Data , Oryza/enzymology , Plants/genetics , Sequence Homology, Nucleic AcidABSTRACT
The ability of immature embryos of wheat (Triticum aestivum L.) to respond in cell culture was examined in crosses between the 'Wichita' monosomic series and a highly regenerable line, 'ND7532'. Segregation in disomic controls and 13 monosomic families showed a good fit to a monogenic ratio indicating a qualitative mode of inheritance. Segregation in the cross involving monosomic 2D showed a high frequency of regeneration (93.6%) and high callus growth rate (1.87 g/90 days) indicating that 2D is a critical chromosome. Modifying genes may be located on other chromosomes. Substitution of chromosomes from a low regenerable cultivar 'Vona' further indicated that the group 2 chromosomes, in particular chromosome 2D, possess genetic factors promoting callus growth and regeneration.
ABSTRACT
The ability of immature embryos of wheat (Triticum aestivum L.) to respond to tissue culture has been shown to involve the group 2 chromosomes. The available group 2 ditelosomic and nullisomic-tetrasomic lines of 'Chinese Spring' wheat were used to determine the chromosome arm location and chromosome dosage effect associated with the expression of tissue culture response (TCR). Significant differences were found between the aneuploid lines and the euploid control for the expression of both regenerable callus formation and callus growth rate. A model is proposed suggesting that a major TCR gene is located on 2DL and that 2AL and 2BS possess minor TCR genes. Furthermore, a major regulatory gene controlling the expression of TCR genes may be located on chromosome 2BL.
