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Title: TRANSCRIPTIONAL INITIATION IN SORGHUM MITOCHONDRIAL DNA INDICATES CONSERVEDAND VARIABLE PROMOTER FEATURES.

Author
item YAN, B. - UNIV. OF FLORIDA
item Pring, Daryl

Submitted to: Current Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/21/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: A component of all plant cells are the mitochondria, which are a major source of energy production, and which contain DNA and critical genes. Mitochondria can also carry genes that cause cytoplasmic male sterility (cms). Each gene must be transcribed into a messenger-RNA (mRNA) before the gene product can be made. Scientists at the USDA, Agricultural Research Service in Gainesville, FL want to learn how mRNA synthesis begins for normal genes and for genes that may cause cms. To do this, they used molecular biology technologies to identify the starting point for mRNAs, and verified each observation in several ways. They learned that synthesis of several mRNAs, from normal genes and genes that may cause cms, begin with DNA sequences that are different from consensus starting points. Therefore, they suggest that the initiation points of mRNA synthesis can be variable and cannot be predicted on the basis of DNA sequences alone. Other scientists interested in how mitochondrial genes are expressed will have to consider these factors when analyzing gene expression.

Technical Abstract: Transcript initiation and processing was examined for three sorghum mitochondrial DNA genes (atp6-1, atp6-2, urf209) and two open reading frames (orf265/130, orf107), to establish transcriptional strategies in this species. The 5'termini of 11 transcripts were determined by primer extension, and mtRNA was capped with guanylytransferase and annealed to antisense riboprobes to identify transcriptional initiation regions. Eight transcript termini were suitable substrates for guanylytransferase, indicating presence of one (atp6-1, atp6-2, urf109),two (orf265/130), or three (orf107) promoters for the five examples. Four of the promoters were associated with single primer extension termini, while the remaining four promoters exhibited two transcript initiation sites. Four examples were characterized by one (atp6-1, atp6-2, urf209) or two (orf265/130) promoters and no transcript processing, indicating that the transcriptional strategy consisted of initiation alone. Each of the putative promoter regions included significant A/T-rich 5' regions, consistent with previous examples, but four exceptions to a consensus core YRTA sequence were identified. The anomalies (AATA, CTTA) suggest plasticity in primary structure of the core region of higher plant mitochondrial DNA promoters.