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Title: The mitochondrial adenine nucleotide translocator from Zea mays L. : gene structure and expression
Author: Day, Christopher David
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1992
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To understand the molecular genetic basis of mitochondrial biogenesis during plant development, and the regulation of oxidative phosphorylation in particular, several nuclear genes encoding maize mitochondrial proteins had previously been cloned. Two of these genes termed ANT1 and ANT2 encode mitochondrial adenine nucleotide translocators. The work presented describes further characterisation of the ANT genes and isolation of a cDNA clone for ANT2. Steady state levels of ANT transcript have been analysed in different maize tissues and compared with other nuclear and mitochondrial genes encoding subunits at ATP synthase. The ANT genes have at least 5 exons termed exon 1 to exon 5 and at leat 4 introns termed intron A to intron D. The 5' end of the gene is more complex than originally concluded (Bathgate et al, 1985). Both ANT genes contain multiple transcript initiation sites, but the position and number of sites are not conserved between the two genes. The sizes of the 5' untranslated regions (5' UTRs) are between 124 bp and 356 bp as predicted from the various primer extension products. Both ANT genes have a minimum of two untranslated exons and two large introns (intron A and intron B) separate the untranslated exons. The 5' and 3' splice sites of intron A have not been accurately determined for ANT1 or ANT2 but the size of the intron in ANT2 is in excess of 2.4 kb. Intron B is 1063 bp and 1021 bp in size in ANT1 and ANT2 respectively and is separated from intron A by exon 2 which is approximately 85 bp and 78 bp in ANT1 and ANT2 respectively. The start of translation is in exon 3 and is 21 bp 3' of the intron B 3' splice site. Sequence of the ANT2 cDNA clone confirmed that the open reading frame includes a presequence which has been reported to be cleaved following import into mitochondria (Winning et al., 1992). ANT transcript steady state levels vary in a tissue specific manner. The highest steady state transcript levels were found in tissues known to exhibit mitochondrial oxidative phosphorylation and high metabolic rates. Tissues with lower metabolic rates or those which are photosynthetically active contain lower transcript levels, hence, a tentative correlation has been made between the transcript steady state level and metabolic activity. Probes which differentiate between the two ANT genes were used to investigate the possibility of differential regulation.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available