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Biomedical subjects

R G Atkinson

Publications and source records attributed to R G Atkinson.

8 recordsLinked to original sources
PubMed2000

MDH1: an apple homeobox gene belonging to the BEL1 family.

Differential display was used to isolate genes differentially expressed early in fruit development of apple (Malus domestica Borkh.). This approach resulted in the isolation of MDH1, a homeobox gene with a homeodomain similar to that of BELL1 (BEL1), which is involved in regulation of ovule development in Arabidopsis. However, outside the homeodomain MDH1 is quite different from BEL1. In apple, MDH1 mRNA was predominantly found in flowers, expanding leaves and expanding fruit. In pre-anthesis flowers, in situ hybridization showed that MDH1 mRNA accumulated in ovules. To further investigate the function of this new homeobox gene, MDH1 was transformed into Arabidopsis thaliana under the control of the cauliflower mosaic virus 35S promoter. The transgenic Arabidopsis plants showed dwarfing, reduced fertility and changes in carpel and fruit (silique) shape. The size and shape of the cells in the transgenic fruit was irregular. Both the transgenic phenotypes in Arabidopsis and the expression pattern of this gene in apple are consistent with the idea that MDH1 is likely to play an important role in control of plant fertility.

Amino Acid Sequence↗
PubMed2000

Polygalacturonase gene expression in kiwifruit: relationship to fruit softening and ethylene production.

In kiwifruit, much of the softening process occurs prior to the respiratory climacteric and production of ethylene. This fruit therefore represents an excellent model system for dissecting the process of softening in the absence of endogenous ethylene production. We have characterized the expression of three polygalacturonase (PG) cDNA clones (CkPGA, B and C) isolated from fruit of Actinidia chinensis. Expression of CkPGA and B was detected by northern analysis only in fruit producing endogenous ethylene, and by RT-PCR in other tissues including flower buds, petals at anthesis, and senescent petals. CkPGA promoter fragments of 1296, 860 and 467 bp fused to the beta-glucuronidase (uidA) reporter gene directed fruit-specific gene expression during the climacteric in transgenic tomato. CkPGC gene expression was observed in softening fruit, and reached maximum levels (50-fold higher than for CkPGA and B) as fruit passed through the climacteric. However, expression of this gene was also readily detected during fruit development and in fruit harvested prior to the onset of softening. Using RT-PCR, expression of CkPGC was also detected at low levels in root tips and in senescent petals. These results suggest that PG expression is required not only during periods of cell wall degeneration, but also during periods of cell wall turnover and expansion.

Amino Acid Sequence↗
PubMed1998

Biochemical and molecular characterisation of xyloglucan endotransglycosylase from ripe kiwifruit.

Xyloglucan endotransglycosylase (XET) from the core tissue of ripe kiwifruit (Actinidia deliciosa [A. Chev.] C.F. Liang et A.R. Ferguson var. deliciosa cv. Hayward) was purified 3000-fold to homogeneity. The enzyme has a molecular weight of 34 kDa, is N-glycosylated, and is active between pH 5.0 and 8.0, with an optimum between 5.5 and 5.8. The Km was 0.6 mg.mL-1 for kiwifruit xyloglucan and 100 microM for [3H]XXXG-ol, a reduced heptasaccharide derived from kiwifruit xyloglucan. Kiwifruit core XET was capable of depolymerising xyloglucan in the absence of [3H]XXXG-ol by hydrolysis, and in the presence of [3H]XXXG-ol by hydrolysis and endotransglycosylation. Six cDNA clones (AdXET1-6) with homology to other reported XETs were isolated from ripe kiwifruit mRNA. The six cDNA clones share 93-99% nucleotide identity and appear to belong to a family of closely related genes. Peptide sequencing indicated that ripe kiwifruit XET was encoded by AdXET6. Northern analysis indicated that expression of the AdXET1-6 gene family was induced in ripening kiwifruit when endogenous ethylene production could first be detected, and peaked in climacteric samples when fruit were soft. A full-length cDNA clone (AdXET5) was overexpressed in E. coli to produce a recombinant protein that showed endotransglycosylase activity when refolded.

Amino Acid Sequence↗
PubMed1998

Apple ACC-oxidase and polygalacturonase: ripening-specific gene expression and promoter analysis in transgenic tomato.

Levels of 1-aminocyclopropane-1-carboxylate (ACC) oxidase and polygalacturonase (PG) mRNAs were characterized during ripening of Royal Gala, Braeburn and Granny Smith apples. Both ACC-oxidase and PG mRNAs were up-regulated in ripening fruit of all three cultivars. Expression in Royal Gala was detected earlier than in Braeburn and Granny Smith, relative to internal ethylene concentration. Genomic clones corresponding to the ACC-oxidase and PG mRNAs expressed in ripe apple fruit were isolated and ca. 2 kb of each promoter was sequenced. The start point of transcription in each gene was mapped by primer extension, and sequences homologous to elements in other ethylene-responsive or PG promoters were identified. The fruit specificity of the apple ACC-oxidase and PG promoters was investigated in transgenic tomato plants using a nested set of promoter fragments fused to the beta-glucuronidase (gusA) reporter gene. For the ACC-oxidase gene, 450 bp of 5' promoter sequence was sufficient to drive GUS expression, although this expression was not specific to ripening fruit. Larger fragments of 1966 and 1159 bp showed both fruit and ripening specificity. For the PG gene, promoter fragments of 1460 and 532 bp conferred ripening-specific expression in transgenic tomato fruit. However GUS expression was down-regulated by 2356 bp of promoter, suggesting the presence of a negative regulatory element between positions -1460 and -2356.

Amino Acid Oxidoreductases↗
PubMed1995

Genomic fingerprinting by microsatellite-primed PCR: a critical evaluation.

Single PCR primers complementary to microsatellite repeats were used to amplify genomic DNA samples from various plant species, as well as from human, yeast, and Escherichia coli DNA. Most primers generated distinct amplification products, resulting in fingerprint-like banding patterns after agarose gel electrophoresis and ethidium bromide staining. These fingerprints allowed distinction among different plant taxa at an interspecific as well as intraspecific level. Unexpectedly, some of the primers produced bands with the E. coli template DNA as well. A detailed examination of the influence of PCR conditions, especially the annealing temperature, on the quality of banding patterns suggested that the majority of bands were generated by mismatch priming in a way similar to random amplified polymorphic DNAs (RAPDs).

Cloning, Molecular↗