Characterization, expression, and regulation of two classes of sucrose synthase genes from potato /
Two classes of sucrose synthase genes were identified in potato. The T-class gene, Stsstl6, and the V-class gene, Stssv65, are both split by 13 introns including a long leader intron. The two genes are 88% and 96% identical at the nucleotide and amino acid level, respectively, in the coding region...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1995.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=742145101&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Two classes of sucrose synthase genes were identified in potato. The T-class gene, Stsstl6, and the V-class gene, Stssv65, are both split by 13 introns including a long leader intron. The two genes are 88% and 96% identical at the nucleotide and amino acid level, respectively, in the coding regions, but diverge outside the coding regions except for a few short conserved sequences. RNA gel blot analysis showed that T-class genes were expressed at much higher levels in tubers than in stems or roots. T-class genes were normally not detectable in leaves, but could be induced to be expressed at high levels by sucrose. In contrast, V-class genes were expressed at higher levels in roots and stems and were not sucrose-inducible. These results, combined with the GUS expression patterns observed in transgenic potato plants driven by regulatory sequences from either Stsstl6 or Stssv65, suggest that a major role of the T-class genes is to supply substrates for starch synthesis in tubers, while the V-class genes serve to supply energy for phloem loading and substrates for general cellular respiration and metabolism. By examining expression of a series of deletion and substitution constructs in transgenic plants, sequences critical for proper expression of the two classes of genes were determined. For the T-class gene, Stsstl6, both high- level expression in tubers and sucrose inducibility required interaction of the 5' sequences and the 3' sequences. Spatial expression was mainly determined by regulatory sequences which acted additively. However, in some cases the expression from combination of elements differ from any of the individual compoments. Removal of the leader intron also had dramatic effects on quantitative, spatial, and sucrose-inducible expression. For the V-class gene, Stssv65, deletion of 3' sequences or the leader intron did not significantly alter expression in vegetative tissues unless assayed in the context of only proximal 5' promoter elements. However, removal of the leader intron reduced expression at later stages of development in the vascular tissue of anthers and markedly increased expression in pollen. |
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| Item Description: | Vita. "Major Subject: Biology". |
| Physical Description: | xii, 119 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references. |