| 1. |
- Schrader, J., et al.
(author)
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Cambial meristem dormancy in trees involves extensive remodelling of the transcriptome
- 2004
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In: The Plant Journal. - Malden : Wiley-Blackwell. - 0960-7412 .- 1365-313X. ; 40:2, s. 173-187
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Journal article (peer-reviewed)abstract
- The establishment of the dormant state in meristems involves considerable physiological and metabolic alterations necessary for surviving unfavourable growth conditions. However, a global molecular analysis of dormancy in meristems has been hampered by the difficulty in isolating meristem cells. We used cryosectioning to isolate purified cambial meristem cells from the woody plant Populus tremula during active growth and dormancy. These samples were used to generate meristem-specific cDNA libraries and for cDNA microarray experiments to define the global transcriptional changes underlying cambial dormancy. The results indicate a significant reduction in the complexity of the cambial transcriptome in the dormant state. Although cell division is terminated in the dormant cambium, the cell cycle machinery appears to be maintained in a skeletal state as suggested by the continued presence of transcripts for several cell cycle regulators. The downregulation of PttPIN1 and PttPIN2 transcripts explains the reduced basipetal polar auxin transport during dormancy. The induction of a member of the SINA family of ubiquitin ligases implicated in auxin signalling indicates a potential mechanism for modulation of auxin sensitivity during cambial dormancy. The metabolic alterations during dormancy are mirrored in the induction of genes involved in starch breakdown and the glyoxysomal cycle. Interestingly, the induction of RGA1 like gene suggests modification of gibberellin signalling in cambial dormancy. The induction of genes such as poplar orthologues of FIE and HAP2 indicates a potential role for these global regulators of transcription in orchestrating extensive changes in gene expression during dormancy.
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| 2. |
- Beaujean, A, et al.
(author)
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Engineering direct fructose production in processed potato tubers by expressing a bifunctional alpha-amylase/glucose isomerase gene complex
- 2000
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In: Biotechnology and Bioengineering. - 0006-3592. ; 70:1, s. 9-16
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Journal article (peer-reviewed)abstract
- Manipulation of starch biosynthesis/degradation and formation of novel molecules in storage organs of plants through genetic engineering is an attractive but technically challenging goal. We report here, for the first time, that starch was degraded and glucose and fructose were produced directly when crushed potato tubers expressing a starch degrading bifunctional gene were heated for 45 minutes at 65 degrees C. To achieve this, we have constructed a fusion gene encoding the thermostable enzymes: alpha-amylase (Bacillus stearothermophilus) and glucose isomerase (Thermus thermophilus). The chimeric gene was placed under the control of the granule-bound-starch synthase promoter. This enzymatic complex produced in transgenic tubers was only active at high temperature (65 degrees C). More than 100 independent transgenic potato plants were regenerated. Molecular analyses confirmed the stable integration of the chimeric gene into the potato genome. The biochemical analyses performed on young and old tubers after high-temperature treatment (65 degrees C) revealed an increase in the formation rate of fructose and glucose by a factor of 16.4 and 5. 7, respectively, in the transgenic tubers as compared to untransformed control tubers. No adverse discernible effect on plant development and metabolism including tuber formation and starch accumulation was observed in the transgenic plants before heat treatment. Our results demonstrate that it is possible to replace starch degradation using microbial enzymes via a system where the enzymes are produced directly in the plants, but active only at high temperature, thus offering novel and viable strategies for starch-processing industries.
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