| 1. |
- Smolka, Anders, et al.
(författare)
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Effects of transgenic rootstocks on growth and development of non-transgenic scion cultivars in apple
- 2010
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Ingår i: Transgenic Research. - : Springer Science and Business Media LLC. - 0962-8819 .- 1573-9368. ; 19, s. 933-948
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Tidskriftsartikel (refereegranskat)abstract
- Although cultivation of genetic modified (GM) annual crops has been steadily increasing in the recent 10 years, the commercial cultivation of GM fruit tree is still very limited and reports of field trials on GM fruit trees are rare. This is probably because development and evaluation of GM fruit trees require a long period of time due to long life cycles of trees. In this study, we report results from a field trial on three rolB transgenic dwarfing apple rootstocks of M26 and M9 together with non-transgenic controls grafted with five non-transgenic scion cultivars. We intended to investigate the effects of transgenic rootstock on non-transgenic scion cultivars under natural conditions as well as to evaluate the potential value of using the rolB gene to modify difficult-to-root rootstocks of fruit trees. The results showed that all rolB transgenic rootstocks significantly reduced vegetative growth including tree height regardless of scion cultivar, compared with the non-transgenic rootstocks. Flowering and fruiting were also decreased for cultivars grown on the transgenic rootstocks in most cases, but the fruit quality was not clearly affected by the transgenic rootstocks. Cutting experiment and RTPCR analysis showed that the rolB gene was stably expressed under field conditions. PCR and RT-PCR analyses displayed that the rolB gene or its mRNA were not detectable in the scion cultivars, indicating no translocation of the transgene or its mRNA from rootstock to scion. Our results suggest that rolB modified rootstocks should be used in combination with vigorous scion cultivars in order to obtain sufficient vegetative growth and good yield. Alternatively, the rolB gene could be used to dwarf vigorous rootstocks of fruit trees or produce bonzai plants as it can significantly reduce the vegetative growth of plants.
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| 2. |
- Smolka, Anders, et al.
(författare)
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Involvement of the ARRO-1 gene in adventitious root formation in apple
- 2009
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Ingår i: Plant Science. - : Elsevier BV. - 0168-9452 .- 1873-2259. ; 177, s. 710-715
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Tidskriftsartikel (refereegranskat)abstract
- Adventitious root formation is a limiting factor for vegetative propagation in apple. The molecular mechanisms underlying the rooting process are still largely unknown and need to be extensively investigated. The Adventitious Rooting Related Oxygenase (ARRO-1) has previously been isolated from apple and has been shown to be upregulated during adventitious root induction. However, the function of this gene is still unclear. The aim of this study was to downregulate the ARRO-1 gene expression, using RNAi technique, to study the function of ARRO-I in adventitious root formation in apple. The apple rootstock M26 was transformed with the RNAi-ARRO-1 construct. The transgenic clones, confirmed by PCR and Southern blot analysis, showed significantly reduced adventitious root formation both with microcuttings and stem discs, indicating the involvement of ARRO-1 in adventitious root formation. The transgenic clones also appeared to be more sensitive to exogenous hormones compared to the untransformed control plants, Suggesting that ARRO-1 may be involved in regulating hormone homeostasis. Relative quantification of the ARRO-1 mRNA showed no obvious difference in transcript levels between untransformed control and the transformants. A possible explanation for this is that the downregulation of the ARRO-1 gene might be translational rather than transcriptional. (C) 2009 Elsevier Ireland Ltd. All rights reserved.
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| 3. |
- Smolka, Anders
(författare)
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Understanding of molecular mechanisms and improving of adventitous root formation in apple
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Adventitious root formation is essential for vegetative propagation, which is the main method for propagation of many horticultural crops, especially woody species. For propagation of apple rootstocks, adventitious root formation is often a limiting step. The molecular mechanisms underlying adventitious root formation are still largely unknown and need to be extensively investigated. In this thesis approaches towards an increased understating of adventitious root formation were made using both apple and the model plant Arabidopsis. For Arabidopsis, a protocol for efficient rooting of hypocotyls and stem segments using two pulses of auxin induction was developed. This protocol was used for studying the expression of a number of rooting related genes during adventitious root formation in both stems and hypocotyls, and for anatomical studies of the timing of the rooting process. The transcript levels of GH3-3, LBD16, LBD29, LRP1 and ARF17 were clearly affected by the auxin treatment, and some of these genes displayed considerable differences between stem segments and hypocotyls. In apple, the function of the rooting related gene ARRO-1 was investigated through down-regulation of the gene using RNAi. The results indicate a possible role for ARRO-1 in promoting adventitious root initiation or regulating hormone homeostasis. The effect of apple rootstocks transformed with the Agrobacterium rolB gene on non-transgenic scions was also investigated, regarding tree growth, flowering and fruit quality. The results showed that the transgenic rootstock had no clear effect on fruit quality but greatly affected vegetative growth. No translocation of transgene mRNA or DNA from rootstock to scion could be detected. Attempts were also made to produce ROLB specific antibodies to investigate if the ROLB protein is transported from the transgenic rootstock into the non-transgenic scion which could be of concern for the consumer.
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| 4. |
- Welander, Margareta, et al.
(författare)
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Origin, timing, and gene expression profile of adventitious rooting in Arabidopsis hypocotyls and stems
- 2014
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Ingår i: American Journal of Botany. - : Wiley. - 0002-9122 .- 1537-2197. ; 101, s. 255-266
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Tidskriftsartikel (refereegranskat)abstract
- Premise of the study: Adventitious root (AR) formation is indispensable for vegetative propagation, but diffi cult to achieve in many crops. Understanding its molecular mechanisms is thus important for such species. Here we aimed at developing a rooting protocol for direct AR formation in stems, locating cellular AR origins in stems and exploring molecular differences underlying adventitious rooting in hypocotyls and stems. Methods: In-vitro-grown hypocotyls or stems of wild-type and transgenic ecotype Columbia (Col-0) of Arabidopsis thalianawere rooted on rooting media. Anatomy of AR formation, qRT-PCR of some rooting-related genes and in situ GUS expression were carried out during rooting from hypocotyls and stems. Key results: We developed a rooting protocol for AR formation in stems and traced back root origins in stems by anatomicaland in situ expression studies. Unlike rooting in hypocotyls, rooting in stems was slower, and AR origins were mainly from lateral parenchyma of vascular bundles and neighboring starch sheath cells as well as, to a lesser extent, from phloem cap and xylem parenchyma. Transcript levels of GH3-3 , LBD16 , LBD29 , and LRP1 in hypocotyls and stems were similar, but transcript accumulation was delayed in stems. In situ expression signals of DR5::GUS , LBD16::GUS , LBD29::GUS , and rolB::GUS reporters in stems mainly occurred at the root initiation sites, suggesting their involvement in AR formation. Conclusions: We have developed an effi cient rooting protocol using half-strength Lepoivre medium for studying AR formation instems, traced back the cellular AR origins in stems, and correlated expression of rooting-related genes with root initiation sites.
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