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Studio funzionale di due geni MADS-box (FaSHP e TM8) coinvolti nello sviluppo di strutture carnose con funzione "frutto"
| Content Provider | Semantic Scholar |
|---|---|
| Author | Daminato, Margherita |
| Copyright Year | 2013 |
| Abstract | The fruit is an ovary derived structure, typical of Angiosperms, that is fundamental for the dispersal of seeds in the environment. Fleshy fruits are particularly efficient because they attract frugivorous animals that disperse the seeds in the environment by means of endozoochory. However the production of fleshy structures for seed dispersal is not limited to flowering plants and can be also found in the Gymnosperms. In fact, some Gymnosperm species surround their seeds with fleshy structures which can be considered fruits from a functional point of view, even if they are not ovary derived. The study of the molecular mechanisms regulating fleshy structure development is therefore interesting from an evolutionary point of view. It was recently discovered that some MADS-box genes, already known to be involved in the development of Angiosperm fruits, are also expressed in Gymnosperm fruits (Lovisetto et al., 2012). This suggests a possible conservation of the molecular mechanisms involved in the development of seed dispersing structures. Since the study of Gymnosperm genes is difficult because these plants are recalcitrant to both transformation and regeneration, we decided to study two Angiosperm genes for this thesis work. In particular the strawberry FaSHP and the tomato TM8 genes, whose homologous ones are also expressed in the Gymnosperm fruits, were studied in strawberry and tomato, respectively. FaSHP is a strawberry AGAMOUS-like MADS-box gene, belonging to the PLENA clade, which was isolated following the screening of a red fruit cDNA library and which is particularly expressed during the ripening phase. Considering the already demonstrated important role of other genes of this group during the development of climacteric fleshy fruits, we decided to investigate FaSHP function by means of transient gene silencing and over-expression experiments in strawberry fruits, which are non-climacteric. FaSHP down- and over-expressing fruits showed respectively a delay and an acceleration of the ripening phase, which were confirmed at the molecular level by means of the altered expression of some ripening related genes. These data led to hypothesize a possible role for FaSHP as general regulator of many aspects of the "ripening syndrome" in strawberry. Moreover FaSHP gene expression analysis following fruit treatments with auxin and ABA (key hormonal regulators of strawberry ripening), and the identification of hormone response sequences in the gene promoter, suggested that FaSHP could at least partially mediate these two hormone role on fruit ripening. Therefore the results of this part of the work suggest that FaSHP could be a "master gene" in strawberry fruit ripening. Considering that AGAMOUS-like genes are also expressed during the development of Gymnosperm fruits, which like strawberries are false fruits, it can be supposed that the Gymnosperm genes could have a similar function during the development of the seed surrounding fleshy structures of these plants. TM8 was the first discovered gene of a poorly studied MADS-box gene group. As well as Gymnosperm TM8-like genes the tomato TM8 gene has an ubiquitary gene expression profile, even if it reaches a maximum in the flower. In order to test the gene role we produced transgenic plants over-expressing TM8 and transgenic plants over-expressing the gene as a chimeric repressor. Since transgenic plants over-expressing TM8 produce flowers having dialytic stamens, we hypothesized that this gene could have a role in the development of male reproductive organs. This idea was supported by the gene expression analysis of other floral organ MADS-box identity genes. Besides TM8 possible function during flower development, the phenotypic and molecular analysis of the plants over-expressing TM8 as a chimeric repressor led to hypothesize a possible function also during the development of other plant organs, both vegetative (leaf) and reproductive (fruit). These roles in several steps of the plant life cycle support the idea that TM8-like genes are very ancient and that they originated early during MADS-box gene evolution. Moreover, TM8 possible function during fruit development suggests that also in Gymnosperms, where TM8-like genes are expressed in seed dispersing structures, they could participate in the development of "fruits" |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://paduaresearch.cab.unipd.it/5512/1/daminato_margherita_tesi.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
