Abstract
The tomato fruit development can be divided in different stages, each one with distinct features. Firstly, the identity of the flowers whorls and secondly the establishment of the floral structures occurs, which is important for the final fruit shape. In tomato, as in all angiosperm, fruit set and seed formation depend on the successful completion of pollination. Even if the flower whorls are completely formed, without the fertilization, the organ tends to abort. Following pollination, cell division and expansion occur, leading to fruit set which has to occur in a synchronized manner. Hormone treatments with auxin and gibberellin (GA) in ovaries at pre-anthesis can trigger fruit development independently of pollination, however, the fruits are seedless. Additionally, some mutants and transgenic lines for hormones pathways can produce parthenocarpic fruits as well. Consistent with this observation, a good example is the natural tomato mutant procera (pro), a point mutation in the GRAS domain of DELLA protein coding gene which leads to constitutive GA responses. As a result, this mutant has a high rate of seedless fruits (parthenocarpic). Besides, transgenic plants displaying downregulation of IAA9 also produce parthenocarpic fruit. Recent works have shown that hormones may act in parallel with transcription factors during fruit set, thus stressing the importance of the control of these genes along fruit development. Interestingly some of these genes are post-transcriptionally regulated by microRNAs (miRNAs). MiRNAs are a group of small non coding RNAs (21-22 nt) that act by regulating post-transcriptionally genes in plants and animals. Additionally, it has already been shown that some microRNAs pathway are tightly related to fruit set. In this proposal, we intend to determinate the roles of the microRNA159 (miR159) pathway during fruit set. The miR159 regulates negatively the transcription factors GAMYB-like, which are upregulated by GA. In Arabidopsis this pathway is important for anther formation (Alonso-Pereal et al., 2010).In addition, abscisic acid (ABA) induces the expression of miR159 during seed germination. Together, these works show that the miR159/GAMYB-like pathway is correlated with hormones in plant development, however, there is no information regarding fruit development (AU)
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