Functional analysis of TOWER OF PISA 1 and TOWER OF PISA 2 transcriptional factors and their role in Arabidopsis gynoecium development.
Carpels, the female floral organs that form the gynoecium, show the highest anatomical and functional complexity among the floral organs. The fruits are basically derived from the gynoecium, being a highly especialized organ which main roles are to ensure maduration and dispersal of the seeds. 
In spite of the huge progress that has taken place in the last few years, there are still open questions about gynoecium morphogenesis and fruit development. An obvious way to contribute on unraveling these questions is to reveal new genetic modulators which mutations affect carpel development.
In this Doctoral Thesis, our aim was to obtain further insights on the genetic pathways involved in gynoecium development and how these different pathways are coordinated. An effort has been made to functionally characterize two B3 transcriptional factors, TOP1 and TOP2, potentially involved in gynoecium development as a common factor to some of the pathways already described. We have tried to identify the genetic and molecular interactions of TOP1 and TOP2 with previously described genes involved in different Arabidopsis gynoecium and fruit development aspects.
For this purpose we have functionally characterized these genes obtaining loss- and gain-of-function lines and phenotypically characterizing them. We have shown that TOP1 and TOP2 are redundantly involved in the development of apical gynoecium tissues promoting style and stigma differentiation. We have analyzed TOP1 and TOP2 spatial and temporal pattern of expression, which overlaps with those regions defective in loss-of-function mutants, style and stigma. Expression has been also detected in other gynoecium tissues, the rest of the floral organs and in leaves and roots, generally associated with positions of primordia emergence or cell proliferation and with regions which have been reported as auxin maxima.
In addition, we have analyzed the genetic interactions of TOP1 and TOP2 with previously characterized genes involved in gynoecium development through generation and characterization of different mutant combinations, the determination of TOP1 expression patterns in different mutant backgrounds, and, conversely, analyzing the effect of top1 and top2 mutations on the expression of different genes.  Thus, we have determined that TOP genes act with STY and SPT directing style and stigma development, likely at the same level since no direct regulation has been observed among them, at least in the apical gynoecium context. In contrast, we have also shown that TOP1 negatively regulates SPT in ovules and seeds. In addition, we have determined that ETT could restrict TOP1 expression to apical gynoecium tissues. In addition, we have shown the TOP genes act sinergistically with LUG in marginal tissue development: style, stigma and septum.
Our results indicate that TOP genes could be involved in auxin synthesis pathways, and that they could also be involved in medial-lateral gynoecium patterning development positively regulating IND direct or indirectly.
Finally, in a yeast two-hybrid assay we have determined that TOP genes physically interact with YAB3 and BRX-L4, two transcriptional regulators with proposed roles in abaxial-adaxial polarity specification and root growth respectively.





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