Master theses

The multicellular female gametophyte develops in a complicated way. To identify proteins which have a key role in the molecular regulation of this developmental differentiation process, a cDNA library of mature ovules from Petunia hybrida was screened. After isolation of plasmids from this library, sequencing the ESTs and looking for homologies with a BLAST search, 956 ESTs were categorized and stored in a database. By clustering those genes the redundancy of the database was estimated to be 32.6%. A putative name and functional class could be determined to 61% of the ESTs.

A protein which is known to be embryo sac specific in orchids (Skp1) was identified. This proves that embryo sac genes are present in the cDNA library. On the other hand the identification of Fbp7, which is expressed in the sporophytic tissue of the ovule, points to some contamination of the cDNA library with sporophyte expressed genes. Based on the annotation, some ESTs which are possibly important regulatory factors in the embryo sac development were selected. These selected genes included a transcription factor, Bel1-like, and a pheromone receptor. Of those genes, and also fbp7 as a control, probes were produced for in situ hybridisation. For all genes some expression in the ovule could be detected, but because structures or cells inside the embryo sac could not be distinguished, it remains unknown whether those genes are expressed inside the embryo sac.

So many genes expressed in mature ovules were identified, including many genes which might have an important regulatory function in the development of the embryo sac. By analysis of mutants and the performance of micro array experiments, the moment and the level of expression of those genes can be determined which may provide more information about the molecular regulation of the female gametophyte development.